John M. Tokish, MD

Take-Home Points

• There is no difference in PROMs following knotless or knotted labral repair.
• Operative time is shorter for knotless compared to knotted glenoid labral tears.
• Knotless constructs may be more predictable than knotted constructs biomechanically.

Orthopedic surgeons often encounter labral pathology, and labral tears historically have required open techniques.^1-3 Arthroscopy allows for advanced visualization and treatment of shoulder lesions,^4,5 including anterior, posterior, and superior labrum anterior to posterior (SLAP) lesions.⁶

The goal of arthroscopic labral repair is to restore joint stability while maintaining range of motion. Arthroscopically repairing the labrum with suture anchors has become the standard technique, and several studies have reported satisfactory biomechanical and clinical results.^1,7-12 Surgeons traditionally have been required to tie knots for these anchors, but knot security varies significantly among experienced arthroscopic surgeons.¹³ In addition, knots can migrate,¹⁴ and bulky knots can cause chondral abrasion.^15,16 Several manufacturers have introduced knotless anchors for soft-tissue fixation.^15,17 The knotless technique provides a low-profile repair with potentially less operating time.⁸ These factors may warrant switching from knotted to knotless techniques if outcomes are clinically acceptable. However, few studies have compared knotted and knotless techniques for glenohumeral labral repair.^8,15,18-21

We conducted a study to compare the clinical results and operative times of knotless and knotted fixation of anterior and posterior glenohumeral labral repairs and SLAP repairs. We hypothesized there would be no difference in patient-reported outcome measures (PROMs) between knotted and knotless techniques.

Methods

We retrospectively evaluated data that had been prospectively collected between 2012 and 2016 in a Surgical Outcomes System (SOS; Arthrex) database. Participation in this registry is elective, and enrollment can occur on a case-by-case basis. The database stores data on basic demographics, PROMs, and operative time. Data for our specific analysis were available for surgeries performed by 115 different surgeons. Inclusion criteria included primary isolated arthroscopic anterior, isolated posterior, and isolated SLAP repair with completely knotted or completely knotless labral repair and minimum 1-year follow-up. Exclusion criteria included hybrid knotted–knotless repair, rotator cuff repair, revision surgery, open surgery, and lack of complete follow-up data.

SOS is a proprietary registry that allows for the collection of basic patient demographics, diagnostic and operative data, and PROMs. PROMs in the SOS shoulder arthroscopy module include Veterans RAND 12-Item Health Survey (VR-12) mental health and physical health component summary scores, visual analog scale (VAS) pain scores, and American Shoulder and Elbow Surgeons (ASES) scores. For this study, PROMs were reviewed before surgery and 6 and 12 months after surgery. In addition, operative times of all procedures were collected.

For the analysis, completely knotted and completely knotless techniques were compared for anterior repair, posterior repair, and SLAP repair. A t test was used to compare the techniques on PROMs, and χ2 test was used to evaluate proportion differences. Statistical significance was set at P < .05. 

Results

Anterior Labral Repairs

Of the 102 knotted anterior labral repairs that met the study criteria, 26 (25%) had minimum 1-year follow-up. Of the 122 knotless labral repairs, 33 (27%) had minimum 1-year follow-up. Seventy-five percent of knotted repairs and 80% of knotless repairs were performed in men. Mean (SD) age was 25.3 (11.7) years for the knotted group and 26.9 (10.6) years for the knotless group (P = .109). Anterior labral repairs did not differ in PROMs at any point (Table 1).

A mean of 2.8 anchors was used for knotted repairs, and a mean of 3.1 anchors was used for knotless repairs. Mean operative time was 75.8 minutes for knotted repairs and 67.5 minutes for knotless repairs. Mean (SD) time per anchor was 30.9 (13.9) minutes for knotted repairs and 25.6 (19.5) minutes for knotless repairs (P = .021). 

Posterior Labral Repairs

Of the 165 knotted posterior labral repairs that met the study criteria, 39 (29%) had minimum 1-year follow-up. Of the 229 knotless labral repairs, 56 (24%) had minimum 1-year follow-up. Eighty-five percent of knotted repairs and 74% of knotless repairs were performed in men. Mean (SD) age was 29.1 (12.0) years for the knotted group and 27.5 (11.9) years for the knotless group (P = .148). Posterior labral repairs did not differ in PROMs before surgery or 1 year after surgery; 6 months after surgery, these repairs differed only in ASES scores (Table 2). 

A mean of 3.6 anchors was used for knotted repairs, and a mean of 3.0 anchors was used for knotless repairs. Mean operative time was 67.0 minutes for knotted repairs and 43.1 minutes for knotless repairs. Mean (SD) time per anchor was 21.1 (10.7) minutes for knotted repairs and 17.5 (14.7) minutes for knotless repairs (P = .031).

SLAP Repairs

Of the 54 knotted SLAP repairs that met the study criteria, 24 (44%) had minimum 1-year follow-up. Of the 138 knotless SLAP repairs, 48 (35%) had minimum 1-year follow-up. Seventy-two percent of knotted repairs and 72% of knotless repairs were performed in men. Mean (SD) age was 32.1 (11.6) years for the knotted group and 35.0 (12.8) years for the knotless group (P = .246). SLAP repairs did not differ in PROMs at any point (Table 3).

A mean of 1.9 anchors was used for knotted repairs, and a mean of 2.1 anchors was used for knotless repairs. Mean operative time was 59.0 minutes for knotted repairs and 40.9 minutes for knotless repairs. Mean (SD) time per anchor was 36.6 (22.4) minutes for knotted repairs and 26.3 (14.0) minutes for knotless repairs (P = .080).

Discussion

Our hypothesis that there would be no difference in PROMs between knotted and knotless labral repairs was confirmed. Our findings are important because this study compared the gold standard of knotted suture anchor with the alternative knotless suture anchor in glenohumeral labral repair. These findings have several important implications for labral repair.

Knot tying traditionally has been used to achieve fixation with an anchor. Although simple in concept, knot tying can be challenging and its quality variable. Thal¹⁵ wrote that good-quality arthroscopic suture anchor repair is difficult to achieve because satisfactory knot tying requires significant practice with certain devices designed specifically for knot tying. Multiple surgeons have noted a significant learning curve associated with knot tying, and there is no agreement on which knot is superior.^22-26 Leedle and Miller¹⁷ even suggested that, because knot tying is difficult, tying knots arthroscopically can lead to knot failure. In their study, they concluded that the knot is consistently the weakest link in suture repair of an anterior labrum construct. In a controlled laboratory study, Hanypsiak and colleagues¹³ found considerable knot-strength variability among expert arthroscopists. Only 65 (18%) of 365 knots tied fell within 20% of the mean for ultimate load failure, and only 128 (36%) of 365 fell within 20% of the mean for clinical failure (3 mm of displacement). These data suggested expert arthroscopists were unable to tie 5 consecutive knots of the same type consistently. Even among experts, it seems, knot strength varies significantly, and knot-strength issues may affect the rates of labral repair failure.

Multiple authors have also reported that bulky knots can cause chondral abrasion or that knots can migrate.^25,27 Rhee and Ha²⁷ reported that, when another knot (eg, a half-hitch knot) is tied to prevent knot failure, the resulting overall knot can be too bulky for a limited space, and chondral abrasion can result. In addition, regardless of size, a knot can migrate and, in its new position, start rubbing against the head of the humerus. Kim and colleagues¹⁴ found that, even when a knot is placed away from the humeral head, migration and repeated contact with the head are possible. Park and colleagues²⁸ found that a significant number of knotted SLAP repairs required arthroscopic knot removal for relief of knot-induced pain and clicking.

Knotless constructs have several theoretical advantages over knotted constructs. Compared with a knotted technique, a knotless technique appears to provide more predictable strength, as variability in knot tying is eliminated (unpublished data). A knotless repair also has a lower profile,8 which should lead to less contact with the humeral head.¹⁹ Last, a knotless repair is more efficient—it takes less time to perform. In our study, operative time was reduced by a mean of 5.3 minutes per anchor for anterior labral repair. Assuming a mean of 3 anchors, this reduction equates to 16 minutes per case. Therefore, a surgeon who performs 25 labral repairs a year can save 6.7 hours a year. Reduced operative time benefits the patient (ie, lower risk of infection and other complications²⁹), the surgeon, and the healthcare system (ie, cost savings). Macario³⁰ found that operating room costs averaged $62 per minute (range, $22-$133 per minute). Therefore, saving 16 minutes per case could lead to saving $992 per case. In summary, a knotless technique appears to be clinically and financially advantageous as long as its results are the same as or better than those of a knotted technique.

A few other studies have compared knotted and knotless techniques. In a cadaveric study, Slabaugh and colleagues²⁰ found no difference in labral height between traditional and knotless suture anchors. Leedle and Miller¹⁷ found that knotless constructs are biomechanically stronger than knotted constructs in anterior labral repair. In a level 3 clinical study, Yang and colleagues²¹ compared a conventional vertical knot with a knotless horizontal mattress suture in 41 patients who underwent SLAP repair. Functional outcome was no different between the 2 groups, but postoperative range of motion was improved in the knotless group. Ng and Kumar³¹ compared 45 patients who had knotted Bankart repair with 42 patients who had knotless Bankart repair and found no difference in functional outcome or rate of recurrent dislocation. Similarly, Kocaoglu and colleagues²² found no difference in recurrence rate between 18 patients who underwent a knotted technique for arthroscopic Bankart repair and 20 patients who underwent a knotless technique. Our findings corroborate the findings of these studies and further support the idea that there is no difference between knotted and knotless constructs with respect to PROMs.

Study Limitations

The major strength of this study was its large cohort and large population of surgeons. However, there were several study limitations. First, we could not detail specific repair techniques, such as simple or horizontal mattress orientation, and rehabilitation protocols and other variables are likely as well. Second, the repair technique was not randomized, and therefore there may have been a selection bias based on tissue quality. Although we cannot prove no bias, we think it was unlikely given that the groups were similar in age. Third, our data did not include information on range of motion or recurrent instability. Our goal was simply to evaluate PROMs among multiple surgeons using the 2 techniques. Fourth, there was substantial follow-up loss, which introduced potential selection bias. Last, there may have been conditions under which a hybrid technique with inferior knot tying, combined with a hybrid knotless construct, could have proved advantageous.

Conclusion

Our data showed that the advantages of knotless repair are not compromised in clinical situations. Although the data showed no significant difference in clinical outcomes, knotless repairs may provide surgeons with shorter surgeries, simpler constructs, less potential for chondral damage, and more consistent suture tensioning. Additional studies may further confirm these results.

Take-Home Points

• There is no difference in PROMs following knotless or knotted labral repair.
• Operative time is shorter for knotless compared to knotted glenoid labral tears.
• Knotless constructs may be more predictable than knotted constructs biomechanically.

Orthopedic surgeons often encounter labral pathology, and labral tears historically have required open techniques.^1-3 Arthroscopy allows for advanced visualization and treatment of shoulder lesions,^4,5 including anterior, posterior, and superior labrum anterior to posterior (SLAP) lesions.⁶

The goal of arthroscopic labral repair is to restore joint stability while maintaining range of motion. Arthroscopically repairing the labrum with suture anchors has become the standard technique, and several studies have reported satisfactory biomechanical and clinical results.^1,7-12 Surgeons traditionally have been required to tie knots for these anchors, but knot security varies significantly among experienced arthroscopic surgeons.¹³ In addition, knots can migrate,¹⁴ and bulky knots can cause chondral abrasion.^15,16 Several manufacturers have introduced knotless anchors for soft-tissue fixation.^15,17 The knotless technique provides a low-profile repair with potentially less operating time.⁸ These factors may warrant switching from knotted to knotless techniques if outcomes are clinically acceptable. However, few studies have compared knotted and knotless techniques for glenohumeral labral repair.^8,15,18-21

We conducted a study to compare the clinical results and operative times of knotless and knotted fixation of anterior and posterior glenohumeral labral repairs and SLAP repairs. We hypothesized there would be no difference in patient-reported outcome measures (PROMs) between knotted and knotless techniques.

Methods

We retrospectively evaluated data that had been prospectively collected between 2012 and 2016 in a Surgical Outcomes System (SOS; Arthrex) database. Participation in this registry is elective, and enrollment can occur on a case-by-case basis. The database stores data on basic demographics, PROMs, and operative time. Data for our specific analysis were available for surgeries performed by 115 different surgeons. Inclusion criteria included primary isolated arthroscopic anterior, isolated posterior, and isolated SLAP repair with completely knotted or completely knotless labral repair and minimum 1-year follow-up. Exclusion criteria included hybrid knotted–knotless repair, rotator cuff repair, revision surgery, open surgery, and lack of complete follow-up data.

SOS is a proprietary registry that allows for the collection of basic patient demographics, diagnostic and operative data, and PROMs. PROMs in the SOS shoulder arthroscopy module include Veterans RAND 12-Item Health Survey (VR-12) mental health and physical health component summary scores, visual analog scale (VAS) pain scores, and American Shoulder and Elbow Surgeons (ASES) scores. For this study, PROMs were reviewed before surgery and 6 and 12 months after surgery. In addition, operative times of all procedures were collected.

For the analysis, completely knotted and completely knotless techniques were compared for anterior repair, posterior repair, and SLAP repair. A t test was used to compare the techniques on PROMs, and χ2 test was used to evaluate proportion differences. Statistical significance was set at P < .05. 

Results

Anterior Labral Repairs

Of the 102 knotted anterior labral repairs that met the study criteria, 26 (25%) had minimum 1-year follow-up. Of the 122 knotless labral repairs, 33 (27%) had minimum 1-year follow-up. Seventy-five percent of knotted repairs and 80% of knotless repairs were performed in men. Mean (SD) age was 25.3 (11.7) years for the knotted group and 26.9 (10.6) years for the knotless group (P = .109). Anterior labral repairs did not differ in PROMs at any point (Table 1).

A mean of 2.8 anchors was used for knotted repairs, and a mean of 3.1 anchors was used for knotless repairs. Mean operative time was 75.8 minutes for knotted repairs and 67.5 minutes for knotless repairs. Mean (SD) time per anchor was 30.9 (13.9) minutes for knotted repairs and 25.6 (19.5) minutes for knotless repairs (P = .021). 

Posterior Labral Repairs

Of the 165 knotted posterior labral repairs that met the study criteria, 39 (29%) had minimum 1-year follow-up. Of the 229 knotless labral repairs, 56 (24%) had minimum 1-year follow-up. Eighty-five percent of knotted repairs and 74% of knotless repairs were performed in men. Mean (SD) age was 29.1 (12.0) years for the knotted group and 27.5 (11.9) years for the knotless group (P = .148). Posterior labral repairs did not differ in PROMs before surgery or 1 year after surgery; 6 months after surgery, these repairs differed only in ASES scores (Table 2). 

A mean of 3.6 anchors was used for knotted repairs, and a mean of 3.0 anchors was used for knotless repairs. Mean operative time was 67.0 minutes for knotted repairs and 43.1 minutes for knotless repairs. Mean (SD) time per anchor was 21.1 (10.7) minutes for knotted repairs and 17.5 (14.7) minutes for knotless repairs (P = .031).

SLAP Repairs

Of the 54 knotted SLAP repairs that met the study criteria, 24 (44%) had minimum 1-year follow-up. Of the 138 knotless SLAP repairs, 48 (35%) had minimum 1-year follow-up. Seventy-two percent of knotted repairs and 72% of knotless repairs were performed in men. Mean (SD) age was 32.1 (11.6) years for the knotted group and 35.0 (12.8) years for the knotless group (P = .246). SLAP repairs did not differ in PROMs at any point (Table 3).

A mean of 1.9 anchors was used for knotted repairs, and a mean of 2.1 anchors was used for knotless repairs. Mean operative time was 59.0 minutes for knotted repairs and 40.9 minutes for knotless repairs. Mean (SD) time per anchor was 36.6 (22.4) minutes for knotted repairs and 26.3 (14.0) minutes for knotless repairs (P = .080).

Discussion

Our hypothesis that there would be no difference in PROMs between knotted and knotless labral repairs was confirmed. Our findings are important because this study compared the gold standard of knotted suture anchor with the alternative knotless suture anchor in glenohumeral labral repair. These findings have several important implications for labral repair.

Knot tying traditionally has been used to achieve fixation with an anchor. Although simple in concept, knot tying can be challenging and its quality variable. Thal¹⁵ wrote that good-quality arthroscopic suture anchor repair is difficult to achieve because satisfactory knot tying requires significant practice with certain devices designed specifically for knot tying. Multiple surgeons have noted a significant learning curve associated with knot tying, and there is no agreement on which knot is superior.^22-26 Leedle and Miller¹⁷ even suggested that, because knot tying is difficult, tying knots arthroscopically can lead to knot failure. In their study, they concluded that the knot is consistently the weakest link in suture repair of an anterior labrum construct. In a controlled laboratory study, Hanypsiak and colleagues¹³ found considerable knot-strength variability among expert arthroscopists. Only 65 (18%) of 365 knots tied fell within 20% of the mean for ultimate load failure, and only 128 (36%) of 365 fell within 20% of the mean for clinical failure (3 mm of displacement). These data suggested expert arthroscopists were unable to tie 5 consecutive knots of the same type consistently. Even among experts, it seems, knot strength varies significantly, and knot-strength issues may affect the rates of labral repair failure.

Multiple authors have also reported that bulky knots can cause chondral abrasion or that knots can migrate.^25,27 Rhee and Ha²⁷ reported that, when another knot (eg, a half-hitch knot) is tied to prevent knot failure, the resulting overall knot can be too bulky for a limited space, and chondral abrasion can result. In addition, regardless of size, a knot can migrate and, in its new position, start rubbing against the head of the humerus. Kim and colleagues¹⁴ found that, even when a knot is placed away from the humeral head, migration and repeated contact with the head are possible. Park and colleagues²⁸ found that a significant number of knotted SLAP repairs required arthroscopic knot removal for relief of knot-induced pain and clicking.

Knotless constructs have several theoretical advantages over knotted constructs. Compared with a knotted technique, a knotless technique appears to provide more predictable strength, as variability in knot tying is eliminated (unpublished data). A knotless repair also has a lower profile,8 which should lead to less contact with the humeral head.¹⁹ Last, a knotless repair is more efficient—it takes less time to perform. In our study, operative time was reduced by a mean of 5.3 minutes per anchor for anterior labral repair. Assuming a mean of 3 anchors, this reduction equates to 16 minutes per case. Therefore, a surgeon who performs 25 labral repairs a year can save 6.7 hours a year. Reduced operative time benefits the patient (ie, lower risk of infection and other complications²⁹), the surgeon, and the healthcare system (ie, cost savings). Macario³⁰ found that operating room costs averaged $62 per minute (range, $22-$133 per minute). Therefore, saving 16 minutes per case could lead to saving $992 per case. In summary, a knotless technique appears to be clinically and financially advantageous as long as its results are the same as or better than those of a knotted technique.

A few other studies have compared knotted and knotless techniques. In a cadaveric study, Slabaugh and colleagues²⁰ found no difference in labral height between traditional and knotless suture anchors. Leedle and Miller¹⁷ found that knotless constructs are biomechanically stronger than knotted constructs in anterior labral repair. In a level 3 clinical study, Yang and colleagues²¹ compared a conventional vertical knot with a knotless horizontal mattress suture in 41 patients who underwent SLAP repair. Functional outcome was no different between the 2 groups, but postoperative range of motion was improved in the knotless group. Ng and Kumar³¹ compared 45 patients who had knotted Bankart repair with 42 patients who had knotless Bankart repair and found no difference in functional outcome or rate of recurrent dislocation. Similarly, Kocaoglu and colleagues²² found no difference in recurrence rate between 18 patients who underwent a knotted technique for arthroscopic Bankart repair and 20 patients who underwent a knotless technique. Our findings corroborate the findings of these studies and further support the idea that there is no difference between knotted and knotless constructs with respect to PROMs.

Study Limitations

The major strength of this study was its large cohort and large population of surgeons. However, there were several study limitations. First, we could not detail specific repair techniques, such as simple or horizontal mattress orientation, and rehabilitation protocols and other variables are likely as well. Second, the repair technique was not randomized, and therefore there may have been a selection bias based on tissue quality. Although we cannot prove no bias, we think it was unlikely given that the groups were similar in age. Third, our data did not include information on range of motion or recurrent instability. Our goal was simply to evaluate PROMs among multiple surgeons using the 2 techniques. Fourth, there was substantial follow-up loss, which introduced potential selection bias. Last, there may have been conditions under which a hybrid technique with inferior knot tying, combined with a hybrid knotless construct, could have proved advantageous.

Conclusion

Our data showed that the advantages of knotless repair are not compromised in clinical situations. Although the data showed no significant difference in clinical outcomes, knotless repairs may provide surgeons with shorter surgeries, simpler constructs, less potential for chondral damage, and more consistent suture tensioning. Additional studies may further confirm these results.

Take-Home Points

• There is no difference in PROMs following knotless or knotted labral repair.
• Operative time is shorter for knotless compared to knotted glenoid labral tears.
• Knotless constructs may be more predictable than knotted constructs biomechanically.

Orthopedic surgeons often encounter labral pathology, and labral tears historically have required open techniques.^1-3 Arthroscopy allows for advanced visualization and treatment of shoulder lesions,^4,5 including anterior, posterior, and superior labrum anterior to posterior (SLAP) lesions.⁶

The goal of arthroscopic labral repair is to restore joint stability while maintaining range of motion. Arthroscopically repairing the labrum with suture anchors has become the standard technique, and several studies have reported satisfactory biomechanical and clinical results.^1,7-12 Surgeons traditionally have been required to tie knots for these anchors, but knot security varies significantly among experienced arthroscopic surgeons.¹³ In addition, knots can migrate,¹⁴ and bulky knots can cause chondral abrasion.^15,16 Several manufacturers have introduced knotless anchors for soft-tissue fixation.^15,17 The knotless technique provides a low-profile repair with potentially less operating time.⁸ These factors may warrant switching from knotted to knotless techniques if outcomes are clinically acceptable. However, few studies have compared knotted and knotless techniques for glenohumeral labral repair.^8,15,18-21

We conducted a study to compare the clinical results and operative times of knotless and knotted fixation of anterior and posterior glenohumeral labral repairs and SLAP repairs. We hypothesized there would be no difference in patient-reported outcome measures (PROMs) between knotted and knotless techniques.

Methods

We retrospectively evaluated data that had been prospectively collected between 2012 and 2016 in a Surgical Outcomes System (SOS; Arthrex) database. Participation in this registry is elective, and enrollment can occur on a case-by-case basis. The database stores data on basic demographics, PROMs, and operative time. Data for our specific analysis were available for surgeries performed by 115 different surgeons. Inclusion criteria included primary isolated arthroscopic anterior, isolated posterior, and isolated SLAP repair with completely knotted or completely knotless labral repair and minimum 1-year follow-up. Exclusion criteria included hybrid knotted–knotless repair, rotator cuff repair, revision surgery, open surgery, and lack of complete follow-up data.

SOS is a proprietary registry that allows for the collection of basic patient demographics, diagnostic and operative data, and PROMs. PROMs in the SOS shoulder arthroscopy module include Veterans RAND 12-Item Health Survey (VR-12) mental health and physical health component summary scores, visual analog scale (VAS) pain scores, and American Shoulder and Elbow Surgeons (ASES) scores. For this study, PROMs were reviewed before surgery and 6 and 12 months after surgery. In addition, operative times of all procedures were collected.

For the analysis, completely knotted and completely knotless techniques were compared for anterior repair, posterior repair, and SLAP repair. A t test was used to compare the techniques on PROMs, and χ2 test was used to evaluate proportion differences. Statistical significance was set at P < .05. 

Results

Anterior Labral Repairs

Of the 102 knotted anterior labral repairs that met the study criteria, 26 (25%) had minimum 1-year follow-up. Of the 122 knotless labral repairs, 33 (27%) had minimum 1-year follow-up. Seventy-five percent of knotted repairs and 80% of knotless repairs were performed in men. Mean (SD) age was 25.3 (11.7) years for the knotted group and 26.9 (10.6) years for the knotless group (P = .109). Anterior labral repairs did not differ in PROMs at any point (Table 1).

A mean of 2.8 anchors was used for knotted repairs, and a mean of 3.1 anchors was used for knotless repairs. Mean operative time was 75.8 minutes for knotted repairs and 67.5 minutes for knotless repairs. Mean (SD) time per anchor was 30.9 (13.9) minutes for knotted repairs and 25.6 (19.5) minutes for knotless repairs (P = .021). 

Posterior Labral Repairs

Of the 165 knotted posterior labral repairs that met the study criteria, 39 (29%) had minimum 1-year follow-up. Of the 229 knotless labral repairs, 56 (24%) had minimum 1-year follow-up. Eighty-five percent of knotted repairs and 74% of knotless repairs were performed in men. Mean (SD) age was 29.1 (12.0) years for the knotted group and 27.5 (11.9) years for the knotless group (P = .148). Posterior labral repairs did not differ in PROMs before surgery or 1 year after surgery; 6 months after surgery, these repairs differed only in ASES scores (Table 2). 

A mean of 3.6 anchors was used for knotted repairs, and a mean of 3.0 anchors was used for knotless repairs. Mean operative time was 67.0 minutes for knotted repairs and 43.1 minutes for knotless repairs. Mean (SD) time per anchor was 21.1 (10.7) minutes for knotted repairs and 17.5 (14.7) minutes for knotless repairs (P = .031).

SLAP Repairs

Of the 54 knotted SLAP repairs that met the study criteria, 24 (44%) had minimum 1-year follow-up. Of the 138 knotless SLAP repairs, 48 (35%) had minimum 1-year follow-up. Seventy-two percent of knotted repairs and 72% of knotless repairs were performed in men. Mean (SD) age was 32.1 (11.6) years for the knotted group and 35.0 (12.8) years for the knotless group (P = .246). SLAP repairs did not differ in PROMs at any point (Table 3).

A mean of 1.9 anchors was used for knotted repairs, and a mean of 2.1 anchors was used for knotless repairs. Mean operative time was 59.0 minutes for knotted repairs and 40.9 minutes for knotless repairs. Mean (SD) time per anchor was 36.6 (22.4) minutes for knotted repairs and 26.3 (14.0) minutes for knotless repairs (P = .080).

Discussion

Our hypothesis that there would be no difference in PROMs between knotted and knotless labral repairs was confirmed. Our findings are important because this study compared the gold standard of knotted suture anchor with the alternative knotless suture anchor in glenohumeral labral repair. These findings have several important implications for labral repair.

Knot tying traditionally has been used to achieve fixation with an anchor. Although simple in concept, knot tying can be challenging and its quality variable. Thal¹⁵ wrote that good-quality arthroscopic suture anchor repair is difficult to achieve because satisfactory knot tying requires significant practice with certain devices designed specifically for knot tying. Multiple surgeons have noted a significant learning curve associated with knot tying, and there is no agreement on which knot is superior.^22-26 Leedle and Miller¹⁷ even suggested that, because knot tying is difficult, tying knots arthroscopically can lead to knot failure. In their study, they concluded that the knot is consistently the weakest link in suture repair of an anterior labrum construct. In a controlled laboratory study, Hanypsiak and colleagues¹³ found considerable knot-strength variability among expert arthroscopists. Only 65 (18%) of 365 knots tied fell within 20% of the mean for ultimate load failure, and only 128 (36%) of 365 fell within 20% of the mean for clinical failure (3 mm of displacement). These data suggested expert arthroscopists were unable to tie 5 consecutive knots of the same type consistently. Even among experts, it seems, knot strength varies significantly, and knot-strength issues may affect the rates of labral repair failure.

Multiple authors have also reported that bulky knots can cause chondral abrasion or that knots can migrate.^25,27 Rhee and Ha²⁷ reported that, when another knot (eg, a half-hitch knot) is tied to prevent knot failure, the resulting overall knot can be too bulky for a limited space, and chondral abrasion can result. In addition, regardless of size, a knot can migrate and, in its new position, start rubbing against the head of the humerus. Kim and colleagues¹⁴ found that, even when a knot is placed away from the humeral head, migration and repeated contact with the head are possible. Park and colleagues²⁸ found that a significant number of knotted SLAP repairs required arthroscopic knot removal for relief of knot-induced pain and clicking.

Knotless constructs have several theoretical advantages over knotted constructs. Compared with a knotted technique, a knotless technique appears to provide more predictable strength, as variability in knot tying is eliminated (unpublished data). A knotless repair also has a lower profile,8 which should lead to less contact with the humeral head.¹⁹ Last, a knotless repair is more efficient—it takes less time to perform. In our study, operative time was reduced by a mean of 5.3 minutes per anchor for anterior labral repair. Assuming a mean of 3 anchors, this reduction equates to 16 minutes per case. Therefore, a surgeon who performs 25 labral repairs a year can save 6.7 hours a year. Reduced operative time benefits the patient (ie, lower risk of infection and other complications²⁹), the surgeon, and the healthcare system (ie, cost savings). Macario³⁰ found that operating room costs averaged $62 per minute (range, $22-$133 per minute). Therefore, saving 16 minutes per case could lead to saving $992 per case. In summary, a knotless technique appears to be clinically and financially advantageous as long as its results are the same as or better than those of a knotted technique.

A few other studies have compared knotted and knotless techniques. In a cadaveric study, Slabaugh and colleagues²⁰ found no difference in labral height between traditional and knotless suture anchors. Leedle and Miller¹⁷ found that knotless constructs are biomechanically stronger than knotted constructs in anterior labral repair. In a level 3 clinical study, Yang and colleagues²¹ compared a conventional vertical knot with a knotless horizontal mattress suture in 41 patients who underwent SLAP repair. Functional outcome was no different between the 2 groups, but postoperative range of motion was improved in the knotless group. Ng and Kumar³¹ compared 45 patients who had knotted Bankart repair with 42 patients who had knotless Bankart repair and found no difference in functional outcome or rate of recurrent dislocation. Similarly, Kocaoglu and colleagues²² found no difference in recurrence rate between 18 patients who underwent a knotted technique for arthroscopic Bankart repair and 20 patients who underwent a knotless technique. Our findings corroborate the findings of these studies and further support the idea that there is no difference between knotted and knotless constructs with respect to PROMs.

Study Limitations

The major strength of this study was its large cohort and large population of surgeons. However, there were several study limitations. First, we could not detail specific repair techniques, such as simple or horizontal mattress orientation, and rehabilitation protocols and other variables are likely as well. Second, the repair technique was not randomized, and therefore there may have been a selection bias based on tissue quality. Although we cannot prove no bias, we think it was unlikely given that the groups were similar in age. Third, our data did not include information on range of motion or recurrent instability. Our goal was simply to evaluate PROMs among multiple surgeons using the 2 techniques. Fourth, there was substantial follow-up loss, which introduced potential selection bias. Last, there may have been conditions under which a hybrid technique with inferior knot tying, combined with a hybrid knotless construct, could have proved advantageous.

Conclusion

Our data showed that the advantages of knotless repair are not compromised in clinical situations. Although the data showed no significant difference in clinical outcomes, knotless repairs may provide surgeons with shorter surgeries, simpler constructs, less potential for chondral damage, and more consistent suture tensioning. Additional studies may further confirm these results.

Take-Home Points

• Arthroscopic stabilization performed early results in better outcomes in patients with Bankart lesions.
• A subcritical level of bone loss of 13.5% has been shown to have a significant effect on outcomes, in addition to the established “critical amount”.
• Bone loss is a bipolar issue. Both sides must be considered in order to properly address shoulder instability.
• Off-track measurement has been shown to be even more positively predictive of outcomes than glenoid bone loss assessment.

• There are several bone loss management options including, the most common coracoid transfer, as well as distal tibial allograft and distal clavicular autograft.

Given its relatively young age, high activity level, and centralized medical care system, the US military population is ideal for studying traumatic anterior shoulder instability. There is a long history of military surgeons who have made significant contributions that have advanced our understanding of this pathology and its treatment and results. In this article, we describe the scope, treatment, and results of this pathology in the US military population.

Incidence and Pathology

At the United States Military Academy (USMA), Owens and colleagues¹ studied the incidence of shoulder instability, including dislocation and subluxation, and found anterior instability events were far more common than in civilian populations. The incidence of shoulder instability was 0.08 per 1000 person-years in the general US population vs 1.69 per 1000 person-years in US military personnel. The factors associated with increased risk of shoulder instability injury in the military population were male sex, white race, junior enlisted rank, and age under 30 years. Owens and colleagues² noted that subluxation accounted for almost 85% of the total anterior instability events. Owens and colleagues³ found the pathology in subluxation events was similar to that in full dislocations, with a soft-tissue anterior Bankart lesion and a Hill-Sachs lesion detected on magnetic resonance imaging in more than 90% of patients. In another study at the USMA, DeBerardino and colleagues⁴ noted that 97% of arthroscopically assessed shoulders in first-time dislocators involved complete detachment of the capsuloligamentous complex from the anterior glenoid rim and neck—a so-called Bankart lesion. Thus, in a military population, anterior instability resulting from subluxation or dislocation is a common finding that is often represented by a soft-tissue Bankart lesion and a Hill-Sachs defect.

Natural History of Traumatic Anterior Shoulder Instability in the Military

Several studies have evaluated the outcomes of nonoperative and operative treatment of shoulder instability. Although most have found better outcomes with operative intervention, Aronen and Regan⁵ reported good results (25% recurrence at nearly 3-year follow-up) with nonoperative treatment and adherence to a strict rehabilitation program. Most other comparative studies in this population have published contrary results. Wheeler and colleagues⁶ studied the natural history of anterior shoulder dislocations in a USMA cadet cohort and found recurrent instability after shoulder dislocation in 92% of cadets who had nonoperative treatment. Similarly, DeBerardino and colleagues⁴ found that, in the USMA, 90% of first-time traumatic anterior shoulder dislocations managed nonoperatively experienced recurrent instability. In a series of Army soldiers with shoulder instability, Bottoni and colleagues⁷ reported that 75% of nonoperatively managed patients had recurrent instability, and, of these, 67% progressed to surgical intervention. Nonoperative treatment for a first-time dislocation is still reasonable if a cadet or soldier needs to quickly return to functional duties. Athletes who develop shoulder instability during their playing season have been studied in a military population as well. In a multicenter study of service academy athletes with anterior instability, Dickens and colleagues⁸ found that, with conservative management and accelerated rehabilitation of in-season shoulder instability, 73% of athletes returned to sport by a mean of 5 days. However, the durability of this treatment should be questioned, as 64% later experienced recurrence.

Arthroscopic Stabilization of Acute Anterior Shoulder Dislocations

In an early series of cases of traumatic anterior shoulder instability in USMA cadets, Wheeler and colleagues⁶ found that, at 14 months, 78% of arthroscopically stabilized cases and 92% of nonoperatively treated cases were successful. Then, in the 1990s, DeBerardino and colleagues⁴ studied a series of young, active patients in the USMA and noted significantly better results with arthroscopic treatment, vs nonoperative treatment, at 2- to 5-year follow-up. Of the arthroscopically treated shoulders, 88% remained stable during the study and returned to preinjury activity levels, and 12% experienced recurrent instability (risk factors included 2+ sulcus sign, poor capsular labral tissue, and history of bilateral shoulder instability). In a long-term follow-up (mean, 11.7 years; range, 9.1-13.9 years) of the same cohort, Owens and colleagues⁹ found that 14% of patients available for follow-up had undergone revision stabilization surgery, and, of these, 21% reported experiencing subluxation events. The authors concluded that, in first-time dislocators in this active military population, acute arthroscopic Bankart repair resulted in excellent return to athletics and subjective function, and had acceptable recurrence and reoperation rates. Bottoni and colleagues,⁷ in a prospective, randomized evaluation of arthroscopic stabilization of acute, traumatic, first-time shoulder dislocations in the Army, noted an 89% success rate for arthroscopic treatment at an average follow-up of 36 months, with no recurrent instability. DeBerardino and colleagues¹⁰ compared West Point patients treated nonoperatively with those arthroscopically treated with staples, transglenoid sutures, or bioabsorbable anchors. Recurrence rates were 85% for nonoperative treatment, 22% for staples, 14% for transglenoid sutures, and 10% for bioabsorbable anchors.

Arthroscopic Versus Open Stabilization of Anterior Shoulder Instability

In a prospective, randomized clinical trial comparing open and arthroscopic shoulder stabilization for recurrent anterior instability in active-duty Army personnel, Bottoni and colleagues¹¹ found comparable clinical outcomes. Stabilization surgery failed clinically in only 3 cases, 2 open and 1 arthroscopic. The authors concluded that arthroscopic stabilization can be safely performed for recurrent shoulder instability and that arthroscopic outcomes are similar to open outcomes. In a series of anterior shoulder subluxations in young athletes with Bankart lesions, Owens and colleagues¹² found that open and arthroscopic stabilization performed early resulted in better outcomes, regardless of technique used. Recurrent subluxation occurred at a mean of 17 months in 3 of the 10 patients in the open group and 3 of the 9 patients in the arthroscopic group, for an overall recurrence rate of 31%. The authors concluded that, in this patient population with Bankart lesions caused by anterior subluxation events, surgery should be performed early.

Bone Lesions

Burkhart and De Beer¹³ first noted that bone loss has emerged as one of the most important considerations in the setting of shoulder instability in active patients. Other authors have found this to be true in military populations.^14,15

The diagnosis of bone loss may include historical findings, such as increased number and ease of dislocations, as well as dislocation in lower positions of abduction. Physical examination findings may include apprehension in the midrange of motion. Advanced imaging, such as magnetic resonance arthrography, has since been validated as equivalent to 3-dimensional computed tomography (3-D CT) in determining glenoid bone loss.¹⁶ In 2007, Mologne and colleagues¹⁵ studied the amount of glenoid bone loss and the presence of fragmented bone or attritional bone loss and its effect on outcomes. They evaluated 21 patients who had arthroscopic treatment for anterior instability with anteroinferior glenoid bone loss between 20% and 30%. Average follow-up was 34 months. All patients received 3 or 4 anterior anchors. No patient with a bone fragment incorporated into the repair experienced recurrence or subluxation, whereas 30% of patients with attritional bone loss had recurrent instability.¹⁵

Classifying Bone Loss and Recognizing Its Effects

Burkhart and De Beer¹³ helped define the role and significance of bone loss in the setting of shoulder instability. They defined significant bone loss as an engaging Hill-Sachs lesion of the humerus in an abducted and externally rotated position or an “inverted pear” lesion of the glenoid. Overall analysis revealed recurrence in 4% of cases without significant bone loss and 65% of cases with significant bone loss. In a subanalysis of contact-sport athletes in the setting of bone loss, the failure rate increased to 89%, from 6.5%. Aiding in the quantitative assessment of glenoid bone loss, Itoi and colleagues¹⁷ showed that 21% glenoid bone loss resulted in instability that would not be corrected by a soft-tissue procedure alone. Bone loss of 20% to 25% has since been considered a “critical amount,” above which an arthroscopic Bankart has been questioned. More recently, several authors have shown that even less bone loss can have a significant effect on outcomes. Shaha and colleagues¹⁸ established that a subcritical level of bone loss (13.5%) on the anteroinferior glenoid resulted in clinical failure (as determined with the Western Ontario Shoulder Instability Index) even in cases in which frank recurrence or subluxation was avoided. It is thought that, in recurrent instability, glenoid bone loss incident rate is as high as 90%, and the corresponding percentage of patients with Hill-Sachs lesions is almost 100%.^19,20 Thus, it is increasingly understood that bone loss is a bipolar issue and that both sides must be considered in order to properly address shoulder instability in this setting. In 2007, Yamamoto and colleagues²¹ introduced the glenoid track, a method for predicting whether a Hill-Sachs lesion will engage. Di Giacomo and colleagues²² refined the track concept to quantitatively determine which lesions will engage in the setting of both glenoid and humeral bone loss. Metzger and colleagues,²³ confirming the track concept arthroscopically, found that manipulation with anesthesia and arthroscopic visualization was well predicted by preoperative track measurements, and thus these measurements can be a good guide for surgical management (Figures 1A, 1B).

Strategies for Addressing Bone Loss in Anterior Shoulder Instability

Several approaches for managing bone loss in shoulder instability have been described—the most common being coracoid transfer (Latarjet procedure). Waterman and colleagues²⁵ recently studied the effects of coracoid transfer, distal tibial allograft, and iliac crest augmentation on anterior shoulder instability in US military patients treated between 2006 and 2012. Of 64 patients who underwent a bone block procedure, 16 (25%) had a complication during short-term follow-up. Complications included neurologic injury, pain, infection, hardware failure, and recurrent instability.

Conclusion

Traumatic anterior shoulder instability is a common pathology that continues to significantly challenge the readiness of the US military. Military surgeon-researchers have a long history of investigating approaches to the treatment of this pathology—applying good science to a large controlled population, using a single medical record, and demonstrating a commitment to return service members to the ready defense of the nation.

Am J Orthop. 2017;46(4):184-189. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.

Take-Home Points

• Arthroscopic stabilization performed early results in better outcomes in patients with Bankart lesions.
• A subcritical level of bone loss of 13.5% has been shown to have a significant effect on outcomes, in addition to the established “critical amount”.
• Bone loss is a bipolar issue. Both sides must be considered in order to properly address shoulder instability.
• Off-track measurement has been shown to be even more positively predictive of outcomes than glenoid bone loss assessment.

• There are several bone loss management options including, the most common coracoid transfer, as well as distal tibial allograft and distal clavicular autograft.

Given its relatively young age, high activity level, and centralized medical care system, the US military population is ideal for studying traumatic anterior shoulder instability. There is a long history of military surgeons who have made significant contributions that have advanced our understanding of this pathology and its treatment and results. In this article, we describe the scope, treatment, and results of this pathology in the US military population.

Incidence and Pathology

At the United States Military Academy (USMA), Owens and colleagues¹ studied the incidence of shoulder instability, including dislocation and subluxation, and found anterior instability events were far more common than in civilian populations. The incidence of shoulder instability was 0.08 per 1000 person-years in the general US population vs 1.69 per 1000 person-years in US military personnel. The factors associated with increased risk of shoulder instability injury in the military population were male sex, white race, junior enlisted rank, and age under 30 years. Owens and colleagues² noted that subluxation accounted for almost 85% of the total anterior instability events. Owens and colleagues³ found the pathology in subluxation events was similar to that in full dislocations, with a soft-tissue anterior Bankart lesion and a Hill-Sachs lesion detected on magnetic resonance imaging in more than 90% of patients. In another study at the USMA, DeBerardino and colleagues⁴ noted that 97% of arthroscopically assessed shoulders in first-time dislocators involved complete detachment of the capsuloligamentous complex from the anterior glenoid rim and neck—a so-called Bankart lesion. Thus, in a military population, anterior instability resulting from subluxation or dislocation is a common finding that is often represented by a soft-tissue Bankart lesion and a Hill-Sachs defect.

Natural History of Traumatic Anterior Shoulder Instability in the Military

Several studies have evaluated the outcomes of nonoperative and operative treatment of shoulder instability. Although most have found better outcomes with operative intervention, Aronen and Regan⁵ reported good results (25% recurrence at nearly 3-year follow-up) with nonoperative treatment and adherence to a strict rehabilitation program. Most other comparative studies in this population have published contrary results. Wheeler and colleagues⁶ studied the natural history of anterior shoulder dislocations in a USMA cadet cohort and found recurrent instability after shoulder dislocation in 92% of cadets who had nonoperative treatment. Similarly, DeBerardino and colleagues⁴ found that, in the USMA, 90% of first-time traumatic anterior shoulder dislocations managed nonoperatively experienced recurrent instability. In a series of Army soldiers with shoulder instability, Bottoni and colleagues⁷ reported that 75% of nonoperatively managed patients had recurrent instability, and, of these, 67% progressed to surgical intervention. Nonoperative treatment for a first-time dislocation is still reasonable if a cadet or soldier needs to quickly return to functional duties. Athletes who develop shoulder instability during their playing season have been studied in a military population as well. In a multicenter study of service academy athletes with anterior instability, Dickens and colleagues⁸ found that, with conservative management and accelerated rehabilitation of in-season shoulder instability, 73% of athletes returned to sport by a mean of 5 days. However, the durability of this treatment should be questioned, as 64% later experienced recurrence.

Arthroscopic Stabilization of Acute Anterior Shoulder Dislocations

In an early series of cases of traumatic anterior shoulder instability in USMA cadets, Wheeler and colleagues⁶ found that, at 14 months, 78% of arthroscopically stabilized cases and 92% of nonoperatively treated cases were successful. Then, in the 1990s, DeBerardino and colleagues⁴ studied a series of young, active patients in the USMA and noted significantly better results with arthroscopic treatment, vs nonoperative treatment, at 2- to 5-year follow-up. Of the arthroscopically treated shoulders, 88% remained stable during the study and returned to preinjury activity levels, and 12% experienced recurrent instability (risk factors included 2+ sulcus sign, poor capsular labral tissue, and history of bilateral shoulder instability). In a long-term follow-up (mean, 11.7 years; range, 9.1-13.9 years) of the same cohort, Owens and colleagues⁹ found that 14% of patients available for follow-up had undergone revision stabilization surgery, and, of these, 21% reported experiencing subluxation events. The authors concluded that, in first-time dislocators in this active military population, acute arthroscopic Bankart repair resulted in excellent return to athletics and subjective function, and had acceptable recurrence and reoperation rates. Bottoni and colleagues,⁷ in a prospective, randomized evaluation of arthroscopic stabilization of acute, traumatic, first-time shoulder dislocations in the Army, noted an 89% success rate for arthroscopic treatment at an average follow-up of 36 months, with no recurrent instability. DeBerardino and colleagues¹⁰ compared West Point patients treated nonoperatively with those arthroscopically treated with staples, transglenoid sutures, or bioabsorbable anchors. Recurrence rates were 85% for nonoperative treatment, 22% for staples, 14% for transglenoid sutures, and 10% for bioabsorbable anchors.

Arthroscopic Versus Open Stabilization of Anterior Shoulder Instability

In a prospective, randomized clinical trial comparing open and arthroscopic shoulder stabilization for recurrent anterior instability in active-duty Army personnel, Bottoni and colleagues¹¹ found comparable clinical outcomes. Stabilization surgery failed clinically in only 3 cases, 2 open and 1 arthroscopic. The authors concluded that arthroscopic stabilization can be safely performed for recurrent shoulder instability and that arthroscopic outcomes are similar to open outcomes. In a series of anterior shoulder subluxations in young athletes with Bankart lesions, Owens and colleagues¹² found that open and arthroscopic stabilization performed early resulted in better outcomes, regardless of technique used. Recurrent subluxation occurred at a mean of 17 months in 3 of the 10 patients in the open group and 3 of the 9 patients in the arthroscopic group, for an overall recurrence rate of 31%. The authors concluded that, in this patient population with Bankart lesions caused by anterior subluxation events, surgery should be performed early.

Bone Lesions

Burkhart and De Beer¹³ first noted that bone loss has emerged as one of the most important considerations in the setting of shoulder instability in active patients. Other authors have found this to be true in military populations.^14,15

The diagnosis of bone loss may include historical findings, such as increased number and ease of dislocations, as well as dislocation in lower positions of abduction. Physical examination findings may include apprehension in the midrange of motion. Advanced imaging, such as magnetic resonance arthrography, has since been validated as equivalent to 3-dimensional computed tomography (3-D CT) in determining glenoid bone loss.¹⁶ In 2007, Mologne and colleagues¹⁵ studied the amount of glenoid bone loss and the presence of fragmented bone or attritional bone loss and its effect on outcomes. They evaluated 21 patients who had arthroscopic treatment for anterior instability with anteroinferior glenoid bone loss between 20% and 30%. Average follow-up was 34 months. All patients received 3 or 4 anterior anchors. No patient with a bone fragment incorporated into the repair experienced recurrence or subluxation, whereas 30% of patients with attritional bone loss had recurrent instability.¹⁵

Classifying Bone Loss and Recognizing Its Effects

Burkhart and De Beer¹³ helped define the role and significance of bone loss in the setting of shoulder instability. They defined significant bone loss as an engaging Hill-Sachs lesion of the humerus in an abducted and externally rotated position or an “inverted pear” lesion of the glenoid. Overall analysis revealed recurrence in 4% of cases without significant bone loss and 65% of cases with significant bone loss. In a subanalysis of contact-sport athletes in the setting of bone loss, the failure rate increased to 89%, from 6.5%. Aiding in the quantitative assessment of glenoid bone loss, Itoi and colleagues¹⁷ showed that 21% glenoid bone loss resulted in instability that would not be corrected by a soft-tissue procedure alone. Bone loss of 20% to 25% has since been considered a “critical amount,” above which an arthroscopic Bankart has been questioned. More recently, several authors have shown that even less bone loss can have a significant effect on outcomes. Shaha and colleagues¹⁸ established that a subcritical level of bone loss (13.5%) on the anteroinferior glenoid resulted in clinical failure (as determined with the Western Ontario Shoulder Instability Index) even in cases in which frank recurrence or subluxation was avoided. It is thought that, in recurrent instability, glenoid bone loss incident rate is as high as 90%, and the corresponding percentage of patients with Hill-Sachs lesions is almost 100%.^19,20 Thus, it is increasingly understood that bone loss is a bipolar issue and that both sides must be considered in order to properly address shoulder instability in this setting. In 2007, Yamamoto and colleagues²¹ introduced the glenoid track, a method for predicting whether a Hill-Sachs lesion will engage. Di Giacomo and colleagues²² refined the track concept to quantitatively determine which lesions will engage in the setting of both glenoid and humeral bone loss. Metzger and colleagues,²³ confirming the track concept arthroscopically, found that manipulation with anesthesia and arthroscopic visualization was well predicted by preoperative track measurements, and thus these measurements can be a good guide for surgical management (Figures 1A, 1B).

Strategies for Addressing Bone Loss in Anterior Shoulder Instability

Several approaches for managing bone loss in shoulder instability have been described—the most common being coracoid transfer (Latarjet procedure). Waterman and colleagues²⁵ recently studied the effects of coracoid transfer, distal tibial allograft, and iliac crest augmentation on anterior shoulder instability in US military patients treated between 2006 and 2012. Of 64 patients who underwent a bone block procedure, 16 (25%) had a complication during short-term follow-up. Complications included neurologic injury, pain, infection, hardware failure, and recurrent instability.

Conclusion

Traumatic anterior shoulder instability is a common pathology that continues to significantly challenge the readiness of the US military. Military surgeon-researchers have a long history of investigating approaches to the treatment of this pathology—applying good science to a large controlled population, using a single medical record, and demonstrating a commitment to return service members to the ready defense of the nation.

Am J Orthop. 2017;46(4):184-189. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.

Take-Home Points

• Arthroscopic stabilization performed early results in better outcomes in patients with Bankart lesions.
• A subcritical level of bone loss of 13.5% has been shown to have a significant effect on outcomes, in addition to the established “critical amount”.
• Bone loss is a bipolar issue. Both sides must be considered in order to properly address shoulder instability.
• Off-track measurement has been shown to be even more positively predictive of outcomes than glenoid bone loss assessment.

• There are several bone loss management options including, the most common coracoid transfer, as well as distal tibial allograft and distal clavicular autograft.

Given its relatively young age, high activity level, and centralized medical care system, the US military population is ideal for studying traumatic anterior shoulder instability. There is a long history of military surgeons who have made significant contributions that have advanced our understanding of this pathology and its treatment and results. In this article, we describe the scope, treatment, and results of this pathology in the US military population.

Incidence and Pathology

At the United States Military Academy (USMA), Owens and colleagues¹ studied the incidence of shoulder instability, including dislocation and subluxation, and found anterior instability events were far more common than in civilian populations. The incidence of shoulder instability was 0.08 per 1000 person-years in the general US population vs 1.69 per 1000 person-years in US military personnel. The factors associated with increased risk of shoulder instability injury in the military population were male sex, white race, junior enlisted rank, and age under 30 years. Owens and colleagues² noted that subluxation accounted for almost 85% of the total anterior instability events. Owens and colleagues³ found the pathology in subluxation events was similar to that in full dislocations, with a soft-tissue anterior Bankart lesion and a Hill-Sachs lesion detected on magnetic resonance imaging in more than 90% of patients. In another study at the USMA, DeBerardino and colleagues⁴ noted that 97% of arthroscopically assessed shoulders in first-time dislocators involved complete detachment of the capsuloligamentous complex from the anterior glenoid rim and neck—a so-called Bankart lesion. Thus, in a military population, anterior instability resulting from subluxation or dislocation is a common finding that is often represented by a soft-tissue Bankart lesion and a Hill-Sachs defect.

Natural History of Traumatic Anterior Shoulder Instability in the Military

Several studies have evaluated the outcomes of nonoperative and operative treatment of shoulder instability. Although most have found better outcomes with operative intervention, Aronen and Regan⁵ reported good results (25% recurrence at nearly 3-year follow-up) with nonoperative treatment and adherence to a strict rehabilitation program. Most other comparative studies in this population have published contrary results. Wheeler and colleagues⁶ studied the natural history of anterior shoulder dislocations in a USMA cadet cohort and found recurrent instability after shoulder dislocation in 92% of cadets who had nonoperative treatment. Similarly, DeBerardino and colleagues⁴ found that, in the USMA, 90% of first-time traumatic anterior shoulder dislocations managed nonoperatively experienced recurrent instability. In a series of Army soldiers with shoulder instability, Bottoni and colleagues⁷ reported that 75% of nonoperatively managed patients had recurrent instability, and, of these, 67% progressed to surgical intervention. Nonoperative treatment for a first-time dislocation is still reasonable if a cadet or soldier needs to quickly return to functional duties. Athletes who develop shoulder instability during their playing season have been studied in a military population as well. In a multicenter study of service academy athletes with anterior instability, Dickens and colleagues⁸ found that, with conservative management and accelerated rehabilitation of in-season shoulder instability, 73% of athletes returned to sport by a mean of 5 days. However, the durability of this treatment should be questioned, as 64% later experienced recurrence.

Arthroscopic Stabilization of Acute Anterior Shoulder Dislocations

In an early series of cases of traumatic anterior shoulder instability in USMA cadets, Wheeler and colleagues⁶ found that, at 14 months, 78% of arthroscopically stabilized cases and 92% of nonoperatively treated cases were successful. Then, in the 1990s, DeBerardino and colleagues⁴ studied a series of young, active patients in the USMA and noted significantly better results with arthroscopic treatment, vs nonoperative treatment, at 2- to 5-year follow-up. Of the arthroscopically treated shoulders, 88% remained stable during the study and returned to preinjury activity levels, and 12% experienced recurrent instability (risk factors included 2+ sulcus sign, poor capsular labral tissue, and history of bilateral shoulder instability). In a long-term follow-up (mean, 11.7 years; range, 9.1-13.9 years) of the same cohort, Owens and colleagues⁹ found that 14% of patients available for follow-up had undergone revision stabilization surgery, and, of these, 21% reported experiencing subluxation events. The authors concluded that, in first-time dislocators in this active military population, acute arthroscopic Bankart repair resulted in excellent return to athletics and subjective function, and had acceptable recurrence and reoperation rates. Bottoni and colleagues,⁷ in a prospective, randomized evaluation of arthroscopic stabilization of acute, traumatic, first-time shoulder dislocations in the Army, noted an 89% success rate for arthroscopic treatment at an average follow-up of 36 months, with no recurrent instability. DeBerardino and colleagues¹⁰ compared West Point patients treated nonoperatively with those arthroscopically treated with staples, transglenoid sutures, or bioabsorbable anchors. Recurrence rates were 85% for nonoperative treatment, 22% for staples, 14% for transglenoid sutures, and 10% for bioabsorbable anchors.

Arthroscopic Versus Open Stabilization of Anterior Shoulder Instability

In a prospective, randomized clinical trial comparing open and arthroscopic shoulder stabilization for recurrent anterior instability in active-duty Army personnel, Bottoni and colleagues¹¹ found comparable clinical outcomes. Stabilization surgery failed clinically in only 3 cases, 2 open and 1 arthroscopic. The authors concluded that arthroscopic stabilization can be safely performed for recurrent shoulder instability and that arthroscopic outcomes are similar to open outcomes. In a series of anterior shoulder subluxations in young athletes with Bankart lesions, Owens and colleagues¹² found that open and arthroscopic stabilization performed early resulted in better outcomes, regardless of technique used. Recurrent subluxation occurred at a mean of 17 months in 3 of the 10 patients in the open group and 3 of the 9 patients in the arthroscopic group, for an overall recurrence rate of 31%. The authors concluded that, in this patient population with Bankart lesions caused by anterior subluxation events, surgery should be performed early.

Bone Lesions

Burkhart and De Beer¹³ first noted that bone loss has emerged as one of the most important considerations in the setting of shoulder instability in active patients. Other authors have found this to be true in military populations.^14,15

The diagnosis of bone loss may include historical findings, such as increased number and ease of dislocations, as well as dislocation in lower positions of abduction. Physical examination findings may include apprehension in the midrange of motion. Advanced imaging, such as magnetic resonance arthrography, has since been validated as equivalent to 3-dimensional computed tomography (3-D CT) in determining glenoid bone loss.¹⁶ In 2007, Mologne and colleagues¹⁵ studied the amount of glenoid bone loss and the presence of fragmented bone or attritional bone loss and its effect on outcomes. They evaluated 21 patients who had arthroscopic treatment for anterior instability with anteroinferior glenoid bone loss between 20% and 30%. Average follow-up was 34 months. All patients received 3 or 4 anterior anchors. No patient with a bone fragment incorporated into the repair experienced recurrence or subluxation, whereas 30% of patients with attritional bone loss had recurrent instability.¹⁵

Classifying Bone Loss and Recognizing Its Effects

Burkhart and De Beer¹³ helped define the role and significance of bone loss in the setting of shoulder instability. They defined significant bone loss as an engaging Hill-Sachs lesion of the humerus in an abducted and externally rotated position or an “inverted pear” lesion of the glenoid. Overall analysis revealed recurrence in 4% of cases without significant bone loss and 65% of cases with significant bone loss. In a subanalysis of contact-sport athletes in the setting of bone loss, the failure rate increased to 89%, from 6.5%. Aiding in the quantitative assessment of glenoid bone loss, Itoi and colleagues¹⁷ showed that 21% glenoid bone loss resulted in instability that would not be corrected by a soft-tissue procedure alone. Bone loss of 20% to 25% has since been considered a “critical amount,” above which an arthroscopic Bankart has been questioned. More recently, several authors have shown that even less bone loss can have a significant effect on outcomes. Shaha and colleagues¹⁸ established that a subcritical level of bone loss (13.5%) on the anteroinferior glenoid resulted in clinical failure (as determined with the Western Ontario Shoulder Instability Index) even in cases in which frank recurrence or subluxation was avoided. It is thought that, in recurrent instability, glenoid bone loss incident rate is as high as 90%, and the corresponding percentage of patients with Hill-Sachs lesions is almost 100%.^19,20 Thus, it is increasingly understood that bone loss is a bipolar issue and that both sides must be considered in order to properly address shoulder instability in this setting. In 2007, Yamamoto and colleagues²¹ introduced the glenoid track, a method for predicting whether a Hill-Sachs lesion will engage. Di Giacomo and colleagues²² refined the track concept to quantitatively determine which lesions will engage in the setting of both glenoid and humeral bone loss. Metzger and colleagues,²³ confirming the track concept arthroscopically, found that manipulation with anesthesia and arthroscopic visualization was well predicted by preoperative track measurements, and thus these measurements can be a good guide for surgical management (Figures 1A, 1B).

Strategies for Addressing Bone Loss in Anterior Shoulder Instability

Several approaches for managing bone loss in shoulder instability have been described—the most common being coracoid transfer (Latarjet procedure). Waterman and colleagues²⁵ recently studied the effects of coracoid transfer, distal tibial allograft, and iliac crest augmentation on anterior shoulder instability in US military patients treated between 2006 and 2012. Of 64 patients who underwent a bone block procedure, 16 (25%) had a complication during short-term follow-up. Complications included neurologic injury, pain, infection, hardware failure, and recurrent instability.

Conclusion

Traumatic anterior shoulder instability is a common pathology that continues to significantly challenge the readiness of the US military. Military surgeon-researchers have a long history of investigating approaches to the treatment of this pathology—applying good science to a large controlled population, using a single medical record, and demonstrating a commitment to return service members to the ready defense of the nation.

Am J Orthop. 2017;46(4):184-189. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.