Biologics

ABSTRACT

The aim of this study was to evaluate the safety and efficacy of using autologous, micro-fractured, minimally manipulated adipose tissue in patients with refractory knee osteoarthritis (OA). A total of 17 subjects (26 knees) with a median age of 72 years (range: 54-78 years) and a history of knee OA (Kellgren–Lawrence, grade of 3 or 4) underwent treatment with ultrasound-guided injection of micro-fractured adipose tissue. Micro-fractured fat was obtained using a minimal manipulation technique in a closed system (Lipogems), without the addition of enzymes or any other additives. The study subjects were clinically evaluated using the numerical pain rating scale (NPRS), the 100-point Knee Society Score (KSS) with its functional component (FXN), and the lower extremity activity scale (LEAS) at 6 weeks, 6 months, and 12 months following this procedure.

When compared with baseline, significant improvements were noted in the mean values of NPRS, FXN, and LEAS at 6 weeks, 6 months, and 12 months. The mean KSS significantly improved at 6 weeks and 12 months. In particular, the average KSS score improved from 74 to 82, the FXN score improved from 65 to 76, and the LEAS score improved from 36 to 47. These values were significantly greater than the previously published minimal clinically important difference described for KSS and FXN in patients who underwent total knee arthroplasty for primary OA. No serious adverse events were reported. The injection of autologous, micro-fractured, minimally manipulated adipose tissue appears to be a safe and effective treatment option for patients with refractory, severe (grade 3 or 4) knee OA.

This study demonstrated significant improvements in pain, quality of life, and function for at least 12 months in this study population. This intervention may represent a nonsurgical treatment option to avoid knee joint replacement in this population; however, further investigation is needed.

Continue to: Knee OA is...

Knee OA is a chronic disease that affects all races, genders, and ages, but it is most prevalent in obese and elderly people. Worldwide, arthritis is considered to be the fourth leading cause of disability.¹ In developing and developed countries, knee OA may cause a significant decline in the quality of life for individuals >65 years due to joint pain and disability.¹ Nonoperative treatment can be successful in patients with mild to moderate arthritis with pain.

Current treatment options for knee OA, including physical therapy and anti-inflammatory drugs, aim to remedy the symptoms, but they do little to treat the underlying causes of knee OA pain. When a patient presents with advanced arthritis of the knee as confirmed by radiographic findings (classified as Kellgren–Lawrence grade of 3 or 4), the standard approach has been a total knee arthroplasty (TKA) after the patient has failed conservative treatment. The annual rate of total knee replacement in the United States has doubled since 2000, especially in those 45 – 65 years.² The total number of procedures performed each year now exceeds 640,000, at a total annual cost of about $10.2 billion.² Multiple studies show that TKA has favorable outcomes in pain relief and functional improvement in patients >60 years when evaluated at a follow-up of 10 years after surgery.²

However, some patients are hesitant to proceed with surgery due to fear of surgical pain and procedural complications. The known complications include deep vein thrombosis, pulmonary embolism, nerve injury, and infection. In addition, up to 20% of patients continue to complain of pain following a total knee replacement.³ Finally, in the young population (<50 years), there are concerns related to the potential need of revision knee surgery in the future.³

Alternative treatments for knee OA have recently emerged, including the use of platelet-rich plasma (PRP). A recent meta-analysis that included 10 randomized controlled trials with a total of 1069 patients demonstrated that, compared with hyaluronic acid and saline, intra-articular PRP injection may have more benefits in pain relief and functional improvement in patients with symptomatic knee OA at 1-year post-injection.⁴ Another smaller study examined patients who had experienced mild knee OA (Kellgren–Lawrence grade <3) for an average of 14 months. Each patient underwent magnetic resonance imaging for the evaluation of joint damage and then received a single PRP injection. The patients were assessed at regular intervals, with improvement in pain lasting up to 12 months.⁵

Additional orthobiologic options include the use of bone marrow and adipose-derived stem cell (ASC) injections for a variety of knee conditions, including knee OA. Mesenchymal stem cells (MSCs) are multipotent cells that have been used for the treatment of OA in clinical trials because of their regeneration potential and anti-inflammatory effects.⁶ Bone marrow stem cells (BMSCs) were first used to repair cartilage damage in humans in 1998. However, BMSCs had particular challenges, including low stem cell yield, pain, and possible morbidities during bone marrow aspiration. An alternative is ASCs, which may be more suitable clinically because of the high stem cell yield from lipoaspirates, faster cell proliferation, and less discomfort and morbidities during the harvesting procedure.⁷ In addition, these adult stem cells can contribute to the chondrogenic, osteogenic, adipogenic, myogenic, and neurogenic lineages.⁸ One study demonstrated that the contents of cartilage glycosaminoglycans significantly increased in specific areas of a knee joint treated with ASCs.^9,10  This increased glycosaminoglycan content in hyaline cartilage may explain the observed visual analog score (VAS) improvement and clinical results. Other studies suggest that the chondrogenic action of ASCs may depend more on regenerative signaling by activated perivascular cells and signaling of trophic and paracrine mediators, such as vascular endothelial growth factor.^9,10 Finally, the mechanism of action may include providing volume, support, cushioning, and filling of soft tissue defects.¹¹

The Lipogems method and device, approved by the U.S. Food and Drug Administration, is used to harvest ASCs, cleanse, and micro-fracture adipose tissue while maintaining the perivascular niche that contains pericytes. The purpose of this study was to evaluate the safety and efficacy of using autologous, micro-fractured, minimally manipulated adipose tissue in patients with severe refractory knee OA.

Continue to: This report details...

STUDY PRESENTATION

This report details the outcome of an IRB-approved study of 17 subjects with 26 symptomatic knees with a history of knee OA (Kellgren–Lawrence grade of 3 or 4) diagnosed by a radiograph. Patient demographics are described in the Table.

_{Abbreviation: BMI, body mass index.}

The study patients were evaluated by an orthopedic surgeon, Mitchell Sheinkop, who commonly performs total joint replacement in his practice and considers potential patients as candidates for TKA. These patients presented with a Kellgren-Lawrence grade of 3 or 4 knee OA, and all had significant pain that was refractory to conservative treatment, which included medications, physical therapy, and injections. The study patients were offered the Lipogems procedure as an alternative to TKA. Following this procedure, the study subjects were clinically evaluated using the numerical pain rating scale (NPRS), the 100-point Knee Society Score (KSS) with its functional component (FXN), and the lower extremity activity scale (LEAS) at 6 weeks, 6 months, and 12 months. The 1989 KSS12 was used for this study. Adverse reactions were also monitored throughout the study period.

METHODS

After obtaining informed consent, the subjects were taken into the operating room, moved to the procedure table, and placed in the prone position for aspiration. After scrubbing with Betadine and draping, 1 mL of lidocaine was used to anesthetize the skin, and a pre-prepared preparation of lidocaine, epinephrine, and sterile saline was infused into the subcutaneous tissue. The micro-fragmented adipose tissue was obtained with minimal manipulation using Lipogems, a closed system using mild mechanical forces and reduction filters. The system processes the lipoaspirate without the addition of enzymes or any other additives. The final product consists of adipose tissue clusters with preserved vascular stromal niche of approximately 500 microns. The lipoaspirate was processed in the same room via a closed system. During the processing, the subject’s puncture wounds were dressed. The knee injection site was prepped with a Betadine swab and DuraPrep. Then, Lipogems was injected intra-articularly under ultrasound guidance.

After the completion of the injection, manual range of motion was administered to the treated joint. The subject was then transferred to the recovery room where vital signs were monitored. Post-procedure instructions were reviewed with the patient by the study staff. The subject was instructed to use an assistive device and avoid weight-bearing for 48 hours and maintain the activities of daily living to a minimum on the day of the procedure. Non-weight-bearing for 48 hours was recommended for reducing discomfort to avoid the use of opioids. Nonsteroidal anti-inflammatory drugs, alcohol, and marijuana must be avoided for 4 weeks after the procedure. Pretreatment and post-treatment outcomes were collected using the NPRS, the 100-point KSS with its FXN, and the LEAS at 6 weeks, 6 months, and 12 months after this procedure. The 1989 KSS12 was used for this study since the same scale was used for previous TKA procedures by our authors, allowing for future comparisons of results.

STATISTICAL ANALYSIS

Mean and standard deviation were used to estimate central tendency and variability. Outcome measures were analyzed using the t test, with the pairwise t test was used for paired and subsequent measurements of the same patient or a knee. All analyses were performed with significance set at P <.05. The minimal clinically important difference (MCID) in patients who underwent TKA for primary OA was between 5.3 and 5.9 for KSS, while the MCID for FXN was between 6.1 and 6.4.13 These values were referenced for our analysis.

Continue to: No significant adverse...

RESULTS

No significant adverse events were reported in the subjects of this study. Common minor adverse events included pain and swelling, which generally resolved in 48 to 72 hours after the procedure.

Compared with baseline, significant improvements were noted in the mean values of NPRS (Figure 1) at 6 weeks, 6 months, and 12 months. The mean KSS significantly improved from baseline at 6 weeks and 12 months (Figure 2). Significant improvements were also noted in the mean values of FXN (Figure 3) and the mean LEAS significantly improved from baseline at 6 weeks and 6 months (Figure 4).

DISCUSSION

Knee OA is a disabling condition that affects a substantial proportion of the aging population. The current treatment methods do little to address the degenerative environment of the joint, which includes cytokines such as IL-1 and IL-2. Orthobiologic agents have been used recently to address these issues, which include PRP and MSCs from various sources, including bone marrow and adipose tissue.

A recent meta-analysis conducted by Cui and colleagues14 evaluated 18 studies of MSC treatment for knee OA with a total of 565 participants (226 males and 339 females). The duration from the onset of knee pain to registration in each study ranged from 3 months to ≥7 years. The follow-up period was 3 months -24 months. The majority of studies recruited patients with knee OA with a severity grade of 1-4 on the K-L scale; K-L grades 1 and 2 and grades 3 and 4 were defined as early OA and advanced OA, respectively. The results suggested that MSC treatment significantly improved pain and functional status, relative to the baseline evaluations in knee OA, and the beneficial effect was maintained for 2 years after treatment. Furthermore, the treatment effectiveness was not reduced over time.¹⁴

Included in the abovementioned meta-analysis were 2 papers by Koh and colleagues in 2012 and 2013 on the use of AMSCs for the treatment of OA. ^15,16 The first study included 18 patients whose adipose tissue was harvested from the inner side of the infrapatellar fat pad via a skin incision after arthroscopic debridement. The cells were centrifuged and injected into the patient’s knee the same day. The results showed a significant reduction of pain and an increased quality of life for all patients, and a positive correlation was found between the number of cells injected and pain improvements. The authors concluded that AMSCs were a valid cell source for treating cartilage damage.¹⁵

In their second study, Koh and colleagues reported their results of treating 30 elderly patients with OA (≥65 years), who had failed conventional treatment, using intra-articular injections of AMSCs.¹⁶ This patient population is important since OA most commonly occurs in the elderly population. Patients underwent arthroscopic lavage and cartilage evaluation before receiving an injection of AMSCs delivered in PRP. The authors demonstrated that AMSC therapy for elderly patients with mild to moderate OA was an effective treatment resulting in reduction of pain and regeneration of cartilage.¹⁶

In another study, Adriani and colleagues¹⁷ performed autologous percutaneous fat injection from January 2012 to March 2015 for the treatment of knee OA. Their 30 patients (12 males and 18 females; mean age of 63.3 years; mean body mass index of 25.1) had stable or progressive knee OA for at least 12 months, no other injection treatments during the previous 12 months, and no prior knee surgeries. The patients were evaluated at baseline and 1 week and at 1, 3, 6, and 12 months after treatment using the NPRS and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) as outcome measures. The average VAS was 7.7 at baseline and improved to 4.3 at 3-month follow-up; however, a slight deterioration (VAS 5.0) was noted at 1 year. Total WOMAC score was 89.9 at baseline, 68.6 at 3 months, and 73.2 at 12-month follow-up.¹⁷

Continue to: The results of...

The results of this study demonstrated significant improvements in pain, quality of life, and function at 12 months after ultrasound-guided injection of ASCs in patients with severe knee OA. Significant improvement that was noted at 6 weeks was maintained through 12 months after the treatment. Improvement was noted in all scales, including the NPRS, the KSS, and the FXN beginning at 3 months and continuing through 12 months. The LEAS was statistically significant through 6 months after the treatment but not significant at 12 months. No serious adverse events were recorded.

In a study by Lee and colleagues,¹³ the MCID was described for KSS and FXN in patients who underwent TKA for primary OA. This is the minimal change in a scoring measure that is perceived by the patient to be beneficial or harmful. The MCID for KSS was noted to be between 5.3 and 5.9, while the MCID for FXN was between 6.1 and 6.4.13 In our study, the KSS score improved from an average of 74.0 at baseline to 79.6 at 6 months and 81.6 at 12 months (a difference of 5.6 and 7.6; P = .18 and.014, respectively). The FXN improved from an average of 65.4 at baseline to 75.2 at 6 months and 76.4 at 12 months (a difference of 9.9 and 11; P = .041 and.014, respectively). Therefore, a clinically important difference of KSS and FXN scores was noted at both 6 and 12 months.

The technique used in this study provides autologous, minimally manipulated, fat graft performed in a short time (60-90 minutes), without expansion and/or enzymatic treatment. In addition, the harvesting and the injection of stem cells on the same day is a simple, office-based procedure, and compliant with the U. S. Food and Drug Administration regulations.¹⁸ The cost of the procedure averages $3500.

A study limitation is that it is a case series with relatively small numbers and not a randomized controlled study. Therefore, a placebo effect may play a role in our results. Further study with a larger number of patients and randomized controlled studies would be beneficial to support the findings of this study.

CONCLUSION

The injection of autologous, micro-fractured, minimally manipulated adipose tissue appears to be a safe and effective treatment option in patients with refractory severe (grade 3 or 4) knee OA. This study showed significant improvements in pain, quality of life, and function for at least 12 months in this study population. This intervention may represent a nonsurgical treatment option to avoid knee joint replacement in this population; however, further investigation is needed.

ABSTRACT

The aim of this study was to evaluate the safety and efficacy of using autologous, micro-fractured, minimally manipulated adipose tissue in patients with refractory knee osteoarthritis (OA). A total of 17 subjects (26 knees) with a median age of 72 years (range: 54-78 years) and a history of knee OA (Kellgren–Lawrence, grade of 3 or 4) underwent treatment with ultrasound-guided injection of micro-fractured adipose tissue. Micro-fractured fat was obtained using a minimal manipulation technique in a closed system (Lipogems), without the addition of enzymes or any other additives. The study subjects were clinically evaluated using the numerical pain rating scale (NPRS), the 100-point Knee Society Score (KSS) with its functional component (FXN), and the lower extremity activity scale (LEAS) at 6 weeks, 6 months, and 12 months following this procedure.

When compared with baseline, significant improvements were noted in the mean values of NPRS, FXN, and LEAS at 6 weeks, 6 months, and 12 months. The mean KSS significantly improved at 6 weeks and 12 months. In particular, the average KSS score improved from 74 to 82, the FXN score improved from 65 to 76, and the LEAS score improved from 36 to 47. These values were significantly greater than the previously published minimal clinically important difference described for KSS and FXN in patients who underwent total knee arthroplasty for primary OA. No serious adverse events were reported. The injection of autologous, micro-fractured, minimally manipulated adipose tissue appears to be a safe and effective treatment option for patients with refractory, severe (grade 3 or 4) knee OA.

This study demonstrated significant improvements in pain, quality of life, and function for at least 12 months in this study population. This intervention may represent a nonsurgical treatment option to avoid knee joint replacement in this population; however, further investigation is needed.

Continue to: Knee OA is...

Knee OA is a chronic disease that affects all races, genders, and ages, but it is most prevalent in obese and elderly people. Worldwide, arthritis is considered to be the fourth leading cause of disability.¹ In developing and developed countries, knee OA may cause a significant decline in the quality of life for individuals >65 years due to joint pain and disability.¹ Nonoperative treatment can be successful in patients with mild to moderate arthritis with pain.

Current treatment options for knee OA, including physical therapy and anti-inflammatory drugs, aim to remedy the symptoms, but they do little to treat the underlying causes of knee OA pain. When a patient presents with advanced arthritis of the knee as confirmed by radiographic findings (classified as Kellgren–Lawrence grade of 3 or 4), the standard approach has been a total knee arthroplasty (TKA) after the patient has failed conservative treatment. The annual rate of total knee replacement in the United States has doubled since 2000, especially in those 45 – 65 years.² The total number of procedures performed each year now exceeds 640,000, at a total annual cost of about $10.2 billion.² Multiple studies show that TKA has favorable outcomes in pain relief and functional improvement in patients >60 years when evaluated at a follow-up of 10 years after surgery.²

However, some patients are hesitant to proceed with surgery due to fear of surgical pain and procedural complications. The known complications include deep vein thrombosis, pulmonary embolism, nerve injury, and infection. In addition, up to 20% of patients continue to complain of pain following a total knee replacement.³ Finally, in the young population (<50 years), there are concerns related to the potential need of revision knee surgery in the future.³

Alternative treatments for knee OA have recently emerged, including the use of platelet-rich plasma (PRP). A recent meta-analysis that included 10 randomized controlled trials with a total of 1069 patients demonstrated that, compared with hyaluronic acid and saline, intra-articular PRP injection may have more benefits in pain relief and functional improvement in patients with symptomatic knee OA at 1-year post-injection.⁴ Another smaller study examined patients who had experienced mild knee OA (Kellgren–Lawrence grade <3) for an average of 14 months. Each patient underwent magnetic resonance imaging for the evaluation of joint damage and then received a single PRP injection. The patients were assessed at regular intervals, with improvement in pain lasting up to 12 months.⁵

Additional orthobiologic options include the use of bone marrow and adipose-derived stem cell (ASC) injections for a variety of knee conditions, including knee OA. Mesenchymal stem cells (MSCs) are multipotent cells that have been used for the treatment of OA in clinical trials because of their regeneration potential and anti-inflammatory effects.⁶ Bone marrow stem cells (BMSCs) were first used to repair cartilage damage in humans in 1998. However, BMSCs had particular challenges, including low stem cell yield, pain, and possible morbidities during bone marrow aspiration. An alternative is ASCs, which may be more suitable clinically because of the high stem cell yield from lipoaspirates, faster cell proliferation, and less discomfort and morbidities during the harvesting procedure.⁷ In addition, these adult stem cells can contribute to the chondrogenic, osteogenic, adipogenic, myogenic, and neurogenic lineages.⁸ One study demonstrated that the contents of cartilage glycosaminoglycans significantly increased in specific areas of a knee joint treated with ASCs.^9,10  This increased glycosaminoglycan content in hyaline cartilage may explain the observed visual analog score (VAS) improvement and clinical results. Other studies suggest that the chondrogenic action of ASCs may depend more on regenerative signaling by activated perivascular cells and signaling of trophic and paracrine mediators, such as vascular endothelial growth factor.^9,10 Finally, the mechanism of action may include providing volume, support, cushioning, and filling of soft tissue defects.¹¹

The Lipogems method and device, approved by the U.S. Food and Drug Administration, is used to harvest ASCs, cleanse, and micro-fracture adipose tissue while maintaining the perivascular niche that contains pericytes. The purpose of this study was to evaluate the safety and efficacy of using autologous, micro-fractured, minimally manipulated adipose tissue in patients with severe refractory knee OA.

Continue to: This report details...

STUDY PRESENTATION

This report details the outcome of an IRB-approved study of 17 subjects with 26 symptomatic knees with a history of knee OA (Kellgren–Lawrence grade of 3 or 4) diagnosed by a radiograph. Patient demographics are described in the Table.

_{Abbreviation: BMI, body mass index.}

The study patients were evaluated by an orthopedic surgeon, Mitchell Sheinkop, who commonly performs total joint replacement in his practice and considers potential patients as candidates for TKA. These patients presented with a Kellgren-Lawrence grade of 3 or 4 knee OA, and all had significant pain that was refractory to conservative treatment, which included medications, physical therapy, and injections. The study patients were offered the Lipogems procedure as an alternative to TKA. Following this procedure, the study subjects were clinically evaluated using the numerical pain rating scale (NPRS), the 100-point Knee Society Score (KSS) with its functional component (FXN), and the lower extremity activity scale (LEAS) at 6 weeks, 6 months, and 12 months. The 1989 KSS12 was used for this study. Adverse reactions were also monitored throughout the study period.

METHODS

After obtaining informed consent, the subjects were taken into the operating room, moved to the procedure table, and placed in the prone position for aspiration. After scrubbing with Betadine and draping, 1 mL of lidocaine was used to anesthetize the skin, and a pre-prepared preparation of lidocaine, epinephrine, and sterile saline was infused into the subcutaneous tissue. The micro-fragmented adipose tissue was obtained with minimal manipulation using Lipogems, a closed system using mild mechanical forces and reduction filters. The system processes the lipoaspirate without the addition of enzymes or any other additives. The final product consists of adipose tissue clusters with preserved vascular stromal niche of approximately 500 microns. The lipoaspirate was processed in the same room via a closed system. During the processing, the subject’s puncture wounds were dressed. The knee injection site was prepped with a Betadine swab and DuraPrep. Then, Lipogems was injected intra-articularly under ultrasound guidance.

After the completion of the injection, manual range of motion was administered to the treated joint. The subject was then transferred to the recovery room where vital signs were monitored. Post-procedure instructions were reviewed with the patient by the study staff. The subject was instructed to use an assistive device and avoid weight-bearing for 48 hours and maintain the activities of daily living to a minimum on the day of the procedure. Non-weight-bearing for 48 hours was recommended for reducing discomfort to avoid the use of opioids. Nonsteroidal anti-inflammatory drugs, alcohol, and marijuana must be avoided for 4 weeks after the procedure. Pretreatment and post-treatment outcomes were collected using the NPRS, the 100-point KSS with its FXN, and the LEAS at 6 weeks, 6 months, and 12 months after this procedure. The 1989 KSS12 was used for this study since the same scale was used for previous TKA procedures by our authors, allowing for future comparisons of results.

STATISTICAL ANALYSIS

Mean and standard deviation were used to estimate central tendency and variability. Outcome measures were analyzed using the t test, with the pairwise t test was used for paired and subsequent measurements of the same patient or a knee. All analyses were performed with significance set at P <.05. The minimal clinically important difference (MCID) in patients who underwent TKA for primary OA was between 5.3 and 5.9 for KSS, while the MCID for FXN was between 6.1 and 6.4.13 These values were referenced for our analysis.

Continue to: No significant adverse...

RESULTS

No significant adverse events were reported in the subjects of this study. Common minor adverse events included pain and swelling, which generally resolved in 48 to 72 hours after the procedure.

Compared with baseline, significant improvements were noted in the mean values of NPRS (Figure 1) at 6 weeks, 6 months, and 12 months. The mean KSS significantly improved from baseline at 6 weeks and 12 months (Figure 2). Significant improvements were also noted in the mean values of FXN (Figure 3) and the mean LEAS significantly improved from baseline at 6 weeks and 6 months (Figure 4).

DISCUSSION

Knee OA is a disabling condition that affects a substantial proportion of the aging population. The current treatment methods do little to address the degenerative environment of the joint, which includes cytokines such as IL-1 and IL-2. Orthobiologic agents have been used recently to address these issues, which include PRP and MSCs from various sources, including bone marrow and adipose tissue.

A recent meta-analysis conducted by Cui and colleagues14 evaluated 18 studies of MSC treatment for knee OA with a total of 565 participants (226 males and 339 females). The duration from the onset of knee pain to registration in each study ranged from 3 months to ≥7 years. The follow-up period was 3 months -24 months. The majority of studies recruited patients with knee OA with a severity grade of 1-4 on the K-L scale; K-L grades 1 and 2 and grades 3 and 4 were defined as early OA and advanced OA, respectively. The results suggested that MSC treatment significantly improved pain and functional status, relative to the baseline evaluations in knee OA, and the beneficial effect was maintained for 2 years after treatment. Furthermore, the treatment effectiveness was not reduced over time.¹⁴

Included in the abovementioned meta-analysis were 2 papers by Koh and colleagues in 2012 and 2013 on the use of AMSCs for the treatment of OA. ^15,16 The first study included 18 patients whose adipose tissue was harvested from the inner side of the infrapatellar fat pad via a skin incision after arthroscopic debridement. The cells were centrifuged and injected into the patient’s knee the same day. The results showed a significant reduction of pain and an increased quality of life for all patients, and a positive correlation was found between the number of cells injected and pain improvements. The authors concluded that AMSCs were a valid cell source for treating cartilage damage.¹⁵

In their second study, Koh and colleagues reported their results of treating 30 elderly patients with OA (≥65 years), who had failed conventional treatment, using intra-articular injections of AMSCs.¹⁶ This patient population is important since OA most commonly occurs in the elderly population. Patients underwent arthroscopic lavage and cartilage evaluation before receiving an injection of AMSCs delivered in PRP. The authors demonstrated that AMSC therapy for elderly patients with mild to moderate OA was an effective treatment resulting in reduction of pain and regeneration of cartilage.¹⁶

In another study, Adriani and colleagues¹⁷ performed autologous percutaneous fat injection from January 2012 to March 2015 for the treatment of knee OA. Their 30 patients (12 males and 18 females; mean age of 63.3 years; mean body mass index of 25.1) had stable or progressive knee OA for at least 12 months, no other injection treatments during the previous 12 months, and no prior knee surgeries. The patients were evaluated at baseline and 1 week and at 1, 3, 6, and 12 months after treatment using the NPRS and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) as outcome measures. The average VAS was 7.7 at baseline and improved to 4.3 at 3-month follow-up; however, a slight deterioration (VAS 5.0) was noted at 1 year. Total WOMAC score was 89.9 at baseline, 68.6 at 3 months, and 73.2 at 12-month follow-up.¹⁷

Continue to: The results of...

The results of this study demonstrated significant improvements in pain, quality of life, and function at 12 months after ultrasound-guided injection of ASCs in patients with severe knee OA. Significant improvement that was noted at 6 weeks was maintained through 12 months after the treatment. Improvement was noted in all scales, including the NPRS, the KSS, and the FXN beginning at 3 months and continuing through 12 months. The LEAS was statistically significant through 6 months after the treatment but not significant at 12 months. No serious adverse events were recorded.

In a study by Lee and colleagues,¹³ the MCID was described for KSS and FXN in patients who underwent TKA for primary OA. This is the minimal change in a scoring measure that is perceived by the patient to be beneficial or harmful. The MCID for KSS was noted to be between 5.3 and 5.9, while the MCID for FXN was between 6.1 and 6.4.13 In our study, the KSS score improved from an average of 74.0 at baseline to 79.6 at 6 months and 81.6 at 12 months (a difference of 5.6 and 7.6; P = .18 and.014, respectively). The FXN improved from an average of 65.4 at baseline to 75.2 at 6 months and 76.4 at 12 months (a difference of 9.9 and 11; P = .041 and.014, respectively). Therefore, a clinically important difference of KSS and FXN scores was noted at both 6 and 12 months.

The technique used in this study provides autologous, minimally manipulated, fat graft performed in a short time (60-90 minutes), without expansion and/or enzymatic treatment. In addition, the harvesting and the injection of stem cells on the same day is a simple, office-based procedure, and compliant with the U. S. Food and Drug Administration regulations.¹⁸ The cost of the procedure averages $3500.

A study limitation is that it is a case series with relatively small numbers and not a randomized controlled study. Therefore, a placebo effect may play a role in our results. Further study with a larger number of patients and randomized controlled studies would be beneficial to support the findings of this study.

CONCLUSION

The injection of autologous, micro-fractured, minimally manipulated adipose tissue appears to be a safe and effective treatment option in patients with refractory severe (grade 3 or 4) knee OA. This study showed significant improvements in pain, quality of life, and function for at least 12 months in this study population. This intervention may represent a nonsurgical treatment option to avoid knee joint replacement in this population; however, further investigation is needed.

ABSTRACT

The aim of this study was to evaluate the safety and efficacy of using autologous, micro-fractured, minimally manipulated adipose tissue in patients with refractory knee osteoarthritis (OA). A total of 17 subjects (26 knees) with a median age of 72 years (range: 54-78 years) and a history of knee OA (Kellgren–Lawrence, grade of 3 or 4) underwent treatment with ultrasound-guided injection of micro-fractured adipose tissue. Micro-fractured fat was obtained using a minimal manipulation technique in a closed system (Lipogems), without the addition of enzymes or any other additives. The study subjects were clinically evaluated using the numerical pain rating scale (NPRS), the 100-point Knee Society Score (KSS) with its functional component (FXN), and the lower extremity activity scale (LEAS) at 6 weeks, 6 months, and 12 months following this procedure.

When compared with baseline, significant improvements were noted in the mean values of NPRS, FXN, and LEAS at 6 weeks, 6 months, and 12 months. The mean KSS significantly improved at 6 weeks and 12 months. In particular, the average KSS score improved from 74 to 82, the FXN score improved from 65 to 76, and the LEAS score improved from 36 to 47. These values were significantly greater than the previously published minimal clinically important difference described for KSS and FXN in patients who underwent total knee arthroplasty for primary OA. No serious adverse events were reported. The injection of autologous, micro-fractured, minimally manipulated adipose tissue appears to be a safe and effective treatment option for patients with refractory, severe (grade 3 or 4) knee OA.

This study demonstrated significant improvements in pain, quality of life, and function for at least 12 months in this study population. This intervention may represent a nonsurgical treatment option to avoid knee joint replacement in this population; however, further investigation is needed.

Continue to: Knee OA is...

Knee OA is a chronic disease that affects all races, genders, and ages, but it is most prevalent in obese and elderly people. Worldwide, arthritis is considered to be the fourth leading cause of disability.¹ In developing and developed countries, knee OA may cause a significant decline in the quality of life for individuals >65 years due to joint pain and disability.¹ Nonoperative treatment can be successful in patients with mild to moderate arthritis with pain.

Current treatment options for knee OA, including physical therapy and anti-inflammatory drugs, aim to remedy the symptoms, but they do little to treat the underlying causes of knee OA pain. When a patient presents with advanced arthritis of the knee as confirmed by radiographic findings (classified as Kellgren–Lawrence grade of 3 or 4), the standard approach has been a total knee arthroplasty (TKA) after the patient has failed conservative treatment. The annual rate of total knee replacement in the United States has doubled since 2000, especially in those 45 – 65 years.² The total number of procedures performed each year now exceeds 640,000, at a total annual cost of about $10.2 billion.² Multiple studies show that TKA has favorable outcomes in pain relief and functional improvement in patients >60 years when evaluated at a follow-up of 10 years after surgery.²

However, some patients are hesitant to proceed with surgery due to fear of surgical pain and procedural complications. The known complications include deep vein thrombosis, pulmonary embolism, nerve injury, and infection. In addition, up to 20% of patients continue to complain of pain following a total knee replacement.³ Finally, in the young population (<50 years), there are concerns related to the potential need of revision knee surgery in the future.³

Alternative treatments for knee OA have recently emerged, including the use of platelet-rich plasma (PRP). A recent meta-analysis that included 10 randomized controlled trials with a total of 1069 patients demonstrated that, compared with hyaluronic acid and saline, intra-articular PRP injection may have more benefits in pain relief and functional improvement in patients with symptomatic knee OA at 1-year post-injection.⁴ Another smaller study examined patients who had experienced mild knee OA (Kellgren–Lawrence grade <3) for an average of 14 months. Each patient underwent magnetic resonance imaging for the evaluation of joint damage and then received a single PRP injection. The patients were assessed at regular intervals, with improvement in pain lasting up to 12 months.⁵

Additional orthobiologic options include the use of bone marrow and adipose-derived stem cell (ASC) injections for a variety of knee conditions, including knee OA. Mesenchymal stem cells (MSCs) are multipotent cells that have been used for the treatment of OA in clinical trials because of their regeneration potential and anti-inflammatory effects.⁶ Bone marrow stem cells (BMSCs) were first used to repair cartilage damage in humans in 1998. However, BMSCs had particular challenges, including low stem cell yield, pain, and possible morbidities during bone marrow aspiration. An alternative is ASCs, which may be more suitable clinically because of the high stem cell yield from lipoaspirates, faster cell proliferation, and less discomfort and morbidities during the harvesting procedure.⁷ In addition, these adult stem cells can contribute to the chondrogenic, osteogenic, adipogenic, myogenic, and neurogenic lineages.⁸ One study demonstrated that the contents of cartilage glycosaminoglycans significantly increased in specific areas of a knee joint treated with ASCs.^9,10  This increased glycosaminoglycan content in hyaline cartilage may explain the observed visual analog score (VAS) improvement and clinical results. Other studies suggest that the chondrogenic action of ASCs may depend more on regenerative signaling by activated perivascular cells and signaling of trophic and paracrine mediators, such as vascular endothelial growth factor.^9,10 Finally, the mechanism of action may include providing volume, support, cushioning, and filling of soft tissue defects.¹¹

The Lipogems method and device, approved by the U.S. Food and Drug Administration, is used to harvest ASCs, cleanse, and micro-fracture adipose tissue while maintaining the perivascular niche that contains pericytes. The purpose of this study was to evaluate the safety and efficacy of using autologous, micro-fractured, minimally manipulated adipose tissue in patients with severe refractory knee OA.

Continue to: This report details...

STUDY PRESENTATION

This report details the outcome of an IRB-approved study of 17 subjects with 26 symptomatic knees with a history of knee OA (Kellgren–Lawrence grade of 3 or 4) diagnosed by a radiograph. Patient demographics are described in the Table.

_{Abbreviation: BMI, body mass index.}

The study patients were evaluated by an orthopedic surgeon, Mitchell Sheinkop, who commonly performs total joint replacement in his practice and considers potential patients as candidates for TKA. These patients presented with a Kellgren-Lawrence grade of 3 or 4 knee OA, and all had significant pain that was refractory to conservative treatment, which included medications, physical therapy, and injections. The study patients were offered the Lipogems procedure as an alternative to TKA. Following this procedure, the study subjects were clinically evaluated using the numerical pain rating scale (NPRS), the 100-point Knee Society Score (KSS) with its functional component (FXN), and the lower extremity activity scale (LEAS) at 6 weeks, 6 months, and 12 months. The 1989 KSS12 was used for this study. Adverse reactions were also monitored throughout the study period.

METHODS

After obtaining informed consent, the subjects were taken into the operating room, moved to the procedure table, and placed in the prone position for aspiration. After scrubbing with Betadine and draping, 1 mL of lidocaine was used to anesthetize the skin, and a pre-prepared preparation of lidocaine, epinephrine, and sterile saline was infused into the subcutaneous tissue. The micro-fragmented adipose tissue was obtained with minimal manipulation using Lipogems, a closed system using mild mechanical forces and reduction filters. The system processes the lipoaspirate without the addition of enzymes or any other additives. The final product consists of adipose tissue clusters with preserved vascular stromal niche of approximately 500 microns. The lipoaspirate was processed in the same room via a closed system. During the processing, the subject’s puncture wounds were dressed. The knee injection site was prepped with a Betadine swab and DuraPrep. Then, Lipogems was injected intra-articularly under ultrasound guidance.

After the completion of the injection, manual range of motion was administered to the treated joint. The subject was then transferred to the recovery room where vital signs were monitored. Post-procedure instructions were reviewed with the patient by the study staff. The subject was instructed to use an assistive device and avoid weight-bearing for 48 hours and maintain the activities of daily living to a minimum on the day of the procedure. Non-weight-bearing for 48 hours was recommended for reducing discomfort to avoid the use of opioids. Nonsteroidal anti-inflammatory drugs, alcohol, and marijuana must be avoided for 4 weeks after the procedure. Pretreatment and post-treatment outcomes were collected using the NPRS, the 100-point KSS with its FXN, and the LEAS at 6 weeks, 6 months, and 12 months after this procedure. The 1989 KSS12 was used for this study since the same scale was used for previous TKA procedures by our authors, allowing for future comparisons of results.

STATISTICAL ANALYSIS

Mean and standard deviation were used to estimate central tendency and variability. Outcome measures were analyzed using the t test, with the pairwise t test was used for paired and subsequent measurements of the same patient or a knee. All analyses were performed with significance set at P <.05. The minimal clinically important difference (MCID) in patients who underwent TKA for primary OA was between 5.3 and 5.9 for KSS, while the MCID for FXN was between 6.1 and 6.4.13 These values were referenced for our analysis.

Continue to: No significant adverse...

RESULTS

No significant adverse events were reported in the subjects of this study. Common minor adverse events included pain and swelling, which generally resolved in 48 to 72 hours after the procedure.

Compared with baseline, significant improvements were noted in the mean values of NPRS (Figure 1) at 6 weeks, 6 months, and 12 months. The mean KSS significantly improved from baseline at 6 weeks and 12 months (Figure 2). Significant improvements were also noted in the mean values of FXN (Figure 3) and the mean LEAS significantly improved from baseline at 6 weeks and 6 months (Figure 4).

DISCUSSION

Knee OA is a disabling condition that affects a substantial proportion of the aging population. The current treatment methods do little to address the degenerative environment of the joint, which includes cytokines such as IL-1 and IL-2. Orthobiologic agents have been used recently to address these issues, which include PRP and MSCs from various sources, including bone marrow and adipose tissue.

A recent meta-analysis conducted by Cui and colleagues14 evaluated 18 studies of MSC treatment for knee OA with a total of 565 participants (226 males and 339 females). The duration from the onset of knee pain to registration in each study ranged from 3 months to ≥7 years. The follow-up period was 3 months -24 months. The majority of studies recruited patients with knee OA with a severity grade of 1-4 on the K-L scale; K-L grades 1 and 2 and grades 3 and 4 were defined as early OA and advanced OA, respectively. The results suggested that MSC treatment significantly improved pain and functional status, relative to the baseline evaluations in knee OA, and the beneficial effect was maintained for 2 years after treatment. Furthermore, the treatment effectiveness was not reduced over time.¹⁴

Included in the abovementioned meta-analysis were 2 papers by Koh and colleagues in 2012 and 2013 on the use of AMSCs for the treatment of OA. ^15,16 The first study included 18 patients whose adipose tissue was harvested from the inner side of the infrapatellar fat pad via a skin incision after arthroscopic debridement. The cells were centrifuged and injected into the patient’s knee the same day. The results showed a significant reduction of pain and an increased quality of life for all patients, and a positive correlation was found between the number of cells injected and pain improvements. The authors concluded that AMSCs were a valid cell source for treating cartilage damage.¹⁵

In their second study, Koh and colleagues reported their results of treating 30 elderly patients with OA (≥65 years), who had failed conventional treatment, using intra-articular injections of AMSCs.¹⁶ This patient population is important since OA most commonly occurs in the elderly population. Patients underwent arthroscopic lavage and cartilage evaluation before receiving an injection of AMSCs delivered in PRP. The authors demonstrated that AMSC therapy for elderly patients with mild to moderate OA was an effective treatment resulting in reduction of pain and regeneration of cartilage.¹⁶

In another study, Adriani and colleagues¹⁷ performed autologous percutaneous fat injection from January 2012 to March 2015 for the treatment of knee OA. Their 30 patients (12 males and 18 females; mean age of 63.3 years; mean body mass index of 25.1) had stable or progressive knee OA for at least 12 months, no other injection treatments during the previous 12 months, and no prior knee surgeries. The patients were evaluated at baseline and 1 week and at 1, 3, 6, and 12 months after treatment using the NPRS and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) as outcome measures. The average VAS was 7.7 at baseline and improved to 4.3 at 3-month follow-up; however, a slight deterioration (VAS 5.0) was noted at 1 year. Total WOMAC score was 89.9 at baseline, 68.6 at 3 months, and 73.2 at 12-month follow-up.¹⁷

Continue to: The results of...

The results of this study demonstrated significant improvements in pain, quality of life, and function at 12 months after ultrasound-guided injection of ASCs in patients with severe knee OA. Significant improvement that was noted at 6 weeks was maintained through 12 months after the treatment. Improvement was noted in all scales, including the NPRS, the KSS, and the FXN beginning at 3 months and continuing through 12 months. The LEAS was statistically significant through 6 months after the treatment but not significant at 12 months. No serious adverse events were recorded.

In a study by Lee and colleagues,¹³ the MCID was described for KSS and FXN in patients who underwent TKA for primary OA. This is the minimal change in a scoring measure that is perceived by the patient to be beneficial or harmful. The MCID for KSS was noted to be between 5.3 and 5.9, while the MCID for FXN was between 6.1 and 6.4.13 In our study, the KSS score improved from an average of 74.0 at baseline to 79.6 at 6 months and 81.6 at 12 months (a difference of 5.6 and 7.6; P = .18 and.014, respectively). The FXN improved from an average of 65.4 at baseline to 75.2 at 6 months and 76.4 at 12 months (a difference of 9.9 and 11; P = .041 and.014, respectively). Therefore, a clinically important difference of KSS and FXN scores was noted at both 6 and 12 months.

The technique used in this study provides autologous, minimally manipulated, fat graft performed in a short time (60-90 minutes), without expansion and/or enzymatic treatment. In addition, the harvesting and the injection of stem cells on the same day is a simple, office-based procedure, and compliant with the U. S. Food and Drug Administration regulations.¹⁸ The cost of the procedure averages $3500.

A study limitation is that it is a case series with relatively small numbers and not a randomized controlled study. Therefore, a placebo effect may play a role in our results. Further study with a larger number of patients and randomized controlled studies would be beneficial to support the findings of this study.

CONCLUSION

The injection of autologous, micro-fractured, minimally manipulated adipose tissue appears to be a safe and effective treatment option in patients with refractory severe (grade 3 or 4) knee OA. This study showed significant improvements in pain, quality of life, and function for at least 12 months in this study population. This intervention may represent a nonsurgical treatment option to avoid knee joint replacement in this population; however, further investigation is needed.

ABSTRACT

Improvements in ultrasound technology have increased the popularity and use of ultrasound as a diagnostic and therapeutic modality for many soccer-related musculoskeletal (MSK) injuries. As a dynamic imaging modality, ultrasound offers increased accuracy and efficacy with minimally invasive procedures, such as guided injections, percutaneous tenotomy, and regenerative therapies, in the clinical setting. Emerging evidence indicates that regenerative therapies, such as platelet-rich-plasma (PRP), mesenchymal stem cells, and amniotic products, are a promising treatment for many MSK injuries and are gaining popularity among professional athletes. PRP is a safe treatment for a number of MSK conditions and has been included in the standard of care. However, conflicting evidence on return-to-play timeframes and efficacy in certain MSK conditions have led to inconsistent recommendations on indications for use, dose, and timing of treatment. Mesenchymal stem cell therapy, while promising, lacks high-level evidence of efficacy despite its increasing use among athletes. Currently, no data are available regarding the outcome of the use of amniotic products for the treatment of injuries in athletes. Furthermore, preparation of many regenerative therapies eclipses the concept of minimal manipulation and is subject to US Food and Drug Administration phase I to III trials. High-level research on regenerative medicine therapies should be continuously conducted to establish their clinical efficacy and safety data.

ABSTRACT

Improvements in ultrasound technology have increased the popularity and use of ultrasound as a diagnostic and therapeutic modality for many soccer-related musculoskeletal (MSK) injuries. As a dynamic imaging modality, ultrasound offers increased accuracy and efficacy with minimally invasive procedures, such as guided injections, percutaneous tenotomy, and regenerative therapies, in the clinical setting. Emerging evidence indicates that regenerative therapies, such as platelet-rich-plasma (PRP), mesenchymal stem cells, and amniotic products, are a promising treatment for many MSK injuries and are gaining popularity among professional athletes. PRP is a safe treatment for a number of MSK conditions and has been included in the standard of care. However, conflicting evidence on return-to-play timeframes and efficacy in certain MSK conditions have led to inconsistent recommendations on indications for use, dose, and timing of treatment. Mesenchymal stem cell therapy, while promising, lacks high-level evidence of efficacy despite its increasing use among athletes. Currently, no data are available regarding the outcome of the use of amniotic products for the treatment of injuries in athletes. Furthermore, preparation of many regenerative therapies eclipses the concept of minimal manipulation and is subject to US Food and Drug Administration phase I to III trials. High-level research on regenerative medicine therapies should be continuously conducted to establish their clinical efficacy and safety data.

ABSTRACT

Improvements in ultrasound technology have increased the popularity and use of ultrasound as a diagnostic and therapeutic modality for many soccer-related musculoskeletal (MSK) injuries. As a dynamic imaging modality, ultrasound offers increased accuracy and efficacy with minimally invasive procedures, such as guided injections, percutaneous tenotomy, and regenerative therapies, in the clinical setting. Emerging evidence indicates that regenerative therapies, such as platelet-rich-plasma (PRP), mesenchymal stem cells, and amniotic products, are a promising treatment for many MSK injuries and are gaining popularity among professional athletes. PRP is a safe treatment for a number of MSK conditions and has been included in the standard of care. However, conflicting evidence on return-to-play timeframes and efficacy in certain MSK conditions have led to inconsistent recommendations on indications for use, dose, and timing of treatment. Mesenchymal stem cell therapy, while promising, lacks high-level evidence of efficacy despite its increasing use among athletes. Currently, no data are available regarding the outcome of the use of amniotic products for the treatment of injuries in athletes. Furthermore, preparation of many regenerative therapies eclipses the concept of minimal manipulation and is subject to US Food and Drug Administration phase I to III trials. High-level research on regenerative medicine therapies should be continuously conducted to establish their clinical efficacy and safety data.

ABSTRACT

In this study, we determine the in vivo effects of injecting sub-populations of leukocytes into normal rat Achilles tendons via a controlled laboratory study. Allogenic monocytes, granulocytes, or plasma were injected into 24 healthy rat Achilles tendons. Treated and contralateral un-treated control tendons then assessed for cellularity, histologic morphology, and vascularity after 7 and 14 days. Significant increases of 221% and 249% in cellularity (P = 0.014) were seen on day 14 within Achilles tendons injected with granulocytes as compared to plasma and monocytes, respectively. Also, significant improvement in morphology (P = 0.029) between days 7 and 14 was seen for the granulocyte injected Achilles tendons. Significant increases in cellularity after an injection of granulocytes, compared to monocytes and plasma, corresponds to a significant increase in inflammation within the tissue, suggesting that leukocyte-rich platelet-rich plasma (PRP) preparations are proinflammatory and potentially catabolic when injected into tendon tissue. The concentration and composition of white blood cells within PRP preparations is variable and needs to be better understood in order to optimize clinical utility of PRP injections.

Continue to: Tendinopathies are debilitating conditions...

Tendinopathies are debilitating conditions affecting patients worldwide every day. They arise most frequently from tendon overuse resulting in pathology.¹ There are 2 major subtypes of tendinopathy: tendinosis and tendinitis. Tendinosis, the more common condition, is characterized by long-term, chronic degradation of tendon tissue resulting in fibrosis from infiltrating fibroblasts.² Tendinitis, the less common condition, is characterized by an acute inflammatory response and inflammatory cell infiltrate.² Both conditions are common, with Achilles tendinopathy affecting 11% of runners and lateral epicondylitis affecting 1% to 3% of the general population.^3,4 Many sports-related overuse injuries, such as tendinopathies, go undiagnosed for extended periods of time because medical attention is avoided in order to prevent time loss from training or competing.⁵ These delays could be eliminated if a non-surgical option for treating tendon pathology was available.

Tendinopathies are believed to result from tendon overuse that causes micro-damage to collagen, as well as from significant changes in protein and enzyme composition within the tendon.⁶ The damage accumulates over time and eventually leads to chronic inflammation or fibrotic change within tendons, in both cases weakening the tendon and causing pain. Currently, accepted treatments for tendinopathies include: nonsteroidal anti-inflammatory drugs, physical therapy, ultrasound, laser-therapy, corticosteroids, glyceryl trinitrate patches, extracorporeal shock wave therapy, sclerotherapy, and surgery.⁷ Recently, platelet-rich plasma (PRP) therapy has emerged as a promising treatment for tendinopathies, as well as a variety of other orthopedic indications.

PRP consists of autologous blood from the patient, centrifuged to increase the amount of platelets in the sample above baseline, and subsequently injected around an affected tendon or joint.⁸ PRP is used to treat tendinopathy because it can supply injured tendons with blood components that aid in healing, which tendons do not receive due to poor vascularity.⁹ These components include growth factors, such as platelet derived growth factor (PDGF), transforming growth factor-β (TGF-β), vascular endothelial growth factor (VEGF), endothelial growth factor, and leukocytes that can stimulate an inflammatory response within the injured tissue.¹⁰ The inflammatory response from the PRP induces a more robust reconstruction and revascularization of the injured tissue, stimulating proliferation, and remodeling.^11,12However, significant variability exists within the platelets, leukocytes, and growth factors that comprise PRP. This is attributed to 3 major causes. First, current commercial preparations of PRP result in differing platelet concentrations, as well as leukocyte-rich and leukocyte-poor compositions.^13,14 Variability in platelet concentrations results in unreliable amounts of growth factors, including cytokines, TGF-β, PDGF, VEGF and basic fibroblast growth factor in each preparation, while leukocyte levels affect inflammation, all leading to variable effects for each preparation.^15,16Second, despite sex and age of the PRP donor not being significant factors influencing variation in growth factor concentrations, the existence of an unexplained variation in concentrations of growth factors between different donors has been observed.¹⁷ Third, the selection of activating agents, bovine thrombin or calcium chloride, and their application, whether to the elbow, shoulder, or knee, produces variability.¹⁸

While the effects of platelets and growth factors in PRP have been well studied, less is known about the effects of differing cell types. Recently it was reported that the concentrations of leukocytes directly affect the outcomes of PRP injections. McCarrel and colleagues^19,20 found that as the number of leukocytes increased, there was a concomitant increase in the expression of inflammatory cytokines and catabolic activity. This effect may result in inferior healing of injured tissues and is attributed to the release of pro-inflammatory cytokines such as interleukin-1β from the leukocytes.²¹ There is also evidence that minimizing the catabolic effect of leukocytes may be just as important to tissue healing as the maximizing anabolic effect of platelets and growth factors.²²

The use of PRP has been highly disputed in recent years due to conflicting reports of its success in treating orthopedic conditions. Numerous favorable studies have shown benefit for treating chronic and acute orthopedic injuries including; rotator cuff tear repair, chronic refractory patellar tendinopathy, and chronic lateral tendinosis/epicondylitis.^23-26 Concurrently, articles demonstrating no significant effects from PRP have also been published. One study claiming that PRP injections did not improve outcomes of chronic Achilles tendinopathy did not differentiate whether patients had tendinosis or tendinitis, and did not consider leukocyte concentration in their PRP preparations²⁷ Another study that determined PRP is not beneficial to the healing of ruptured Achilles tendons after surgical repair also failed to consider the concentration of leukocytes in their PRP preparations.²⁸ One of the difficulties in comparing these studies is their heterogeneous nature. This arises from the use of different conditions in each study that makes the studies incomparable. Variations in PRP preparations lead to different concentrations of growth factors, platelets, and leukocyte concentrations. Additionally, tendinopathy models were not specified as tendinosis and tendonitis, and models or patients were not controlled for age, sex, or comorbidities. Given that leukocyte-rich and leukocyte-poor PRP preparations are currently widely used in clinical practice, the discovery of which type of preparation is indicated in which setting is paramount to evidence-based use of this treatment modality. Due to reports suggesting that leukocytes may be detrimental to tendon healing, determining which types of leukocytes are responsible for these effects is vital. As such, the purpose of this study is to determine the in vivo effects of sub-populations of leukocytes on normal rat tendons. This study design allowed us to isolate the effects of the injections to induce a response and remove confounding effects of normal healing response to a damaged tendon and effects from the injection itself. Our hypothesis was that the injection of leukocytes would cause an inflammatory response in rat tendons, leading to catabolic outcomes.

Continue to: METHODS...

 

 

METHODS

This was a prospective, in vivo, placebo controlled, randomized animal study. The University’s Institutional Animal Care and Use Committee approved all procedures prior to initiation. Twenty-four male Sprague-Dawley rats were randomized to 3 treatment groups (n = 8): monocytes; granulocytes, and; plasma, as a negative control.

Allogenic blood from 6 additional rats was collected into K2EDTA tubes via cardiac puncture. Allogenic, as opposed to autogenic, blood is commonly used in rat models because of low immunogenic response to blood from rats of the same strain and litter.^29,30 The blood was then pooled and the red cells lysed by incubation with Red Blood Cell Lysis Buffer (Roche). The samples were then sorted into fractions containing monocytes and granulocytes using fluorescence activated cell sorting (FACS) using a FACSAria (BD Biosciences). Cells were sorted using Purified PE Mouse Anti-Rat CD11b/c antibodies (BD Pharmingen) specific to monocytes, granulocytes, macrophages, dendritic cells, and microglia, APC-Cy7 Mouse Anti-Rat CD45 antibodies (BD Pharmingen) specific to all hematopoietic cells except erythrocytes, and FITC Mouse Anti-Rat CD42d antibodies (BD Pharmingen) specific to megakaryocytes and platelets. 20 μL of 0.2 mg/mL CD11b/c, 20 μL of 0.2 mg/mL CD 45, and 10 μL of 0.5 mg/mL CD42d antibodies were added to 1 mL of condensed non-red cells collected from the 6 rats and incubated at room temperature in the dark for 15 minutes. A fraction containing only platelet-poor plasma was also collected. For all treatments the injection volume was 75 μL. Rats in the monocyte group were injected with 200,000 cells in platelet-poor plasma, those in the granulocyte group were injected with 900,000 cells in platelet-poor plasma, and rats in the plasma control group received only platelet-poor plasma. The cell concentrations were based on previous studies that documented these concentrations that are found in typical leukocyte-rich PRP preparations.¹³

The animals were anesthetized with isoflurane gas and then injected aseptically once into their right Achilles tendon. The left Achilles tendon was used as an un-injected control, giving a total of 48 total Achilles tendons studied. At days 7 and 14 post-injection, 4 rats from each group were euthanized and the Achilles tendons were harvested.

The tendons were fixed in neutral buffered formalin for 24 hours and then embedded in paraffin and sectioned sagittally at 12 μm. The tendons were then stained with hematoxylin and eosin (H&E) using standard histological protocols and examined by 3 individuals trained to assess cellularity and morphology. All samples were assigned unrecognizable numbers and randomized prior to examination by individuals. Cell counts were based on the number of nuclei present in 3 mid-tendon high-power fields (400x) per sample. Morphology was graded on a scale of 1 to 3, with 1 being a normal tendon and 3 having severe pathology with total loss of alignment and crimping on 3 low-power fields (100x) per sample (Figures 1A-1G).

Vascularity was assessed by immunohistochemical staining using Rabbit Polyclonal Anti-CD31 antibodies (Abcam), a marker for vascular endothelial cells, using a Vectastain ABC Kit (Vector Laboratories) system and the ImmPACT AEC Peroxidase (HRP) Substrate (Vector Laboratories). Following staining, automated image analysis was performed (Bioquant). Briefly, all areas that did not contain tendon were masked. CD31 positive areas were then quantified using global thresholding. Vascularity was then calculated as ratio of CD31 positive area to total tendon area. Analyses were performed on 3 mid-tendon medium-power (200x) fields per sample.

For cellularity and morphology, the results for the injected tendons were normalized to those of their contralateral untreated controls and reported as a percentage. Results for vascularity were compared directly between treated tendons. Differences were assessed between groups at each time-point using Independent Samples Median Tests. When significant differences were identified, pairwise comparisons were performed to identify the source of the differences. All analyses were conducted using SPSS (V22, SAS Institute) with significant differences determined for values of P < 0.05.

RESULTS

No significant differences in cellularity between groups were seen at day 7 (P = 0.368) (Figures 1A-1G). However, a significant difference in cellularity between groups was seen at day 14 (P = 0.014). Pairwise tests showed there to be a significant increase in the number of cells in the tendons treated with granulocytes from 221% and 249% in cellularity (P = 0.014) on day 14, as compared to both monocytes and plasma, respectively. Morphologically, no significant differences were seen between groups at either time-point (P = 0.091 for day 7 and P = 1.000 for day 14) (Figures 2A-2G). However, a significant improvement in morphology was observed from day 7 to day 14 in the granulocyte group from 60% to 165% (P = 0.029). Finally, no differences were seen in vascularity between treatment groups at either time-point (P = 0.368 for day 7 and P = 0.535 for day 14) (Figures 3A-3G).

Continue to: DISCUSSION...

 

 

DISCUSSION

Our hypothesis that the injection of leukocytes would cause an inflammatory response in rat tendons leading to catabolic outcomes was confirmed in the granulocyte group. It should be noted that prior to the catabolic outcome, there was a transient anabolic effect in the granulocyte group during the second week. Deterioration in morphology was observed in the tendons injected with granulocytes on day 7, which subsequently recovered in the following week. We found that injecting granulocytes into normal tendons resulted in an increase in inflammatory cellularity, when compared to monocytes and plasma injections. 

Limitations inherent in this study are those similar to other in vivo studies. To begin with, the results of injections into rat tendons may not be translatable to human tendons. Despite this limitation, the rat is a common model for tendon research.³¹ Another limitation is that this study injected healthy Achilles tendons, rather than tendons with preexisting tendinopathy. In a naturally occurring tendinopathy, there may be other factors present that interact with PRP, and this model negates the contribution of these factors. Finally, while the immunohistochemistry (IHC) and morphological data are clear, the cellularity data are not clear in identifying the type of cells that were increased by granulocyte injection.  However, the cells appeared rounded, resembling inflammatory infiltrate; a common cell type seen in tendons.² While fibroblasts are also a common infiltrate during chronic tendinopathy, they are generally flat and appear on H&E as long spindle shaped cells. Thus, we believe the increased cellularity of the tendons after granulocyte injections is representative of an increase in inflammation. The increased cellularity could be due to the increased number of cells injected into the tendon; however, our conclusions are consistent with the increased inflammation previously reported linking leukocytes to tendon inflammation.^20,22,32

In terms of morphology, we hypothesized that degenerative changes would be seen in the tendons that were injected with granulocytes due to the inflammatory action of these cells. As part of the granulocyte response, neutrophils release proteases and macrophages can stimulate collagen synthesis via fibroblasts, both causing change within the extracellular matrix.^33,34 Indeed, we observed a significant change in tissue morphology in the granulocyte group over the course of 14 days. As the degenerative and regenerative effects of granulocytes take time to present, this is likely what we observed to occur between day 7 and 14 after treatment. These observations are also consistent with prior observations that leukocyte-rich PRP injections can be detrimental to tendon healing, but beneficial to tissue degeneration in the setting of chronic tendonitis.²⁰

We hypothesized that the vascularity of the tendons would be similar in all preparations. This was based on previous studies demonstrating that the lack of platelets in the platelet-poor plasma fraction is sufficient to deplete VEGF, the angiogenic agent in PRP.³⁵ In this study, there were no observable differences in vascularity of platelet-poor plasma, monocyte, and granulocyte injections. We attribute this to the lack of VEGF in any of these preparations. The aforementioned study also showed that the lack of platelets in injection was enough to prevent the angiogenic effect of this treatment.³⁵

Continue to: The goal of this study was...

 

 

The goal of this study was to assess the morphology, cellularity, and vascularity of normal tendons after injections of different leukocyte populations. This is clinically important because of the potential to tailor future PRP injections on a patient-by-patient basis. In patients requiring an anabolic response, leukocyte-poor PRP may be the best option. In contrast, when patient pathology requires an inflammatory response to improve healing³⁶ or breakdown fibrotic tissue, as seen in tendinosis, leukocyte-rich PRP may be warranted. Further, properly controlled clinical studies are needed to validate these recommendations.

Limitations inherent in this study are those similar to other in vivo studies. First, the results of injections into rat tendons may not be translatable to human tendons. Despite this limitation, the rat is a common model for tendon research.³¹ A second limitation is that this study injected healthy Achilles tendons, rather than tendons with preexisting tendinopathy. In a naturally occurring tendinopathy, there may be other factors present that interact with PRP, and this model negates the contribution of these factors. Finally, while the IHC and morphological data show clear changes, the cellularity data are not clear in identifying the type of cells that were increased by granulocyte injection. However, the cells appeared rounded, resembling inflammatory infiltrate; a common cell type seen in tendons.² While fibroblasts are also a common infiltrate during chronic tendinopathy, they are generally flat and appear on H&E as long spindle shaped cells. The last limitation of this study is the lack of functional mechanical testing since, clinically, healing of the tendon is also related to the strength of the tendon. Thus, we believe the increased cellularity of the tendons after granulocyte injections is representative of an increase in inflammation. Moreover, our results are consistent with the increased inflammation previously reported linking leukocytes to tendon inflammation.^20,22,32 It is interesting to note that the increase in inflammation does not lead to an increase in vascularity as could be expected.

CONCLUSION

We found that the injection of leukocytes into healthy rat Achilles tendons increases inflammation, as evidenced by increased cellularity and disrupted morphology, which suggests that leukocyte-rich PRP preparations may be contraindicated in settings of acute tendonitis. However, these preparations may be useful for a specific subset of tendinopathies, including chronic tendinosis.

ABSTRACT

In this study, we determine the in vivo effects of injecting sub-populations of leukocytes into normal rat Achilles tendons via a controlled laboratory study. Allogenic monocytes, granulocytes, or plasma were injected into 24 healthy rat Achilles tendons. Treated and contralateral un-treated control tendons then assessed for cellularity, histologic morphology, and vascularity after 7 and 14 days. Significant increases of 221% and 249% in cellularity (P = 0.014) were seen on day 14 within Achilles tendons injected with granulocytes as compared to plasma and monocytes, respectively. Also, significant improvement in morphology (P = 0.029) between days 7 and 14 was seen for the granulocyte injected Achilles tendons. Significant increases in cellularity after an injection of granulocytes, compared to monocytes and plasma, corresponds to a significant increase in inflammation within the tissue, suggesting that leukocyte-rich platelet-rich plasma (PRP) preparations are proinflammatory and potentially catabolic when injected into tendon tissue. The concentration and composition of white blood cells within PRP preparations is variable and needs to be better understood in order to optimize clinical utility of PRP injections.

Continue to: Tendinopathies are debilitating conditions...

Tendinopathies are debilitating conditions affecting patients worldwide every day. They arise most frequently from tendon overuse resulting in pathology.¹ There are 2 major subtypes of tendinopathy: tendinosis and tendinitis. Tendinosis, the more common condition, is characterized by long-term, chronic degradation of tendon tissue resulting in fibrosis from infiltrating fibroblasts.² Tendinitis, the less common condition, is characterized by an acute inflammatory response and inflammatory cell infiltrate.² Both conditions are common, with Achilles tendinopathy affecting 11% of runners and lateral epicondylitis affecting 1% to 3% of the general population.^3,4 Many sports-related overuse injuries, such as tendinopathies, go undiagnosed for extended periods of time because medical attention is avoided in order to prevent time loss from training or competing.⁵ These delays could be eliminated if a non-surgical option for treating tendon pathology was available.

Tendinopathies are believed to result from tendon overuse that causes micro-damage to collagen, as well as from significant changes in protein and enzyme composition within the tendon.⁶ The damage accumulates over time and eventually leads to chronic inflammation or fibrotic change within tendons, in both cases weakening the tendon and causing pain. Currently, accepted treatments for tendinopathies include: nonsteroidal anti-inflammatory drugs, physical therapy, ultrasound, laser-therapy, corticosteroids, glyceryl trinitrate patches, extracorporeal shock wave therapy, sclerotherapy, and surgery.⁷ Recently, platelet-rich plasma (PRP) therapy has emerged as a promising treatment for tendinopathies, as well as a variety of other orthopedic indications.

PRP consists of autologous blood from the patient, centrifuged to increase the amount of platelets in the sample above baseline, and subsequently injected around an affected tendon or joint.⁸ PRP is used to treat tendinopathy because it can supply injured tendons with blood components that aid in healing, which tendons do not receive due to poor vascularity.⁹ These components include growth factors, such as platelet derived growth factor (PDGF), transforming growth factor-β (TGF-β), vascular endothelial growth factor (VEGF), endothelial growth factor, and leukocytes that can stimulate an inflammatory response within the injured tissue.¹⁰ The inflammatory response from the PRP induces a more robust reconstruction and revascularization of the injured tissue, stimulating proliferation, and remodeling.^11,12However, significant variability exists within the platelets, leukocytes, and growth factors that comprise PRP. This is attributed to 3 major causes. First, current commercial preparations of PRP result in differing platelet concentrations, as well as leukocyte-rich and leukocyte-poor compositions.^13,14 Variability in platelet concentrations results in unreliable amounts of growth factors, including cytokines, TGF-β, PDGF, VEGF and basic fibroblast growth factor in each preparation, while leukocyte levels affect inflammation, all leading to variable effects for each preparation.^15,16Second, despite sex and age of the PRP donor not being significant factors influencing variation in growth factor concentrations, the existence of an unexplained variation in concentrations of growth factors between different donors has been observed.¹⁷ Third, the selection of activating agents, bovine thrombin or calcium chloride, and their application, whether to the elbow, shoulder, or knee, produces variability.¹⁸

While the effects of platelets and growth factors in PRP have been well studied, less is known about the effects of differing cell types. Recently it was reported that the concentrations of leukocytes directly affect the outcomes of PRP injections. McCarrel and colleagues^19,20 found that as the number of leukocytes increased, there was a concomitant increase in the expression of inflammatory cytokines and catabolic activity. This effect may result in inferior healing of injured tissues and is attributed to the release of pro-inflammatory cytokines such as interleukin-1β from the leukocytes.²¹ There is also evidence that minimizing the catabolic effect of leukocytes may be just as important to tissue healing as the maximizing anabolic effect of platelets and growth factors.²²

The use of PRP has been highly disputed in recent years due to conflicting reports of its success in treating orthopedic conditions. Numerous favorable studies have shown benefit for treating chronic and acute orthopedic injuries including; rotator cuff tear repair, chronic refractory patellar tendinopathy, and chronic lateral tendinosis/epicondylitis.^23-26 Concurrently, articles demonstrating no significant effects from PRP have also been published. One study claiming that PRP injections did not improve outcomes of chronic Achilles tendinopathy did not differentiate whether patients had tendinosis or tendinitis, and did not consider leukocyte concentration in their PRP preparations²⁷ Another study that determined PRP is not beneficial to the healing of ruptured Achilles tendons after surgical repair also failed to consider the concentration of leukocytes in their PRP preparations.²⁸ One of the difficulties in comparing these studies is their heterogeneous nature. This arises from the use of different conditions in each study that makes the studies incomparable. Variations in PRP preparations lead to different concentrations of growth factors, platelets, and leukocyte concentrations. Additionally, tendinopathy models were not specified as tendinosis and tendonitis, and models or patients were not controlled for age, sex, or comorbidities. Given that leukocyte-rich and leukocyte-poor PRP preparations are currently widely used in clinical practice, the discovery of which type of preparation is indicated in which setting is paramount to evidence-based use of this treatment modality. Due to reports suggesting that leukocytes may be detrimental to tendon healing, determining which types of leukocytes are responsible for these effects is vital. As such, the purpose of this study is to determine the in vivo effects of sub-populations of leukocytes on normal rat tendons. This study design allowed us to isolate the effects of the injections to induce a response and remove confounding effects of normal healing response to a damaged tendon and effects from the injection itself. Our hypothesis was that the injection of leukocytes would cause an inflammatory response in rat tendons, leading to catabolic outcomes.

Continue to: METHODS...

 

 

METHODS

This was a prospective, in vivo, placebo controlled, randomized animal study. The University’s Institutional Animal Care and Use Committee approved all procedures prior to initiation. Twenty-four male Sprague-Dawley rats were randomized to 3 treatment groups (n = 8): monocytes; granulocytes, and; plasma, as a negative control.

Allogenic blood from 6 additional rats was collected into K2EDTA tubes via cardiac puncture. Allogenic, as opposed to autogenic, blood is commonly used in rat models because of low immunogenic response to blood from rats of the same strain and litter.^29,30 The blood was then pooled and the red cells lysed by incubation with Red Blood Cell Lysis Buffer (Roche). The samples were then sorted into fractions containing monocytes and granulocytes using fluorescence activated cell sorting (FACS) using a FACSAria (BD Biosciences). Cells were sorted using Purified PE Mouse Anti-Rat CD11b/c antibodies (BD Pharmingen) specific to monocytes, granulocytes, macrophages, dendritic cells, and microglia, APC-Cy7 Mouse Anti-Rat CD45 antibodies (BD Pharmingen) specific to all hematopoietic cells except erythrocytes, and FITC Mouse Anti-Rat CD42d antibodies (BD Pharmingen) specific to megakaryocytes and platelets. 20 μL of 0.2 mg/mL CD11b/c, 20 μL of 0.2 mg/mL CD 45, and 10 μL of 0.5 mg/mL CD42d antibodies were added to 1 mL of condensed non-red cells collected from the 6 rats and incubated at room temperature in the dark for 15 minutes. A fraction containing only platelet-poor plasma was also collected. For all treatments the injection volume was 75 μL. Rats in the monocyte group were injected with 200,000 cells in platelet-poor plasma, those in the granulocyte group were injected with 900,000 cells in platelet-poor plasma, and rats in the plasma control group received only platelet-poor plasma. The cell concentrations were based on previous studies that documented these concentrations that are found in typical leukocyte-rich PRP preparations.¹³

The animals were anesthetized with isoflurane gas and then injected aseptically once into their right Achilles tendon. The left Achilles tendon was used as an un-injected control, giving a total of 48 total Achilles tendons studied. At days 7 and 14 post-injection, 4 rats from each group were euthanized and the Achilles tendons were harvested.

The tendons were fixed in neutral buffered formalin for 24 hours and then embedded in paraffin and sectioned sagittally at 12 μm. The tendons were then stained with hematoxylin and eosin (H&E) using standard histological protocols and examined by 3 individuals trained to assess cellularity and morphology. All samples were assigned unrecognizable numbers and randomized prior to examination by individuals. Cell counts were based on the number of nuclei present in 3 mid-tendon high-power fields (400x) per sample. Morphology was graded on a scale of 1 to 3, with 1 being a normal tendon and 3 having severe pathology with total loss of alignment and crimping on 3 low-power fields (100x) per sample (Figures 1A-1G).

Vascularity was assessed by immunohistochemical staining using Rabbit Polyclonal Anti-CD31 antibodies (Abcam), a marker for vascular endothelial cells, using a Vectastain ABC Kit (Vector Laboratories) system and the ImmPACT AEC Peroxidase (HRP) Substrate (Vector Laboratories). Following staining, automated image analysis was performed (Bioquant). Briefly, all areas that did not contain tendon were masked. CD31 positive areas were then quantified using global thresholding. Vascularity was then calculated as ratio of CD31 positive area to total tendon area. Analyses were performed on 3 mid-tendon medium-power (200x) fields per sample.

For cellularity and morphology, the results for the injected tendons were normalized to those of their contralateral untreated controls and reported as a percentage. Results for vascularity were compared directly between treated tendons. Differences were assessed between groups at each time-point using Independent Samples Median Tests. When significant differences were identified, pairwise comparisons were performed to identify the source of the differences. All analyses were conducted using SPSS (V22, SAS Institute) with significant differences determined for values of P < 0.05.

RESULTS

No significant differences in cellularity between groups were seen at day 7 (P = 0.368) (Figures 1A-1G). However, a significant difference in cellularity between groups was seen at day 14 (P = 0.014). Pairwise tests showed there to be a significant increase in the number of cells in the tendons treated with granulocytes from 221% and 249% in cellularity (P = 0.014) on day 14, as compared to both monocytes and plasma, respectively. Morphologically, no significant differences were seen between groups at either time-point (P = 0.091 for day 7 and P = 1.000 for day 14) (Figures 2A-2G). However, a significant improvement in morphology was observed from day 7 to day 14 in the granulocyte group from 60% to 165% (P = 0.029). Finally, no differences were seen in vascularity between treatment groups at either time-point (P = 0.368 for day 7 and P = 0.535 for day 14) (Figures 3A-3G).

Continue to: DISCUSSION...

 

 

DISCUSSION

Our hypothesis that the injection of leukocytes would cause an inflammatory response in rat tendons leading to catabolic outcomes was confirmed in the granulocyte group. It should be noted that prior to the catabolic outcome, there was a transient anabolic effect in the granulocyte group during the second week. Deterioration in morphology was observed in the tendons injected with granulocytes on day 7, which subsequently recovered in the following week. We found that injecting granulocytes into normal tendons resulted in an increase in inflammatory cellularity, when compared to monocytes and plasma injections. 

Limitations inherent in this study are those similar to other in vivo studies. To begin with, the results of injections into rat tendons may not be translatable to human tendons. Despite this limitation, the rat is a common model for tendon research.³¹ Another limitation is that this study injected healthy Achilles tendons, rather than tendons with preexisting tendinopathy. In a naturally occurring tendinopathy, there may be other factors present that interact with PRP, and this model negates the contribution of these factors. Finally, while the immunohistochemistry (IHC) and morphological data are clear, the cellularity data are not clear in identifying the type of cells that were increased by granulocyte injection.  However, the cells appeared rounded, resembling inflammatory infiltrate; a common cell type seen in tendons.² While fibroblasts are also a common infiltrate during chronic tendinopathy, they are generally flat and appear on H&E as long spindle shaped cells. Thus, we believe the increased cellularity of the tendons after granulocyte injections is representative of an increase in inflammation. The increased cellularity could be due to the increased number of cells injected into the tendon; however, our conclusions are consistent with the increased inflammation previously reported linking leukocytes to tendon inflammation.^20,22,32

In terms of morphology, we hypothesized that degenerative changes would be seen in the tendons that were injected with granulocytes due to the inflammatory action of these cells. As part of the granulocyte response, neutrophils release proteases and macrophages can stimulate collagen synthesis via fibroblasts, both causing change within the extracellular matrix.^33,34 Indeed, we observed a significant change in tissue morphology in the granulocyte group over the course of 14 days. As the degenerative and regenerative effects of granulocytes take time to present, this is likely what we observed to occur between day 7 and 14 after treatment. These observations are also consistent with prior observations that leukocyte-rich PRP injections can be detrimental to tendon healing, but beneficial to tissue degeneration in the setting of chronic tendonitis.²⁰

We hypothesized that the vascularity of the tendons would be similar in all preparations. This was based on previous studies demonstrating that the lack of platelets in the platelet-poor plasma fraction is sufficient to deplete VEGF, the angiogenic agent in PRP.³⁵ In this study, there were no observable differences in vascularity of platelet-poor plasma, monocyte, and granulocyte injections. We attribute this to the lack of VEGF in any of these preparations. The aforementioned study also showed that the lack of platelets in injection was enough to prevent the angiogenic effect of this treatment.³⁵

Continue to: The goal of this study was...

 

 

The goal of this study was to assess the morphology, cellularity, and vascularity of normal tendons after injections of different leukocyte populations. This is clinically important because of the potential to tailor future PRP injections on a patient-by-patient basis. In patients requiring an anabolic response, leukocyte-poor PRP may be the best option. In contrast, when patient pathology requires an inflammatory response to improve healing³⁶ or breakdown fibrotic tissue, as seen in tendinosis, leukocyte-rich PRP may be warranted. Further, properly controlled clinical studies are needed to validate these recommendations.

Limitations inherent in this study are those similar to other in vivo studies. First, the results of injections into rat tendons may not be translatable to human tendons. Despite this limitation, the rat is a common model for tendon research.³¹ A second limitation is that this study injected healthy Achilles tendons, rather than tendons with preexisting tendinopathy. In a naturally occurring tendinopathy, there may be other factors present that interact with PRP, and this model negates the contribution of these factors. Finally, while the IHC and morphological data show clear changes, the cellularity data are not clear in identifying the type of cells that were increased by granulocyte injection. However, the cells appeared rounded, resembling inflammatory infiltrate; a common cell type seen in tendons.² While fibroblasts are also a common infiltrate during chronic tendinopathy, they are generally flat and appear on H&E as long spindle shaped cells. The last limitation of this study is the lack of functional mechanical testing since, clinically, healing of the tendon is also related to the strength of the tendon. Thus, we believe the increased cellularity of the tendons after granulocyte injections is representative of an increase in inflammation. Moreover, our results are consistent with the increased inflammation previously reported linking leukocytes to tendon inflammation.^20,22,32 It is interesting to note that the increase in inflammation does not lead to an increase in vascularity as could be expected.

CONCLUSION

We found that the injection of leukocytes into healthy rat Achilles tendons increases inflammation, as evidenced by increased cellularity and disrupted morphology, which suggests that leukocyte-rich PRP preparations may be contraindicated in settings of acute tendonitis. However, these preparations may be useful for a specific subset of tendinopathies, including chronic tendinosis.

ABSTRACT

In this study, we determine the in vivo effects of injecting sub-populations of leukocytes into normal rat Achilles tendons via a controlled laboratory study. Allogenic monocytes, granulocytes, or plasma were injected into 24 healthy rat Achilles tendons. Treated and contralateral un-treated control tendons then assessed for cellularity, histologic morphology, and vascularity after 7 and 14 days. Significant increases of 221% and 249% in cellularity (P = 0.014) were seen on day 14 within Achilles tendons injected with granulocytes as compared to plasma and monocytes, respectively. Also, significant improvement in morphology (P = 0.029) between days 7 and 14 was seen for the granulocyte injected Achilles tendons. Significant increases in cellularity after an injection of granulocytes, compared to monocytes and plasma, corresponds to a significant increase in inflammation within the tissue, suggesting that leukocyte-rich platelet-rich plasma (PRP) preparations are proinflammatory and potentially catabolic when injected into tendon tissue. The concentration and composition of white blood cells within PRP preparations is variable and needs to be better understood in order to optimize clinical utility of PRP injections.

Continue to: Tendinopathies are debilitating conditions...

Tendinopathies are debilitating conditions affecting patients worldwide every day. They arise most frequently from tendon overuse resulting in pathology.¹ There are 2 major subtypes of tendinopathy: tendinosis and tendinitis. Tendinosis, the more common condition, is characterized by long-term, chronic degradation of tendon tissue resulting in fibrosis from infiltrating fibroblasts.² Tendinitis, the less common condition, is characterized by an acute inflammatory response and inflammatory cell infiltrate.² Both conditions are common, with Achilles tendinopathy affecting 11% of runners and lateral epicondylitis affecting 1% to 3% of the general population.^3,4 Many sports-related overuse injuries, such as tendinopathies, go undiagnosed for extended periods of time because medical attention is avoided in order to prevent time loss from training or competing.⁵ These delays could be eliminated if a non-surgical option for treating tendon pathology was available.

Tendinopathies are believed to result from tendon overuse that causes micro-damage to collagen, as well as from significant changes in protein and enzyme composition within the tendon.⁶ The damage accumulates over time and eventually leads to chronic inflammation or fibrotic change within tendons, in both cases weakening the tendon and causing pain. Currently, accepted treatments for tendinopathies include: nonsteroidal anti-inflammatory drugs, physical therapy, ultrasound, laser-therapy, corticosteroids, glyceryl trinitrate patches, extracorporeal shock wave therapy, sclerotherapy, and surgery.⁷ Recently, platelet-rich plasma (PRP) therapy has emerged as a promising treatment for tendinopathies, as well as a variety of other orthopedic indications.

PRP consists of autologous blood from the patient, centrifuged to increase the amount of platelets in the sample above baseline, and subsequently injected around an affected tendon or joint.⁸ PRP is used to treat tendinopathy because it can supply injured tendons with blood components that aid in healing, which tendons do not receive due to poor vascularity.⁹ These components include growth factors, such as platelet derived growth factor (PDGF), transforming growth factor-β (TGF-β), vascular endothelial growth factor (VEGF), endothelial growth factor, and leukocytes that can stimulate an inflammatory response within the injured tissue.¹⁰ The inflammatory response from the PRP induces a more robust reconstruction and revascularization of the injured tissue, stimulating proliferation, and remodeling.^11,12However, significant variability exists within the platelets, leukocytes, and growth factors that comprise PRP. This is attributed to 3 major causes. First, current commercial preparations of PRP result in differing platelet concentrations, as well as leukocyte-rich and leukocyte-poor compositions.^13,14 Variability in platelet concentrations results in unreliable amounts of growth factors, including cytokines, TGF-β, PDGF, VEGF and basic fibroblast growth factor in each preparation, while leukocyte levels affect inflammation, all leading to variable effects for each preparation.^15,16Second, despite sex and age of the PRP donor not being significant factors influencing variation in growth factor concentrations, the existence of an unexplained variation in concentrations of growth factors between different donors has been observed.¹⁷ Third, the selection of activating agents, bovine thrombin or calcium chloride, and their application, whether to the elbow, shoulder, or knee, produces variability.¹⁸

While the effects of platelets and growth factors in PRP have been well studied, less is known about the effects of differing cell types. Recently it was reported that the concentrations of leukocytes directly affect the outcomes of PRP injections. McCarrel and colleagues^19,20 found that as the number of leukocytes increased, there was a concomitant increase in the expression of inflammatory cytokines and catabolic activity. This effect may result in inferior healing of injured tissues and is attributed to the release of pro-inflammatory cytokines such as interleukin-1β from the leukocytes.²¹ There is also evidence that minimizing the catabolic effect of leukocytes may be just as important to tissue healing as the maximizing anabolic effect of platelets and growth factors.²²

The use of PRP has been highly disputed in recent years due to conflicting reports of its success in treating orthopedic conditions. Numerous favorable studies have shown benefit for treating chronic and acute orthopedic injuries including; rotator cuff tear repair, chronic refractory patellar tendinopathy, and chronic lateral tendinosis/epicondylitis.^23-26 Concurrently, articles demonstrating no significant effects from PRP have also been published. One study claiming that PRP injections did not improve outcomes of chronic Achilles tendinopathy did not differentiate whether patients had tendinosis or tendinitis, and did not consider leukocyte concentration in their PRP preparations²⁷ Another study that determined PRP is not beneficial to the healing of ruptured Achilles tendons after surgical repair also failed to consider the concentration of leukocytes in their PRP preparations.²⁸ One of the difficulties in comparing these studies is their heterogeneous nature. This arises from the use of different conditions in each study that makes the studies incomparable. Variations in PRP preparations lead to different concentrations of growth factors, platelets, and leukocyte concentrations. Additionally, tendinopathy models were not specified as tendinosis and tendonitis, and models or patients were not controlled for age, sex, or comorbidities. Given that leukocyte-rich and leukocyte-poor PRP preparations are currently widely used in clinical practice, the discovery of which type of preparation is indicated in which setting is paramount to evidence-based use of this treatment modality. Due to reports suggesting that leukocytes may be detrimental to tendon healing, determining which types of leukocytes are responsible for these effects is vital. As such, the purpose of this study is to determine the in vivo effects of sub-populations of leukocytes on normal rat tendons. This study design allowed us to isolate the effects of the injections to induce a response and remove confounding effects of normal healing response to a damaged tendon and effects from the injection itself. Our hypothesis was that the injection of leukocytes would cause an inflammatory response in rat tendons, leading to catabolic outcomes.

Continue to: METHODS...

 

 

METHODS

This was a prospective, in vivo, placebo controlled, randomized animal study. The University’s Institutional Animal Care and Use Committee approved all procedures prior to initiation. Twenty-four male Sprague-Dawley rats were randomized to 3 treatment groups (n = 8): monocytes; granulocytes, and; plasma, as a negative control.

Allogenic blood from 6 additional rats was collected into K2EDTA tubes via cardiac puncture. Allogenic, as opposed to autogenic, blood is commonly used in rat models because of low immunogenic response to blood from rats of the same strain and litter.^29,30 The blood was then pooled and the red cells lysed by incubation with Red Blood Cell Lysis Buffer (Roche). The samples were then sorted into fractions containing monocytes and granulocytes using fluorescence activated cell sorting (FACS) using a FACSAria (BD Biosciences). Cells were sorted using Purified PE Mouse Anti-Rat CD11b/c antibodies (BD Pharmingen) specific to monocytes, granulocytes, macrophages, dendritic cells, and microglia, APC-Cy7 Mouse Anti-Rat CD45 antibodies (BD Pharmingen) specific to all hematopoietic cells except erythrocytes, and FITC Mouse Anti-Rat CD42d antibodies (BD Pharmingen) specific to megakaryocytes and platelets. 20 μL of 0.2 mg/mL CD11b/c, 20 μL of 0.2 mg/mL CD 45, and 10 μL of 0.5 mg/mL CD42d antibodies were added to 1 mL of condensed non-red cells collected from the 6 rats and incubated at room temperature in the dark for 15 minutes. A fraction containing only platelet-poor plasma was also collected. For all treatments the injection volume was 75 μL. Rats in the monocyte group were injected with 200,000 cells in platelet-poor plasma, those in the granulocyte group were injected with 900,000 cells in platelet-poor plasma, and rats in the plasma control group received only platelet-poor plasma. The cell concentrations were based on previous studies that documented these concentrations that are found in typical leukocyte-rich PRP preparations.¹³

The animals were anesthetized with isoflurane gas and then injected aseptically once into their right Achilles tendon. The left Achilles tendon was used as an un-injected control, giving a total of 48 total Achilles tendons studied. At days 7 and 14 post-injection, 4 rats from each group were euthanized and the Achilles tendons were harvested.

The tendons were fixed in neutral buffered formalin for 24 hours and then embedded in paraffin and sectioned sagittally at 12 μm. The tendons were then stained with hematoxylin and eosin (H&E) using standard histological protocols and examined by 3 individuals trained to assess cellularity and morphology. All samples were assigned unrecognizable numbers and randomized prior to examination by individuals. Cell counts were based on the number of nuclei present in 3 mid-tendon high-power fields (400x) per sample. Morphology was graded on a scale of 1 to 3, with 1 being a normal tendon and 3 having severe pathology with total loss of alignment and crimping on 3 low-power fields (100x) per sample (Figures 1A-1G).

Vascularity was assessed by immunohistochemical staining using Rabbit Polyclonal Anti-CD31 antibodies (Abcam), a marker for vascular endothelial cells, using a Vectastain ABC Kit (Vector Laboratories) system and the ImmPACT AEC Peroxidase (HRP) Substrate (Vector Laboratories). Following staining, automated image analysis was performed (Bioquant). Briefly, all areas that did not contain tendon were masked. CD31 positive areas were then quantified using global thresholding. Vascularity was then calculated as ratio of CD31 positive area to total tendon area. Analyses were performed on 3 mid-tendon medium-power (200x) fields per sample.

For cellularity and morphology, the results for the injected tendons were normalized to those of their contralateral untreated controls and reported as a percentage. Results for vascularity were compared directly between treated tendons. Differences were assessed between groups at each time-point using Independent Samples Median Tests. When significant differences were identified, pairwise comparisons were performed to identify the source of the differences. All analyses were conducted using SPSS (V22, SAS Institute) with significant differences determined for values of P < 0.05.

RESULTS

No significant differences in cellularity between groups were seen at day 7 (P = 0.368) (Figures 1A-1G). However, a significant difference in cellularity between groups was seen at day 14 (P = 0.014). Pairwise tests showed there to be a significant increase in the number of cells in the tendons treated with granulocytes from 221% and 249% in cellularity (P = 0.014) on day 14, as compared to both monocytes and plasma, respectively. Morphologically, no significant differences were seen between groups at either time-point (P = 0.091 for day 7 and P = 1.000 for day 14) (Figures 2A-2G). However, a significant improvement in morphology was observed from day 7 to day 14 in the granulocyte group from 60% to 165% (P = 0.029). Finally, no differences were seen in vascularity between treatment groups at either time-point (P = 0.368 for day 7 and P = 0.535 for day 14) (Figures 3A-3G).

Continue to: DISCUSSION...

 

 

DISCUSSION

Our hypothesis that the injection of leukocytes would cause an inflammatory response in rat tendons leading to catabolic outcomes was confirmed in the granulocyte group. It should be noted that prior to the catabolic outcome, there was a transient anabolic effect in the granulocyte group during the second week. Deterioration in morphology was observed in the tendons injected with granulocytes on day 7, which subsequently recovered in the following week. We found that injecting granulocytes into normal tendons resulted in an increase in inflammatory cellularity, when compared to monocytes and plasma injections. 

Limitations inherent in this study are those similar to other in vivo studies. To begin with, the results of injections into rat tendons may not be translatable to human tendons. Despite this limitation, the rat is a common model for tendon research.³¹ Another limitation is that this study injected healthy Achilles tendons, rather than tendons with preexisting tendinopathy. In a naturally occurring tendinopathy, there may be other factors present that interact with PRP, and this model negates the contribution of these factors. Finally, while the immunohistochemistry (IHC) and morphological data are clear, the cellularity data are not clear in identifying the type of cells that were increased by granulocyte injection.  However, the cells appeared rounded, resembling inflammatory infiltrate; a common cell type seen in tendons.² While fibroblasts are also a common infiltrate during chronic tendinopathy, they are generally flat and appear on H&E as long spindle shaped cells. Thus, we believe the increased cellularity of the tendons after granulocyte injections is representative of an increase in inflammation. The increased cellularity could be due to the increased number of cells injected into the tendon; however, our conclusions are consistent with the increased inflammation previously reported linking leukocytes to tendon inflammation.^20,22,32

In terms of morphology, we hypothesized that degenerative changes would be seen in the tendons that were injected with granulocytes due to the inflammatory action of these cells. As part of the granulocyte response, neutrophils release proteases and macrophages can stimulate collagen synthesis via fibroblasts, both causing change within the extracellular matrix.^33,34 Indeed, we observed a significant change in tissue morphology in the granulocyte group over the course of 14 days. As the degenerative and regenerative effects of granulocytes take time to present, this is likely what we observed to occur between day 7 and 14 after treatment. These observations are also consistent with prior observations that leukocyte-rich PRP injections can be detrimental to tendon healing, but beneficial to tissue degeneration in the setting of chronic tendonitis.²⁰

We hypothesized that the vascularity of the tendons would be similar in all preparations. This was based on previous studies demonstrating that the lack of platelets in the platelet-poor plasma fraction is sufficient to deplete VEGF, the angiogenic agent in PRP.³⁵ In this study, there were no observable differences in vascularity of platelet-poor plasma, monocyte, and granulocyte injections. We attribute this to the lack of VEGF in any of these preparations. The aforementioned study also showed that the lack of platelets in injection was enough to prevent the angiogenic effect of this treatment.³⁵

Continue to: The goal of this study was...

 

 

The goal of this study was to assess the morphology, cellularity, and vascularity of normal tendons after injections of different leukocyte populations. This is clinically important because of the potential to tailor future PRP injections on a patient-by-patient basis. In patients requiring an anabolic response, leukocyte-poor PRP may be the best option. In contrast, when patient pathology requires an inflammatory response to improve healing³⁶ or breakdown fibrotic tissue, as seen in tendinosis, leukocyte-rich PRP may be warranted. Further, properly controlled clinical studies are needed to validate these recommendations.

Limitations inherent in this study are those similar to other in vivo studies. First, the results of injections into rat tendons may not be translatable to human tendons. Despite this limitation, the rat is a common model for tendon research.³¹ A second limitation is that this study injected healthy Achilles tendons, rather than tendons with preexisting tendinopathy. In a naturally occurring tendinopathy, there may be other factors present that interact with PRP, and this model negates the contribution of these factors. Finally, while the IHC and morphological data show clear changes, the cellularity data are not clear in identifying the type of cells that were increased by granulocyte injection. However, the cells appeared rounded, resembling inflammatory infiltrate; a common cell type seen in tendons.² While fibroblasts are also a common infiltrate during chronic tendinopathy, they are generally flat and appear on H&E as long spindle shaped cells. The last limitation of this study is the lack of functional mechanical testing since, clinically, healing of the tendon is also related to the strength of the tendon. Thus, we believe the increased cellularity of the tendons after granulocyte injections is representative of an increase in inflammation. Moreover, our results are consistent with the increased inflammation previously reported linking leukocytes to tendon inflammation.^20,22,32 It is interesting to note that the increase in inflammation does not lead to an increase in vascularity as could be expected.

CONCLUSION

We found that the injection of leukocytes into healthy rat Achilles tendons increases inflammation, as evidenced by increased cellularity and disrupted morphology, which suggests that leukocyte-rich PRP preparations may be contraindicated in settings of acute tendonitis. However, these preparations may be useful for a specific subset of tendinopathies, including chronic tendinosis.

ABSTRACT

Osteoarthritis (OA) of the knee is a top cause of disability among the elderly. Total knee replacement (TKR) has been available as an effective and definite surgical method to treat severe OA of the knee. However, TKR is a significant procedure with potential risk for serious complications and high costs. Alternative lower risk therapies that can delay or obviate TKR are valuable to those who are poor candidates for surgery or wish to avoid TKR as long as possible. Given the chondroprotective effects of hyaluronic acid (HA) injections, they are a safe and effective treatment to improve pain, function, and longevity of the knee. Thus, HA features the potential to delay or obviate TKR.

We aim to study the safety and effectiveness of repeated courses of HA on the time to TKR over a 3-year period using data from a large US health plan administrative claims database.

Retrospective analyses were conducted by identifying knee OA patients during the selection period (2007-2010). The follow-up period was 36 months, post-index date of initial HA injection. Procedural outcomes and adverse events of interest were tabulated and analyzed. A Cox proportional hazards model was used to model the risk of TKR.

A total of 50,389 patients who received HA for treatment of knee OA and met the study inclusion criteria were analyzed. Successive courses of HA showed a good safety profile and led to high proportions of patients without TKR 3 years after treatment initiation. Multivariate statistical modeling showed that multiple courses of HA injections significantly decreased the rates of TKR (95.0% without TKR for ≥5 courses vs 71.6% without TKR for 1 course; hazard ratio, 0.138; P < .0001).

Repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effect of repeated HA courses on delaying TKR beyond a 3-year time horizon.

Continue to: Osteoarthritis (OA) of the knee...

Osteoarthritis (OA) of the knee has emerged as one of the main causes of disability in the United States. Although no currently known cure of OA can reverse the progression of the disease, total knee replacement (TKR) is an effective and definitive treatment. However, TKR is an invasive procedure with potential risk for serious complications, and it has imposed high costs on the US healthcare system, with expenses accounting for hospital expenditures of TKR estimated at $28.5 billion in 2009.¹Alternative low-risk therapies that can delay or obviate TKR are valuable to a number of patients, especially the poor candidates for surgery or those who wish to avoid TKR.

Intra-articular (IA) hyaluronic acid (HA) injections have been available as a safe and effective treatment option to alleviate pain and to improve joint functions.² Results of randomized double-blind controlled clinical trials have demonstrated the pain-relieving effect of IA HA injections.^3-5 Furthermore, a recent network meta-analysis comparing various pharmacologic interventions for knee OA has confirmed the efficacy of IA HA injections, which outperformed other interventions when compared with oral placebos.^6,7 IA therapies are more effective than oral therapies for knee OA pain, with IA HA injections demonstrating the most pain reduction, potentially due to the benefit associated with needle injection and aspiration. Recent experimental studies have also suggested that IA HA may provide cartilage protection, reduce inflammation, and boost the viscosity of synovial fluid;⁸ IA HA may also exert therapeutic effects by inhibiting bone formation in OA patients.^9,10 HA possesses the potential to delay or obviate TKR. Previous research with a case series review of patients in an orthopedic specialty practice reported that the use of IA HA injections in patients with grade IV OA delayed TKR substantially.¹¹ One study analyzed retrospective medical claims data from a single private insurer and discovered potential evidence for the modest benefit of IA HA injections in delaying TKR.¹²

More detailed research work on a large sample of patients with knee OA and the requirement of TKR as a condition for inclusion using US administrative claims data has demonstrated the TKR-delaying effects of IA HA injections in comparison with a control group without claims for IA HA injections.^13,14 This study also uses real-world US administrative data but utilizes a different approach by starting with a sample of patients with knee OA and evidence of IA HA injections and then assessing the effect of repeated courses of HA treatment on the delay of TKR, without TKR as a mandatory condition for inclusion. All patients with knee OA within the time window were included, regardless of the need for TKR compared with previous studies which only considered patients who ultimately received TKR. Safety information and effectiveness information were examined to achieve a balanced risk-benefit assessment. We also analyzed how multiple courses of HA treatment and other potentially relevant covariates at baseline affected the risk of receiving TKR in a multivariate survival model. We aimed to achieve a realistic assessment of the clinical utility of HA injections in delaying TKR in a real-world setting using both safety and effectiveness data.

METHODS

DATA SOURCE

A retrospective cohort observational study using IMS Health’s PharMetrics Plus Health Plan Claims Database was conducted by identifying knee OA patients with claims indicating initiation of HA injection at an index date during the selection period (July 1, 2007 to June 30, 2010). All common HA agents in the US market during this period (Euflexxa, Hyalgan, Orthovisc, Supartz, and Synvisc) were selected via the corresponding J-codes and pooled for investigation of HA class effects. The follow-up period was 36 months, post-index date of the initial HA injection. Outcomes were measured, and adverse events were identified during this period. The time window for identification of adverse events was within 2 weeks from any injection during the course of therapy (evidence of an emergency room visit and/or physician office visit with requisite code). The data during the 12-month pre-index baseline period from the claims database was used to obtain information about baseline patient characteristics, such as age, gender, type of coverage, physician specialty, Charlson Comorbidity Index (CCI), major comorbidities, and major medications of interest commonly used among patients with knee OA.

STUDY SAMPLE SELECTION

The eligible patients required an outpatient claim indicating the initiation of HA injection. The date of the first claim for the patient within the selection window was defined as their index date. Patients had to be ≥18 years of age in the year of their index date. They had to present at least 1 clinical knee OA diagnosis at any point in the 12-month pre-index period (including the index date), and only patients who were continuously enrolled from 12 months pre-index to 36 months post-index date were evaluated. Among these patients (approximately 1.4 million), the following were excluded to minimize complications in data analysis and interpretation: patients with evidence of any HA use in the pre-index period; patients with evidence of a different kind of HA index medication in the post-index period; patients with evidence of TKR within 30 days of the index event during the post-index period; patients with evidence of 2 different kinds of HA index medications on the index date; and patients with evidence of diagnosis of hip OA, fibromyalgia, rheumatoid arthritis, lupus, or gout during the pre-index period.

Five patient cohorts were defined according to the number of courses of IA HA injections over the entire post-index period.

Continue to: Statistical analysis...

STATISTICAL ANALYSIS

All statistical analyses were performed using SAS version 9.2 (SAS Institute Inc.). Descriptive statistics such as means, standard deviations, medians, and 25% and 75% percentiles (Q1 and Q3, respectively) were provided for the continuous variables. Numbers and percentages were provided for the categorical variables. For statistical testing, Student’s t-tests were applied for the continuous variables and chi-square tests for the categorical variables. All the statistical tests were two-tailed. The sample sizes in this database study are remarkably large, such that differences that are not clinically important could still be statistically significant at the conventional alpha level of 0.05. Thus, we applied a more stringent requirement of the alpha level of 0.0001 to identify highly statistically significant results. The number and percentage of patients within each cohort with at least 1 instance of an adverse event of interest (those adverse events commonly expected for patients who receive IA injections for knee OA) were assessed. Times to TKR during the 36-month post-index period were analyzed and compared among different cohorts. Any patients who had not undergone TKR by the end of the post-index period were considered censored at 36 months. The Kaplan-Meier method was employed to model survival curves with time to TKR data, and log-rank tests were used to compare survival curves among different cohorts. A Cox proportional hazards model (PHM) was used to model the risk of TKR with a pre-specified set of covariates adjusted for baseline attributes, such as age, gender, comorbidities, and pre-index healthcare costs. Hazard ratios with 95% confidence intervals were used to examine the measures of event risk.

RESULTS

PATIENT CHARACTERISTICS

Applying study selection criteria to the claims database yielded 50,389 patients (Figure 1), providing an ample sample size for the statistical analysis. Only patients with evidence of knee OA and use of HA injections (the index medication of interest) were selected, regardless of whether they received TKR during the post-index period. The requirement for a knee OA diagnosis during the 12-month pre-index period resulted in the significant attrition of patients, with 584,956 patients being excluded. Among the 50,389 patients who received HA for treatment of knee OA, 36,260 (72.0%) received a single course of treatment, 8709 (17.3%) received 2 courses, 3179 (6.3%) received 3 courses, 1354 (2.7%) received 4 courses, and 887 (1.8%) received ≥5 courses of treatment.

Comparison of baseline characteristics among the 5 IA HA cohorts showed the fairly similar baseline characteristics of all cohorts (Table 1). Geographic region, physician specialty, and opioid use showed differences among the cohorts. Cohorts with ≥5 HA courses presented lower proportions of patients from Southern US states, patients seeing orthopedic surgeons, and patients using opioids than cohorts with fewer HA courses.

PROCEDURES OF INTEREST

An analysis of the procedures patients received after HA treatment initiation showed that higher numbers of HA treatment courses resulted in lower proportions of patients receiving TKR within 3 years after HA treatment initiation (Table 2). With an increasing number of HA treatment courses, the proportion of patients with TKR within 3 years post-index consistently decreased from 28.4% (for 1 HA course) to 5.0% (for ≥5 HA courses), with all differences being highly statistically significant (P < .0001). Similarly, partial knee replacement exhibited a similar trend, with the proportion of patients decreasing from 3.3% (for 1 HA course) to 0.8% (for ≥5 HA courses; P < .0001). Among the patients with TKR within 3 years post-index, increasing numbers of treatment courses correlated with increasing time to TKR, with a mean of 375.6 days (for 1 HA course) rising to a mean of 971.5 days (for ≥5 HA courses; P < .0001). On the other hand, patients with multiple courses of HA treatment were more likely to undergo radiologic examinations of the knee, arthrocenteses, and image-guided injections than patients with only a single course of HA treatment (P < .0001).

ADVERSE EVENTS

Arthralgia and joint pain in the knee were the most commonly recorded adverse events (Table 3). More courses of HA treatment were associated with higher rates of adverse events. Overall, the reported adverse events profile of repeated courses of HA treatment consisted of mostly common and mild adverse events and displayed no safety concern for patients with knee OA that was followed-up for 3 years. The causality of these adverse events directly related to HA injections vs a specific disease state cannot be determined from an administrative claims data set.

TIME TO TKR

Successive courses of HA led to high proportions of patients without TKR 3 years after HA treatment initiation. This result is evident in the Kaplan-Meier survival curves of time to TKR for different HA cohorts (Figure 2), with log-rank tests of multiple courses vs a single course of HA (P < .0001) showing highly statistically significance. Tabulation of proportions of patients without TKR by various time points showed that increasing numbers of HA treatment courses correlated with higher proportions of patients without TKR at almost all time points (Table 4); within 3 years post-index, 71.6% of patients in the 1 HA course cohort exhibited no TKR, whereas 95.0% of patients in ≥5 HA courses cohort presented no TKR. We also performed a multivariate Cox PHM (Table 5) to account for baseline characteristics of different HA cohorts with covariates when estimating the risks of receiving TKR. The results of the Cox PHM showed that multiple courses of HA treatment significantly decreased the risk of TKR (hazard ratio, 0.138 for ≥5 HA courses vs 1 HA course; P < .0001). Inspection of other highly significant covariates showed that being older, living in the Midwest region of the US (vs the Northeast), receiving pre-index corticosteroids, having an orthopedic surgeon as a treating physician (vs a general practitioner, a rheumatologist, or a physical medicine and rehabilitation specialist), experiencing hypertension or hyperlipidemia, and higher pre-index total healthcare costs were associated with an increased risk of TKR (all P < .0001). Vascular disease and high CCI scores were associated with a decreased risk of TKR (P < .0001).

Continue to: Discussion...

DISCUSSION

This study demonstrated that multiple courses of HA treatment can delay the need for surgery for up to 3 years, with risk for both TKR and partial knee replacement decreasing in a dose-dependent manner. The potentially confounding effect of differences in baseline characteristics that could influence patients’ propensity to receive TKR in a database study was controlled by performing a multivariate analysis with covariate adjustment. The TKR-delaying effect of HA injection was more prominent in cohorts with a high number of HA treatment courses: 19 out of 20 patients in the cohort of ≥5 HA courses were free of TKR at the end of the 3-year post-index period. Such a high proportion of patients avoiding TKR with repeated courses of HA suggests that some patients may be able to successfully delay TKR well beyond the 3-year time span. This finding is counter-evidence to the frequently made assumption¹⁵ that all patients with knee OA will eventually progress to a state of disability, making TKR inevitable. The patients with end-stage radiographic knee OA can also benefit from IA HA injections for an extended period of time;¹⁶ the latest evidence indicates that nonoperative management can improve symptoms irrespective of radiographic disease severity, implying that TKR needs not to be the only therapeutic option for patients with end-stage radiographic knee OA.¹⁷ This finding suggests that HA treatment should be considered an important clinical treatment option for patients with knee OA.

Although the incidence rates of certain adverse events, such as arthralgia/joint pain, are sizable, these temporary adverse events commonly occur among patients who receive IA injections for knee OA; most of these events may simply include symptoms of the remaining underlying knee OA. These results are consistent with those of previous literature reporting the safety of repeated treatment with IA HA injections in a prospective clinical trial¹⁸ and demonstrating that repeated courses of HA treatment pose no greater safety risk than a single course of HA treatment.

Multivariate modeling outcomes of factors influencing risk of receiving TKR are broadly consistent with the generally accepted notions that different levels of disease severity and patients’ willingness to consider TKR at baseline influence the likelihood and timing of receiving TKR.^19,20 Age and obesity are common risk factors for progression of OA. Orthopedic surgeons are more likely to recommend surgery than non-surgeons. The pre-index use of corticosteroids and high pre-index healthcare costs could be associated with more severe symptoms at baseline. Patients with vascular disease or severe comorbidities, as evidenced by high CCI scores, make poor candidates for major elective surgeries such as TKR. These results are intuitive and validate the clinical insights of this study. Moreover, inclusion of these covariates in the analysis model allows for indirect adjustment of the most important prognostic factors for TKR at baseline, permitting proper statistical comparison of the results for different cohort groups.

Recently, the efficacy of HA injections for OA patients has become the subject of debate when the American Academy of Orthopaedic Surgeons (AAOS) revised its clinical practice guideline, recommending against the use of HA.²¹ The AAOS’ findings differ from those of other clinical societies, such as the American College of Rheumatology²² and the European League Against Rheumatism,²³ which provide no strong recommendation against the use of HA injections. The announcement of the new guideline by AAOS caused concern among clinicians and payers who had valued IA HA injections as a means to control knee OA pain before patients progress to TKR;²⁴ on the other hand, the demand for nonoperative treatment of knee OA remains high. Utilization rates of TKR have increased dramatically, and surgeries are now performed on younger patients with increasing burden on the healthcare system,^25,26 in spite of the fact that as high as a third of TKR surgeries may have been performed in inappropriate patients.²⁷ Part of the confusion surrounding clinical utility of HA stems from the fact that up until recently, relatively little research looked into the practical benefits of HA in actual clinical practice. Analyses of databases such as registries are now gaining attention to overcome that problem. Examination of large administrative databases maintained by commercial payers offers the benefit of probing realistically the safety and efficacy of treatments in actual clinical environments in a very large number of patients with heterogeneous backgrounds. Recently, the Agency for Healthcare Research and Quality’s Technology Assessment Program in the US called for such studies to determine whether HA injections can delay progression to TKR.²⁸ The results of this study and several others^11,13,14,16 suggest that use of HA to treat OA of the knee is associated with the delay of TKR, supporting the utility of HA in clinical practice and the healthcare system. Potential clinical benefits of delaying TKR may include the reduced risk of aseptic loosening if younger patients can wait for TKR or more time to allow the modification of risk factors in patients who will ultimately undergo TKR.

LIMITATIONS

Follow-up period was limited to 3 years post-index date because longer follow-up data were not available at the time of the study design. If an incorrect adverse event or OA diagnosis was listed in the medical record, or if the medical record was incomplete, then patients might have been misclassified, resulting in selection bias. The claims dataset includes no uninsured and Medicare patients, as the population in the database consisted primarily of commercially-insured patients in the US. Therefore, the results are most generalizable to other commercially-insured patients in the US. Generalizability to other populations may not be assured if they differ in their accessibility to physician services or prescriptions from the patients in this study. Other treatments such as the nonsteroidal anti-inflammatory drugs used by patients were not included within the pre-specified statistical model because their potential effects were assumed to be short-lived and much less than those of corticosteroid. Including these treatments would overload the statistical model with too many covariates, leading to potential computational instability. The database used provides no information on systemic factors, including plan limits on medication use, that could affect care. Given the large and diverse nature of the healthcare plans in the database. However, these factors should not have materially affected our study results. The claims database also lacks direct indicators of OA disease severity, such as Kellgren-Lawrence scores or patient-reported outcomes, including pain and function questionnaire scores. Our multivariate analysis indirectly makes up for this deficiency by considering other baseline characteristics or clinical indicators that may be correlated with information unavailable in a claims database. Patients who opt to undergo repeated courses of HA treatment may be more inclined to avoid surgery or may naturally experience OA disease progression more slowly, making them potentially different from patients who select to undergo surgery earlier without repeated courses of HA treatment. This condition may introduce a bias that causes difficulty in proving the causality between repeated HA use and delay of TKR.

CONCLUSION

Analysis of the knee OA patient data from a real-world database showed that repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effects of repeated HA courses on delaying TKR beyond a 3-year period.

ABSTRACT

Osteoarthritis (OA) of the knee is a top cause of disability among the elderly. Total knee replacement (TKR) has been available as an effective and definite surgical method to treat severe OA of the knee. However, TKR is a significant procedure with potential risk for serious complications and high costs. Alternative lower risk therapies that can delay or obviate TKR are valuable to those who are poor candidates for surgery or wish to avoid TKR as long as possible. Given the chondroprotective effects of hyaluronic acid (HA) injections, they are a safe and effective treatment to improve pain, function, and longevity of the knee. Thus, HA features the potential to delay or obviate TKR.

We aim to study the safety and effectiveness of repeated courses of HA on the time to TKR over a 3-year period using data from a large US health plan administrative claims database.

Retrospective analyses were conducted by identifying knee OA patients during the selection period (2007-2010). The follow-up period was 36 months, post-index date of initial HA injection. Procedural outcomes and adverse events of interest were tabulated and analyzed. A Cox proportional hazards model was used to model the risk of TKR.

A total of 50,389 patients who received HA for treatment of knee OA and met the study inclusion criteria were analyzed. Successive courses of HA showed a good safety profile and led to high proportions of patients without TKR 3 years after treatment initiation. Multivariate statistical modeling showed that multiple courses of HA injections significantly decreased the rates of TKR (95.0% without TKR for ≥5 courses vs 71.6% without TKR for 1 course; hazard ratio, 0.138; P < .0001).

Repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effect of repeated HA courses on delaying TKR beyond a 3-year time horizon.

Continue to: Osteoarthritis (OA) of the knee...

Osteoarthritis (OA) of the knee has emerged as one of the main causes of disability in the United States. Although no currently known cure of OA can reverse the progression of the disease, total knee replacement (TKR) is an effective and definitive treatment. However, TKR is an invasive procedure with potential risk for serious complications, and it has imposed high costs on the US healthcare system, with expenses accounting for hospital expenditures of TKR estimated at $28.5 billion in 2009.¹Alternative low-risk therapies that can delay or obviate TKR are valuable to a number of patients, especially the poor candidates for surgery or those who wish to avoid TKR.

Intra-articular (IA) hyaluronic acid (HA) injections have been available as a safe and effective treatment option to alleviate pain and to improve joint functions.² Results of randomized double-blind controlled clinical trials have demonstrated the pain-relieving effect of IA HA injections.^3-5 Furthermore, a recent network meta-analysis comparing various pharmacologic interventions for knee OA has confirmed the efficacy of IA HA injections, which outperformed other interventions when compared with oral placebos.^6,7 IA therapies are more effective than oral therapies for knee OA pain, with IA HA injections demonstrating the most pain reduction, potentially due to the benefit associated with needle injection and aspiration. Recent experimental studies have also suggested that IA HA may provide cartilage protection, reduce inflammation, and boost the viscosity of synovial fluid;⁸ IA HA may also exert therapeutic effects by inhibiting bone formation in OA patients.^9,10 HA possesses the potential to delay or obviate TKR. Previous research with a case series review of patients in an orthopedic specialty practice reported that the use of IA HA injections in patients with grade IV OA delayed TKR substantially.¹¹ One study analyzed retrospective medical claims data from a single private insurer and discovered potential evidence for the modest benefit of IA HA injections in delaying TKR.¹²

More detailed research work on a large sample of patients with knee OA and the requirement of TKR as a condition for inclusion using US administrative claims data has demonstrated the TKR-delaying effects of IA HA injections in comparison with a control group without claims for IA HA injections.^13,14 This study also uses real-world US administrative data but utilizes a different approach by starting with a sample of patients with knee OA and evidence of IA HA injections and then assessing the effect of repeated courses of HA treatment on the delay of TKR, without TKR as a mandatory condition for inclusion. All patients with knee OA within the time window were included, regardless of the need for TKR compared with previous studies which only considered patients who ultimately received TKR. Safety information and effectiveness information were examined to achieve a balanced risk-benefit assessment. We also analyzed how multiple courses of HA treatment and other potentially relevant covariates at baseline affected the risk of receiving TKR in a multivariate survival model. We aimed to achieve a realistic assessment of the clinical utility of HA injections in delaying TKR in a real-world setting using both safety and effectiveness data.

METHODS

DATA SOURCE

A retrospective cohort observational study using IMS Health’s PharMetrics Plus Health Plan Claims Database was conducted by identifying knee OA patients with claims indicating initiation of HA injection at an index date during the selection period (July 1, 2007 to June 30, 2010). All common HA agents in the US market during this period (Euflexxa, Hyalgan, Orthovisc, Supartz, and Synvisc) were selected via the corresponding J-codes and pooled for investigation of HA class effects. The follow-up period was 36 months, post-index date of the initial HA injection. Outcomes were measured, and adverse events were identified during this period. The time window for identification of adverse events was within 2 weeks from any injection during the course of therapy (evidence of an emergency room visit and/or physician office visit with requisite code). The data during the 12-month pre-index baseline period from the claims database was used to obtain information about baseline patient characteristics, such as age, gender, type of coverage, physician specialty, Charlson Comorbidity Index (CCI), major comorbidities, and major medications of interest commonly used among patients with knee OA.

STUDY SAMPLE SELECTION

The eligible patients required an outpatient claim indicating the initiation of HA injection. The date of the first claim for the patient within the selection window was defined as their index date. Patients had to be ≥18 years of age in the year of their index date. They had to present at least 1 clinical knee OA diagnosis at any point in the 12-month pre-index period (including the index date), and only patients who were continuously enrolled from 12 months pre-index to 36 months post-index date were evaluated. Among these patients (approximately 1.4 million), the following were excluded to minimize complications in data analysis and interpretation: patients with evidence of any HA use in the pre-index period; patients with evidence of a different kind of HA index medication in the post-index period; patients with evidence of TKR within 30 days of the index event during the post-index period; patients with evidence of 2 different kinds of HA index medications on the index date; and patients with evidence of diagnosis of hip OA, fibromyalgia, rheumatoid arthritis, lupus, or gout during the pre-index period.

Five patient cohorts were defined according to the number of courses of IA HA injections over the entire post-index period.

Continue to: Statistical analysis...

STATISTICAL ANALYSIS

All statistical analyses were performed using SAS version 9.2 (SAS Institute Inc.). Descriptive statistics such as means, standard deviations, medians, and 25% and 75% percentiles (Q1 and Q3, respectively) were provided for the continuous variables. Numbers and percentages were provided for the categorical variables. For statistical testing, Student’s t-tests were applied for the continuous variables and chi-square tests for the categorical variables. All the statistical tests were two-tailed. The sample sizes in this database study are remarkably large, such that differences that are not clinically important could still be statistically significant at the conventional alpha level of 0.05. Thus, we applied a more stringent requirement of the alpha level of 0.0001 to identify highly statistically significant results. The number and percentage of patients within each cohort with at least 1 instance of an adverse event of interest (those adverse events commonly expected for patients who receive IA injections for knee OA) were assessed. Times to TKR during the 36-month post-index period were analyzed and compared among different cohorts. Any patients who had not undergone TKR by the end of the post-index period were considered censored at 36 months. The Kaplan-Meier method was employed to model survival curves with time to TKR data, and log-rank tests were used to compare survival curves among different cohorts. A Cox proportional hazards model (PHM) was used to model the risk of TKR with a pre-specified set of covariates adjusted for baseline attributes, such as age, gender, comorbidities, and pre-index healthcare costs. Hazard ratios with 95% confidence intervals were used to examine the measures of event risk.

RESULTS

PATIENT CHARACTERISTICS

Applying study selection criteria to the claims database yielded 50,389 patients (Figure 1), providing an ample sample size for the statistical analysis. Only patients with evidence of knee OA and use of HA injections (the index medication of interest) were selected, regardless of whether they received TKR during the post-index period. The requirement for a knee OA diagnosis during the 12-month pre-index period resulted in the significant attrition of patients, with 584,956 patients being excluded. Among the 50,389 patients who received HA for treatment of knee OA, 36,260 (72.0%) received a single course of treatment, 8709 (17.3%) received 2 courses, 3179 (6.3%) received 3 courses, 1354 (2.7%) received 4 courses, and 887 (1.8%) received ≥5 courses of treatment.

Comparison of baseline characteristics among the 5 IA HA cohorts showed the fairly similar baseline characteristics of all cohorts (Table 1). Geographic region, physician specialty, and opioid use showed differences among the cohorts. Cohorts with ≥5 HA courses presented lower proportions of patients from Southern US states, patients seeing orthopedic surgeons, and patients using opioids than cohorts with fewer HA courses.

PROCEDURES OF INTEREST

An analysis of the procedures patients received after HA treatment initiation showed that higher numbers of HA treatment courses resulted in lower proportions of patients receiving TKR within 3 years after HA treatment initiation (Table 2). With an increasing number of HA treatment courses, the proportion of patients with TKR within 3 years post-index consistently decreased from 28.4% (for 1 HA course) to 5.0% (for ≥5 HA courses), with all differences being highly statistically significant (P < .0001). Similarly, partial knee replacement exhibited a similar trend, with the proportion of patients decreasing from 3.3% (for 1 HA course) to 0.8% (for ≥5 HA courses; P < .0001). Among the patients with TKR within 3 years post-index, increasing numbers of treatment courses correlated with increasing time to TKR, with a mean of 375.6 days (for 1 HA course) rising to a mean of 971.5 days (for ≥5 HA courses; P < .0001). On the other hand, patients with multiple courses of HA treatment were more likely to undergo radiologic examinations of the knee, arthrocenteses, and image-guided injections than patients with only a single course of HA treatment (P < .0001).

ADVERSE EVENTS

Arthralgia and joint pain in the knee were the most commonly recorded adverse events (Table 3). More courses of HA treatment were associated with higher rates of adverse events. Overall, the reported adverse events profile of repeated courses of HA treatment consisted of mostly common and mild adverse events and displayed no safety concern for patients with knee OA that was followed-up for 3 years. The causality of these adverse events directly related to HA injections vs a specific disease state cannot be determined from an administrative claims data set.

TIME TO TKR

Successive courses of HA led to high proportions of patients without TKR 3 years after HA treatment initiation. This result is evident in the Kaplan-Meier survival curves of time to TKR for different HA cohorts (Figure 2), with log-rank tests of multiple courses vs a single course of HA (P < .0001) showing highly statistically significance. Tabulation of proportions of patients without TKR by various time points showed that increasing numbers of HA treatment courses correlated with higher proportions of patients without TKR at almost all time points (Table 4); within 3 years post-index, 71.6% of patients in the 1 HA course cohort exhibited no TKR, whereas 95.0% of patients in ≥5 HA courses cohort presented no TKR. We also performed a multivariate Cox PHM (Table 5) to account for baseline characteristics of different HA cohorts with covariates when estimating the risks of receiving TKR. The results of the Cox PHM showed that multiple courses of HA treatment significantly decreased the risk of TKR (hazard ratio, 0.138 for ≥5 HA courses vs 1 HA course; P < .0001). Inspection of other highly significant covariates showed that being older, living in the Midwest region of the US (vs the Northeast), receiving pre-index corticosteroids, having an orthopedic surgeon as a treating physician (vs a general practitioner, a rheumatologist, or a physical medicine and rehabilitation specialist), experiencing hypertension or hyperlipidemia, and higher pre-index total healthcare costs were associated with an increased risk of TKR (all P < .0001). Vascular disease and high CCI scores were associated with a decreased risk of TKR (P < .0001).

Continue to: Discussion...

DISCUSSION

This study demonstrated that multiple courses of HA treatment can delay the need for surgery for up to 3 years, with risk for both TKR and partial knee replacement decreasing in a dose-dependent manner. The potentially confounding effect of differences in baseline characteristics that could influence patients’ propensity to receive TKR in a database study was controlled by performing a multivariate analysis with covariate adjustment. The TKR-delaying effect of HA injection was more prominent in cohorts with a high number of HA treatment courses: 19 out of 20 patients in the cohort of ≥5 HA courses were free of TKR at the end of the 3-year post-index period. Such a high proportion of patients avoiding TKR with repeated courses of HA suggests that some patients may be able to successfully delay TKR well beyond the 3-year time span. This finding is counter-evidence to the frequently made assumption¹⁵ that all patients with knee OA will eventually progress to a state of disability, making TKR inevitable. The patients with end-stage radiographic knee OA can also benefit from IA HA injections for an extended period of time;¹⁶ the latest evidence indicates that nonoperative management can improve symptoms irrespective of radiographic disease severity, implying that TKR needs not to be the only therapeutic option for patients with end-stage radiographic knee OA.¹⁷ This finding suggests that HA treatment should be considered an important clinical treatment option for patients with knee OA.

Although the incidence rates of certain adverse events, such as arthralgia/joint pain, are sizable, these temporary adverse events commonly occur among patients who receive IA injections for knee OA; most of these events may simply include symptoms of the remaining underlying knee OA. These results are consistent with those of previous literature reporting the safety of repeated treatment with IA HA injections in a prospective clinical trial¹⁸ and demonstrating that repeated courses of HA treatment pose no greater safety risk than a single course of HA treatment.

Multivariate modeling outcomes of factors influencing risk of receiving TKR are broadly consistent with the generally accepted notions that different levels of disease severity and patients’ willingness to consider TKR at baseline influence the likelihood and timing of receiving TKR.^19,20 Age and obesity are common risk factors for progression of OA. Orthopedic surgeons are more likely to recommend surgery than non-surgeons. The pre-index use of corticosteroids and high pre-index healthcare costs could be associated with more severe symptoms at baseline. Patients with vascular disease or severe comorbidities, as evidenced by high CCI scores, make poor candidates for major elective surgeries such as TKR. These results are intuitive and validate the clinical insights of this study. Moreover, inclusion of these covariates in the analysis model allows for indirect adjustment of the most important prognostic factors for TKR at baseline, permitting proper statistical comparison of the results for different cohort groups.

Recently, the efficacy of HA injections for OA patients has become the subject of debate when the American Academy of Orthopaedic Surgeons (AAOS) revised its clinical practice guideline, recommending against the use of HA.²¹ The AAOS’ findings differ from those of other clinical societies, such as the American College of Rheumatology²² and the European League Against Rheumatism,²³ which provide no strong recommendation against the use of HA injections. The announcement of the new guideline by AAOS caused concern among clinicians and payers who had valued IA HA injections as a means to control knee OA pain before patients progress to TKR;²⁴ on the other hand, the demand for nonoperative treatment of knee OA remains high. Utilization rates of TKR have increased dramatically, and surgeries are now performed on younger patients with increasing burden on the healthcare system,^25,26 in spite of the fact that as high as a third of TKR surgeries may have been performed in inappropriate patients.²⁷ Part of the confusion surrounding clinical utility of HA stems from the fact that up until recently, relatively little research looked into the practical benefits of HA in actual clinical practice. Analyses of databases such as registries are now gaining attention to overcome that problem. Examination of large administrative databases maintained by commercial payers offers the benefit of probing realistically the safety and efficacy of treatments in actual clinical environments in a very large number of patients with heterogeneous backgrounds. Recently, the Agency for Healthcare Research and Quality’s Technology Assessment Program in the US called for such studies to determine whether HA injections can delay progression to TKR.²⁸ The results of this study and several others^11,13,14,16 suggest that use of HA to treat OA of the knee is associated with the delay of TKR, supporting the utility of HA in clinical practice and the healthcare system. Potential clinical benefits of delaying TKR may include the reduced risk of aseptic loosening if younger patients can wait for TKR or more time to allow the modification of risk factors in patients who will ultimately undergo TKR.

LIMITATIONS

Follow-up period was limited to 3 years post-index date because longer follow-up data were not available at the time of the study design. If an incorrect adverse event or OA diagnosis was listed in the medical record, or if the medical record was incomplete, then patients might have been misclassified, resulting in selection bias. The claims dataset includes no uninsured and Medicare patients, as the population in the database consisted primarily of commercially-insured patients in the US. Therefore, the results are most generalizable to other commercially-insured patients in the US. Generalizability to other populations may not be assured if they differ in their accessibility to physician services or prescriptions from the patients in this study. Other treatments such as the nonsteroidal anti-inflammatory drugs used by patients were not included within the pre-specified statistical model because their potential effects were assumed to be short-lived and much less than those of corticosteroid. Including these treatments would overload the statistical model with too many covariates, leading to potential computational instability. The database used provides no information on systemic factors, including plan limits on medication use, that could affect care. Given the large and diverse nature of the healthcare plans in the database. However, these factors should not have materially affected our study results. The claims database also lacks direct indicators of OA disease severity, such as Kellgren-Lawrence scores or patient-reported outcomes, including pain and function questionnaire scores. Our multivariate analysis indirectly makes up for this deficiency by considering other baseline characteristics or clinical indicators that may be correlated with information unavailable in a claims database. Patients who opt to undergo repeated courses of HA treatment may be more inclined to avoid surgery or may naturally experience OA disease progression more slowly, making them potentially different from patients who select to undergo surgery earlier without repeated courses of HA treatment. This condition may introduce a bias that causes difficulty in proving the causality between repeated HA use and delay of TKR.

CONCLUSION

Analysis of the knee OA patient data from a real-world database showed that repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effects of repeated HA courses on delaying TKR beyond a 3-year period.

ABSTRACT

Osteoarthritis (OA) of the knee is a top cause of disability among the elderly. Total knee replacement (TKR) has been available as an effective and definite surgical method to treat severe OA of the knee. However, TKR is a significant procedure with potential risk for serious complications and high costs. Alternative lower risk therapies that can delay or obviate TKR are valuable to those who are poor candidates for surgery or wish to avoid TKR as long as possible. Given the chondroprotective effects of hyaluronic acid (HA) injections, they are a safe and effective treatment to improve pain, function, and longevity of the knee. Thus, HA features the potential to delay or obviate TKR.

We aim to study the safety and effectiveness of repeated courses of HA on the time to TKR over a 3-year period using data from a large US health plan administrative claims database.

Retrospective analyses were conducted by identifying knee OA patients during the selection period (2007-2010). The follow-up period was 36 months, post-index date of initial HA injection. Procedural outcomes and adverse events of interest were tabulated and analyzed. A Cox proportional hazards model was used to model the risk of TKR.

A total of 50,389 patients who received HA for treatment of knee OA and met the study inclusion criteria were analyzed. Successive courses of HA showed a good safety profile and led to high proportions of patients without TKR 3 years after treatment initiation. Multivariate statistical modeling showed that multiple courses of HA injections significantly decreased the rates of TKR (95.0% without TKR for ≥5 courses vs 71.6% without TKR for 1 course; hazard ratio, 0.138; P < .0001).

Repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effect of repeated HA courses on delaying TKR beyond a 3-year time horizon.

Continue to: Osteoarthritis (OA) of the knee...

Osteoarthritis (OA) of the knee has emerged as one of the main causes of disability in the United States. Although no currently known cure of OA can reverse the progression of the disease, total knee replacement (TKR) is an effective and definitive treatment. However, TKR is an invasive procedure with potential risk for serious complications, and it has imposed high costs on the US healthcare system, with expenses accounting for hospital expenditures of TKR estimated at $28.5 billion in 2009.¹Alternative low-risk therapies that can delay or obviate TKR are valuable to a number of patients, especially the poor candidates for surgery or those who wish to avoid TKR.

Intra-articular (IA) hyaluronic acid (HA) injections have been available as a safe and effective treatment option to alleviate pain and to improve joint functions.² Results of randomized double-blind controlled clinical trials have demonstrated the pain-relieving effect of IA HA injections.^3-5 Furthermore, a recent network meta-analysis comparing various pharmacologic interventions for knee OA has confirmed the efficacy of IA HA injections, which outperformed other interventions when compared with oral placebos.^6,7 IA therapies are more effective than oral therapies for knee OA pain, with IA HA injections demonstrating the most pain reduction, potentially due to the benefit associated with needle injection and aspiration. Recent experimental studies have also suggested that IA HA may provide cartilage protection, reduce inflammation, and boost the viscosity of synovial fluid;⁸ IA HA may also exert therapeutic effects by inhibiting bone formation in OA patients.^9,10 HA possesses the potential to delay or obviate TKR. Previous research with a case series review of patients in an orthopedic specialty practice reported that the use of IA HA injections in patients with grade IV OA delayed TKR substantially.¹¹ One study analyzed retrospective medical claims data from a single private insurer and discovered potential evidence for the modest benefit of IA HA injections in delaying TKR.¹²

More detailed research work on a large sample of patients with knee OA and the requirement of TKR as a condition for inclusion using US administrative claims data has demonstrated the TKR-delaying effects of IA HA injections in comparison with a control group without claims for IA HA injections.^13,14 This study also uses real-world US administrative data but utilizes a different approach by starting with a sample of patients with knee OA and evidence of IA HA injections and then assessing the effect of repeated courses of HA treatment on the delay of TKR, without TKR as a mandatory condition for inclusion. All patients with knee OA within the time window were included, regardless of the need for TKR compared with previous studies which only considered patients who ultimately received TKR. Safety information and effectiveness information were examined to achieve a balanced risk-benefit assessment. We also analyzed how multiple courses of HA treatment and other potentially relevant covariates at baseline affected the risk of receiving TKR in a multivariate survival model. We aimed to achieve a realistic assessment of the clinical utility of HA injections in delaying TKR in a real-world setting using both safety and effectiveness data.

METHODS

DATA SOURCE

A retrospective cohort observational study using IMS Health’s PharMetrics Plus Health Plan Claims Database was conducted by identifying knee OA patients with claims indicating initiation of HA injection at an index date during the selection period (July 1, 2007 to June 30, 2010). All common HA agents in the US market during this period (Euflexxa, Hyalgan, Orthovisc, Supartz, and Synvisc) were selected via the corresponding J-codes and pooled for investigation of HA class effects. The follow-up period was 36 months, post-index date of the initial HA injection. Outcomes were measured, and adverse events were identified during this period. The time window for identification of adverse events was within 2 weeks from any injection during the course of therapy (evidence of an emergency room visit and/or physician office visit with requisite code). The data during the 12-month pre-index baseline period from the claims database was used to obtain information about baseline patient characteristics, such as age, gender, type of coverage, physician specialty, Charlson Comorbidity Index (CCI), major comorbidities, and major medications of interest commonly used among patients with knee OA.

STUDY SAMPLE SELECTION

The eligible patients required an outpatient claim indicating the initiation of HA injection. The date of the first claim for the patient within the selection window was defined as their index date. Patients had to be ≥18 years of age in the year of their index date. They had to present at least 1 clinical knee OA diagnosis at any point in the 12-month pre-index period (including the index date), and only patients who were continuously enrolled from 12 months pre-index to 36 months post-index date were evaluated. Among these patients (approximately 1.4 million), the following were excluded to minimize complications in data analysis and interpretation: patients with evidence of any HA use in the pre-index period; patients with evidence of a different kind of HA index medication in the post-index period; patients with evidence of TKR within 30 days of the index event during the post-index period; patients with evidence of 2 different kinds of HA index medications on the index date; and patients with evidence of diagnosis of hip OA, fibromyalgia, rheumatoid arthritis, lupus, or gout during the pre-index period.

Five patient cohorts were defined according to the number of courses of IA HA injections over the entire post-index period.

Continue to: Statistical analysis...

STATISTICAL ANALYSIS

All statistical analyses were performed using SAS version 9.2 (SAS Institute Inc.). Descriptive statistics such as means, standard deviations, medians, and 25% and 75% percentiles (Q1 and Q3, respectively) were provided for the continuous variables. Numbers and percentages were provided for the categorical variables. For statistical testing, Student’s t-tests were applied for the continuous variables and chi-square tests for the categorical variables. All the statistical tests were two-tailed. The sample sizes in this database study are remarkably large, such that differences that are not clinically important could still be statistically significant at the conventional alpha level of 0.05. Thus, we applied a more stringent requirement of the alpha level of 0.0001 to identify highly statistically significant results. The number and percentage of patients within each cohort with at least 1 instance of an adverse event of interest (those adverse events commonly expected for patients who receive IA injections for knee OA) were assessed. Times to TKR during the 36-month post-index period were analyzed and compared among different cohorts. Any patients who had not undergone TKR by the end of the post-index period were considered censored at 36 months. The Kaplan-Meier method was employed to model survival curves with time to TKR data, and log-rank tests were used to compare survival curves among different cohorts. A Cox proportional hazards model (PHM) was used to model the risk of TKR with a pre-specified set of covariates adjusted for baseline attributes, such as age, gender, comorbidities, and pre-index healthcare costs. Hazard ratios with 95% confidence intervals were used to examine the measures of event risk.

RESULTS

PATIENT CHARACTERISTICS

Applying study selection criteria to the claims database yielded 50,389 patients (Figure 1), providing an ample sample size for the statistical analysis. Only patients with evidence of knee OA and use of HA injections (the index medication of interest) were selected, regardless of whether they received TKR during the post-index period. The requirement for a knee OA diagnosis during the 12-month pre-index period resulted in the significant attrition of patients, with 584,956 patients being excluded. Among the 50,389 patients who received HA for treatment of knee OA, 36,260 (72.0%) received a single course of treatment, 8709 (17.3%) received 2 courses, 3179 (6.3%) received 3 courses, 1354 (2.7%) received 4 courses, and 887 (1.8%) received ≥5 courses of treatment.

Comparison of baseline characteristics among the 5 IA HA cohorts showed the fairly similar baseline characteristics of all cohorts (Table 1). Geographic region, physician specialty, and opioid use showed differences among the cohorts. Cohorts with ≥5 HA courses presented lower proportions of patients from Southern US states, patients seeing orthopedic surgeons, and patients using opioids than cohorts with fewer HA courses.

PROCEDURES OF INTEREST

An analysis of the procedures patients received after HA treatment initiation showed that higher numbers of HA treatment courses resulted in lower proportions of patients receiving TKR within 3 years after HA treatment initiation (Table 2). With an increasing number of HA treatment courses, the proportion of patients with TKR within 3 years post-index consistently decreased from 28.4% (for 1 HA course) to 5.0% (for ≥5 HA courses), with all differences being highly statistically significant (P < .0001). Similarly, partial knee replacement exhibited a similar trend, with the proportion of patients decreasing from 3.3% (for 1 HA course) to 0.8% (for ≥5 HA courses; P < .0001). Among the patients with TKR within 3 years post-index, increasing numbers of treatment courses correlated with increasing time to TKR, with a mean of 375.6 days (for 1 HA course) rising to a mean of 971.5 days (for ≥5 HA courses; P < .0001). On the other hand, patients with multiple courses of HA treatment were more likely to undergo radiologic examinations of the knee, arthrocenteses, and image-guided injections than patients with only a single course of HA treatment (P < .0001).

ADVERSE EVENTS

Arthralgia and joint pain in the knee were the most commonly recorded adverse events (Table 3). More courses of HA treatment were associated with higher rates of adverse events. Overall, the reported adverse events profile of repeated courses of HA treatment consisted of mostly common and mild adverse events and displayed no safety concern for patients with knee OA that was followed-up for 3 years. The causality of these adverse events directly related to HA injections vs a specific disease state cannot be determined from an administrative claims data set.

TIME TO TKR

Successive courses of HA led to high proportions of patients without TKR 3 years after HA treatment initiation. This result is evident in the Kaplan-Meier survival curves of time to TKR for different HA cohorts (Figure 2), with log-rank tests of multiple courses vs a single course of HA (P < .0001) showing highly statistically significance. Tabulation of proportions of patients without TKR by various time points showed that increasing numbers of HA treatment courses correlated with higher proportions of patients without TKR at almost all time points (Table 4); within 3 years post-index, 71.6% of patients in the 1 HA course cohort exhibited no TKR, whereas 95.0% of patients in ≥5 HA courses cohort presented no TKR. We also performed a multivariate Cox PHM (Table 5) to account for baseline characteristics of different HA cohorts with covariates when estimating the risks of receiving TKR. The results of the Cox PHM showed that multiple courses of HA treatment significantly decreased the risk of TKR (hazard ratio, 0.138 for ≥5 HA courses vs 1 HA course; P < .0001). Inspection of other highly significant covariates showed that being older, living in the Midwest region of the US (vs the Northeast), receiving pre-index corticosteroids, having an orthopedic surgeon as a treating physician (vs a general practitioner, a rheumatologist, or a physical medicine and rehabilitation specialist), experiencing hypertension or hyperlipidemia, and higher pre-index total healthcare costs were associated with an increased risk of TKR (all P < .0001). Vascular disease and high CCI scores were associated with a decreased risk of TKR (P < .0001).

Continue to: Discussion...

DISCUSSION

This study demonstrated that multiple courses of HA treatment can delay the need for surgery for up to 3 years, with risk for both TKR and partial knee replacement decreasing in a dose-dependent manner. The potentially confounding effect of differences in baseline characteristics that could influence patients’ propensity to receive TKR in a database study was controlled by performing a multivariate analysis with covariate adjustment. The TKR-delaying effect of HA injection was more prominent in cohorts with a high number of HA treatment courses: 19 out of 20 patients in the cohort of ≥5 HA courses were free of TKR at the end of the 3-year post-index period. Such a high proportion of patients avoiding TKR with repeated courses of HA suggests that some patients may be able to successfully delay TKR well beyond the 3-year time span. This finding is counter-evidence to the frequently made assumption¹⁵ that all patients with knee OA will eventually progress to a state of disability, making TKR inevitable. The patients with end-stage radiographic knee OA can also benefit from IA HA injections for an extended period of time;¹⁶ the latest evidence indicates that nonoperative management can improve symptoms irrespective of radiographic disease severity, implying that TKR needs not to be the only therapeutic option for patients with end-stage radiographic knee OA.¹⁷ This finding suggests that HA treatment should be considered an important clinical treatment option for patients with knee OA.

Although the incidence rates of certain adverse events, such as arthralgia/joint pain, are sizable, these temporary adverse events commonly occur among patients who receive IA injections for knee OA; most of these events may simply include symptoms of the remaining underlying knee OA. These results are consistent with those of previous literature reporting the safety of repeated treatment with IA HA injections in a prospective clinical trial¹⁸ and demonstrating that repeated courses of HA treatment pose no greater safety risk than a single course of HA treatment.

Multivariate modeling outcomes of factors influencing risk of receiving TKR are broadly consistent with the generally accepted notions that different levels of disease severity and patients’ willingness to consider TKR at baseline influence the likelihood and timing of receiving TKR.^19,20 Age and obesity are common risk factors for progression of OA. Orthopedic surgeons are more likely to recommend surgery than non-surgeons. The pre-index use of corticosteroids and high pre-index healthcare costs could be associated with more severe symptoms at baseline. Patients with vascular disease or severe comorbidities, as evidenced by high CCI scores, make poor candidates for major elective surgeries such as TKR. These results are intuitive and validate the clinical insights of this study. Moreover, inclusion of these covariates in the analysis model allows for indirect adjustment of the most important prognostic factors for TKR at baseline, permitting proper statistical comparison of the results for different cohort groups.

Recently, the efficacy of HA injections for OA patients has become the subject of debate when the American Academy of Orthopaedic Surgeons (AAOS) revised its clinical practice guideline, recommending against the use of HA.²¹ The AAOS’ findings differ from those of other clinical societies, such as the American College of Rheumatology²² and the European League Against Rheumatism,²³ which provide no strong recommendation against the use of HA injections. The announcement of the new guideline by AAOS caused concern among clinicians and payers who had valued IA HA injections as a means to control knee OA pain before patients progress to TKR;²⁴ on the other hand, the demand for nonoperative treatment of knee OA remains high. Utilization rates of TKR have increased dramatically, and surgeries are now performed on younger patients with increasing burden on the healthcare system,^25,26 in spite of the fact that as high as a third of TKR surgeries may have been performed in inappropriate patients.²⁷ Part of the confusion surrounding clinical utility of HA stems from the fact that up until recently, relatively little research looked into the practical benefits of HA in actual clinical practice. Analyses of databases such as registries are now gaining attention to overcome that problem. Examination of large administrative databases maintained by commercial payers offers the benefit of probing realistically the safety and efficacy of treatments in actual clinical environments in a very large number of patients with heterogeneous backgrounds. Recently, the Agency for Healthcare Research and Quality’s Technology Assessment Program in the US called for such studies to determine whether HA injections can delay progression to TKR.²⁸ The results of this study and several others^11,13,14,16 suggest that use of HA to treat OA of the knee is associated with the delay of TKR, supporting the utility of HA in clinical practice and the healthcare system. Potential clinical benefits of delaying TKR may include the reduced risk of aseptic loosening if younger patients can wait for TKR or more time to allow the modification of risk factors in patients who will ultimately undergo TKR.

LIMITATIONS

Follow-up period was limited to 3 years post-index date because longer follow-up data were not available at the time of the study design. If an incorrect adverse event or OA diagnosis was listed in the medical record, or if the medical record was incomplete, then patients might have been misclassified, resulting in selection bias. The claims dataset includes no uninsured and Medicare patients, as the population in the database consisted primarily of commercially-insured patients in the US. Therefore, the results are most generalizable to other commercially-insured patients in the US. Generalizability to other populations may not be assured if they differ in their accessibility to physician services or prescriptions from the patients in this study. Other treatments such as the nonsteroidal anti-inflammatory drugs used by patients were not included within the pre-specified statistical model because their potential effects were assumed to be short-lived and much less than those of corticosteroid. Including these treatments would overload the statistical model with too many covariates, leading to potential computational instability. The database used provides no information on systemic factors, including plan limits on medication use, that could affect care. Given the large and diverse nature of the healthcare plans in the database. However, these factors should not have materially affected our study results. The claims database also lacks direct indicators of OA disease severity, such as Kellgren-Lawrence scores or patient-reported outcomes, including pain and function questionnaire scores. Our multivariate analysis indirectly makes up for this deficiency by considering other baseline characteristics or clinical indicators that may be correlated with information unavailable in a claims database. Patients who opt to undergo repeated courses of HA treatment may be more inclined to avoid surgery or may naturally experience OA disease progression more slowly, making them potentially different from patients who select to undergo surgery earlier without repeated courses of HA treatment. This condition may introduce a bias that causes difficulty in proving the causality between repeated HA use and delay of TKR.

CONCLUSION

Analysis of the knee OA patient data from a real-world database showed that repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effects of repeated HA courses on delaying TKR beyond a 3-year period.

ABSTRACT

Despite advancements in surgical technique and understanding of throwing mechanics, controversy persists regarding the treatment of grade III acromioclavicular (AC) joint separations, particularly in throwing athletes. Twenty-eight major league baseball (MLB) orthopedic team physicians were surveyed to determine their definitive management of a grade III AC separation in the dominant arm of a professional baseball pitcher and their experience treating AC joint separations in starting pitchers and position players. Return-to-play outcomes were also evaluated. Twenty (71.4%) team physicians recommended nonoperative intervention compared to 8 (28.6%) who would have operated acutely. Eighteen (64.3%) team physicians had treated at least 1 professional pitcher with a grade III AC separation; 51 (77.3%) pitchers had been treated nonoperatively compared to 15 (22.7%) operatively. No difference was observed in the proportion of pitchers who returned to the same level of play (P = .54), had full, unrestricted range of motion (P = .23), or had full pain relief (P = .19) between the operatively and nonoperatively treated MLB pitchers. The majority (53.6%) of physicians would not include an injection if the injury was treated nonoperatively. Open coracoclavicular reconstruction (65.2%) was preferred for operative cases; 66.7% of surgeons would also include distal clavicle excision as an adjunct procedure. About 90% of physicians would return pitchers to throwing >12 weeks after surgery compared to after 4 to 6 weeks in nonoperatively treated cases. In conclusion, MLB team physicians preferred nonoperative management for an acute grade III AC joint separation in professional pitchers. If operative intervention is required, ligament reconstruction with adjunct distal clavicle excision were the most commonly performed procedures.

Continue to: Despite advancements in surgucal technique...

Despite advancements in surgical technique and improved understanding of the physiology of throwing mechanics, controversy persists regarding the preferred treatment for grade III acromioclavicular (AC) joint separations.^1-6 Nonsurgical management has demonstrated return to prior function with fewer complications.⁷ However, there is a growing body of evidence demonstrating that surgical intervention is associated with more favorable outcomes⁸ and should be considered in patients who place high functional demands on their shoulders.⁹

The reported results on professional athletes in the literature remain ambivalent. Multiple small case reports/series have reported successful nonoperative treatment of elite athletes.^10-12 Not surprisingly, McFarland and colleagues¹³ reported in 1997 that 69% of major league baseball (MLB) team physicians preferred nonoperative treatment for a theoretical starting pitcher sustaining a grade III AC separation 1 week prior to the start of the season. In contrast, reports of an inability to throw at a pre-injury level are equally commonplace.^14,15 Nevertheless, all of these studies were limited to small cohorts, as the incidence of grade III AC separations in elite throwing athletes is relatively uncommon.^13,16

In this study, we re-evaluated the study performed by McFarland and colleagues¹³ in 1997 by surveying all active MLB team orthopedic surgeons. We asked them how they would treat a grade III AC separation in a starting professional baseball pitcher. The physicians were also asked about their personal experience evaluating outcomes in these elite athletes. Given our improved understanding of the anatomy, pathophysiology, and surgical techniques for treating grade III AC separations, we hypothesize that more MLB team physicians would favor operative intervention treatment in professional baseball pitchers, as their vocation places higher demands on their shoulders.

MATERIALS AND METHODS

A questionnaire (Appendix A) was distributed to the team physicians of all 30 MLB teams. In addition to surgeon demographics, including age, years in practice, and years of taking care of an MLB team, the initial section of the questionnaire asked orthopedic surgeons how they would treat a theoretical starting pitcher who sustained a grade III AC joint separation of the dominant throwing arm 1 week prior to the start of the season. Physicians who preferred nonoperative treatment were asked whether they would use an injection (and what type), as well as when they would allow the pitcher to start a progressive interval throwing program. Physicians who preferred operative treatment were asked to rank their indications for operating, what procedure they would use (eg, open vs arthroscopic or coracoclavicular ligament repair vs reconstruction), and whether the surgical intervention would include distal clavicle excision. Both groups of physicians were also asked if their preferred treatment would change if the injury were to occur at the end of the season.

The second portion of the questionnaire asked surgeons about their experience treating AC joint separations in both starting pitchers and position players, as well as to describe the long-term outcomes of their preferred treatment, including time to return to full clearance for pitching, whether their patients returned to their prior level of play, and whether these patients had full pain relief. Finally, physicians were asked if any of the nonoperatively treated players ultimately crossed over and required operative intervention.

Continue to: Statistics...

STATISTICS

Descriptive statistics were used for continuous variables, and frequencies were used for categorical variables. Linear regression was performed to determine the correlation between the physician’s training or experience in treating AC joint separations and their recommended treatment. Fischer’s exact test/chi-square analysis was used to compare categorical variables. All tests were conducted using 2-sided hypothesis testing with statistical significance set at P < .05. All statistical analyses were conducted with SPSS 21.0 software (IBM Corporation).

RESULTS

A total of 28 MLB team physicians completed the questionnaires from 18 of the 30 MLB teams. The average age of the responders was 50.5 years (range, 34-60 years), with an average of 18.2 years in practice (range, 2-30 years) and 10.8 years (range, 1-24 years) taking care of their current professional baseball team. About 82% of the team physicians completed a sports medicine fellowship. On average, physicians saw 16.6 (range, 5-50) grade III or higher AC joint separations per year, and operated on 4.6 (range, 0-10) per year.

Nonoperative treatment was the preferred treatment for a grade III AC joint separation in a starting professional baseball pitcher for the majority of team physicians (20/28). No correlation was observed between the physician’s age (P = .881), years in practice (P = .915), years taking care of their professional team (P = .989), percentage of practice focused on shoulders (P = .986), number of AC joint injuries seen (P = .325), or number of surgeries performed per year (P = .807) with the team physician’s preferred treatment. Compared to the proportion reported originally by McFarland and colleagues¹³ in 1997 (69%), there was no difference in the proportion of team physicians that recommended nonoperative treatment (P = 1).

If treating this injury nonoperatively, 46.4% of physicians would also use an injection, with orthobiologics (eg, platelet-rich plasma) as the most popular choice (Table 1). No consensus was provided on the timeframe to return pitchers back to a progressive interval throwing program; however, 46.67% of physicians would return pitchers 4 to 6 weeks after a nonoperatively treated injury, while 35.7% would return pitchers 7 to 12 weeks after the initial injury.

Table 1. Treatment Preferences of Grade III AC Separation by MLB Team Physicians

^aRespondents were allowed to choose more than 1 treatment in each category. ^bChosen as an adjunct treatment.

Abbreviations: AC, acromioclavicular; MLB, major league baseball.

Most physicians (64.3%) cited functional limitations as the most important reason for indicating operative treatment, followed by pain (21.4%), and a deformity (14.3%). About 65% preferred open coracoclavicular ligament reconstruction. No physician recommended the Weaver-Dunn procedure or use of hardware (eg, hook plate). Of those who preferred an operative intervention, 66.7% would also include a distal clavicle excision, which is significantly higher than the proportion reported by McFarland and colleagues¹³ (23%, P = .0170). About 90% of physicians would return pitchers to play >12 weeks after operative treatment.

Continue to: If the injury occurred at the end ...

If the injury occurred at the end of the season, 7 of the 20 orthopedists (35%) who recommended nonoperative treatment said they would change to an operative intervention. Eighteen of 28 responders would have the same algorithm for MLB position players. Team physicians were less likely to recommend operative intervention in position players due to less demand on the arm and increased ability to accommodate the injury by altering their throwing mechanics.

Eighteen (64%) of the team physicians had treated at least 1 professional pitcher with a grade III AC separation in his dominant arm, and 11 (39.3%) had treated >1. Collectively, team physicians had treated 15 professional pitchers operatively, and 51 nonoperatively; only 3 patients converted to operative intervention after a failed nonoperative treatment.

Of the pitchers treated operatively, 93.3% (14) of pitchers returned to their prior level of pitching. The 1 patient who failed to return to the same level of pitching retired instead of returning to play. About 80% (12) of the pitchers had full pain relief, and 93.3% (14) had full range of motion (ROM). The pitcher who failed to regain full ROM also had a concomitant rotator cuff repair. The only complication reported from an operative intervention was a pitcher who sustained a coracoid fracture 10 months postoperatively while throwing 100 mph. Of the pitchers treated nonoperatively, 96% returned to their prior level of pitching, 92.2% (47) had full complete pain relief when throwing, and 100% had full ROM. No differences were observed between the proportion of pitchers who returned to their prior level of pitching, regained full ROM, or had full pain relief in the operative and nonoperative groups (Table 2).

Table 2. Outcomes of Treatment of Grade III AC Separation in 58 Professional Baseball Players

Abbreviations: AC, acromioclavicular; ROM, range of motion.

DISCUSSION 

Controversy persists regarding the optimal management of acute grade III AC separations, with the current available evidence potentially suggesting better cosmetic and radiological results but no definite differences in clinical results.^1-6,17,18 In the absence of formal clinical practice guidelines, surgeons rely on their own experience or defer to the anecdotal experience of experts in the field. Our initial hypothesis was false in this survey of MLB team physicians taking care of overhead throwing athletes at the highest level. Our results demonstrate that despite improved techniques and an increased understanding of the pathophysiology of AC joint separations, conservative management is still the preferred treatment for acute grade III AC joint separations in professional baseball pitchers. The proportion of team physicians recommending nonoperative treatment in our series was essentially equivalent to the results reported by McFarland and colleagues¹³ in 1997, suggesting that the pendulum continues to favor conservative management initially. This status quo likely reflects both the dearth of literature suggesting a substantial benefit of acute operative repair, as well as the ability to accommodate with conservative measures after most grade III AC injuries, even at the highest level of athletic competition.

These results are also consistent with trends from the last few decades. In the 1970s, the overwhelming preference for treating an acute complete AC joint separation was surgical repair, with Powers and Bach¹⁰ reporting in a 1974 survey of 163 chairmen of orthopedic programs around the country that 91.5% advocated surgical treatment. However, surgical preference had reversed by the 1990s. Of the 187 chairmen and 59 team physicians surveyed by Cox¹⁹ in 1992, 72% and 86% respectively preferred nonoperative treatment in a theoretical 21-year-old athlete with a grade III AC separation. Nissen and Chatterjee²⁰ reported in 2007 on a survey of all American Orthopaedic Society for Sports Medicine surgeons (N = 577) and Accreditation Council for Graduate Medical Education orthopedic program residency directors (N = 87) that >80% of responders preferred conservative measures for this acute injury. The reversal of trends has also been corroborated by recent multicenter trials demonstrating no difference in clinical outcomes between operative and nonoperative treatment of high grade AC joint dislocations, albeit these patients were not all high level overhead throwing athletes.^17,18

Continue to: The trends in surgical interventions are notable...

The trends in surgical interventions are notable within the smaller subset of patients who are indicated for operative repair. Use of hardware and primary ligament repair, while popular in the surveys conducted in the 1970s¹⁰ and 1990s¹³ and even present in Nissen and Chatterjee’s²⁰ 2007 survey, were noticeably absent from our survey results, with the majority of respondents preferring open coracoclavicular ligament reconstruction. The role of distal clavicle excision has also expanded, from 23% of team physicians recommending it in 1997¹³ to 57% to 59% in Nissen and Chatterjee’s²⁰ 2007 survey, to 66.7% in our series. This trend is not surprising as several recent cadaveric biomechanical studies have demonstrated that not only do peak graft forces not increase significantly,²¹ the anterior-posterior and superior-inferior motion at the AC joint following ligament reconstruction is maintained despite resection of the lateral clavicle.²² Additionally, primary distal clavicle excision may prevent the development of post-traumatic arthritis at the AC joint and osteolysis of the distal clavicle as a possible pain generator in the future.²³ However, some respondents cautioned against performing a concomitant distal clavicle excision, as some biomechanical data demonstrate that resecting the distal clavicle may lead to increased horizontal translation at the AC joint despite intact superior and posterior AC capsules.²⁴ Professional baseball pitchers may also be more lax and thus prone to more instability. Primary repair or reconstruction may not always lead to complete pre-injury stability in these individuals. This subtle unrecognized instability is hard to diagnosis and may be a persistent source of pain; thus, adding a distal clavicle excision may actually exacerbate the instability.

The nuanced indications for operative intervention, such as the presence of associated lesions were not captured by our survey.²⁵ While most team physicians cited functional limitations as their most common reason for offering surgery, several MLB orthopedic surgeons also commented on evaluating the stability of the AC joint after a grade III injury, akin to the consensus statement from the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) Upper Extremity Committee²⁶ in 2014 that diversified the Rockwood Grade III AC joint separation into its IIIA and IIIB classifications. The ISAKOS recommendations include initial conservative management and a second evaluation (both clinical and radiographic) for grade III lesions 3 to 6 weeks after the injury. However, as professional baseball is an incredibly profitable sport with an annual revenue approaching $9.5 billion²⁷ and pitching salaries up to $32.5 million in 2015, serious financial considerations must be given to players who wish to avoid undergoing delayed surgery.

This study has shortcomings typical of expert opinion papers. The retrospective nature of this study places the data at risk of recall bias. Objective data (eg, terminal ROM, pain relief, and return to play) were obtained from a retrospective chart review; however, no standard documentation or collection method was used given the number of surgeons involved and, thus, conclusions based on treatment outcomes are imperfect. Another major weakness of this survey is the relatively small number of patients and respondents. An a priori power analysis was not available, as this was a retrospective review. A comparative trial will be necessary to definitively support one treatment over another. Assuming a 95% return to play in the nonoperatively treated group, approximately 300 patients would be needed in a prospective 2-armed study with 80% power to detect a 10% reduction in the incidence of return to play using an alpha level of 0.05 and assuming no loss to follow-up. This sample size would be difficult to achieve in this patient population.

However, compared to past series,¹³ the number of professional baseball players treated by the collective experience of these MLB team physicians is the largest reported to date. As suggested above, the rarity of this condition in elite athletes precludes the ability to have matched controls to definitively determine the optimal treatment, which may explain the lack of difference in the return to play, ROM, and pain relief outcomes. Instead, we can only extrapolate based on the collective anecdotal experience of the MLB team physicians.

CONCLUSION

Despite advances in surgical technique and understanding of throwing mechanics, the majority of MLB team physicians preferred nonoperative management for an acute grade III AC joint separation in a professional baseball pitcher. Open coracoclavicular ligament reconstruction was preferred for those who preferred operative intervention. An increasing number of orthopedic surgeons now consider a distal clavicle excision as an adjunct procedure.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

Despite advancements in surgical technique and understanding of throwing mechanics, controversy persists regarding the treatment of grade III acromioclavicular (AC) joint separations, particularly in throwing athletes. Twenty-eight major league baseball (MLB) orthopedic team physicians were surveyed to determine their definitive management of a grade III AC separation in the dominant arm of a professional baseball pitcher and their experience treating AC joint separations in starting pitchers and position players. Return-to-play outcomes were also evaluated. Twenty (71.4%) team physicians recommended nonoperative intervention compared to 8 (28.6%) who would have operated acutely. Eighteen (64.3%) team physicians had treated at least 1 professional pitcher with a grade III AC separation; 51 (77.3%) pitchers had been treated nonoperatively compared to 15 (22.7%) operatively. No difference was observed in the proportion of pitchers who returned to the same level of play (P = .54), had full, unrestricted range of motion (P = .23), or had full pain relief (P = .19) between the operatively and nonoperatively treated MLB pitchers. The majority (53.6%) of physicians would not include an injection if the injury was treated nonoperatively. Open coracoclavicular reconstruction (65.2%) was preferred for operative cases; 66.7% of surgeons would also include distal clavicle excision as an adjunct procedure. About 90% of physicians would return pitchers to throwing >12 weeks after surgery compared to after 4 to 6 weeks in nonoperatively treated cases. In conclusion, MLB team physicians preferred nonoperative management for an acute grade III AC joint separation in professional pitchers. If operative intervention is required, ligament reconstruction with adjunct distal clavicle excision were the most commonly performed procedures.

Continue to: Despite advancements in surgucal technique...

Despite advancements in surgical technique and improved understanding of the physiology of throwing mechanics, controversy persists regarding the preferred treatment for grade III acromioclavicular (AC) joint separations.^1-6 Nonsurgical management has demonstrated return to prior function with fewer complications.⁷ However, there is a growing body of evidence demonstrating that surgical intervention is associated with more favorable outcomes⁸ and should be considered in patients who place high functional demands on their shoulders.⁹

The reported results on professional athletes in the literature remain ambivalent. Multiple small case reports/series have reported successful nonoperative treatment of elite athletes.^10-12 Not surprisingly, McFarland and colleagues¹³ reported in 1997 that 69% of major league baseball (MLB) team physicians preferred nonoperative treatment for a theoretical starting pitcher sustaining a grade III AC separation 1 week prior to the start of the season. In contrast, reports of an inability to throw at a pre-injury level are equally commonplace.^14,15 Nevertheless, all of these studies were limited to small cohorts, as the incidence of grade III AC separations in elite throwing athletes is relatively uncommon.^13,16

In this study, we re-evaluated the study performed by McFarland and colleagues¹³ in 1997 by surveying all active MLB team orthopedic surgeons. We asked them how they would treat a grade III AC separation in a starting professional baseball pitcher. The physicians were also asked about their personal experience evaluating outcomes in these elite athletes. Given our improved understanding of the anatomy, pathophysiology, and surgical techniques for treating grade III AC separations, we hypothesize that more MLB team physicians would favor operative intervention treatment in professional baseball pitchers, as their vocation places higher demands on their shoulders.

MATERIALS AND METHODS

A questionnaire (Appendix A) was distributed to the team physicians of all 30 MLB teams. In addition to surgeon demographics, including age, years in practice, and years of taking care of an MLB team, the initial section of the questionnaire asked orthopedic surgeons how they would treat a theoretical starting pitcher who sustained a grade III AC joint separation of the dominant throwing arm 1 week prior to the start of the season. Physicians who preferred nonoperative treatment were asked whether they would use an injection (and what type), as well as when they would allow the pitcher to start a progressive interval throwing program. Physicians who preferred operative treatment were asked to rank their indications for operating, what procedure they would use (eg, open vs arthroscopic or coracoclavicular ligament repair vs reconstruction), and whether the surgical intervention would include distal clavicle excision. Both groups of physicians were also asked if their preferred treatment would change if the injury were to occur at the end of the season.

The second portion of the questionnaire asked surgeons about their experience treating AC joint separations in both starting pitchers and position players, as well as to describe the long-term outcomes of their preferred treatment, including time to return to full clearance for pitching, whether their patients returned to their prior level of play, and whether these patients had full pain relief. Finally, physicians were asked if any of the nonoperatively treated players ultimately crossed over and required operative intervention.

Continue to: Statistics...

STATISTICS

Descriptive statistics were used for continuous variables, and frequencies were used for categorical variables. Linear regression was performed to determine the correlation between the physician’s training or experience in treating AC joint separations and their recommended treatment. Fischer’s exact test/chi-square analysis was used to compare categorical variables. All tests were conducted using 2-sided hypothesis testing with statistical significance set at P < .05. All statistical analyses were conducted with SPSS 21.0 software (IBM Corporation).

RESULTS

A total of 28 MLB team physicians completed the questionnaires from 18 of the 30 MLB teams. The average age of the responders was 50.5 years (range, 34-60 years), with an average of 18.2 years in practice (range, 2-30 years) and 10.8 years (range, 1-24 years) taking care of their current professional baseball team. About 82% of the team physicians completed a sports medicine fellowship. On average, physicians saw 16.6 (range, 5-50) grade III or higher AC joint separations per year, and operated on 4.6 (range, 0-10) per year.

Nonoperative treatment was the preferred treatment for a grade III AC joint separation in a starting professional baseball pitcher for the majority of team physicians (20/28). No correlation was observed between the physician’s age (P = .881), years in practice (P = .915), years taking care of their professional team (P = .989), percentage of practice focused on shoulders (P = .986), number of AC joint injuries seen (P = .325), or number of surgeries performed per year (P = .807) with the team physician’s preferred treatment. Compared to the proportion reported originally by McFarland and colleagues¹³ in 1997 (69%), there was no difference in the proportion of team physicians that recommended nonoperative treatment (P = 1).

If treating this injury nonoperatively, 46.4% of physicians would also use an injection, with orthobiologics (eg, platelet-rich plasma) as the most popular choice (Table 1). No consensus was provided on the timeframe to return pitchers back to a progressive interval throwing program; however, 46.67% of physicians would return pitchers 4 to 6 weeks after a nonoperatively treated injury, while 35.7% would return pitchers 7 to 12 weeks after the initial injury.

Table 1. Treatment Preferences of Grade III AC Separation by MLB Team Physicians

^aRespondents were allowed to choose more than 1 treatment in each category. ^bChosen as an adjunct treatment.

Abbreviations: AC, acromioclavicular; MLB, major league baseball.

Most physicians (64.3%) cited functional limitations as the most important reason for indicating operative treatment, followed by pain (21.4%), and a deformity (14.3%). About 65% preferred open coracoclavicular ligament reconstruction. No physician recommended the Weaver-Dunn procedure or use of hardware (eg, hook plate). Of those who preferred an operative intervention, 66.7% would also include a distal clavicle excision, which is significantly higher than the proportion reported by McFarland and colleagues¹³ (23%, P = .0170). About 90% of physicians would return pitchers to play >12 weeks after operative treatment.

Continue to: If the injury occurred at the end ...

If the injury occurred at the end of the season, 7 of the 20 orthopedists (35%) who recommended nonoperative treatment said they would change to an operative intervention. Eighteen of 28 responders would have the same algorithm for MLB position players. Team physicians were less likely to recommend operative intervention in position players due to less demand on the arm and increased ability to accommodate the injury by altering their throwing mechanics.

Eighteen (64%) of the team physicians had treated at least 1 professional pitcher with a grade III AC separation in his dominant arm, and 11 (39.3%) had treated >1. Collectively, team physicians had treated 15 professional pitchers operatively, and 51 nonoperatively; only 3 patients converted to operative intervention after a failed nonoperative treatment.

Of the pitchers treated operatively, 93.3% (14) of pitchers returned to their prior level of pitching. The 1 patient who failed to return to the same level of pitching retired instead of returning to play. About 80% (12) of the pitchers had full pain relief, and 93.3% (14) had full range of motion (ROM). The pitcher who failed to regain full ROM also had a concomitant rotator cuff repair. The only complication reported from an operative intervention was a pitcher who sustained a coracoid fracture 10 months postoperatively while throwing 100 mph. Of the pitchers treated nonoperatively, 96% returned to their prior level of pitching, 92.2% (47) had full complete pain relief when throwing, and 100% had full ROM. No differences were observed between the proportion of pitchers who returned to their prior level of pitching, regained full ROM, or had full pain relief in the operative and nonoperative groups (Table 2).

Table 2. Outcomes of Treatment of Grade III AC Separation in 58 Professional Baseball Players

Abbreviations: AC, acromioclavicular; ROM, range of motion.

DISCUSSION 

Controversy persists regarding the optimal management of acute grade III AC separations, with the current available evidence potentially suggesting better cosmetic and radiological results but no definite differences in clinical results.^1-6,17,18 In the absence of formal clinical practice guidelines, surgeons rely on their own experience or defer to the anecdotal experience of experts in the field. Our initial hypothesis was false in this survey of MLB team physicians taking care of overhead throwing athletes at the highest level. Our results demonstrate that despite improved techniques and an increased understanding of the pathophysiology of AC joint separations, conservative management is still the preferred treatment for acute grade III AC joint separations in professional baseball pitchers. The proportion of team physicians recommending nonoperative treatment in our series was essentially equivalent to the results reported by McFarland and colleagues¹³ in 1997, suggesting that the pendulum continues to favor conservative management initially. This status quo likely reflects both the dearth of literature suggesting a substantial benefit of acute operative repair, as well as the ability to accommodate with conservative measures after most grade III AC injuries, even at the highest level of athletic competition.

These results are also consistent with trends from the last few decades. In the 1970s, the overwhelming preference for treating an acute complete AC joint separation was surgical repair, with Powers and Bach¹⁰ reporting in a 1974 survey of 163 chairmen of orthopedic programs around the country that 91.5% advocated surgical treatment. However, surgical preference had reversed by the 1990s. Of the 187 chairmen and 59 team physicians surveyed by Cox¹⁹ in 1992, 72% and 86% respectively preferred nonoperative treatment in a theoretical 21-year-old athlete with a grade III AC separation. Nissen and Chatterjee²⁰ reported in 2007 on a survey of all American Orthopaedic Society for Sports Medicine surgeons (N = 577) and Accreditation Council for Graduate Medical Education orthopedic program residency directors (N = 87) that >80% of responders preferred conservative measures for this acute injury. The reversal of trends has also been corroborated by recent multicenter trials demonstrating no difference in clinical outcomes between operative and nonoperative treatment of high grade AC joint dislocations, albeit these patients were not all high level overhead throwing athletes.^17,18

Continue to: The trends in surgical interventions are notable...

The trends in surgical interventions are notable within the smaller subset of patients who are indicated for operative repair. Use of hardware and primary ligament repair, while popular in the surveys conducted in the 1970s¹⁰ and 1990s¹³ and even present in Nissen and Chatterjee’s²⁰ 2007 survey, were noticeably absent from our survey results, with the majority of respondents preferring open coracoclavicular ligament reconstruction. The role of distal clavicle excision has also expanded, from 23% of team physicians recommending it in 1997¹³ to 57% to 59% in Nissen and Chatterjee’s²⁰ 2007 survey, to 66.7% in our series. This trend is not surprising as several recent cadaveric biomechanical studies have demonstrated that not only do peak graft forces not increase significantly,²¹ the anterior-posterior and superior-inferior motion at the AC joint following ligament reconstruction is maintained despite resection of the lateral clavicle.²² Additionally, primary distal clavicle excision may prevent the development of post-traumatic arthritis at the AC joint and osteolysis of the distal clavicle as a possible pain generator in the future.²³ However, some respondents cautioned against performing a concomitant distal clavicle excision, as some biomechanical data demonstrate that resecting the distal clavicle may lead to increased horizontal translation at the AC joint despite intact superior and posterior AC capsules.²⁴ Professional baseball pitchers may also be more lax and thus prone to more instability. Primary repair or reconstruction may not always lead to complete pre-injury stability in these individuals. This subtle unrecognized instability is hard to diagnosis and may be a persistent source of pain; thus, adding a distal clavicle excision may actually exacerbate the instability.

The nuanced indications for operative intervention, such as the presence of associated lesions were not captured by our survey.²⁵ While most team physicians cited functional limitations as their most common reason for offering surgery, several MLB orthopedic surgeons also commented on evaluating the stability of the AC joint after a grade III injury, akin to the consensus statement from the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) Upper Extremity Committee²⁶ in 2014 that diversified the Rockwood Grade III AC joint separation into its IIIA and IIIB classifications. The ISAKOS recommendations include initial conservative management and a second evaluation (both clinical and radiographic) for grade III lesions 3 to 6 weeks after the injury. However, as professional baseball is an incredibly profitable sport with an annual revenue approaching $9.5 billion²⁷ and pitching salaries up to $32.5 million in 2015, serious financial considerations must be given to players who wish to avoid undergoing delayed surgery.

This study has shortcomings typical of expert opinion papers. The retrospective nature of this study places the data at risk of recall bias. Objective data (eg, terminal ROM, pain relief, and return to play) were obtained from a retrospective chart review; however, no standard documentation or collection method was used given the number of surgeons involved and, thus, conclusions based on treatment outcomes are imperfect. Another major weakness of this survey is the relatively small number of patients and respondents. An a priori power analysis was not available, as this was a retrospective review. A comparative trial will be necessary to definitively support one treatment over another. Assuming a 95% return to play in the nonoperatively treated group, approximately 300 patients would be needed in a prospective 2-armed study with 80% power to detect a 10% reduction in the incidence of return to play using an alpha level of 0.05 and assuming no loss to follow-up. This sample size would be difficult to achieve in this patient population.

However, compared to past series,¹³ the number of professional baseball players treated by the collective experience of these MLB team physicians is the largest reported to date. As suggested above, the rarity of this condition in elite athletes precludes the ability to have matched controls to definitively determine the optimal treatment, which may explain the lack of difference in the return to play, ROM, and pain relief outcomes. Instead, we can only extrapolate based on the collective anecdotal experience of the MLB team physicians.

CONCLUSION

Despite advances in surgical technique and understanding of throwing mechanics, the majority of MLB team physicians preferred nonoperative management for an acute grade III AC joint separation in a professional baseball pitcher. Open coracoclavicular ligament reconstruction was preferred for those who preferred operative intervention. An increasing number of orthopedic surgeons now consider a distal clavicle excision as an adjunct procedure.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

Despite advancements in surgical technique and understanding of throwing mechanics, controversy persists regarding the treatment of grade III acromioclavicular (AC) joint separations, particularly in throwing athletes. Twenty-eight major league baseball (MLB) orthopedic team physicians were surveyed to determine their definitive management of a grade III AC separation in the dominant arm of a professional baseball pitcher and their experience treating AC joint separations in starting pitchers and position players. Return-to-play outcomes were also evaluated. Twenty (71.4%) team physicians recommended nonoperative intervention compared to 8 (28.6%) who would have operated acutely. Eighteen (64.3%) team physicians had treated at least 1 professional pitcher with a grade III AC separation; 51 (77.3%) pitchers had been treated nonoperatively compared to 15 (22.7%) operatively. No difference was observed in the proportion of pitchers who returned to the same level of play (P = .54), had full, unrestricted range of motion (P = .23), or had full pain relief (P = .19) between the operatively and nonoperatively treated MLB pitchers. The majority (53.6%) of physicians would not include an injection if the injury was treated nonoperatively. Open coracoclavicular reconstruction (65.2%) was preferred for operative cases; 66.7% of surgeons would also include distal clavicle excision as an adjunct procedure. About 90% of physicians would return pitchers to throwing >12 weeks after surgery compared to after 4 to 6 weeks in nonoperatively treated cases. In conclusion, MLB team physicians preferred nonoperative management for an acute grade III AC joint separation in professional pitchers. If operative intervention is required, ligament reconstruction with adjunct distal clavicle excision were the most commonly performed procedures.

Continue to: Despite advancements in surgucal technique...

Despite advancements in surgical technique and improved understanding of the physiology of throwing mechanics, controversy persists regarding the preferred treatment for grade III acromioclavicular (AC) joint separations.^1-6 Nonsurgical management has demonstrated return to prior function with fewer complications.⁷ However, there is a growing body of evidence demonstrating that surgical intervention is associated with more favorable outcomes⁸ and should be considered in patients who place high functional demands on their shoulders.⁹

The reported results on professional athletes in the literature remain ambivalent. Multiple small case reports/series have reported successful nonoperative treatment of elite athletes.^10-12 Not surprisingly, McFarland and colleagues¹³ reported in 1997 that 69% of major league baseball (MLB) team physicians preferred nonoperative treatment for a theoretical starting pitcher sustaining a grade III AC separation 1 week prior to the start of the season. In contrast, reports of an inability to throw at a pre-injury level are equally commonplace.^14,15 Nevertheless, all of these studies were limited to small cohorts, as the incidence of grade III AC separations in elite throwing athletes is relatively uncommon.^13,16

In this study, we re-evaluated the study performed by McFarland and colleagues¹³ in 1997 by surveying all active MLB team orthopedic surgeons. We asked them how they would treat a grade III AC separation in a starting professional baseball pitcher. The physicians were also asked about their personal experience evaluating outcomes in these elite athletes. Given our improved understanding of the anatomy, pathophysiology, and surgical techniques for treating grade III AC separations, we hypothesize that more MLB team physicians would favor operative intervention treatment in professional baseball pitchers, as their vocation places higher demands on their shoulders.

MATERIALS AND METHODS

A questionnaire (Appendix A) was distributed to the team physicians of all 30 MLB teams. In addition to surgeon demographics, including age, years in practice, and years of taking care of an MLB team, the initial section of the questionnaire asked orthopedic surgeons how they would treat a theoretical starting pitcher who sustained a grade III AC joint separation of the dominant throwing arm 1 week prior to the start of the season. Physicians who preferred nonoperative treatment were asked whether they would use an injection (and what type), as well as when they would allow the pitcher to start a progressive interval throwing program. Physicians who preferred operative treatment were asked to rank their indications for operating, what procedure they would use (eg, open vs arthroscopic or coracoclavicular ligament repair vs reconstruction), and whether the surgical intervention would include distal clavicle excision. Both groups of physicians were also asked if their preferred treatment would change if the injury were to occur at the end of the season.

The second portion of the questionnaire asked surgeons about their experience treating AC joint separations in both starting pitchers and position players, as well as to describe the long-term outcomes of their preferred treatment, including time to return to full clearance for pitching, whether their patients returned to their prior level of play, and whether these patients had full pain relief. Finally, physicians were asked if any of the nonoperatively treated players ultimately crossed over and required operative intervention.

Continue to: Statistics...

STATISTICS

Descriptive statistics were used for continuous variables, and frequencies were used for categorical variables. Linear regression was performed to determine the correlation between the physician’s training or experience in treating AC joint separations and their recommended treatment. Fischer’s exact test/chi-square analysis was used to compare categorical variables. All tests were conducted using 2-sided hypothesis testing with statistical significance set at P < .05. All statistical analyses were conducted with SPSS 21.0 software (IBM Corporation).

RESULTS

A total of 28 MLB team physicians completed the questionnaires from 18 of the 30 MLB teams. The average age of the responders was 50.5 years (range, 34-60 years), with an average of 18.2 years in practice (range, 2-30 years) and 10.8 years (range, 1-24 years) taking care of their current professional baseball team. About 82% of the team physicians completed a sports medicine fellowship. On average, physicians saw 16.6 (range, 5-50) grade III or higher AC joint separations per year, and operated on 4.6 (range, 0-10) per year.

Nonoperative treatment was the preferred treatment for a grade III AC joint separation in a starting professional baseball pitcher for the majority of team physicians (20/28). No correlation was observed between the physician’s age (P = .881), years in practice (P = .915), years taking care of their professional team (P = .989), percentage of practice focused on shoulders (P = .986), number of AC joint injuries seen (P = .325), or number of surgeries performed per year (P = .807) with the team physician’s preferred treatment. Compared to the proportion reported originally by McFarland and colleagues¹³ in 1997 (69%), there was no difference in the proportion of team physicians that recommended nonoperative treatment (P = 1).

If treating this injury nonoperatively, 46.4% of physicians would also use an injection, with orthobiologics (eg, platelet-rich plasma) as the most popular choice (Table 1). No consensus was provided on the timeframe to return pitchers back to a progressive interval throwing program; however, 46.67% of physicians would return pitchers 4 to 6 weeks after a nonoperatively treated injury, while 35.7% would return pitchers 7 to 12 weeks after the initial injury.

Table 1. Treatment Preferences of Grade III AC Separation by MLB Team Physicians

^aRespondents were allowed to choose more than 1 treatment in each category. ^bChosen as an adjunct treatment.

Abbreviations: AC, acromioclavicular; MLB, major league baseball.

Most physicians (64.3%) cited functional limitations as the most important reason for indicating operative treatment, followed by pain (21.4%), and a deformity (14.3%). About 65% preferred open coracoclavicular ligament reconstruction. No physician recommended the Weaver-Dunn procedure or use of hardware (eg, hook plate). Of those who preferred an operative intervention, 66.7% would also include a distal clavicle excision, which is significantly higher than the proportion reported by McFarland and colleagues¹³ (23%, P = .0170). About 90% of physicians would return pitchers to play >12 weeks after operative treatment.

Continue to: If the injury occurred at the end ...

If the injury occurred at the end of the season, 7 of the 20 orthopedists (35%) who recommended nonoperative treatment said they would change to an operative intervention. Eighteen of 28 responders would have the same algorithm for MLB position players. Team physicians were less likely to recommend operative intervention in position players due to less demand on the arm and increased ability to accommodate the injury by altering their throwing mechanics.

Eighteen (64%) of the team physicians had treated at least 1 professional pitcher with a grade III AC separation in his dominant arm, and 11 (39.3%) had treated >1. Collectively, team physicians had treated 15 professional pitchers operatively, and 51 nonoperatively; only 3 patients converted to operative intervention after a failed nonoperative treatment.

Of the pitchers treated operatively, 93.3% (14) of pitchers returned to their prior level of pitching. The 1 patient who failed to return to the same level of pitching retired instead of returning to play. About 80% (12) of the pitchers had full pain relief, and 93.3% (14) had full range of motion (ROM). The pitcher who failed to regain full ROM also had a concomitant rotator cuff repair. The only complication reported from an operative intervention was a pitcher who sustained a coracoid fracture 10 months postoperatively while throwing 100 mph. Of the pitchers treated nonoperatively, 96% returned to their prior level of pitching, 92.2% (47) had full complete pain relief when throwing, and 100% had full ROM. No differences were observed between the proportion of pitchers who returned to their prior level of pitching, regained full ROM, or had full pain relief in the operative and nonoperative groups (Table 2).

Table 2. Outcomes of Treatment of Grade III AC Separation in 58 Professional Baseball Players

Abbreviations: AC, acromioclavicular; ROM, range of motion.

DISCUSSION 

Controversy persists regarding the optimal management of acute grade III AC separations, with the current available evidence potentially suggesting better cosmetic and radiological results but no definite differences in clinical results.^1-6,17,18 In the absence of formal clinical practice guidelines, surgeons rely on their own experience or defer to the anecdotal experience of experts in the field. Our initial hypothesis was false in this survey of MLB team physicians taking care of overhead throwing athletes at the highest level. Our results demonstrate that despite improved techniques and an increased understanding of the pathophysiology of AC joint separations, conservative management is still the preferred treatment for acute grade III AC joint separations in professional baseball pitchers. The proportion of team physicians recommending nonoperative treatment in our series was essentially equivalent to the results reported by McFarland and colleagues¹³ in 1997, suggesting that the pendulum continues to favor conservative management initially. This status quo likely reflects both the dearth of literature suggesting a substantial benefit of acute operative repair, as well as the ability to accommodate with conservative measures after most grade III AC injuries, even at the highest level of athletic competition.

These results are also consistent with trends from the last few decades. In the 1970s, the overwhelming preference for treating an acute complete AC joint separation was surgical repair, with Powers and Bach¹⁰ reporting in a 1974 survey of 163 chairmen of orthopedic programs around the country that 91.5% advocated surgical treatment. However, surgical preference had reversed by the 1990s. Of the 187 chairmen and 59 team physicians surveyed by Cox¹⁹ in 1992, 72% and 86% respectively preferred nonoperative treatment in a theoretical 21-year-old athlete with a grade III AC separation. Nissen and Chatterjee²⁰ reported in 2007 on a survey of all American Orthopaedic Society for Sports Medicine surgeons (N = 577) and Accreditation Council for Graduate Medical Education orthopedic program residency directors (N = 87) that >80% of responders preferred conservative measures for this acute injury. The reversal of trends has also been corroborated by recent multicenter trials demonstrating no difference in clinical outcomes between operative and nonoperative treatment of high grade AC joint dislocations, albeit these patients were not all high level overhead throwing athletes.^17,18

Continue to: The trends in surgical interventions are notable...

The trends in surgical interventions are notable within the smaller subset of patients who are indicated for operative repair. Use of hardware and primary ligament repair, while popular in the surveys conducted in the 1970s¹⁰ and 1990s¹³ and even present in Nissen and Chatterjee’s²⁰ 2007 survey, were noticeably absent from our survey results, with the majority of respondents preferring open coracoclavicular ligament reconstruction. The role of distal clavicle excision has also expanded, from 23% of team physicians recommending it in 1997¹³ to 57% to 59% in Nissen and Chatterjee’s²⁰ 2007 survey, to 66.7% in our series. This trend is not surprising as several recent cadaveric biomechanical studies have demonstrated that not only do peak graft forces not increase significantly,²¹ the anterior-posterior and superior-inferior motion at the AC joint following ligament reconstruction is maintained despite resection of the lateral clavicle.²² Additionally, primary distal clavicle excision may prevent the development of post-traumatic arthritis at the AC joint and osteolysis of the distal clavicle as a possible pain generator in the future.²³ However, some respondents cautioned against performing a concomitant distal clavicle excision, as some biomechanical data demonstrate that resecting the distal clavicle may lead to increased horizontal translation at the AC joint despite intact superior and posterior AC capsules.²⁴ Professional baseball pitchers may also be more lax and thus prone to more instability. Primary repair or reconstruction may not always lead to complete pre-injury stability in these individuals. This subtle unrecognized instability is hard to diagnosis and may be a persistent source of pain; thus, adding a distal clavicle excision may actually exacerbate the instability.

The nuanced indications for operative intervention, such as the presence of associated lesions were not captured by our survey.²⁵ While most team physicians cited functional limitations as their most common reason for offering surgery, several MLB orthopedic surgeons also commented on evaluating the stability of the AC joint after a grade III injury, akin to the consensus statement from the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) Upper Extremity Committee²⁶ in 2014 that diversified the Rockwood Grade III AC joint separation into its IIIA and IIIB classifications. The ISAKOS recommendations include initial conservative management and a second evaluation (both clinical and radiographic) for grade III lesions 3 to 6 weeks after the injury. However, as professional baseball is an incredibly profitable sport with an annual revenue approaching $9.5 billion²⁷ and pitching salaries up to $32.5 million in 2015, serious financial considerations must be given to players who wish to avoid undergoing delayed surgery.

This study has shortcomings typical of expert opinion papers. The retrospective nature of this study places the data at risk of recall bias. Objective data (eg, terminal ROM, pain relief, and return to play) were obtained from a retrospective chart review; however, no standard documentation or collection method was used given the number of surgeons involved and, thus, conclusions based on treatment outcomes are imperfect. Another major weakness of this survey is the relatively small number of patients and respondents. An a priori power analysis was not available, as this was a retrospective review. A comparative trial will be necessary to definitively support one treatment over another. Assuming a 95% return to play in the nonoperatively treated group, approximately 300 patients would be needed in a prospective 2-armed study with 80% power to detect a 10% reduction in the incidence of return to play using an alpha level of 0.05 and assuming no loss to follow-up. This sample size would be difficult to achieve in this patient population.

However, compared to past series,¹³ the number of professional baseball players treated by the collective experience of these MLB team physicians is the largest reported to date. As suggested above, the rarity of this condition in elite athletes precludes the ability to have matched controls to definitively determine the optimal treatment, which may explain the lack of difference in the return to play, ROM, and pain relief outcomes. Instead, we can only extrapolate based on the collective anecdotal experience of the MLB team physicians.

CONCLUSION

Despite advances in surgical technique and understanding of throwing mechanics, the majority of MLB team physicians preferred nonoperative management for an acute grade III AC joint separation in a professional baseball pitcher. Open coracoclavicular ligament reconstruction was preferred for those who preferred operative intervention. An increasing number of orthopedic surgeons now consider a distal clavicle excision as an adjunct procedure.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

The aim of this study was to provide clinical recommendations about the use of platelet-rich plasma (PRP) that was subjected to short-term storage at room temperature. We determined bioactive growth factor and cytokine concentrations as indicators of platelet and white blood cell degranulation in blood and PRP. Additionally, this study sought to validate the use of manual, direct smear analysis as an alternative to automated methods for platelet quantification in PRP.

Blood was used to generate low-leukocyte PRP (L^lo PRP) or high-leukocyte PRP (L^hi PRP). Blood was either processed immediately or kept at room temperature for 2 or 4 hours prior to generation of PRP, which was then held at room temperature for 0, 1, 2, or 4 hours. Subsequently, bioactive transforming growth factor beta-1 and matrix metalloproteinase-9 were measured by ELISA (enzyme-linked immunosorbent assay). Manual and automated platelet counts were performed on all blood and PRP samples.

There were no differences in growth factor or cytokine concentration when blood or L^lo PRP or L^hi PRP was retained at room temperature for up to 4 hours. Manual, direct smear analysis for platelet quantification was not different from the use of automated machine counting for PRP samples, but in the starting blood samples, manual platelet counts were significantly higher than those generated using automated technology.

When there is a delay of up to 4 hours in the generation of PRP from blood or in the application of PRP to the patient, bioactive growth factor and cytokine concentrations remain stable in both blood and PRP. A manual direct counting method is a simple, cost-effective, and valid method to measure the contents of the PRP product being delivered to the patient.

Platelet-rich plasma (PRP) is used to promote healing in many areas of medicine, such as dental surgery,^1,2 soft-tissue injury,^3,4 orthopedic surgery,^5,6 wound healing,⁷ and veterinary medicine.^8,9 Despite its extensive use, there are still questions about the clinical efficacy of PRP.^10-12 Due to biological heterogeneity between patients^13,14 and differences between available manufacturing kits,^13,15 PRP can be highly variable between patients. There are classification schemes to categorize the various types of PRP,^16-18 which can be divided broadly into low-leukocyte PRP (L^lo PRP) and high-leukocyte PRP (L^hi PRP). PRP can be used as a point of care therapy, prepared and used immediately, or it can be used during a surgical procedure. In some institutions, blood is drawn by a phlebotomist, processed in the hospital laboratory, and then delivered to the operating room. In other instances, PRP is generated patient-side by the primary attending physician’s team, who draws the blood and processes it for immediate use.^5,19 Delays at any step in these various scenarios could lead to the blood or the resultant PRP remaining at room temperature from minutes to several hours prior to administration to the patient. This variability in PRP protocols between clinical and surgical settings adds to concerns regarding the stability and efficacy of the biologic.

Continue to: When performing clinical or research...

The primary aim of this study was to determine if retention of blood or PRP at room temperature for various time intervals had an effect on final growth factor or catabolic cytokine concentration. Bioactive transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) were measured as representatives of growth factors and catabolic cytokines, respectively. The secondary aim was to identify if manual platelet counts were an accurate reflection of automated counts. The outcomes of these experiments should provide immediately relevant information for the clinical application of PRP.

MATERIALS AND METHODS

Blood Collection and Generation of PRP

Under Institutional Review Board approval, blood (105 mL) was collected from healthy human volunteers (N = 5) into a syringe containing acid citrate dextrose anticoagulant to a final concentration of 10% acid citrate dextrose. Three 15-mL aliquots of blood were used to generate L^lo PRP (Autologous Conditioned Plasma Double Syringe, Arthrex) and three 20-mL aliquots were used to generate L^hi PRP (SmartPReP 2, Harvest Technologies) (Figure 1). 

Automated and Manual Counts

Automated complete blood counts were performed by a board certified clinical pathologist in the clinical pathology department of Cornell University on all blood, L^lo PRP, and L^hi PRP samples. A manual platelet count, using a modified Giemsa stain,²² was performed on smears of all blood and PRP samples (Video). Slides were scanned at 10x magnification to identify an area where many red blood cells were present while maintaining a clear field of view (Figure 2A). The magnification was then increased to 100x using oil immersion, and the total number of platelets was counted in 10 fields of view (Figure 2B). 

Growth Factor and Catabolic Cytokine Measurements

Blood and PRP samples were thawed for ELISA (enzyme-linked immunosorbent assay) analysis. TGF-β1 concentration was determined using the TGF-β1 Emax ImmunoAssay System (Promega Corporation), which measures biologically active TGF-β1. We chose TGF-β1 because it is commonly measured in PRP studies as an anabolic cytokine with multiple effects on tissue healing. The functions of TGF-β1 include stimulation of undifferentiated mesenchymal cell proliferation; regulation of endothelial, fibroblast, and osteoblast mitogenesis; coordination of collagen synthesis; promotion of endothelial chemotaxis and angiogenesis; activation of extracellular matrix synthesis in cartilage; and reduction of the catabolic activity of interluekin-1 and MMPs.^23-25 In addition, TGF-β1 concentration strongly correlates with platelet concentration.²⁶ MMP-9 concentration was determined using the MMP-9 Biotrak Activity Assay (GE Healthcare Biosciences) which measures both active and pro- forms of MMP-9. In PRP, MMP-9 was measured as an indicator of white blood cell (WBC) concentration.²⁶ A catabolic cytokine capable of degrading collagen,^13,27 MMP-9 has been linked to poor healing.²⁸ For both assays, samples were measured in duplicate using a multiple detection plate reader (Tecan Safire).

Continue to: Statistical Analysis...

Statistical Analysis

Data were tested for the normal distribution to determine the appropriate statistical test. Manual and automated platelet counts were compared to each other in whole blood, L^lo PRP, and L^hi PRP samples using a paired t test. Bioactive TGF-β1 concentrations in blood, L^lo PRP, and L^hi PRP, were compared using a Kruskal-Wallis one-way analysis of variance (ANOVA) with Dunn’s all-pairwise comparison. Bioactive and pro-MMP-9 concentrations measured in the retained blood or PRP samples were compared using a one-way ANOVA with Tukey’s all-pairwise comparison. Statistical analyses were performed using Statistix 9 software (Analytical Software). A P value of <0.05 was considered significant.

RESULTS

Validation of PRP

PRP, as defined by an increase in platelet concentration in PRP compared with blood, was successfully generated in all samples by both systems. There was an average 1.98 ± 0.14-fold increase in platelet concentration in L^lo PRP and an average 3.06 ± 0.24-fold increase in L^hi PRP. Platelet concentration was significantly higher in L^hi PRP than in L^lo PRP (P = 0.001). Compared to whole blood, WBC concentration was 0.47 ± 0.07-fold lower in L^lo PRP and 1.98 ± 0.14-fold greater in L^hi PRP. Similar to platelets, WBCs were significantly greater in L^hi PRP than in L^lo PRP (P = 0.02).

Bioactive TGF-β1 and MMP-9 Concentration in Blood Retained at Room Temperature

To reflect the clinical situation where blood would be drawn from a patient, but there would be a delay in processing the blood to generate PRP, blood samples were retained at room temperature for up to 4 hours prior to analysis. Neither bioactive TGF-β1 (Figure 3) nor bioactive/pro-MMP-9 concentrations (Figure 4) changed significantly over time when blood was retained at room temperature prior to centrifugation to generate PRP.

Bioactive TGF-β1 and MMP-9 Concentration in PRP Retained at Room Temperature

In order to mimic the clinical situation where PRP would be generated but might sit out prior to being administered to the patient, PRP samples were retained at room temperature for up to 4 hours prior to analysis. In these samples, bioactive TGF-β1 concentrations were not significantly different between PRP products analyzed immediately and those samples retained at room temperature for up to 4 hours (Figure 5). 

Automatic vs Manual Platelet Count

Manual platelet counts were compared to automated platelet counts to determine if a manual platelet smear analysis could be a reliable method for analyzing PRP in clinical and pre-clinical studies. There was a significant difference between the automated and manual platelet counts in blood samples (Table) (P = 0.05, N = 5) with the manual platelet count having a higher average (99.1 thou/uL) platelet concentration than automated counts. Platelet clumping was identified in 2 automated counts, which falsely decreased platelet concentration by an unknown quantity. Manual platelet counts for both L^lo PRP (n = 30) and L^hi PRP (n = 30) were not different from automated platelet counts. Platelet clumping was not reported on any manual platelet counts performed on PRP samples.

Table. Platelet Concentrations of Whole Blood, L^lo PRP, and L^hi PRP (N = 5)

A paired t test was performed to compare results obtained from an automated platelet count and those obtained from a manual count.

Abbreviations: L^hi PRP, high-leukocyte platelet-rich plasma; L^lo PRP, low-leukocyte platelet-rich plasma; SD, standard deviation.

Continue to:The primary aim of this study...

DISCUSSION

The primary aim of this study was to improve the clinical use of PRP by characterizing changes that might occur due to extended preparation times. Physicians commonly question the stability of blood or PRP if it is retained at room temperature prior to being administered to the patient. Clinical recommendations to optimize PRP preparation can be derived from a better understanding of the stability of platelets and WBCs, which contribute to the anabolic and catabolic cytokines in PRP.

The results of this study suggest that platelets and WBCs remain stable in blood and both L^lo PRP and L^hi PRP for up to 4 hours. The use of bioactive ELISAs to measure TGF-β1 and MMP-9 allows for determination of stability of the PRP product retained at room temperature for up to 4 hours. This provides a time buffer to allow for delays from either institutional logistics or unanticipated clinical delays, without adverse effects on the generation of the final PRP product. As with all biologics, there are many factors that contribute to variability, but a relatively short delay of up to 4 hours in either generation of PRP from blood or in administration of PRP to the patient does not appear to contribute to that variability. Similar studies have been performed on equine PRP and suggest that growth factor concentrations remain stable for up to 6 hours after preparation of PRP²⁹ and in human PRP, which implies that although samples degrade over time, platelet integrity might be acceptable for clinical use for up to 5 days after preparation, particularly if stored in oxygen.³⁰ In contrast to this study, neither of the previously published reports used assays to measure biological activity in the stored PRP. Regardless of the variability between the studies with respect to the type of PRP evaluated and the outcome measures used, all of the studies support the concept that PRP can be stored at room temperature for at least a few hours before clinical use.

Centrifugation of blood does not guarantee the generation of PRP.^13,14 In some cases, platelet counts in PRP are similar to or even less than that in the starting whole blood sample. To determine whether a clinical outcome is attributed to PRP, it is vital to know the platelet concentration and, arguably, the WBC concentration in the blood used to generate PRP and in the PRP sample administered to the patient. The platelet concentration in blood and PRP samples can be quantified using automated or manual methods. The use of automated methods can add significant cost to a study or procedure. Manually evaluating a blood smear is an accepted, though more time consuming, method of analyzing cellular components of a blood sample. Depending on the standard operating procedure of the laboratory, manual smears are often done in conjunction with an automated count. This identifies abnormalities in cellular shape or size, or platelet clumping, which are not consistently recognized by automated methods. Manually evaluating a blood smear does take some training, but the material cost is very low, which has added value for clinical or preclinical research studies. Interestingly, the results of this study indicate that manual platelet counts in blood may be more accurate than the count generated from an automated counter because the automated platelet counts were falsely low due to platelet clumping. Platelet clumping can occur as early as 1 hour after blood collection, regardless of the type of anticoagulant used.³¹

LIMITATIONS

The sample size of this study was small. However, variability in PRP has been well documented in multiple other studies using slightly larger sample sizes.^13,14,16 Another potential limitation of this study could be that only one growth factor, TGF-β1, and one catabolic cytokine, MMP-9, were used as surrogate measures to represent platelet and WBC stability, respectively. We chose TGF-β1 because it is correlated with platelet concentrations^14,15,26 and MMP-9 because it is an indicator of catabolic factors in PRP that have been correlated with WBC concentrations.²⁶

CONCLUSION

This study illustrated that growth factor and cytokine concentrations in both L^lo PRP and L^hi PRP are stable for up to 4 hours. The clinical implications of these results suggest that if the generation or administration of PRP is delayed by up to 4 hours, the resultant PRP retains its bioactivity and is acceptable for clinical application. However, given the known variability of PRP generated due to patient and manufacturer variability,^13,14 it is still important to ensure that the product is indeed PRP, with an increase in platelet number over the starting sample of blood. This validation can be performed with a simple and cost-effective manual smear analysis of blood and PRP. The results of this study provide information that can be immediately translated into clinical, surgical, and research practices.

ABSTRACT

The aim of this study was to provide clinical recommendations about the use of platelet-rich plasma (PRP) that was subjected to short-term storage at room temperature. We determined bioactive growth factor and cytokine concentrations as indicators of platelet and white blood cell degranulation in blood and PRP. Additionally, this study sought to validate the use of manual, direct smear analysis as an alternative to automated methods for platelet quantification in PRP.

Blood was used to generate low-leukocyte PRP (L^lo PRP) or high-leukocyte PRP (L^hi PRP). Blood was either processed immediately or kept at room temperature for 2 or 4 hours prior to generation of PRP, which was then held at room temperature for 0, 1, 2, or 4 hours. Subsequently, bioactive transforming growth factor beta-1 and matrix metalloproteinase-9 were measured by ELISA (enzyme-linked immunosorbent assay). Manual and automated platelet counts were performed on all blood and PRP samples.

There were no differences in growth factor or cytokine concentration when blood or L^lo PRP or L^hi PRP was retained at room temperature for up to 4 hours. Manual, direct smear analysis for platelet quantification was not different from the use of automated machine counting for PRP samples, but in the starting blood samples, manual platelet counts were significantly higher than those generated using automated technology.

When there is a delay of up to 4 hours in the generation of PRP from blood or in the application of PRP to the patient, bioactive growth factor and cytokine concentrations remain stable in both blood and PRP. A manual direct counting method is a simple, cost-effective, and valid method to measure the contents of the PRP product being delivered to the patient.

Platelet-rich plasma (PRP) is used to promote healing in many areas of medicine, such as dental surgery,^1,2 soft-tissue injury,^3,4 orthopedic surgery,^5,6 wound healing,⁷ and veterinary medicine.^8,9 Despite its extensive use, there are still questions about the clinical efficacy of PRP.^10-12 Due to biological heterogeneity between patients^13,14 and differences between available manufacturing kits,^13,15 PRP can be highly variable between patients. There are classification schemes to categorize the various types of PRP,^16-18 which can be divided broadly into low-leukocyte PRP (L^lo PRP) and high-leukocyte PRP (L^hi PRP). PRP can be used as a point of care therapy, prepared and used immediately, or it can be used during a surgical procedure. In some institutions, blood is drawn by a phlebotomist, processed in the hospital laboratory, and then delivered to the operating room. In other instances, PRP is generated patient-side by the primary attending physician’s team, who draws the blood and processes it for immediate use.^5,19 Delays at any step in these various scenarios could lead to the blood or the resultant PRP remaining at room temperature from minutes to several hours prior to administration to the patient. This variability in PRP protocols between clinical and surgical settings adds to concerns regarding the stability and efficacy of the biologic.

Continue to: When performing clinical or research...

The primary aim of this study was to determine if retention of blood or PRP at room temperature for various time intervals had an effect on final growth factor or catabolic cytokine concentration. Bioactive transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) were measured as representatives of growth factors and catabolic cytokines, respectively. The secondary aim was to identify if manual platelet counts were an accurate reflection of automated counts. The outcomes of these experiments should provide immediately relevant information for the clinical application of PRP.

MATERIALS AND METHODS

Blood Collection and Generation of PRP

Under Institutional Review Board approval, blood (105 mL) was collected from healthy human volunteers (N = 5) into a syringe containing acid citrate dextrose anticoagulant to a final concentration of 10% acid citrate dextrose. Three 15-mL aliquots of blood were used to generate L^lo PRP (Autologous Conditioned Plasma Double Syringe, Arthrex) and three 20-mL aliquots were used to generate L^hi PRP (SmartPReP 2, Harvest Technologies) (Figure 1). 

Automated and Manual Counts

Automated complete blood counts were performed by a board certified clinical pathologist in the clinical pathology department of Cornell University on all blood, L^lo PRP, and L^hi PRP samples. A manual platelet count, using a modified Giemsa stain,²² was performed on smears of all blood and PRP samples (Video). Slides were scanned at 10x magnification to identify an area where many red blood cells were present while maintaining a clear field of view (Figure 2A). The magnification was then increased to 100x using oil immersion, and the total number of platelets was counted in 10 fields of view (Figure 2B). 

Growth Factor and Catabolic Cytokine Measurements

Blood and PRP samples were thawed for ELISA (enzyme-linked immunosorbent assay) analysis. TGF-β1 concentration was determined using the TGF-β1 Emax ImmunoAssay System (Promega Corporation), which measures biologically active TGF-β1. We chose TGF-β1 because it is commonly measured in PRP studies as an anabolic cytokine with multiple effects on tissue healing. The functions of TGF-β1 include stimulation of undifferentiated mesenchymal cell proliferation; regulation of endothelial, fibroblast, and osteoblast mitogenesis; coordination of collagen synthesis; promotion of endothelial chemotaxis and angiogenesis; activation of extracellular matrix synthesis in cartilage; and reduction of the catabolic activity of interluekin-1 and MMPs.^23-25 In addition, TGF-β1 concentration strongly correlates with platelet concentration.²⁶ MMP-9 concentration was determined using the MMP-9 Biotrak Activity Assay (GE Healthcare Biosciences) which measures both active and pro- forms of MMP-9. In PRP, MMP-9 was measured as an indicator of white blood cell (WBC) concentration.²⁶ A catabolic cytokine capable of degrading collagen,^13,27 MMP-9 has been linked to poor healing.²⁸ For both assays, samples were measured in duplicate using a multiple detection plate reader (Tecan Safire).

Continue to: Statistical Analysis...

Statistical Analysis

Data were tested for the normal distribution to determine the appropriate statistical test. Manual and automated platelet counts were compared to each other in whole blood, L^lo PRP, and L^hi PRP samples using a paired t test. Bioactive TGF-β1 concentrations in blood, L^lo PRP, and L^hi PRP, were compared using a Kruskal-Wallis one-way analysis of variance (ANOVA) with Dunn’s all-pairwise comparison. Bioactive and pro-MMP-9 concentrations measured in the retained blood or PRP samples were compared using a one-way ANOVA with Tukey’s all-pairwise comparison. Statistical analyses were performed using Statistix 9 software (Analytical Software). A P value of <0.05 was considered significant.

RESULTS

Validation of PRP

PRP, as defined by an increase in platelet concentration in PRP compared with blood, was successfully generated in all samples by both systems. There was an average 1.98 ± 0.14-fold increase in platelet concentration in L^lo PRP and an average 3.06 ± 0.24-fold increase in L^hi PRP. Platelet concentration was significantly higher in L^hi PRP than in L^lo PRP (P = 0.001). Compared to whole blood, WBC concentration was 0.47 ± 0.07-fold lower in L^lo PRP and 1.98 ± 0.14-fold greater in L^hi PRP. Similar to platelets, WBCs were significantly greater in L^hi PRP than in L^lo PRP (P = 0.02).

Bioactive TGF-β1 and MMP-9 Concentration in Blood Retained at Room Temperature

To reflect the clinical situation where blood would be drawn from a patient, but there would be a delay in processing the blood to generate PRP, blood samples were retained at room temperature for up to 4 hours prior to analysis. Neither bioactive TGF-β1 (Figure 3) nor bioactive/pro-MMP-9 concentrations (Figure 4) changed significantly over time when blood was retained at room temperature prior to centrifugation to generate PRP.

Bioactive TGF-β1 and MMP-9 Concentration in PRP Retained at Room Temperature

In order to mimic the clinical situation where PRP would be generated but might sit out prior to being administered to the patient, PRP samples were retained at room temperature for up to 4 hours prior to analysis. In these samples, bioactive TGF-β1 concentrations were not significantly different between PRP products analyzed immediately and those samples retained at room temperature for up to 4 hours (Figure 5). 

Automatic vs Manual Platelet Count

Manual platelet counts were compared to automated platelet counts to determine if a manual platelet smear analysis could be a reliable method for analyzing PRP in clinical and pre-clinical studies. There was a significant difference between the automated and manual platelet counts in blood samples (Table) (P = 0.05, N = 5) with the manual platelet count having a higher average (99.1 thou/uL) platelet concentration than automated counts. Platelet clumping was identified in 2 automated counts, which falsely decreased platelet concentration by an unknown quantity. Manual platelet counts for both L^lo PRP (n = 30) and L^hi PRP (n = 30) were not different from automated platelet counts. Platelet clumping was not reported on any manual platelet counts performed on PRP samples.

Table. Platelet Concentrations of Whole Blood, L^lo PRP, and L^hi PRP (N = 5)

A paired t test was performed to compare results obtained from an automated platelet count and those obtained from a manual count.

Abbreviations: L^hi PRP, high-leukocyte platelet-rich plasma; L^lo PRP, low-leukocyte platelet-rich plasma; SD, standard deviation.

Continue to:The primary aim of this study...

DISCUSSION

The primary aim of this study was to improve the clinical use of PRP by characterizing changes that might occur due to extended preparation times. Physicians commonly question the stability of blood or PRP if it is retained at room temperature prior to being administered to the patient. Clinical recommendations to optimize PRP preparation can be derived from a better understanding of the stability of platelets and WBCs, which contribute to the anabolic and catabolic cytokines in PRP.

The results of this study suggest that platelets and WBCs remain stable in blood and both L^lo PRP and L^hi PRP for up to 4 hours. The use of bioactive ELISAs to measure TGF-β1 and MMP-9 allows for determination of stability of the PRP product retained at room temperature for up to 4 hours. This provides a time buffer to allow for delays from either institutional logistics or unanticipated clinical delays, without adverse effects on the generation of the final PRP product. As with all biologics, there are many factors that contribute to variability, but a relatively short delay of up to 4 hours in either generation of PRP from blood or in administration of PRP to the patient does not appear to contribute to that variability. Similar studies have been performed on equine PRP and suggest that growth factor concentrations remain stable for up to 6 hours after preparation of PRP²⁹ and in human PRP, which implies that although samples degrade over time, platelet integrity might be acceptable for clinical use for up to 5 days after preparation, particularly if stored in oxygen.³⁰ In contrast to this study, neither of the previously published reports used assays to measure biological activity in the stored PRP. Regardless of the variability between the studies with respect to the type of PRP evaluated and the outcome measures used, all of the studies support the concept that PRP can be stored at room temperature for at least a few hours before clinical use.

Centrifugation of blood does not guarantee the generation of PRP.^13,14 In some cases, platelet counts in PRP are similar to or even less than that in the starting whole blood sample. To determine whether a clinical outcome is attributed to PRP, it is vital to know the platelet concentration and, arguably, the WBC concentration in the blood used to generate PRP and in the PRP sample administered to the patient. The platelet concentration in blood and PRP samples can be quantified using automated or manual methods. The use of automated methods can add significant cost to a study or procedure. Manually evaluating a blood smear is an accepted, though more time consuming, method of analyzing cellular components of a blood sample. Depending on the standard operating procedure of the laboratory, manual smears are often done in conjunction with an automated count. This identifies abnormalities in cellular shape or size, or platelet clumping, which are not consistently recognized by automated methods. Manually evaluating a blood smear does take some training, but the material cost is very low, which has added value for clinical or preclinical research studies. Interestingly, the results of this study indicate that manual platelet counts in blood may be more accurate than the count generated from an automated counter because the automated platelet counts were falsely low due to platelet clumping. Platelet clumping can occur as early as 1 hour after blood collection, regardless of the type of anticoagulant used.³¹

LIMITATIONS

The sample size of this study was small. However, variability in PRP has been well documented in multiple other studies using slightly larger sample sizes.^13,14,16 Another potential limitation of this study could be that only one growth factor, TGF-β1, and one catabolic cytokine, MMP-9, were used as surrogate measures to represent platelet and WBC stability, respectively. We chose TGF-β1 because it is correlated with platelet concentrations^14,15,26 and MMP-9 because it is an indicator of catabolic factors in PRP that have been correlated with WBC concentrations.²⁶

CONCLUSION

This study illustrated that growth factor and cytokine concentrations in both L^lo PRP and L^hi PRP are stable for up to 4 hours. The clinical implications of these results suggest that if the generation or administration of PRP is delayed by up to 4 hours, the resultant PRP retains its bioactivity and is acceptable for clinical application. However, given the known variability of PRP generated due to patient and manufacturer variability,^13,14 it is still important to ensure that the product is indeed PRP, with an increase in platelet number over the starting sample of blood. This validation can be performed with a simple and cost-effective manual smear analysis of blood and PRP. The results of this study provide information that can be immediately translated into clinical, surgical, and research practices.

ABSTRACT

The aim of this study was to provide clinical recommendations about the use of platelet-rich plasma (PRP) that was subjected to short-term storage at room temperature. We determined bioactive growth factor and cytokine concentrations as indicators of platelet and white blood cell degranulation in blood and PRP. Additionally, this study sought to validate the use of manual, direct smear analysis as an alternative to automated methods for platelet quantification in PRP.

Blood was used to generate low-leukocyte PRP (L^lo PRP) or high-leukocyte PRP (L^hi PRP). Blood was either processed immediately or kept at room temperature for 2 or 4 hours prior to generation of PRP, which was then held at room temperature for 0, 1, 2, or 4 hours. Subsequently, bioactive transforming growth factor beta-1 and matrix metalloproteinase-9 were measured by ELISA (enzyme-linked immunosorbent assay). Manual and automated platelet counts were performed on all blood and PRP samples.

There were no differences in growth factor or cytokine concentration when blood or L^lo PRP or L^hi PRP was retained at room temperature for up to 4 hours. Manual, direct smear analysis for platelet quantification was not different from the use of automated machine counting for PRP samples, but in the starting blood samples, manual platelet counts were significantly higher than those generated using automated technology.

When there is a delay of up to 4 hours in the generation of PRP from blood or in the application of PRP to the patient, bioactive growth factor and cytokine concentrations remain stable in both blood and PRP. A manual direct counting method is a simple, cost-effective, and valid method to measure the contents of the PRP product being delivered to the patient.

Platelet-rich plasma (PRP) is used to promote healing in many areas of medicine, such as dental surgery,^1,2 soft-tissue injury,^3,4 orthopedic surgery,^5,6 wound healing,⁷ and veterinary medicine.^8,9 Despite its extensive use, there are still questions about the clinical efficacy of PRP.^10-12 Due to biological heterogeneity between patients^13,14 and differences between available manufacturing kits,^13,15 PRP can be highly variable between patients. There are classification schemes to categorize the various types of PRP,^16-18 which can be divided broadly into low-leukocyte PRP (L^lo PRP) and high-leukocyte PRP (L^hi PRP). PRP can be used as a point of care therapy, prepared and used immediately, or it can be used during a surgical procedure. In some institutions, blood is drawn by a phlebotomist, processed in the hospital laboratory, and then delivered to the operating room. In other instances, PRP is generated patient-side by the primary attending physician’s team, who draws the blood and processes it for immediate use.^5,19 Delays at any step in these various scenarios could lead to the blood or the resultant PRP remaining at room temperature from minutes to several hours prior to administration to the patient. This variability in PRP protocols between clinical and surgical settings adds to concerns regarding the stability and efficacy of the biologic.

Continue to: When performing clinical or research...

The primary aim of this study was to determine if retention of blood or PRP at room temperature for various time intervals had an effect on final growth factor or catabolic cytokine concentration. Bioactive transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) were measured as representatives of growth factors and catabolic cytokines, respectively. The secondary aim was to identify if manual platelet counts were an accurate reflection of automated counts. The outcomes of these experiments should provide immediately relevant information for the clinical application of PRP.

MATERIALS AND METHODS

Blood Collection and Generation of PRP

Under Institutional Review Board approval, blood (105 mL) was collected from healthy human volunteers (N = 5) into a syringe containing acid citrate dextrose anticoagulant to a final concentration of 10% acid citrate dextrose. Three 15-mL aliquots of blood were used to generate L^lo PRP (Autologous Conditioned Plasma Double Syringe, Arthrex) and three 20-mL aliquots were used to generate L^hi PRP (SmartPReP 2, Harvest Technologies) (Figure 1). 

Automated and Manual Counts

Automated complete blood counts were performed by a board certified clinical pathologist in the clinical pathology department of Cornell University on all blood, L^lo PRP, and L^hi PRP samples. A manual platelet count, using a modified Giemsa stain,²² was performed on smears of all blood and PRP samples (Video). Slides were scanned at 10x magnification to identify an area where many red blood cells were present while maintaining a clear field of view (Figure 2A). The magnification was then increased to 100x using oil immersion, and the total number of platelets was counted in 10 fields of view (Figure 2B). 

Growth Factor and Catabolic Cytokine Measurements

Blood and PRP samples were thawed for ELISA (enzyme-linked immunosorbent assay) analysis. TGF-β1 concentration was determined using the TGF-β1 Emax ImmunoAssay System (Promega Corporation), which measures biologically active TGF-β1. We chose TGF-β1 because it is commonly measured in PRP studies as an anabolic cytokine with multiple effects on tissue healing. The functions of TGF-β1 include stimulation of undifferentiated mesenchymal cell proliferation; regulation of endothelial, fibroblast, and osteoblast mitogenesis; coordination of collagen synthesis; promotion of endothelial chemotaxis and angiogenesis; activation of extracellular matrix synthesis in cartilage; and reduction of the catabolic activity of interluekin-1 and MMPs.^23-25 In addition, TGF-β1 concentration strongly correlates with platelet concentration.²⁶ MMP-9 concentration was determined using the MMP-9 Biotrak Activity Assay (GE Healthcare Biosciences) which measures both active and pro- forms of MMP-9. In PRP, MMP-9 was measured as an indicator of white blood cell (WBC) concentration.²⁶ A catabolic cytokine capable of degrading collagen,^13,27 MMP-9 has been linked to poor healing.²⁸ For both assays, samples were measured in duplicate using a multiple detection plate reader (Tecan Safire).

Continue to: Statistical Analysis...

Statistical Analysis

Data were tested for the normal distribution to determine the appropriate statistical test. Manual and automated platelet counts were compared to each other in whole blood, L^lo PRP, and L^hi PRP samples using a paired t test. Bioactive TGF-β1 concentrations in blood, L^lo PRP, and L^hi PRP, were compared using a Kruskal-Wallis one-way analysis of variance (ANOVA) with Dunn’s all-pairwise comparison. Bioactive and pro-MMP-9 concentrations measured in the retained blood or PRP samples were compared using a one-way ANOVA with Tukey’s all-pairwise comparison. Statistical analyses were performed using Statistix 9 software (Analytical Software). A P value of <0.05 was considered significant.

RESULTS

Validation of PRP

PRP, as defined by an increase in platelet concentration in PRP compared with blood, was successfully generated in all samples by both systems. There was an average 1.98 ± 0.14-fold increase in platelet concentration in L^lo PRP and an average 3.06 ± 0.24-fold increase in L^hi PRP. Platelet concentration was significantly higher in L^hi PRP than in L^lo PRP (P = 0.001). Compared to whole blood, WBC concentration was 0.47 ± 0.07-fold lower in L^lo PRP and 1.98 ± 0.14-fold greater in L^hi PRP. Similar to platelets, WBCs were significantly greater in L^hi PRP than in L^lo PRP (P = 0.02).

Bioactive TGF-β1 and MMP-9 Concentration in Blood Retained at Room Temperature

To reflect the clinical situation where blood would be drawn from a patient, but there would be a delay in processing the blood to generate PRP, blood samples were retained at room temperature for up to 4 hours prior to analysis. Neither bioactive TGF-β1 (Figure 3) nor bioactive/pro-MMP-9 concentrations (Figure 4) changed significantly over time when blood was retained at room temperature prior to centrifugation to generate PRP.

Bioactive TGF-β1 and MMP-9 Concentration in PRP Retained at Room Temperature

In order to mimic the clinical situation where PRP would be generated but might sit out prior to being administered to the patient, PRP samples were retained at room temperature for up to 4 hours prior to analysis. In these samples, bioactive TGF-β1 concentrations were not significantly different between PRP products analyzed immediately and those samples retained at room temperature for up to 4 hours (Figure 5). 

Automatic vs Manual Platelet Count

Manual platelet counts were compared to automated platelet counts to determine if a manual platelet smear analysis could be a reliable method for analyzing PRP in clinical and pre-clinical studies. There was a significant difference between the automated and manual platelet counts in blood samples (Table) (P = 0.05, N = 5) with the manual platelet count having a higher average (99.1 thou/uL) platelet concentration than automated counts. Platelet clumping was identified in 2 automated counts, which falsely decreased platelet concentration by an unknown quantity. Manual platelet counts for both L^lo PRP (n = 30) and L^hi PRP (n = 30) were not different from automated platelet counts. Platelet clumping was not reported on any manual platelet counts performed on PRP samples.

Table. Platelet Concentrations of Whole Blood, L^lo PRP, and L^hi PRP (N = 5)

A paired t test was performed to compare results obtained from an automated platelet count and those obtained from a manual count.

Abbreviations: L^hi PRP, high-leukocyte platelet-rich plasma; L^lo PRP, low-leukocyte platelet-rich plasma; SD, standard deviation.

Continue to:The primary aim of this study...

DISCUSSION

The primary aim of this study was to improve the clinical use of PRP by characterizing changes that might occur due to extended preparation times. Physicians commonly question the stability of blood or PRP if it is retained at room temperature prior to being administered to the patient. Clinical recommendations to optimize PRP preparation can be derived from a better understanding of the stability of platelets and WBCs, which contribute to the anabolic and catabolic cytokines in PRP.

The results of this study suggest that platelets and WBCs remain stable in blood and both L^lo PRP and L^hi PRP for up to 4 hours. The use of bioactive ELISAs to measure TGF-β1 and MMP-9 allows for determination of stability of the PRP product retained at room temperature for up to 4 hours. This provides a time buffer to allow for delays from either institutional logistics or unanticipated clinical delays, without adverse effects on the generation of the final PRP product. As with all biologics, there are many factors that contribute to variability, but a relatively short delay of up to 4 hours in either generation of PRP from blood or in administration of PRP to the patient does not appear to contribute to that variability. Similar studies have been performed on equine PRP and suggest that growth factor concentrations remain stable for up to 6 hours after preparation of PRP²⁹ and in human PRP, which implies that although samples degrade over time, platelet integrity might be acceptable for clinical use for up to 5 days after preparation, particularly if stored in oxygen.³⁰ In contrast to this study, neither of the previously published reports used assays to measure biological activity in the stored PRP. Regardless of the variability between the studies with respect to the type of PRP evaluated and the outcome measures used, all of the studies support the concept that PRP can be stored at room temperature for at least a few hours before clinical use.

Centrifugation of blood does not guarantee the generation of PRP.^13,14 In some cases, platelet counts in PRP are similar to or even less than that in the starting whole blood sample. To determine whether a clinical outcome is attributed to PRP, it is vital to know the platelet concentration and, arguably, the WBC concentration in the blood used to generate PRP and in the PRP sample administered to the patient. The platelet concentration in blood and PRP samples can be quantified using automated or manual methods. The use of automated methods can add significant cost to a study or procedure. Manually evaluating a blood smear is an accepted, though more time consuming, method of analyzing cellular components of a blood sample. Depending on the standard operating procedure of the laboratory, manual smears are often done in conjunction with an automated count. This identifies abnormalities in cellular shape or size, or platelet clumping, which are not consistently recognized by automated methods. Manually evaluating a blood smear does take some training, but the material cost is very low, which has added value for clinical or preclinical research studies. Interestingly, the results of this study indicate that manual platelet counts in blood may be more accurate than the count generated from an automated counter because the automated platelet counts were falsely low due to platelet clumping. Platelet clumping can occur as early as 1 hour after blood collection, regardless of the type of anticoagulant used.³¹

LIMITATIONS

The sample size of this study was small. However, variability in PRP has been well documented in multiple other studies using slightly larger sample sizes.^13,14,16 Another potential limitation of this study could be that only one growth factor, TGF-β1, and one catabolic cytokine, MMP-9, were used as surrogate measures to represent platelet and WBC stability, respectively. We chose TGF-β1 because it is correlated with platelet concentrations^14,15,26 and MMP-9 because it is an indicator of catabolic factors in PRP that have been correlated with WBC concentrations.²⁶

CONCLUSION

This study illustrated that growth factor and cytokine concentrations in both L^lo PRP and L^hi PRP are stable for up to 4 hours. The clinical implications of these results suggest that if the generation or administration of PRP is delayed by up to 4 hours, the resultant PRP retains its bioactivity and is acceptable for clinical application. However, given the known variability of PRP generated due to patient and manufacturer variability,^13,14 it is still important to ensure that the product is indeed PRP, with an increase in platelet number over the starting sample of blood. This validation can be performed with a simple and cost-effective manual smear analysis of blood and PRP. The results of this study provide information that can be immediately translated into clinical, surgical, and research practices.

Take-Home Points

• Malignant transformation of a benign GCT is extremely rare.
• It is difficult to distinguish between an early malignant transformation and an overlooked malignancy.
• The most common clinical presentation of transformation of GCT into malignancy is pain, often with swelling.
• Interval monitoring of GCTs may be necessary in patients with symptoms concerning for malignant transformation.
• Clinicians should maintain a high clinical suspicion for malignant transformation or late recurrence of GCT in a patient with new pain at the wound site.

Giant cell tumors (GCTs) of bone account for about 5% of all primary bone tumors in adults, with a predominance in the third decade in life.¹ Clinically, GCT of bone often presents with pain, pathologic fracture, and/or soft- tissue expansion in the epiphysis of long bones. However, GCT of bone also has been reported in non-long bones, such as the talus and the calcaneus.^2,3 Histologically, GCT of bone consists of neoplastic stromal cells, mononuclear histiocytic cells, and multinucleated giant cells that resemble osteoclasts.⁴ The radiologic appearance of GCT is often described as a lytic, eccentrically located bony lesion that extends near the articular surface in patients with closed physes. Many GCTs have aggressive radiologic features with possible extensive bony destruction and soft-tissue extension. 

Although categorized as a benign lesion, GCT can be locally aggressive, with a variable local recurrence rate of 0% to 65%, depending on treatment modality and skeletal location. Given the aggressiveness of GCT of bone, recommendations for operative intervention include intralesional curettage with adjuvant therapy (eg, cryotherapy, phenol, argon beam, electrocautery) and placement of bone void fillers (eg, bone graft polymethylmethacrylate). Wide resection is recommended when the articular surface is no longer viable for reconstruction secondary to extensive destruction. Some authors have reported that surgical margin is the only risk factor in local recurrence,^5,6 and thus complete resection may be needed for tumor eradication. In addition, about 3% of GCTs demonstrate benign pulmonary implants, which have been cited as cause of death in 16% to 25% of reported cases of pulmonary spread.^7,8

The literature includes few reports of primary or secondary malignant transformation of GCT. Hutter and colleagues⁹ defined primary malignant GCT as GCT with sarcomatous tissue juxtaposed with zones of typical benign GCT cells. Secondary malignant GCT is a sarcomatous lesion at the site of a previously documented benign GCT. Secondary malignant GCT of bone histologically has been classified as a fibrosarcoma, malignant fibrous histiocytoma, or osteosarcoma transformation.¹⁰ 

Most malignant transformations of GCT of bone have been attributed to previous irradiation of the lesion.^11,12 However, there are some case reports of benign bone GCT malignant transformation in situ without any other medical intervention. It was reported that non-radiation-induced secondary transformations occur relatively early after GCT treatment.¹³ During the early stages of tumor recurrence, however, it is difficult to distinguish between malignant transformation and primary disease overlooked as a result of sampling error.

We report a case of secondary malignant transformation of GCT of bone 11 years after surgical curettage, cryotherapy, and cementation without adjuvant radiation therapy. To our knowledge, this case report is the first to describe transformation of a nonirradiated benign GCT into an aggressive, high-grade epithelioid angiosarcoma, a very rare vascular bone tumor. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

In July 2003, a 46-year-old woman presented with left heel pain of several months’ duration. Plain radiographs showed a nonaggressive-appearing lytic lesion of the superior aspect of the posterior calcaneal tuberosity with a small cortical incongruity along the superior margin of the lesion (Figures 1A-1D).

A postoperative splint was placed, and weight-bearing progressed over 6 weeks. The patient was followed at 2- to 3-month intervals over the first 5 postoperative years. She was able to work and perform activities of daily living, but her postoperative course was complicated by significant chronic pain in multiple extremities and long-term treatment by the chronic pain service. At no time did postoperative imaging—magnetic resonance imaging (MRI) at 6 years, whole-body bone scan at 7 years, plain radiographs at 10 years—show evidence of recurrence.

Radiographs showed stable postoperative changes with a small radiolucent area (with sclerotic rim) surrounding the cement-bone interface. Given its proximity to the Achilles tendon and more motion than usual at the wound site, the radiolucency likely was caused by small movements of the interface. The radiolucent area remained stable over a 15-month period.

Whole-body bone scan showed a small area of osteoblastic activity in the left calcaneus, consistent with inflammation surrounding the bone- cement interface, but the uptake was minor relative to other areas of signal, and there were no significant inflammatory reactive changes on MRI (Figures 3A, 3B).

Over 11 years, regular 6- to 12-month follow-up examinations revealed no significant changes in the left foot or in plain radiographs of the chest. In addition, physical examinations revealed no evidence of a palpable mass of the left foot.

In July 2014 (11 years after curettage and cementation), the patient presented to her pain clinic appointment with severe left foot pain. She said that, over a few weeks, she experienced a significant increase in pain and developed posterolateral foot swelling, which limited her ability to ambulate. Plain radiographs showed a significant soft-tissue prominence around the posterior calcaneus, increased lucency around the bone-cement interface in the calcaneus with elevation, and a cortical break of the superior margin of the posterior calcaneus (Figures 3C, 3D). MRI showed a large lobular mass in the calcaneus and surrounding soft tissue with T1 and T2 signal heterogeneity and enhancement after administration of gadolinium (Figures 4A-4D). There was a large extraosseous extension of the calcaneus-based mass laterally and superiorly with edema in the surrounding hindfoot region (Figure 4).

Physical examination revealed exquisite tenderness along the lateral and posterior aspects of the left hindfoot. The patient was unable to bear weight and had soft-tissue swelling throughout the foot and mid calf as well as a palpable mass in the posterior heel. She was otherwise neurovascularly intact through all distributions of the left lower extremity. It was unclear if the GCT of the calcaneus had recurred or if there was a new, secondary tumor. Given her severe pain and morbidity, the patient decided to proceed with open biopsy and a pathology-pending plan for possible amputation in the near future.

In August 2014, an open biopsy with intraoperative frozen evaluation yielded a diagnosis of malignant neoplasm not otherwise specified. Permanent sections showed a proliferation of malignant epithelioid cells with extensive necrosis, hemorrhage, and hemosiderin deposition but no multinucleated giant cells.

Transformation of the GCT into a high-grade epithelioid angiosarcoma prompted presentation of the patient’s case to a multidisciplinary board of physicians with a focused clinical practice in sarcoma management. The board included board-certified specialists in orthopedic oncology, pathology, musculoskeletal radiology, medical oncology, and radiation oncology. Although discussion included pre-resection use of neoadjuvant chemotherapy to evaluate for disease response, the patient’s severe pain led her to forgo this treatment and proceed directly to below-knee amputation.

Amputation revealed a 7.7-cm hemorrhagic necrotic mass composed of a highly cellular spindle and epithelioid malignancy with abundant hemosiderin deposition (Figure 5). In addition, several atypical mitotic figures and malignant multinucleated tumor giant cells were randomly scattered throughout the neoplasm.

At first follow-up, the patient reported significant pain relief and asked to begin titrating off her chronic pain medicine. Clinical staging, which involved performing whole-body positron emission tomography/computed tomography, revealed nothing concerning for metastases. When this report was being written, the patient was being monitored for recurrent disease in accordance with National Comprehensive Cancer Network guidelines. In the absence of residual sarcoma, our medical oncology team discussed adjuvant chemotherapy options with her. Subsequently, however, she proceeded only with observation and periodic imaging.

Malignant transformation of a benign GCT is extremely rare, especially in cases in which the tumor bed has not previously undergone radiation therapy. Although the literature includes historical case reports, primary and secondary malignant GCTs comprise <9% of all GCTs.^11,13,14 Primary bone epithelioid angiosarcoma is also extremely rare, especially in the calcaneus; only 1 case is described in the literature.¹⁵ In this article, we report on a benign GCT of bone that transformed into an epithelioid angiosarcoma more than a decade after the GCT was treated with curettage and cementation.

The fact that the malignant areas of a previous tumor may have been missed because of sampling error is important for benign GCT of bone in the early postoperative period, as distinguishing between early malignant transformation and an overlooked malignancy may not be possible. However, transformation is more likely the case when a benign GCT becomes a high-grade malignancy after a long disease-free interval. Several authors have indicated that a benign GCT tumor recurring with a secondary malignancy 2 to 5 years after initial GCT treatment suggests malignant transformation.¹⁶ Grote and colleagues¹⁰ compiled reports of malignant transformation of GCT of bone and described the clinicopathologic features of secondary malignant transformation of GCTs. The data they compiled and data from several other studies indicate a poor prognosis after malignant transformation of GCT; 4 years after diagnosis, mean survival is 40% to 50%.^10,16 The most common clinical presentation of transformation of GCT into malignancy is pain, often with coincident swelling of the native wound bed. However, a few cases have been identified with radiologic imaging alone and without a period of clinical symptoms.¹⁶

To our knowledge, this case report is the first to describe a longitudinal assessment of the transformation of a benign GCT of bone into an epithelioid angiosarcoma. Whereas an earlier reported GCT of bone transformed into epithelioid angiosarcoma after irradiation,¹² our patient’s GCT of bone transformed without irradiation. GCTs of bone are locally aggressive benign tumors and are relatively rare. Malignant transformation of a benign bone tumor a decade after initial, definitive treatment is concerning, especially given the poor prognosis after malignant transformation in this clinical scenario. Current adjuvant treatments have not changed the prognosis. The literature includes a wide variety of histologic transformations, including high-grade sarcomas, after a long disease-free interval. Although malignant transformation of benign GCTs is rare, clinicians should be aware of the potential. Interval monitoring of GCTs may be necessary in patients with symptoms concerning for malignant transformation—pain or swelling in the wound bed—and patients should know to immediately inform their physician of any changes in pain level or local wound bed. Clinicians should maintain a high clinical suspicion for malignant transformation or late recurrence of GCT in a patient with new pain at the site of a previously treated GCT of bone with a disease-free interval of several years.

Take-Home Points

• Malignant transformation of a benign GCT is extremely rare.
• It is difficult to distinguish between an early malignant transformation and an overlooked malignancy.
• The most common clinical presentation of transformation of GCT into malignancy is pain, often with swelling.
• Interval monitoring of GCTs may be necessary in patients with symptoms concerning for malignant transformation.
• Clinicians should maintain a high clinical suspicion for malignant transformation or late recurrence of GCT in a patient with new pain at the wound site.

Giant cell tumors (GCTs) of bone account for about 5% of all primary bone tumors in adults, with a predominance in the third decade in life.¹ Clinically, GCT of bone often presents with pain, pathologic fracture, and/or soft- tissue expansion in the epiphysis of long bones. However, GCT of bone also has been reported in non-long bones, such as the talus and the calcaneus.^2,3 Histologically, GCT of bone consists of neoplastic stromal cells, mononuclear histiocytic cells, and multinucleated giant cells that resemble osteoclasts.⁴ The radiologic appearance of GCT is often described as a lytic, eccentrically located bony lesion that extends near the articular surface in patients with closed physes. Many GCTs have aggressive radiologic features with possible extensive bony destruction and soft-tissue extension. 

Although categorized as a benign lesion, GCT can be locally aggressive, with a variable local recurrence rate of 0% to 65%, depending on treatment modality and skeletal location. Given the aggressiveness of GCT of bone, recommendations for operative intervention include intralesional curettage with adjuvant therapy (eg, cryotherapy, phenol, argon beam, electrocautery) and placement of bone void fillers (eg, bone graft polymethylmethacrylate). Wide resection is recommended when the articular surface is no longer viable for reconstruction secondary to extensive destruction. Some authors have reported that surgical margin is the only risk factor in local recurrence,^5,6 and thus complete resection may be needed for tumor eradication. In addition, about 3% of GCTs demonstrate benign pulmonary implants, which have been cited as cause of death in 16% to 25% of reported cases of pulmonary spread.^7,8

The literature includes few reports of primary or secondary malignant transformation of GCT. Hutter and colleagues⁹ defined primary malignant GCT as GCT with sarcomatous tissue juxtaposed with zones of typical benign GCT cells. Secondary malignant GCT is a sarcomatous lesion at the site of a previously documented benign GCT. Secondary malignant GCT of bone histologically has been classified as a fibrosarcoma, malignant fibrous histiocytoma, or osteosarcoma transformation.¹⁰ 

Most malignant transformations of GCT of bone have been attributed to previous irradiation of the lesion.^11,12 However, there are some case reports of benign bone GCT malignant transformation in situ without any other medical intervention. It was reported that non-radiation-induced secondary transformations occur relatively early after GCT treatment.¹³ During the early stages of tumor recurrence, however, it is difficult to distinguish between malignant transformation and primary disease overlooked as a result of sampling error.

We report a case of secondary malignant transformation of GCT of bone 11 years after surgical curettage, cryotherapy, and cementation without adjuvant radiation therapy. To our knowledge, this case report is the first to describe transformation of a nonirradiated benign GCT into an aggressive, high-grade epithelioid angiosarcoma, a very rare vascular bone tumor. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

In July 2003, a 46-year-old woman presented with left heel pain of several months’ duration. Plain radiographs showed a nonaggressive-appearing lytic lesion of the superior aspect of the posterior calcaneal tuberosity with a small cortical incongruity along the superior margin of the lesion (Figures 1A-1D).

A postoperative splint was placed, and weight-bearing progressed over 6 weeks. The patient was followed at 2- to 3-month intervals over the first 5 postoperative years. She was able to work and perform activities of daily living, but her postoperative course was complicated by significant chronic pain in multiple extremities and long-term treatment by the chronic pain service. At no time did postoperative imaging—magnetic resonance imaging (MRI) at 6 years, whole-body bone scan at 7 years, plain radiographs at 10 years—show evidence of recurrence.

Radiographs showed stable postoperative changes with a small radiolucent area (with sclerotic rim) surrounding the cement-bone interface. Given its proximity to the Achilles tendon and more motion than usual at the wound site, the radiolucency likely was caused by small movements of the interface. The radiolucent area remained stable over a 15-month period.

Whole-body bone scan showed a small area of osteoblastic activity in the left calcaneus, consistent with inflammation surrounding the bone- cement interface, but the uptake was minor relative to other areas of signal, and there were no significant inflammatory reactive changes on MRI (Figures 3A, 3B).

Over 11 years, regular 6- to 12-month follow-up examinations revealed no significant changes in the left foot or in plain radiographs of the chest. In addition, physical examinations revealed no evidence of a palpable mass of the left foot.

In July 2014 (11 years after curettage and cementation), the patient presented to her pain clinic appointment with severe left foot pain. She said that, over a few weeks, she experienced a significant increase in pain and developed posterolateral foot swelling, which limited her ability to ambulate. Plain radiographs showed a significant soft-tissue prominence around the posterior calcaneus, increased lucency around the bone-cement interface in the calcaneus with elevation, and a cortical break of the superior margin of the posterior calcaneus (Figures 3C, 3D). MRI showed a large lobular mass in the calcaneus and surrounding soft tissue with T1 and T2 signal heterogeneity and enhancement after administration of gadolinium (Figures 4A-4D). There was a large extraosseous extension of the calcaneus-based mass laterally and superiorly with edema in the surrounding hindfoot region (Figure 4).

Physical examination revealed exquisite tenderness along the lateral and posterior aspects of the left hindfoot. The patient was unable to bear weight and had soft-tissue swelling throughout the foot and mid calf as well as a palpable mass in the posterior heel. She was otherwise neurovascularly intact through all distributions of the left lower extremity. It was unclear if the GCT of the calcaneus had recurred or if there was a new, secondary tumor. Given her severe pain and morbidity, the patient decided to proceed with open biopsy and a pathology-pending plan for possible amputation in the near future.

In August 2014, an open biopsy with intraoperative frozen evaluation yielded a diagnosis of malignant neoplasm not otherwise specified. Permanent sections showed a proliferation of malignant epithelioid cells with extensive necrosis, hemorrhage, and hemosiderin deposition but no multinucleated giant cells.

Transformation of the GCT into a high-grade epithelioid angiosarcoma prompted presentation of the patient’s case to a multidisciplinary board of physicians with a focused clinical practice in sarcoma management. The board included board-certified specialists in orthopedic oncology, pathology, musculoskeletal radiology, medical oncology, and radiation oncology. Although discussion included pre-resection use of neoadjuvant chemotherapy to evaluate for disease response, the patient’s severe pain led her to forgo this treatment and proceed directly to below-knee amputation.

Amputation revealed a 7.7-cm hemorrhagic necrotic mass composed of a highly cellular spindle and epithelioid malignancy with abundant hemosiderin deposition (Figure 5). In addition, several atypical mitotic figures and malignant multinucleated tumor giant cells were randomly scattered throughout the neoplasm.

At first follow-up, the patient reported significant pain relief and asked to begin titrating off her chronic pain medicine. Clinical staging, which involved performing whole-body positron emission tomography/computed tomography, revealed nothing concerning for metastases. When this report was being written, the patient was being monitored for recurrent disease in accordance with National Comprehensive Cancer Network guidelines. In the absence of residual sarcoma, our medical oncology team discussed adjuvant chemotherapy options with her. Subsequently, however, she proceeded only with observation and periodic imaging.

Malignant transformation of a benign GCT is extremely rare, especially in cases in which the tumor bed has not previously undergone radiation therapy. Although the literature includes historical case reports, primary and secondary malignant GCTs comprise <9% of all GCTs.^11,13,14 Primary bone epithelioid angiosarcoma is also extremely rare, especially in the calcaneus; only 1 case is described in the literature.¹⁵ In this article, we report on a benign GCT of bone that transformed into an epithelioid angiosarcoma more than a decade after the GCT was treated with curettage and cementation.

The fact that the malignant areas of a previous tumor may have been missed because of sampling error is important for benign GCT of bone in the early postoperative period, as distinguishing between early malignant transformation and an overlooked malignancy may not be possible. However, transformation is more likely the case when a benign GCT becomes a high-grade malignancy after a long disease-free interval. Several authors have indicated that a benign GCT tumor recurring with a secondary malignancy 2 to 5 years after initial GCT treatment suggests malignant transformation.¹⁶ Grote and colleagues¹⁰ compiled reports of malignant transformation of GCT of bone and described the clinicopathologic features of secondary malignant transformation of GCTs. The data they compiled and data from several other studies indicate a poor prognosis after malignant transformation of GCT; 4 years after diagnosis, mean survival is 40% to 50%.^10,16 The most common clinical presentation of transformation of GCT into malignancy is pain, often with coincident swelling of the native wound bed. However, a few cases have been identified with radiologic imaging alone and without a period of clinical symptoms.¹⁶

To our knowledge, this case report is the first to describe a longitudinal assessment of the transformation of a benign GCT of bone into an epithelioid angiosarcoma. Whereas an earlier reported GCT of bone transformed into epithelioid angiosarcoma after irradiation,¹² our patient’s GCT of bone transformed without irradiation. GCTs of bone are locally aggressive benign tumors and are relatively rare. Malignant transformation of a benign bone tumor a decade after initial, definitive treatment is concerning, especially given the poor prognosis after malignant transformation in this clinical scenario. Current adjuvant treatments have not changed the prognosis. The literature includes a wide variety of histologic transformations, including high-grade sarcomas, after a long disease-free interval. Although malignant transformation of benign GCTs is rare, clinicians should be aware of the potential. Interval monitoring of GCTs may be necessary in patients with symptoms concerning for malignant transformation—pain or swelling in the wound bed—and patients should know to immediately inform their physician of any changes in pain level or local wound bed. Clinicians should maintain a high clinical suspicion for malignant transformation or late recurrence of GCT in a patient with new pain at the site of a previously treated GCT of bone with a disease-free interval of several years.

Take-Home Points

• Malignant transformation of a benign GCT is extremely rare.
• It is difficult to distinguish between an early malignant transformation and an overlooked malignancy.
• The most common clinical presentation of transformation of GCT into malignancy is pain, often with swelling.
• Interval monitoring of GCTs may be necessary in patients with symptoms concerning for malignant transformation.
• Clinicians should maintain a high clinical suspicion for malignant transformation or late recurrence of GCT in a patient with new pain at the wound site.

Giant cell tumors (GCTs) of bone account for about 5% of all primary bone tumors in adults, with a predominance in the third decade in life.¹ Clinically, GCT of bone often presents with pain, pathologic fracture, and/or soft- tissue expansion in the epiphysis of long bones. However, GCT of bone also has been reported in non-long bones, such as the talus and the calcaneus.^2,3 Histologically, GCT of bone consists of neoplastic stromal cells, mononuclear histiocytic cells, and multinucleated giant cells that resemble osteoclasts.⁴ The radiologic appearance of GCT is often described as a lytic, eccentrically located bony lesion that extends near the articular surface in patients with closed physes. Many GCTs have aggressive radiologic features with possible extensive bony destruction and soft-tissue extension. 

Although categorized as a benign lesion, GCT can be locally aggressive, with a variable local recurrence rate of 0% to 65%, depending on treatment modality and skeletal location. Given the aggressiveness of GCT of bone, recommendations for operative intervention include intralesional curettage with adjuvant therapy (eg, cryotherapy, phenol, argon beam, electrocautery) and placement of bone void fillers (eg, bone graft polymethylmethacrylate). Wide resection is recommended when the articular surface is no longer viable for reconstruction secondary to extensive destruction. Some authors have reported that surgical margin is the only risk factor in local recurrence,^5,6 and thus complete resection may be needed for tumor eradication. In addition, about 3% of GCTs demonstrate benign pulmonary implants, which have been cited as cause of death in 16% to 25% of reported cases of pulmonary spread.^7,8

The literature includes few reports of primary or secondary malignant transformation of GCT. Hutter and colleagues⁹ defined primary malignant GCT as GCT with sarcomatous tissue juxtaposed with zones of typical benign GCT cells. Secondary malignant GCT is a sarcomatous lesion at the site of a previously documented benign GCT. Secondary malignant GCT of bone histologically has been classified as a fibrosarcoma, malignant fibrous histiocytoma, or osteosarcoma transformation.¹⁰ 

Most malignant transformations of GCT of bone have been attributed to previous irradiation of the lesion.^11,12 However, there are some case reports of benign bone GCT malignant transformation in situ without any other medical intervention. It was reported that non-radiation-induced secondary transformations occur relatively early after GCT treatment.¹³ During the early stages of tumor recurrence, however, it is difficult to distinguish between malignant transformation and primary disease overlooked as a result of sampling error.

We report a case of secondary malignant transformation of GCT of bone 11 years after surgical curettage, cryotherapy, and cementation without adjuvant radiation therapy. To our knowledge, this case report is the first to describe transformation of a nonirradiated benign GCT into an aggressive, high-grade epithelioid angiosarcoma, a very rare vascular bone tumor. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

In July 2003, a 46-year-old woman presented with left heel pain of several months’ duration. Plain radiographs showed a nonaggressive-appearing lytic lesion of the superior aspect of the posterior calcaneal tuberosity with a small cortical incongruity along the superior margin of the lesion (Figures 1A-1D).

A postoperative splint was placed, and weight-bearing progressed over 6 weeks. The patient was followed at 2- to 3-month intervals over the first 5 postoperative years. She was able to work and perform activities of daily living, but her postoperative course was complicated by significant chronic pain in multiple extremities and long-term treatment by the chronic pain service. At no time did postoperative imaging—magnetic resonance imaging (MRI) at 6 years, whole-body bone scan at 7 years, plain radiographs at 10 years—show evidence of recurrence.

Radiographs showed stable postoperative changes with a small radiolucent area (with sclerotic rim) surrounding the cement-bone interface. Given its proximity to the Achilles tendon and more motion than usual at the wound site, the radiolucency likely was caused by small movements of the interface. The radiolucent area remained stable over a 15-month period.

Whole-body bone scan showed a small area of osteoblastic activity in the left calcaneus, consistent with inflammation surrounding the bone- cement interface, but the uptake was minor relative to other areas of signal, and there were no significant inflammatory reactive changes on MRI (Figures 3A, 3B).

Over 11 years, regular 6- to 12-month follow-up examinations revealed no significant changes in the left foot or in plain radiographs of the chest. In addition, physical examinations revealed no evidence of a palpable mass of the left foot.

In July 2014 (11 years after curettage and cementation), the patient presented to her pain clinic appointment with severe left foot pain. She said that, over a few weeks, she experienced a significant increase in pain and developed posterolateral foot swelling, which limited her ability to ambulate. Plain radiographs showed a significant soft-tissue prominence around the posterior calcaneus, increased lucency around the bone-cement interface in the calcaneus with elevation, and a cortical break of the superior margin of the posterior calcaneus (Figures 3C, 3D). MRI showed a large lobular mass in the calcaneus and surrounding soft tissue with T1 and T2 signal heterogeneity and enhancement after administration of gadolinium (Figures 4A-4D). There was a large extraosseous extension of the calcaneus-based mass laterally and superiorly with edema in the surrounding hindfoot region (Figure 4).

Physical examination revealed exquisite tenderness along the lateral and posterior aspects of the left hindfoot. The patient was unable to bear weight and had soft-tissue swelling throughout the foot and mid calf as well as a palpable mass in the posterior heel. She was otherwise neurovascularly intact through all distributions of the left lower extremity. It was unclear if the GCT of the calcaneus had recurred or if there was a new, secondary tumor. Given her severe pain and morbidity, the patient decided to proceed with open biopsy and a pathology-pending plan for possible amputation in the near future.

In August 2014, an open biopsy with intraoperative frozen evaluation yielded a diagnosis of malignant neoplasm not otherwise specified. Permanent sections showed a proliferation of malignant epithelioid cells with extensive necrosis, hemorrhage, and hemosiderin deposition but no multinucleated giant cells.

Transformation of the GCT into a high-grade epithelioid angiosarcoma prompted presentation of the patient’s case to a multidisciplinary board of physicians with a focused clinical practice in sarcoma management. The board included board-certified specialists in orthopedic oncology, pathology, musculoskeletal radiology, medical oncology, and radiation oncology. Although discussion included pre-resection use of neoadjuvant chemotherapy to evaluate for disease response, the patient’s severe pain led her to forgo this treatment and proceed directly to below-knee amputation.

Amputation revealed a 7.7-cm hemorrhagic necrotic mass composed of a highly cellular spindle and epithelioid malignancy with abundant hemosiderin deposition (Figure 5). In addition, several atypical mitotic figures and malignant multinucleated tumor giant cells were randomly scattered throughout the neoplasm.

At first follow-up, the patient reported significant pain relief and asked to begin titrating off her chronic pain medicine. Clinical staging, which involved performing whole-body positron emission tomography/computed tomography, revealed nothing concerning for metastases. When this report was being written, the patient was being monitored for recurrent disease in accordance with National Comprehensive Cancer Network guidelines. In the absence of residual sarcoma, our medical oncology team discussed adjuvant chemotherapy options with her. Subsequently, however, she proceeded only with observation and periodic imaging.

Malignant transformation of a benign GCT is extremely rare, especially in cases in which the tumor bed has not previously undergone radiation therapy. Although the literature includes historical case reports, primary and secondary malignant GCTs comprise <9% of all GCTs.^11,13,14 Primary bone epithelioid angiosarcoma is also extremely rare, especially in the calcaneus; only 1 case is described in the literature.¹⁵ In this article, we report on a benign GCT of bone that transformed into an epithelioid angiosarcoma more than a decade after the GCT was treated with curettage and cementation.

The fact that the malignant areas of a previous tumor may have been missed because of sampling error is important for benign GCT of bone in the early postoperative period, as distinguishing between early malignant transformation and an overlooked malignancy may not be possible. However, transformation is more likely the case when a benign GCT becomes a high-grade malignancy after a long disease-free interval. Several authors have indicated that a benign GCT tumor recurring with a secondary malignancy 2 to 5 years after initial GCT treatment suggests malignant transformation.¹⁶ Grote and colleagues¹⁰ compiled reports of malignant transformation of GCT of bone and described the clinicopathologic features of secondary malignant transformation of GCTs. The data they compiled and data from several other studies indicate a poor prognosis after malignant transformation of GCT; 4 years after diagnosis, mean survival is 40% to 50%.^10,16 The most common clinical presentation of transformation of GCT into malignancy is pain, often with coincident swelling of the native wound bed. However, a few cases have been identified with radiologic imaging alone and without a period of clinical symptoms.¹⁶

To our knowledge, this case report is the first to describe a longitudinal assessment of the transformation of a benign GCT of bone into an epithelioid angiosarcoma. Whereas an earlier reported GCT of bone transformed into epithelioid angiosarcoma after irradiation,¹² our patient’s GCT of bone transformed without irradiation. GCTs of bone are locally aggressive benign tumors and are relatively rare. Malignant transformation of a benign bone tumor a decade after initial, definitive treatment is concerning, especially given the poor prognosis after malignant transformation in this clinical scenario. Current adjuvant treatments have not changed the prognosis. The literature includes a wide variety of histologic transformations, including high-grade sarcomas, after a long disease-free interval. Although malignant transformation of benign GCTs is rare, clinicians should be aware of the potential. Interval monitoring of GCTs may be necessary in patients with symptoms concerning for malignant transformation—pain or swelling in the wound bed—and patients should know to immediately inform their physician of any changes in pain level or local wound bed. Clinicians should maintain a high clinical suspicion for malignant transformation or late recurrence of GCT in a patient with new pain at the site of a previously treated GCT of bone with a disease-free interval of several years.

The amniotic membrane is a multilayer tissue forming the innermost layer of the amniotic sac that surrounds the developing fetus. It is comprised of 5 layers, from the inside out: a single layer of epithelial cells, a thick basement membrane, a compact layer, a fibroblast layer, and a spongy layer that abuts the surrounding chorion (Figure 1).¹

Amniotic epithelial cells are derived from the pluripotent epiblast at approximately day 8 of gestation. This is well before gastrulation occurs at days 15 to 17, considered the “tipping point” when pluripotent cells differentiate into ectoderm, mesoderm, and endoderm.³ These cells express Oct-4 and Nanog, 2 molecular markers that are indicative of pluripotency.³ Two cell types have been identified in amniotic tissues that possess stem cell-like characteristics: human amniotic epithelial cells and human amniotic mesenchymal stromal cells.⁴ Both of these cell types have demonstrated the ability to differentiate into various cell lineages, including endothelial cells, adipocytes, myogenic cells, neurogenic cells, chondrocytes, tenocytes, and osteogenic cells.^5-7 These previously reported findings indicate that amniotic cells and tissue have the capability to generate mesenchymal tissues.

FDA Classification and Available Forms

The US Food and Drug Administration (FDA) classifies amnion as an allograft tissue under Human Cells, Tissues, and Cellular and Tissue-Based Products (HCT/Ps) 361. To meet criteria, the tissue needs to be minimally manipulated. It is to be for homologous use and cannot be combined with other cells or tissues. There can be no systemic effect or dependence on the metabolic activity of living cells to achieve its primary function. The tissue has to have a localized effect in vivo. Therefore, amnion allograft tissue can be commercialized, provided it is not marketed as a stem cell product or to contain viable cells.

Amniotic tissue is commercially available in several forms.

Safety

Amniotic tissue has been used for over 100 years in burn, ophthalmology, and chronic wound patients with favorable outcomes and no adverse effects reported in the literature. Unlike embryonic stem cells, which may be tumorigenic,⁸ amniotic cells do not possess any known tumorigenicity.⁹ In one study, 50 immunodeficient mice were injected with 1 to 2 million amniotic epithelial cells and observed for a maximum of 516 days with no tumorigenicity observed in any of the animals.¹⁰ In another study, amniotic epithelial cells were implanted into the forearms of healthy volunteers and no immunologic response was observed in any of the recipients.¹¹ Furthermore, viable amniotic cells were recovered via biopsy 7 weeks following transplantation, demonstrating viability of the transplanted cells.¹¹ The lack of tumorigenicity and immunologic response in hosts is due in part to the fact that amniotic cells do not express human leukocyte antigen class II antigens and only express class I antigens in small amounts.³

Advantages of Amnion Tissue

Amniotic tissue is readily available, as it is often discarded after childbirth. The use of this tissue poses no added risk to the fetus or mother, eliminating the ethical concerns associated with obtaining embryonic stem cells. Amniotic tissue is comprised of an extracellular matrix, which acts as a natural scaffold for cellular attachment and structural support for cells as well as collagen types I, III, IV, V, and VI, hyaluronic acid, and a host of growth factors.¹² In addition, it possesses antimicrobial properties, including beta-defensins.¹³

Amniotic tissue has been shown to exert an anti-inflammatory effect by inhibiting the inflammatory cascade. Specifically, it has been shown to inhibit cytokines such as tumor necrosis factor-alpha in the presence of dendritic cells,¹⁴ as well as inhibiting transforming growth factor-beta, interleukin-8, and fibroblast proliferation.¹⁵ These findings indicate that amniotic tissue has the ability to dampen the “cytokine storm” that occurs after an injury in an adult, which would lead to beneficial impacts on healing and scar formation in patients.¹⁶

Basic Science and Animal Studies

Several studies have demonstrated promising outcomes for orthopedic applications in vitro. A comparison of osteogenic potential found that amniotic fluid-derived cells were able to produce approximately 5 times more mineralized matrix than bone marrow-derived mesenchymal stem cells.¹⁷ More recently, Si and colleagues¹⁸ compared the osteogenic potential of human amniotic epithelial cells, amniotic cells, and human bone marrow-derived mesenchymal stem cells. They found that all 3 cell lines were osteogenic, though the amniotic epithelial cells had better immunomodulatory properties and marginally less osteogenic potential than the other 2 cell types. Furthermore, several in vivo animal studies have demonstrated the ability of human amniotic cells to stimulate bone growth in rats,^19,20 rabbits,²¹ and sheep.²²

Amniotic tissue also possesses potential for chondrogenesis. Cryopreserved human amniotic membrane cells used for in vitro human osteoarthritis tissue scaffolds did not differentiate in culture, and they integrated and repaired damaged articular cartilage.²³ Various in vitro^24,25 and animal in vivo^26,27 studies have reported similar supportive findings. Kunisaki and colleagues²⁸ used sheep amniotic fluid mesenchymal stem cells to reconstruct lamb tracheal cartilage in utero, concluding that cells obtained from the amniotic fluid possess chondrogenic capabilities. Further in utero lamb studies of cartilage artificial defects, given 7 days to settle before adding a hypocellular matrix as a scaffold, showed chondrocyte density and cell architecture was restored at the defect site after 28 days without the formation of an inflammatory response or scar tissue.²⁹

Amniotic tissue has had similar success in tendon repair studies in vivo.^9,30,31 Barboni and colleagues³² implanted amniotic epithelial cells (AECs) into artificially created sheep Achilles tendon defects in situ, inducing superior structural and mechanical recovery in the defects at a faster rate compared to controls not receiving AECs. Healing via AECs started at the healthy tissue around the borders of the defect and progressed centrally, suggesting recruitment of native progenitor cells to the lesion.³² Kueckelhaus and colleagues³³ investigated the role of amnion-derived cellular cytokine solution in the healing of transections of rat Achilles tendons, reporting improved mechanical properties of healing tendons at early time points compared to controls. Beredjiklian and colleagues³⁴ compared the healing of transected extensor tendons of pregnant ewes and of their fetus in utero, reporting a reparative form of healing with scar formation in adult subjects and regenerative form of healing without scar formation or inflammation in fetal subjects.

Amniotic tissue has properties that prevent adhesion formation around tendons following injury and reconstruction.³⁵ Ozgenel³⁶ investigated the effects of hyaluronic acid and amniotic membrane alone and in combination on the presence of adhesions and the rate of healing following chicken flexor tendon repair. The study found amniotic membrane wrapped around the repaired tendon was superior in preventing adhesion formation. Kim and colleagues³⁷ report a similar reduction in fibrosis and adhesion following application of a human amniotic membrane wrap to rabbit ulnar neurorrhaphy sites.

This barrier function of amniotic tissue has also been investigated in the prevention of surgical scarring and peridural fibrosis in animal models following spinal discectomy. A study in canine models showed a reduction of scarring following the application of cross-linked amniotic membrane compared to freeze dried amniotic membrane.³⁸ Similar reductions in scarring in rat models with the application of freeze-dried amniotic membrane compared to negative controls have been reported.³⁹

Human Studies

A randomized trial investigated the outcomes of prenatal vs postnatal repair of myelomeningocele in humans, finding a reduced need for implanted shunts and improved functional outcomes at 30 months of life in the prenatal intervention group compared to the postnatal group.⁴⁰ This study was concluded early due to the efficacy of prenatal surgery and the benefit of nervous system repair in utero in the presence of amniotic growth factors.

Vines and colleagues⁴¹ performed a 6-patient feasibility study using amnion injections to treat symptomatic knee osteoarthritis. Each patient received a single intra-articular cryopreserved amniotic suspension allograft (ASA) injection and was followed for 1 year. No adverse outcomes were reported, with the only abnormal finding being a small increase in serum immunoglobulin G and immunoglobulin E levels. Intra-articular ASA injection was found to be safe, but a large-scale trial investigating symptomatic relief was recommended.⁴¹

Most of the human studies using amnion pertain to foot and ankle surgery. Its use as a treatment for diabetic foot ulcers and recalcitrant plantar fasciitis was one of the early-recognized successes.^42-45 Zelen and colleagues⁴⁶ investigated the applications of injectable micronized dehydrated human amniotic/chorionic membrane as an alternative to surgical intervention in the treatment of refractory plantar fasciitis. This prospective, randomized trial with 45 patients showed significant improvement in plantar fasciitis symptoms at 8 weeks compared to controls (saline injections). A similar study compared the use of cryopreserved human amniotic membrane (c-hAM) injections to corticosteroid injections in plantar fasciitis patients.⁴⁷ The results indicated that c-hAM is safe and comparable to corticosteroids, with the authors noting that pain improvement was greatest in patients receiving 2 injections of c-hAM at 18 weeks.

Tendon wrapping, in which the amniotic membrane is laid over a tendon repair, has been reported with success. Amniotic membrane is superior to collagen for tendon wrapping as it actively contributes to healing while minimizing adhesions, which collagen alone cannot do.⁴⁸ The membrane serves as a protective sheath around repaired tendons with anti-inflammatory, anti-adhesive, immunomodulatory, and antimicrobial benefits. A 124-patient study demonstrated the safety of using amnion in this manner, and the authors reported a decreased rate of complication compared to previously published data.⁴⁹ Another study of 14 patients undergoing foot and ankle surgery with tendon wrapping reported clinical improvement with reduced pain and greater functional outcomes postoperatively compared to preoperative measurements.⁵⁰

Conclusion

Amniotic membrane-derived tissues are safe and non-tumorigenic, producing an abundance of growth factors that have shown promise as tissue scaffolds and as aids in the regeneration of human bone and soft tissues. Amnion applications in orthopedic surgery may be numerous, but development is ongoing. Given the vast array of in vitro and in vivo animal data supporting the benefits of amnion in tissue regeneration, orthopedic surgeons and researchers should place emphasis on conducting clinical studies to validate the safety and efficacy of amniotic cells in the treatment of orthopedic conditions.

Am J Orthop. 2016;45(7):E421-E425. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The amniotic membrane is a multilayer tissue forming the innermost layer of the amniotic sac that surrounds the developing fetus. It is comprised of 5 layers, from the inside out: a single layer of epithelial cells, a thick basement membrane, a compact layer, a fibroblast layer, and a spongy layer that abuts the surrounding chorion (Figure 1).¹

Amniotic epithelial cells are derived from the pluripotent epiblast at approximately day 8 of gestation. This is well before gastrulation occurs at days 15 to 17, considered the “tipping point” when pluripotent cells differentiate into ectoderm, mesoderm, and endoderm.³ These cells express Oct-4 and Nanog, 2 molecular markers that are indicative of pluripotency.³ Two cell types have been identified in amniotic tissues that possess stem cell-like characteristics: human amniotic epithelial cells and human amniotic mesenchymal stromal cells.⁴ Both of these cell types have demonstrated the ability to differentiate into various cell lineages, including endothelial cells, adipocytes, myogenic cells, neurogenic cells, chondrocytes, tenocytes, and osteogenic cells.^5-7 These previously reported findings indicate that amniotic cells and tissue have the capability to generate mesenchymal tissues.

FDA Classification and Available Forms

The US Food and Drug Administration (FDA) classifies amnion as an allograft tissue under Human Cells, Tissues, and Cellular and Tissue-Based Products (HCT/Ps) 361. To meet criteria, the tissue needs to be minimally manipulated. It is to be for homologous use and cannot be combined with other cells or tissues. There can be no systemic effect or dependence on the metabolic activity of living cells to achieve its primary function. The tissue has to have a localized effect in vivo. Therefore, amnion allograft tissue can be commercialized, provided it is not marketed as a stem cell product or to contain viable cells.

Amniotic tissue is commercially available in several forms.

Safety

Amniotic tissue has been used for over 100 years in burn, ophthalmology, and chronic wound patients with favorable outcomes and no adverse effects reported in the literature. Unlike embryonic stem cells, which may be tumorigenic,⁸ amniotic cells do not possess any known tumorigenicity.⁹ In one study, 50 immunodeficient mice were injected with 1 to 2 million amniotic epithelial cells and observed for a maximum of 516 days with no tumorigenicity observed in any of the animals.¹⁰ In another study, amniotic epithelial cells were implanted into the forearms of healthy volunteers and no immunologic response was observed in any of the recipients.¹¹ Furthermore, viable amniotic cells were recovered via biopsy 7 weeks following transplantation, demonstrating viability of the transplanted cells.¹¹ The lack of tumorigenicity and immunologic response in hosts is due in part to the fact that amniotic cells do not express human leukocyte antigen class II antigens and only express class I antigens in small amounts.³

Advantages of Amnion Tissue

Amniotic tissue is readily available, as it is often discarded after childbirth. The use of this tissue poses no added risk to the fetus or mother, eliminating the ethical concerns associated with obtaining embryonic stem cells. Amniotic tissue is comprised of an extracellular matrix, which acts as a natural scaffold for cellular attachment and structural support for cells as well as collagen types I, III, IV, V, and VI, hyaluronic acid, and a host of growth factors.¹² In addition, it possesses antimicrobial properties, including beta-defensins.¹³

Amniotic tissue has been shown to exert an anti-inflammatory effect by inhibiting the inflammatory cascade. Specifically, it has been shown to inhibit cytokines such as tumor necrosis factor-alpha in the presence of dendritic cells,¹⁴ as well as inhibiting transforming growth factor-beta, interleukin-8, and fibroblast proliferation.¹⁵ These findings indicate that amniotic tissue has the ability to dampen the “cytokine storm” that occurs after an injury in an adult, which would lead to beneficial impacts on healing and scar formation in patients.¹⁶

Basic Science and Animal Studies

Several studies have demonstrated promising outcomes for orthopedic applications in vitro. A comparison of osteogenic potential found that amniotic fluid-derived cells were able to produce approximately 5 times more mineralized matrix than bone marrow-derived mesenchymal stem cells.¹⁷ More recently, Si and colleagues¹⁸ compared the osteogenic potential of human amniotic epithelial cells, amniotic cells, and human bone marrow-derived mesenchymal stem cells. They found that all 3 cell lines were osteogenic, though the amniotic epithelial cells had better immunomodulatory properties and marginally less osteogenic potential than the other 2 cell types. Furthermore, several in vivo animal studies have demonstrated the ability of human amniotic cells to stimulate bone growth in rats,^19,20 rabbits,²¹ and sheep.²²

Amniotic tissue also possesses potential for chondrogenesis. Cryopreserved human amniotic membrane cells used for in vitro human osteoarthritis tissue scaffolds did not differentiate in culture, and they integrated and repaired damaged articular cartilage.²³ Various in vitro^24,25 and animal in vivo^26,27 studies have reported similar supportive findings. Kunisaki and colleagues²⁸ used sheep amniotic fluid mesenchymal stem cells to reconstruct lamb tracheal cartilage in utero, concluding that cells obtained from the amniotic fluid possess chondrogenic capabilities. Further in utero lamb studies of cartilage artificial defects, given 7 days to settle before adding a hypocellular matrix as a scaffold, showed chondrocyte density and cell architecture was restored at the defect site after 28 days without the formation of an inflammatory response or scar tissue.²⁹

Amniotic tissue has had similar success in tendon repair studies in vivo.^9,30,31 Barboni and colleagues³² implanted amniotic epithelial cells (AECs) into artificially created sheep Achilles tendon defects in situ, inducing superior structural and mechanical recovery in the defects at a faster rate compared to controls not receiving AECs. Healing via AECs started at the healthy tissue around the borders of the defect and progressed centrally, suggesting recruitment of native progenitor cells to the lesion.³² Kueckelhaus and colleagues³³ investigated the role of amnion-derived cellular cytokine solution in the healing of transections of rat Achilles tendons, reporting improved mechanical properties of healing tendons at early time points compared to controls. Beredjiklian and colleagues³⁴ compared the healing of transected extensor tendons of pregnant ewes and of their fetus in utero, reporting a reparative form of healing with scar formation in adult subjects and regenerative form of healing without scar formation or inflammation in fetal subjects.

Amniotic tissue has properties that prevent adhesion formation around tendons following injury and reconstruction.³⁵ Ozgenel³⁶ investigated the effects of hyaluronic acid and amniotic membrane alone and in combination on the presence of adhesions and the rate of healing following chicken flexor tendon repair. The study found amniotic membrane wrapped around the repaired tendon was superior in preventing adhesion formation. Kim and colleagues³⁷ report a similar reduction in fibrosis and adhesion following application of a human amniotic membrane wrap to rabbit ulnar neurorrhaphy sites.

This barrier function of amniotic tissue has also been investigated in the prevention of surgical scarring and peridural fibrosis in animal models following spinal discectomy. A study in canine models showed a reduction of scarring following the application of cross-linked amniotic membrane compared to freeze dried amniotic membrane.³⁸ Similar reductions in scarring in rat models with the application of freeze-dried amniotic membrane compared to negative controls have been reported.³⁹

Human Studies

A randomized trial investigated the outcomes of prenatal vs postnatal repair of myelomeningocele in humans, finding a reduced need for implanted shunts and improved functional outcomes at 30 months of life in the prenatal intervention group compared to the postnatal group.⁴⁰ This study was concluded early due to the efficacy of prenatal surgery and the benefit of nervous system repair in utero in the presence of amniotic growth factors.

Vines and colleagues⁴¹ performed a 6-patient feasibility study using amnion injections to treat symptomatic knee osteoarthritis. Each patient received a single intra-articular cryopreserved amniotic suspension allograft (ASA) injection and was followed for 1 year. No adverse outcomes were reported, with the only abnormal finding being a small increase in serum immunoglobulin G and immunoglobulin E levels. Intra-articular ASA injection was found to be safe, but a large-scale trial investigating symptomatic relief was recommended.⁴¹

Most of the human studies using amnion pertain to foot and ankle surgery. Its use as a treatment for diabetic foot ulcers and recalcitrant plantar fasciitis was one of the early-recognized successes.^42-45 Zelen and colleagues⁴⁶ investigated the applications of injectable micronized dehydrated human amniotic/chorionic membrane as an alternative to surgical intervention in the treatment of refractory plantar fasciitis. This prospective, randomized trial with 45 patients showed significant improvement in plantar fasciitis symptoms at 8 weeks compared to controls (saline injections). A similar study compared the use of cryopreserved human amniotic membrane (c-hAM) injections to corticosteroid injections in plantar fasciitis patients.⁴⁷ The results indicated that c-hAM is safe and comparable to corticosteroids, with the authors noting that pain improvement was greatest in patients receiving 2 injections of c-hAM at 18 weeks.

Tendon wrapping, in which the amniotic membrane is laid over a tendon repair, has been reported with success. Amniotic membrane is superior to collagen for tendon wrapping as it actively contributes to healing while minimizing adhesions, which collagen alone cannot do.⁴⁸ The membrane serves as a protective sheath around repaired tendons with anti-inflammatory, anti-adhesive, immunomodulatory, and antimicrobial benefits. A 124-patient study demonstrated the safety of using amnion in this manner, and the authors reported a decreased rate of complication compared to previously published data.⁴⁹ Another study of 14 patients undergoing foot and ankle surgery with tendon wrapping reported clinical improvement with reduced pain and greater functional outcomes postoperatively compared to preoperative measurements.⁵⁰

Conclusion

Amniotic membrane-derived tissues are safe and non-tumorigenic, producing an abundance of growth factors that have shown promise as tissue scaffolds and as aids in the regeneration of human bone and soft tissues. Amnion applications in orthopedic surgery may be numerous, but development is ongoing. Given the vast array of in vitro and in vivo animal data supporting the benefits of amnion in tissue regeneration, orthopedic surgeons and researchers should place emphasis on conducting clinical studies to validate the safety and efficacy of amniotic cells in the treatment of orthopedic conditions.

Am J Orthop. 2016;45(7):E421-E425. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The amniotic membrane is a multilayer tissue forming the innermost layer of the amniotic sac that surrounds the developing fetus. It is comprised of 5 layers, from the inside out: a single layer of epithelial cells, a thick basement membrane, a compact layer, a fibroblast layer, and a spongy layer that abuts the surrounding chorion (Figure 1).¹

Amniotic epithelial cells are derived from the pluripotent epiblast at approximately day 8 of gestation. This is well before gastrulation occurs at days 15 to 17, considered the “tipping point” when pluripotent cells differentiate into ectoderm, mesoderm, and endoderm.³ These cells express Oct-4 and Nanog, 2 molecular markers that are indicative of pluripotency.³ Two cell types have been identified in amniotic tissues that possess stem cell-like characteristics: human amniotic epithelial cells and human amniotic mesenchymal stromal cells.⁴ Both of these cell types have demonstrated the ability to differentiate into various cell lineages, including endothelial cells, adipocytes, myogenic cells, neurogenic cells, chondrocytes, tenocytes, and osteogenic cells.^5-7 These previously reported findings indicate that amniotic cells and tissue have the capability to generate mesenchymal tissues.

FDA Classification and Available Forms

The US Food and Drug Administration (FDA) classifies amnion as an allograft tissue under Human Cells, Tissues, and Cellular and Tissue-Based Products (HCT/Ps) 361. To meet criteria, the tissue needs to be minimally manipulated. It is to be for homologous use and cannot be combined with other cells or tissues. There can be no systemic effect or dependence on the metabolic activity of living cells to achieve its primary function. The tissue has to have a localized effect in vivo. Therefore, amnion allograft tissue can be commercialized, provided it is not marketed as a stem cell product or to contain viable cells.

Amniotic tissue is commercially available in several forms.

Safety

Amniotic tissue has been used for over 100 years in burn, ophthalmology, and chronic wound patients with favorable outcomes and no adverse effects reported in the literature. Unlike embryonic stem cells, which may be tumorigenic,⁸ amniotic cells do not possess any known tumorigenicity.⁹ In one study, 50 immunodeficient mice were injected with 1 to 2 million amniotic epithelial cells and observed for a maximum of 516 days with no tumorigenicity observed in any of the animals.¹⁰ In another study, amniotic epithelial cells were implanted into the forearms of healthy volunteers and no immunologic response was observed in any of the recipients.¹¹ Furthermore, viable amniotic cells were recovered via biopsy 7 weeks following transplantation, demonstrating viability of the transplanted cells.¹¹ The lack of tumorigenicity and immunologic response in hosts is due in part to the fact that amniotic cells do not express human leukocyte antigen class II antigens and only express class I antigens in small amounts.³

Advantages of Amnion Tissue

Amniotic tissue is readily available, as it is often discarded after childbirth. The use of this tissue poses no added risk to the fetus or mother, eliminating the ethical concerns associated with obtaining embryonic stem cells. Amniotic tissue is comprised of an extracellular matrix, which acts as a natural scaffold for cellular attachment and structural support for cells as well as collagen types I, III, IV, V, and VI, hyaluronic acid, and a host of growth factors.¹² In addition, it possesses antimicrobial properties, including beta-defensins.¹³

Amniotic tissue has been shown to exert an anti-inflammatory effect by inhibiting the inflammatory cascade. Specifically, it has been shown to inhibit cytokines such as tumor necrosis factor-alpha in the presence of dendritic cells,¹⁴ as well as inhibiting transforming growth factor-beta, interleukin-8, and fibroblast proliferation.¹⁵ These findings indicate that amniotic tissue has the ability to dampen the “cytokine storm” that occurs after an injury in an adult, which would lead to beneficial impacts on healing and scar formation in patients.¹⁶

Basic Science and Animal Studies

Several studies have demonstrated promising outcomes for orthopedic applications in vitro. A comparison of osteogenic potential found that amniotic fluid-derived cells were able to produce approximately 5 times more mineralized matrix than bone marrow-derived mesenchymal stem cells.¹⁷ More recently, Si and colleagues¹⁸ compared the osteogenic potential of human amniotic epithelial cells, amniotic cells, and human bone marrow-derived mesenchymal stem cells. They found that all 3 cell lines were osteogenic, though the amniotic epithelial cells had better immunomodulatory properties and marginally less osteogenic potential than the other 2 cell types. Furthermore, several in vivo animal studies have demonstrated the ability of human amniotic cells to stimulate bone growth in rats,^19,20 rabbits,²¹ and sheep.²²

Amniotic tissue also possesses potential for chondrogenesis. Cryopreserved human amniotic membrane cells used for in vitro human osteoarthritis tissue scaffolds did not differentiate in culture, and they integrated and repaired damaged articular cartilage.²³ Various in vitro^24,25 and animal in vivo^26,27 studies have reported similar supportive findings. Kunisaki and colleagues²⁸ used sheep amniotic fluid mesenchymal stem cells to reconstruct lamb tracheal cartilage in utero, concluding that cells obtained from the amniotic fluid possess chondrogenic capabilities. Further in utero lamb studies of cartilage artificial defects, given 7 days to settle before adding a hypocellular matrix as a scaffold, showed chondrocyte density and cell architecture was restored at the defect site after 28 days without the formation of an inflammatory response or scar tissue.²⁹

Amniotic tissue has had similar success in tendon repair studies in vivo.^9,30,31 Barboni and colleagues³² implanted amniotic epithelial cells (AECs) into artificially created sheep Achilles tendon defects in situ, inducing superior structural and mechanical recovery in the defects at a faster rate compared to controls not receiving AECs. Healing via AECs started at the healthy tissue around the borders of the defect and progressed centrally, suggesting recruitment of native progenitor cells to the lesion.³² Kueckelhaus and colleagues³³ investigated the role of amnion-derived cellular cytokine solution in the healing of transections of rat Achilles tendons, reporting improved mechanical properties of healing tendons at early time points compared to controls. Beredjiklian and colleagues³⁴ compared the healing of transected extensor tendons of pregnant ewes and of their fetus in utero, reporting a reparative form of healing with scar formation in adult subjects and regenerative form of healing without scar formation or inflammation in fetal subjects.

Amniotic tissue has properties that prevent adhesion formation around tendons following injury and reconstruction.³⁵ Ozgenel³⁶ investigated the effects of hyaluronic acid and amniotic membrane alone and in combination on the presence of adhesions and the rate of healing following chicken flexor tendon repair. The study found amniotic membrane wrapped around the repaired tendon was superior in preventing adhesion formation. Kim and colleagues³⁷ report a similar reduction in fibrosis and adhesion following application of a human amniotic membrane wrap to rabbit ulnar neurorrhaphy sites.

This barrier function of amniotic tissue has also been investigated in the prevention of surgical scarring and peridural fibrosis in animal models following spinal discectomy. A study in canine models showed a reduction of scarring following the application of cross-linked amniotic membrane compared to freeze dried amniotic membrane.³⁸ Similar reductions in scarring in rat models with the application of freeze-dried amniotic membrane compared to negative controls have been reported.³⁹

Human Studies

A randomized trial investigated the outcomes of prenatal vs postnatal repair of myelomeningocele in humans, finding a reduced need for implanted shunts and improved functional outcomes at 30 months of life in the prenatal intervention group compared to the postnatal group.⁴⁰ This study was concluded early due to the efficacy of prenatal surgery and the benefit of nervous system repair in utero in the presence of amniotic growth factors.

Vines and colleagues⁴¹ performed a 6-patient feasibility study using amnion injections to treat symptomatic knee osteoarthritis. Each patient received a single intra-articular cryopreserved amniotic suspension allograft (ASA) injection and was followed for 1 year. No adverse outcomes were reported, with the only abnormal finding being a small increase in serum immunoglobulin G and immunoglobulin E levels. Intra-articular ASA injection was found to be safe, but a large-scale trial investigating symptomatic relief was recommended.⁴¹

Most of the human studies using amnion pertain to foot and ankle surgery. Its use as a treatment for diabetic foot ulcers and recalcitrant plantar fasciitis was one of the early-recognized successes.^42-45 Zelen and colleagues⁴⁶ investigated the applications of injectable micronized dehydrated human amniotic/chorionic membrane as an alternative to surgical intervention in the treatment of refractory plantar fasciitis. This prospective, randomized trial with 45 patients showed significant improvement in plantar fasciitis symptoms at 8 weeks compared to controls (saline injections). A similar study compared the use of cryopreserved human amniotic membrane (c-hAM) injections to corticosteroid injections in plantar fasciitis patients.⁴⁷ The results indicated that c-hAM is safe and comparable to corticosteroids, with the authors noting that pain improvement was greatest in patients receiving 2 injections of c-hAM at 18 weeks.

Tendon wrapping, in which the amniotic membrane is laid over a tendon repair, has been reported with success. Amniotic membrane is superior to collagen for tendon wrapping as it actively contributes to healing while minimizing adhesions, which collagen alone cannot do.⁴⁸ The membrane serves as a protective sheath around repaired tendons with anti-inflammatory, anti-adhesive, immunomodulatory, and antimicrobial benefits. A 124-patient study demonstrated the safety of using amnion in this manner, and the authors reported a decreased rate of complication compared to previously published data.⁴⁹ Another study of 14 patients undergoing foot and ankle surgery with tendon wrapping reported clinical improvement with reduced pain and greater functional outcomes postoperatively compared to preoperative measurements.⁵⁰

Conclusion

Amniotic membrane-derived tissues are safe and non-tumorigenic, producing an abundance of growth factors that have shown promise as tissue scaffolds and as aids in the regeneration of human bone and soft tissues. Amnion applications in orthopedic surgery may be numerous, but development is ongoing. Given the vast array of in vitro and in vivo animal data supporting the benefits of amnion in tissue regeneration, orthopedic surgeons and researchers should place emphasis on conducting clinical studies to validate the safety and efficacy of amniotic cells in the treatment of orthopedic conditions.

Am J Orthop. 2016;45(7):E421-E425. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.