Justin J. Mitchell, MD

ABSTRACT

The lateral tibial eminence shares a close relationship with the anterior root of the lateral meniscus. Limited studies have reported traumatic injury to the anterior meniscal roots in the setting of tibial eminence fractures, and reported rates of occurrence of concomitant meniscal and chondral injuries vary widely. The purpose of this article is to describe the case of a 28-year-old woman who had a complete avulsion of the anterolateral meniscal root caused by a tibial eminence fracture with resultant malunion and root displacement. The anterolateral meniscal root was anatomically repaired following arthroscopic resection of the malunited fragment.

The lateral tibial eminence is intimately associated with the root attachment of the anterior horn of the lateral meniscus.^1-3 Previous studies have demonstrated both the close proximity of the anterior cruciate ligament (ACL) insertion to the meniscal roots and the potential for disruption in surgical interventions, such as tibial tunnel drilling in ACL reconstruction or placement of intramedullary tibial nails.^4-6 The meniscal roots play a crucial role in force distribution, and disruption of these structures has been shown to significantly increase joint contact forces. Despite the deleterious effects of this injury, limited studies have reported on traumatic injury to the meniscal roots in the setting of tibial eminence fractures.

Reported rates of occurrence of concomitant meniscal and chondral injuries occurring with tibial eminence fractures vary widely, ranging from <5% to 40%.^7,8 Although fractures to the tibial eminence are more common in children, an association between these injuries and concomitant soft tissue injuries, including meniscal, chondral, and collateral ligament injuries, in the adult population has been reported.⁷ Monto and Cameron-Donaldson⁸ used magnetic resonance imaging (MRI) to evaluate tibial eminence fractures in adults and found that 23% of study subjects had associated medial meniscus tears and 18% had lateral meniscus tears. In a similar study, Ishibashi and colleagues⁹ found that 25% of tibial eminence fractures were associated with lateral meniscus tears and 16% with medial meniscus tears.

These studies demonstrate the potential for meniscus injuries during tibial eminence fractures. However, the authors are unaware of any reports of complete tearing of the anterior horn of the lateral meniscus in association with this injury. This is an important injury to recognize and identify intraoperatively because an injury of this nature could potentially compromise the mechanical loading patterns and health of the articular cartilage of the lateral compartment of the knee. The purpose of this article is to describe a complete avulsion of the anterolateral meniscal root due to a tibial eminence fracture with resultant malunion and displacement of the root in a nonanatomical position. The patient provided written informed consent for print and electronic publication of this case report.

Continue to: A 28-year-old active woman...

 

CASE

A 28-year-old active woman presented to our clinic 22 months after sustaining a right knee tibial eminence fracture that was initially treated with extension immobilization, which resulted in a fibrous malunion. She subsequently sustained a second injury resulting in displacement of the malunion fracture fragment, and was treated at another institution 10 months prior to presentation at our clinic with arthroscopic reduction and internal fixation with a cannulated screw and washer of the tibial eminence fracture. This was followed by hardware removal 6 months prior to her office visit at our clinic. At presentation, she reported worsening right knee pain, mechanical symptoms, and loss of both flexion and extension compared with her uninjured knee. Conservative management, including activity modification, extensive physical therapy, and anti-inflammatory medication following her most recent procedure, had not resulted in improvement of her symptoms.

Physical examination revealed significantly reduced knee flexion and extension (+15°-120° on the affected side compared with 5° of hyperextension to 130° flexion of the contralateral knee). Ligamentous examination demonstrated no laxity with varus or valgus stress at 0° to 30° of flexion, negative posterior drawer, and a Grade 2 Lachman and positive pivot shift. She also exhibited pain with attempted right knee terminal extension. Radiographs and computed tomography scans were obtained and reviewed. They revealed a malunited tibial eminence fracture (Figures 1A-1D).  

The fragment was located anterior and lateral to its native location, which created a mechanical block during knee motion. Additionally, MRI demonstrated that the anterior horn of the lateral meniscus was displaced and attached to the malunited fragment (Figures 2A, 2B) as well as to nonfunctional ACL fibers.

  On the basis of the mechanical block restricting extension and the displaced anterior horn of the lateral meniscus compromising meniscal function, we recommended arthroscopic surgery. After discussion of the risks and benefits of the procedure with the patient, she provided informed consent, and it was decided that the patient would undergo arthroscopic fragment excision followed by anatomic repair of the anterior root of the lateral meniscus, and that we would proceed with ACL reconstruction in the future given her subjective instability and physical examination findings of ACL insufficiency.

Arthroscopic assessment of the right knee demonstrated the large osseous fragment located in the anterolateral aspect of the joint with the displaced anterior horn of the lateral meniscus attached as well as significant anterior impingement limiting knee extension. Probing of the anterolateral meniscal root in the lateral compartment showed abundant surrounding scar tissue with an abnormal attachment, representing a chronic root avulsion. A mechanical shaver was used to débride the scar tissue and expose the malunited fragment, followed by complete osseous fragment excision with a high-speed burr (Figure 3). 

The knee was taken through full range of motion (ROM) from 5° of hyperextension to 130° of flexion with arthroscopic confirmation of no further anterior impingement.

A soft tissue anterolateral meniscal root repair was performed by creating a 2-cm to 3-cm incision on the anterolateral tibia, just distal to the medial aspect of the Gerdy tubercle. To best restore the footprint of the repair and increase the potential for biologic healing, 2 transtibial tunnels were created at the location of the root attachment. An ACL aiming device with a cannulated sleeve was used to drill 2 bony tunnels approximately 5 mm apart, exiting at the anatomic root footprint. The drill pins were removed, leaving the 2 cannulas in place for later suture passage. A suture-passing device was used to pass 2 separate sutures through the detached meniscal root. 

A looped passing wire was directed up the previously placed cannulas, and 1 suture was shuttled down each tunnel. The sutures were securely tied down over a bony bridge with a cortical fixation button on the anterolateral tibia. This was visualized arthroscopically to ensure proper positioning and tension of the root to its native footprint (Figure 4).  A comparison of preoperative and postoperative anteroposterior and lateral knee radiographs is shown in Figures 5A, 5B.

Continue to: Postoperatively, the patient was placed...

 

Postoperatively, the patient was placed on a non-weight-bearing protocol for her operative lower extremity for 6 weeks. A brace locked in extension was used for the same period of time (being removed only for physical therapy exercises). Enoxaparin was used for the first 2 weeks for deep vein thrombosis prophylaxis, followed by aspirin for an additional 4 weeks. Physical therapy was started on postoperative day 1 to begin working on early passive ROM exercises. Knee flexion was limited to 0° to 90° of flexion for the first 2 weeks and then progressed as tolerated.

DISCUSSION

This article describes a rare case of a patient with lateral meniscal anterior root avulsion in the setting of a tibial eminence fracture with subsequent malunion and root displacement. In a case such as this, delineation of the true extent of the injury is difficult because the anterior meniscal root can be torn, displaced, and nonanatomically scarred to surrounding soft tissues, making MRI interpretation challenging. Clinically, patients can present with a wide range of symptoms, including pain, mechanical symptoms, instability, and loss of knee motion.¹⁰

The anterior root of the lateral meniscus has been reported to be attached anterior to the lateral tibial eminence and adjacent to the insertion of the ACL. Fibrous connections extending from the anterior horn of the lateral meniscus attachment to the lateral tibial eminence are constant.¹¹ Furumatsu and colleagues¹² demonstrated the existence of dense fibers linking the anterior root of the lateral meniscus with the lateral aspect of the ACL tibial insertion. Acknowledging the close relationship of these structures is key to comprehending the importance of evaluating the anterior horn of the lateral meniscus in cases of tibial eminence fractures at the initial time of injury. Failure to diagnose this pathology can lead to poor clinical outcomes and early degenerative changes of the knee.

Tibial intercondylar eminence avulsion fractures are most likely to occur in children and adolescents, and are equivalent to an ACL tear in adults.¹³ When tibial eminence fractures occur in an older cohort, they are often combined with lesions of the menisci, capsule, or collateral ligaments.¹⁴ The initial injury in our patient demonstrated concomitant anterior root injury that progressed with time to nonanatomical healing of the root, leading to altered biomechanics. Surgical techniques available for meniscal root repair are broadly divided into transosseous suture repairs and suture anchor repairs.¹⁰ The transtibial pullout technique using 2 transtibial bone tunnels as described in this report is the senior author’s (RFL) preference because it provides a strong construct with minimal displacement of the repaired meniscus.^15-17

This article describes a complete avulsion of the anterolateral meniscal root caused by a tibial eminence fracture with resultant malunion and displacement of the root in a nonanatomic position. Anterior meniscal root tears have been reported to result in altered biomechanics and force transmission across the knee, and therefore, anatomic repair of the anterior root is indicated.

ABSTRACT

The lateral tibial eminence shares a close relationship with the anterior root of the lateral meniscus. Limited studies have reported traumatic injury to the anterior meniscal roots in the setting of tibial eminence fractures, and reported rates of occurrence of concomitant meniscal and chondral injuries vary widely. The purpose of this article is to describe the case of a 28-year-old woman who had a complete avulsion of the anterolateral meniscal root caused by a tibial eminence fracture with resultant malunion and root displacement. The anterolateral meniscal root was anatomically repaired following arthroscopic resection of the malunited fragment.

The lateral tibial eminence is intimately associated with the root attachment of the anterior horn of the lateral meniscus.^1-3 Previous studies have demonstrated both the close proximity of the anterior cruciate ligament (ACL) insertion to the meniscal roots and the potential for disruption in surgical interventions, such as tibial tunnel drilling in ACL reconstruction or placement of intramedullary tibial nails.^4-6 The meniscal roots play a crucial role in force distribution, and disruption of these structures has been shown to significantly increase joint contact forces. Despite the deleterious effects of this injury, limited studies have reported on traumatic injury to the meniscal roots in the setting of tibial eminence fractures.

Reported rates of occurrence of concomitant meniscal and chondral injuries occurring with tibial eminence fractures vary widely, ranging from <5% to 40%.^7,8 Although fractures to the tibial eminence are more common in children, an association between these injuries and concomitant soft tissue injuries, including meniscal, chondral, and collateral ligament injuries, in the adult population has been reported.⁷ Monto and Cameron-Donaldson⁸ used magnetic resonance imaging (MRI) to evaluate tibial eminence fractures in adults and found that 23% of study subjects had associated medial meniscus tears and 18% had lateral meniscus tears. In a similar study, Ishibashi and colleagues⁹ found that 25% of tibial eminence fractures were associated with lateral meniscus tears and 16% with medial meniscus tears.

These studies demonstrate the potential for meniscus injuries during tibial eminence fractures. However, the authors are unaware of any reports of complete tearing of the anterior horn of the lateral meniscus in association with this injury. This is an important injury to recognize and identify intraoperatively because an injury of this nature could potentially compromise the mechanical loading patterns and health of the articular cartilage of the lateral compartment of the knee. The purpose of this article is to describe a complete avulsion of the anterolateral meniscal root due to a tibial eminence fracture with resultant malunion and displacement of the root in a nonanatomical position. The patient provided written informed consent for print and electronic publication of this case report.

Continue to: A 28-year-old active woman...

 

CASE

A 28-year-old active woman presented to our clinic 22 months after sustaining a right knee tibial eminence fracture that was initially treated with extension immobilization, which resulted in a fibrous malunion. She subsequently sustained a second injury resulting in displacement of the malunion fracture fragment, and was treated at another institution 10 months prior to presentation at our clinic with arthroscopic reduction and internal fixation with a cannulated screw and washer of the tibial eminence fracture. This was followed by hardware removal 6 months prior to her office visit at our clinic. At presentation, she reported worsening right knee pain, mechanical symptoms, and loss of both flexion and extension compared with her uninjured knee. Conservative management, including activity modification, extensive physical therapy, and anti-inflammatory medication following her most recent procedure, had not resulted in improvement of her symptoms.

Physical examination revealed significantly reduced knee flexion and extension (+15°-120° on the affected side compared with 5° of hyperextension to 130° flexion of the contralateral knee). Ligamentous examination demonstrated no laxity with varus or valgus stress at 0° to 30° of flexion, negative posterior drawer, and a Grade 2 Lachman and positive pivot shift. She also exhibited pain with attempted right knee terminal extension. Radiographs and computed tomography scans were obtained and reviewed. They revealed a malunited tibial eminence fracture (Figures 1A-1D).  

The fragment was located anterior and lateral to its native location, which created a mechanical block during knee motion. Additionally, MRI demonstrated that the anterior horn of the lateral meniscus was displaced and attached to the malunited fragment (Figures 2A, 2B) as well as to nonfunctional ACL fibers.

  On the basis of the mechanical block restricting extension and the displaced anterior horn of the lateral meniscus compromising meniscal function, we recommended arthroscopic surgery. After discussion of the risks and benefits of the procedure with the patient, she provided informed consent, and it was decided that the patient would undergo arthroscopic fragment excision followed by anatomic repair of the anterior root of the lateral meniscus, and that we would proceed with ACL reconstruction in the future given her subjective instability and physical examination findings of ACL insufficiency.

Arthroscopic assessment of the right knee demonstrated the large osseous fragment located in the anterolateral aspect of the joint with the displaced anterior horn of the lateral meniscus attached as well as significant anterior impingement limiting knee extension. Probing of the anterolateral meniscal root in the lateral compartment showed abundant surrounding scar tissue with an abnormal attachment, representing a chronic root avulsion. A mechanical shaver was used to débride the scar tissue and expose the malunited fragment, followed by complete osseous fragment excision with a high-speed burr (Figure 3). 

The knee was taken through full range of motion (ROM) from 5° of hyperextension to 130° of flexion with arthroscopic confirmation of no further anterior impingement.

A soft tissue anterolateral meniscal root repair was performed by creating a 2-cm to 3-cm incision on the anterolateral tibia, just distal to the medial aspect of the Gerdy tubercle. To best restore the footprint of the repair and increase the potential for biologic healing, 2 transtibial tunnels were created at the location of the root attachment. An ACL aiming device with a cannulated sleeve was used to drill 2 bony tunnels approximately 5 mm apart, exiting at the anatomic root footprint. The drill pins were removed, leaving the 2 cannulas in place for later suture passage. A suture-passing device was used to pass 2 separate sutures through the detached meniscal root. 

A looped passing wire was directed up the previously placed cannulas, and 1 suture was shuttled down each tunnel. The sutures were securely tied down over a bony bridge with a cortical fixation button on the anterolateral tibia. This was visualized arthroscopically to ensure proper positioning and tension of the root to its native footprint (Figure 4).  A comparison of preoperative and postoperative anteroposterior and lateral knee radiographs is shown in Figures 5A, 5B.

Continue to: Postoperatively, the patient was placed...

 

Postoperatively, the patient was placed on a non-weight-bearing protocol for her operative lower extremity for 6 weeks. A brace locked in extension was used for the same period of time (being removed only for physical therapy exercises). Enoxaparin was used for the first 2 weeks for deep vein thrombosis prophylaxis, followed by aspirin for an additional 4 weeks. Physical therapy was started on postoperative day 1 to begin working on early passive ROM exercises. Knee flexion was limited to 0° to 90° of flexion for the first 2 weeks and then progressed as tolerated.

DISCUSSION

This article describes a rare case of a patient with lateral meniscal anterior root avulsion in the setting of a tibial eminence fracture with subsequent malunion and root displacement. In a case such as this, delineation of the true extent of the injury is difficult because the anterior meniscal root can be torn, displaced, and nonanatomically scarred to surrounding soft tissues, making MRI interpretation challenging. Clinically, patients can present with a wide range of symptoms, including pain, mechanical symptoms, instability, and loss of knee motion.¹⁰

The anterior root of the lateral meniscus has been reported to be attached anterior to the lateral tibial eminence and adjacent to the insertion of the ACL. Fibrous connections extending from the anterior horn of the lateral meniscus attachment to the lateral tibial eminence are constant.¹¹ Furumatsu and colleagues¹² demonstrated the existence of dense fibers linking the anterior root of the lateral meniscus with the lateral aspect of the ACL tibial insertion. Acknowledging the close relationship of these structures is key to comprehending the importance of evaluating the anterior horn of the lateral meniscus in cases of tibial eminence fractures at the initial time of injury. Failure to diagnose this pathology can lead to poor clinical outcomes and early degenerative changes of the knee.

Tibial intercondylar eminence avulsion fractures are most likely to occur in children and adolescents, and are equivalent to an ACL tear in adults.¹³ When tibial eminence fractures occur in an older cohort, they are often combined with lesions of the menisci, capsule, or collateral ligaments.¹⁴ The initial injury in our patient demonstrated concomitant anterior root injury that progressed with time to nonanatomical healing of the root, leading to altered biomechanics. Surgical techniques available for meniscal root repair are broadly divided into transosseous suture repairs and suture anchor repairs.¹⁰ The transtibial pullout technique using 2 transtibial bone tunnels as described in this report is the senior author’s (RFL) preference because it provides a strong construct with minimal displacement of the repaired meniscus.^15-17

This article describes a complete avulsion of the anterolateral meniscal root caused by a tibial eminence fracture with resultant malunion and displacement of the root in a nonanatomic position. Anterior meniscal root tears have been reported to result in altered biomechanics and force transmission across the knee, and therefore, anatomic repair of the anterior root is indicated.

ABSTRACT

The lateral tibial eminence shares a close relationship with the anterior root of the lateral meniscus. Limited studies have reported traumatic injury to the anterior meniscal roots in the setting of tibial eminence fractures, and reported rates of occurrence of concomitant meniscal and chondral injuries vary widely. The purpose of this article is to describe the case of a 28-year-old woman who had a complete avulsion of the anterolateral meniscal root caused by a tibial eminence fracture with resultant malunion and root displacement. The anterolateral meniscal root was anatomically repaired following arthroscopic resection of the malunited fragment.

The lateral tibial eminence is intimately associated with the root attachment of the anterior horn of the lateral meniscus.^1-3 Previous studies have demonstrated both the close proximity of the anterior cruciate ligament (ACL) insertion to the meniscal roots and the potential for disruption in surgical interventions, such as tibial tunnel drilling in ACL reconstruction or placement of intramedullary tibial nails.^4-6 The meniscal roots play a crucial role in force distribution, and disruption of these structures has been shown to significantly increase joint contact forces. Despite the deleterious effects of this injury, limited studies have reported on traumatic injury to the meniscal roots in the setting of tibial eminence fractures.

Reported rates of occurrence of concomitant meniscal and chondral injuries occurring with tibial eminence fractures vary widely, ranging from <5% to 40%.^7,8 Although fractures to the tibial eminence are more common in children, an association between these injuries and concomitant soft tissue injuries, including meniscal, chondral, and collateral ligament injuries, in the adult population has been reported.⁷ Monto and Cameron-Donaldson⁸ used magnetic resonance imaging (MRI) to evaluate tibial eminence fractures in adults and found that 23% of study subjects had associated medial meniscus tears and 18% had lateral meniscus tears. In a similar study, Ishibashi and colleagues⁹ found that 25% of tibial eminence fractures were associated with lateral meniscus tears and 16% with medial meniscus tears.

These studies demonstrate the potential for meniscus injuries during tibial eminence fractures. However, the authors are unaware of any reports of complete tearing of the anterior horn of the lateral meniscus in association with this injury. This is an important injury to recognize and identify intraoperatively because an injury of this nature could potentially compromise the mechanical loading patterns and health of the articular cartilage of the lateral compartment of the knee. The purpose of this article is to describe a complete avulsion of the anterolateral meniscal root due to a tibial eminence fracture with resultant malunion and displacement of the root in a nonanatomical position. The patient provided written informed consent for print and electronic publication of this case report.

Continue to: A 28-year-old active woman...

 

CASE

A 28-year-old active woman presented to our clinic 22 months after sustaining a right knee tibial eminence fracture that was initially treated with extension immobilization, which resulted in a fibrous malunion. She subsequently sustained a second injury resulting in displacement of the malunion fracture fragment, and was treated at another institution 10 months prior to presentation at our clinic with arthroscopic reduction and internal fixation with a cannulated screw and washer of the tibial eminence fracture. This was followed by hardware removal 6 months prior to her office visit at our clinic. At presentation, she reported worsening right knee pain, mechanical symptoms, and loss of both flexion and extension compared with her uninjured knee. Conservative management, including activity modification, extensive physical therapy, and anti-inflammatory medication following her most recent procedure, had not resulted in improvement of her symptoms.

Physical examination revealed significantly reduced knee flexion and extension (+15°-120° on the affected side compared with 5° of hyperextension to 130° flexion of the contralateral knee). Ligamentous examination demonstrated no laxity with varus or valgus stress at 0° to 30° of flexion, negative posterior drawer, and a Grade 2 Lachman and positive pivot shift. She also exhibited pain with attempted right knee terminal extension. Radiographs and computed tomography scans were obtained and reviewed. They revealed a malunited tibial eminence fracture (Figures 1A-1D).  

The fragment was located anterior and lateral to its native location, which created a mechanical block during knee motion. Additionally, MRI demonstrated that the anterior horn of the lateral meniscus was displaced and attached to the malunited fragment (Figures 2A, 2B) as well as to nonfunctional ACL fibers.

  On the basis of the mechanical block restricting extension and the displaced anterior horn of the lateral meniscus compromising meniscal function, we recommended arthroscopic surgery. After discussion of the risks and benefits of the procedure with the patient, she provided informed consent, and it was decided that the patient would undergo arthroscopic fragment excision followed by anatomic repair of the anterior root of the lateral meniscus, and that we would proceed with ACL reconstruction in the future given her subjective instability and physical examination findings of ACL insufficiency.

Arthroscopic assessment of the right knee demonstrated the large osseous fragment located in the anterolateral aspect of the joint with the displaced anterior horn of the lateral meniscus attached as well as significant anterior impingement limiting knee extension. Probing of the anterolateral meniscal root in the lateral compartment showed abundant surrounding scar tissue with an abnormal attachment, representing a chronic root avulsion. A mechanical shaver was used to débride the scar tissue and expose the malunited fragment, followed by complete osseous fragment excision with a high-speed burr (Figure 3). 

The knee was taken through full range of motion (ROM) from 5° of hyperextension to 130° of flexion with arthroscopic confirmation of no further anterior impingement.

A soft tissue anterolateral meniscal root repair was performed by creating a 2-cm to 3-cm incision on the anterolateral tibia, just distal to the medial aspect of the Gerdy tubercle. To best restore the footprint of the repair and increase the potential for biologic healing, 2 transtibial tunnels were created at the location of the root attachment. An ACL aiming device with a cannulated sleeve was used to drill 2 bony tunnels approximately 5 mm apart, exiting at the anatomic root footprint. The drill pins were removed, leaving the 2 cannulas in place for later suture passage. A suture-passing device was used to pass 2 separate sutures through the detached meniscal root. 

A looped passing wire was directed up the previously placed cannulas, and 1 suture was shuttled down each tunnel. The sutures were securely tied down over a bony bridge with a cortical fixation button on the anterolateral tibia. This was visualized arthroscopically to ensure proper positioning and tension of the root to its native footprint (Figure 4).  A comparison of preoperative and postoperative anteroposterior and lateral knee radiographs is shown in Figures 5A, 5B.

Continue to: Postoperatively, the patient was placed...

 

Postoperatively, the patient was placed on a non-weight-bearing protocol for her operative lower extremity for 6 weeks. A brace locked in extension was used for the same period of time (being removed only for physical therapy exercises). Enoxaparin was used for the first 2 weeks for deep vein thrombosis prophylaxis, followed by aspirin for an additional 4 weeks. Physical therapy was started on postoperative day 1 to begin working on early passive ROM exercises. Knee flexion was limited to 0° to 90° of flexion for the first 2 weeks and then progressed as tolerated.

DISCUSSION

This article describes a rare case of a patient with lateral meniscal anterior root avulsion in the setting of a tibial eminence fracture with subsequent malunion and root displacement. In a case such as this, delineation of the true extent of the injury is difficult because the anterior meniscal root can be torn, displaced, and nonanatomically scarred to surrounding soft tissues, making MRI interpretation challenging. Clinically, patients can present with a wide range of symptoms, including pain, mechanical symptoms, instability, and loss of knee motion.¹⁰

The anterior root of the lateral meniscus has been reported to be attached anterior to the lateral tibial eminence and adjacent to the insertion of the ACL. Fibrous connections extending from the anterior horn of the lateral meniscus attachment to the lateral tibial eminence are constant.¹¹ Furumatsu and colleagues¹² demonstrated the existence of dense fibers linking the anterior root of the lateral meniscus with the lateral aspect of the ACL tibial insertion. Acknowledging the close relationship of these structures is key to comprehending the importance of evaluating the anterior horn of the lateral meniscus in cases of tibial eminence fractures at the initial time of injury. Failure to diagnose this pathology can lead to poor clinical outcomes and early degenerative changes of the knee.

Tibial intercondylar eminence avulsion fractures are most likely to occur in children and adolescents, and are equivalent to an ACL tear in adults.¹³ When tibial eminence fractures occur in an older cohort, they are often combined with lesions of the menisci, capsule, or collateral ligaments.¹⁴ The initial injury in our patient demonstrated concomitant anterior root injury that progressed with time to nonanatomical healing of the root, leading to altered biomechanics. Surgical techniques available for meniscal root repair are broadly divided into transosseous suture repairs and suture anchor repairs.¹⁰ The transtibial pullout technique using 2 transtibial bone tunnels as described in this report is the senior author’s (RFL) preference because it provides a strong construct with minimal displacement of the repaired meniscus.^15-17

This article describes a complete avulsion of the anterolateral meniscal root caused by a tibial eminence fracture with resultant malunion and displacement of the root in a nonanatomic position. Anterior meniscal root tears have been reported to result in altered biomechanics and force transmission across the knee, and therefore, anatomic repair of the anterior root is indicated.

Take-Home Points

• Injuries to the medial knee are the most common knee ligament injuries, and often occur in the athletic population.
• Complete posteromedial corner injuries require surgical treatment to restore joint stability and biomechanics.
• Biomechanical evidence has demonstrated an important load-sharing distribution between the sMCL and the POL.
• Valgus instability caused by a medial side injury, can lead to both ACL/posterior cruciate ligament reconstruction graft failure if the medial sided injury is not concurrently repaired or reconstructed.
• Anatomic posteromedial corner reconstruction yields excellent biomechanical and patient-reported outcomes.

Most injuries of the medial structures of the knee are treated conservatively.^1-3 In severe acute injuries and chronic symptomatic instabilities, however, surgical treatment is needed to restore knee stability and to prevent degenerative changes secondary to instability.⁴ Three structures involved in medial stability are the superficial medial collateral ligament (sMCL), which is the primary valgus restraint; the posterior oblique ligament (POL), which is the primary restraint to internal rotation and the secondary valgus restraint; and the semimembranosus.^5,6

Surgical techniques for posteromedial knee reconstruction include direct repair,⁷ repair with augmentation,^8,9 advancement of the tibial insertion of the sMCL,¹⁰ and transfer of the pes anserine tendons.¹¹ In anatomical reconstruction of the posteromedial corner, which has been described before, the sMCL and the POL are reconstructed to reproduce the native motion and stability of the knee.¹² Clinically, repair and reconstruction have similar patient-reported outcomes and medial opening evaluations over the short term.

These approaches require large incisions and extensive dissection of soft tissue on the medial aspect of the knee.⁵ Given these drawbacks, it is reasonable to consider less invasive options. Minimally invasive surgery has the advantages of reduced scarring and blood loss, less disruption of surrounding tissue, faster recovery, and improved aesthetics.⁴

We conducted a study of a minimally invasive technique for reconstructing the posteromedial structures of the knee. We compared medial compartment stability measured on valgus stress radiographs in intact, sectioned, and reconstructed states in cadaveric knees. We hypothesized that a minimally invasive technique using autogenous hamstring graft in the appropriate anatomical location would return valgus stability to its nearly native state.

Materials and Methods

This study was conducted at the Buenos Aires British Hospital in Buenos Aires, Argentina, and at the University of Colorado Hospital in Aurora. Ten fresh-frozen cadaveric knees with no evidence of ligamentous injuries, osteoarthritis, or previous surgery were used. Mean donor age was 69.4 years (range, 45-87 years). Each specimen was maintained at room temperature for 24 hours before use. The femur was sectioned 20 cm proximal to the knee joint. The tibia was sectioned 12.5 cm distal to the knee joint.

Identification and Sectioning of Posteromedial Structures

Anatomical insertion sites of the sMCL, the deep MCL (dMCL), and the POL were identified on the tibia through an oblique 3-cm incision on the posteromedial aspect of the knee (Figures 1A-1C). A valgus stress radiograph with medial compartment gap measurement was obtained for each of the 10 knees before sectioning the medial stabilizing structures.

After intact-state evaluation, each knee’s sMCL, dMCL, and POL were sectioned at their tibial insertion. Valgus stress radiograph was repeated and medial compartment gap was remeasured for comparison of the sectioned state with the intact and reconstructed states.

Anatomical Reconstruction With Mini-Invasive Technique

After sectioning of medial stabilizing structures, minimally invasive reconstruction was performed through 2 small incisions on the medial aspect of each of the 10 knees, as follows. First, the semitendinosus tendon was identified through the oblique incision that had been used for sectioning. Then, an open-ended tendon stripper was placed around the circumference of the semitendinosus and was passed proximomedially, transecting the tendon at its musculotendinous junction. While the tendon stripper was being passed, care was taken to maintain the nearby tibial insertion of the sartorius fascia (Figures 1D-1F).

The proximal end of the semitendinosus tendon (~5 cm proximal to incision) was then cleared of all muscular and fatty soft-tissue remnants and whipstitched with No. 2 Vycril suture (Figure 2). Then, the medial epicondyle was visualized and identified under radiographic guidance. A 1-cm incision was made 10 mm posterior and 2 mm proximal to the epicondyle (midpoint of femoral attachment of sMCL and POL).¹² A 1.8-mm Kirschner wire was inserted into the femur at this location. A blunt awl was used for deep (under sartorius fascia) passage of the semitendinosus tendon, from distal to proximal, and the tendon was looped over the top of the wire and brought through the incision.

With the semitendinosus tendon looped around the wire, isometricity was tested by pulling the suture within the tendon and moving the knee through a full range of motion. The isometric point was confirmed by tendon migration of <2 mm.¹³ Migration was measured by marking the graft 2 mm from its insertion; the graft was then pulled to ensure correct isometric point position. An 18-mm cannulated spiked screw and washer (Arthrex) were then passed over the wire and partially secured to the femur—the attachment point for the proximal sMCL portion of the semitendinosus graft. The semitendinosus tendon was then secured beneath the spiked washer with the knee in 20° of flexion with neutral rotation, recreating the sMCL.

Posteriorly, the distal insertion site of the POL was identified at the posteromedial aspect of the tibia through the oblique incision previously described. A 7-mm tunnel was drilled starting posteromedial (10 mm under tibial articular surface) and exiting just distal and medial to the Gerdy tubercle.

The graft was passed subcutaneously and below the sartorius fascia from posterior to anterior and was secured with a 7-mm × 23-mm cannulated titanium screw. Fixation was performed at full extension with neutral rotation (Figures 3A-3C, 4). 

After final fixation, the medial knee was openly dissected to assess the inverted-V ligament reconstruction for anatomical placement and avoidance of crucial structures.

Stability Testing

Per International Knee Documentation Committee guidelines for stressing the medial compartment,¹⁴ valgus stress radiographs were obtained for all specimens at 0° and 20° of flexion in intact, sectioned, and reconstructed states.

For all radiographs, performed by Dr. Chahla, a 10-N valgus force (measured by dynamometer) was applied to an intramedullary rod placed in the femur while the tibia was firmly attached to a specially designed base¹⁵ (Figures 5A-5C). A situation of 1 df was recreated to allow only varus/valgus motion during testing. 

 

The medial gap formed by the femoral condyle and its corresponding tibial plateau (at site of maximal separation) was tested in all 3 state conditions (intact, sectioned, reconstructed). Distances were digitally measured with a picture archiving and communication system viewer (Imagecast; IDX Systems Corporation). Medial gap was measured by taking the shortest distance between the subchondral bone surface of the most distal aspect of the medial femoral condyle and the corresponding medial tibial plateau. Three independent examiners took all the measurements; each examiner was blinded to the others’ measurements.

Statistics

Paired Student t tests were used to compare the 3 conditions, and the Shapiro-Wilk test was used to check for a normally distributed population. Statistical significance was set at P < .05. Statistical analyses were performed with GraphPad software.

Results

In all 10 specimens, the sMCL, the dMCL, and the POL were successfully identified and sectioned through a medial oblique incision over the distal insertion of the structures.

During all valgus testing states, there was no loss of graft fixation, and there was no gross graft slippage. In addition, all grafts remained in continuity with no evidence of failure, and there were no failures or breakages of the proximal or distal screw.

After posteromedial sectioning, mean medial gap was statistically significantly larger (P = .0002) at full extension (11 mm vs 3.3 mm) and at 20° of flexion (12.6 mm vs 3.8 mm). There was no statistically significant difference between the value of the intact state and the value after minimally invasive reconstruction at 0° (P = .56) or 20° (P = .102) of flexion.

Each knee had a notable endpoint in valgus stress noted on clinical examination after reconstruction. All individual results are listed in the Table. Interobserver reliability for the measurements was almost perfect¹⁶ (κ = 0.86).

Discussion

In this article, we describe a minimally invasive technique for anatomical posteromedial reconstruction of the knee in a cadaveric model. This technique restores the knee’s native valgus stability without causing extensive damage to the surrounding soft tissues and thereby potentially prevents scar formation and reduces blood loss.

Superficial MCL injury, one of the most common knee ligament injuries, is often associated with POL injury.⁷ Although most sMCL injuries are treated nonoperatively, with good results,³ surgical treatment is needed for severe (grade III) instabilities, symptomatic chronic instabilities, and knee dislocations.^12,17 Most posteromedial reconstruction techniques require an extensive approach that causes damage to surrounding soft tissue,^6,7,9,10 which in turn may compromise healing and positive patient outcomes. Surgical techniques include direct repair with sutures or anchors,¹⁸ capsular procedures,¹⁹ augmentations,⁹ internal bracing,⁶ and complete reconstruction of the posteromedial corner.²⁰

LaPrade and Wijdicks¹² have previously described anatomical reconstruction of the posteromedial corner. In their technique, a split semitendinosus autograft is used to reconstruct the sMCL and the POL separately, using 4 implants and reproducing each ligament’s anatomical attachment site. In this proposed technique, the distal attachment of the semitendinosus insertion is left intact, and uses 1 attachment point on the distal femur and 1 on the proximal tibia, allowing use of only 2 implants. In addition, it is performed with a minimally invasive approach, reduces cost, limits surgical exposure, and with experience may shorten operative time. To reduce the graft failure rate, the technique of LaPrade and Wijdicks¹² positions the sMCL tibial attachment as posterior as possible, which can be performed with this minimally invasive approach as well.

To reduce the graft failure rate, the technique of LaPrade and Wijdicks¹² positions the sMCL as posterior as possible. Despite the potential for increased graft stress with an anterior position, as in our modified technique, our group of 10 knees had no graft fixation failures in isolated valgus stress testing in either extension or flexion. Our minimally invasive posteromedial knee reconstruction significantly improved knee stability over the sectioned state as well as medial compartment gapping with valgus stress. There was no significant difference in medial compartment gapping between the intact and reconstructed states.

Our technique was built on open procedures (described by Kim and colleagues¹³) that carefully identify the isometric point of the graft. In addition, it adopted the modification (proposed by Lind and colleagues²¹) in which a fixation point is added at the distal insertion of the POL instead of being sutured to the direct arm of the semitendinosus tendon.

Furthermore, our technique, despite being similar to those described by Dong and colleagues²² and Borden and colleagues,²³  has the advantages of minimally invasive surgery and reduced disruption of soft tissues. Dong and colleagues²² reported on 64 patients with a mean follow-up of 34 months; patients’ medial opening measurements were significantly decreased at follow-up and fell within the normal range. 

The present study had several limitations. First, the age of our specimens was higher than the mean age of patients with knee ligament injury, potentially leading to firmer or more fibrotic tendons less susceptible to elongation. Second, we did not evaluate the knees’ rotational stability, and anterior cruciate ligaments (ACLs) were intact. As most posteromedial injuries co-occur with ACL injuries, a more realistic situation would have been reproduced by assessing rotational stability while performing both ACL reconstruction and the proposed posteromedial reconstruction. Third, static specimen measurements do not reflect the dynamic function of the posteromedial corner. Prospective clinical studies are needed to assess the true effectiveness of the posteromedial corner in the clinical scenario.

Knowledge of the anatomy of the medial aspect of the knee is vital to reconstruction of the medial side of the knee. Our results suggest that a minimally invasive technique can restore valgus stability without the need for extensive dissection and disruption of surrounding soft tissues. More research is needed to determine the results of this technique in vivo.

Take-Home Points

• Injuries to the medial knee are the most common knee ligament injuries, and often occur in the athletic population.
• Complete posteromedial corner injuries require surgical treatment to restore joint stability and biomechanics.
• Biomechanical evidence has demonstrated an important load-sharing distribution between the sMCL and the POL.
• Valgus instability caused by a medial side injury, can lead to both ACL/posterior cruciate ligament reconstruction graft failure if the medial sided injury is not concurrently repaired or reconstructed.
• Anatomic posteromedial corner reconstruction yields excellent biomechanical and patient-reported outcomes.

Most injuries of the medial structures of the knee are treated conservatively.^1-3 In severe acute injuries and chronic symptomatic instabilities, however, surgical treatment is needed to restore knee stability and to prevent degenerative changes secondary to instability.⁴ Three structures involved in medial stability are the superficial medial collateral ligament (sMCL), which is the primary valgus restraint; the posterior oblique ligament (POL), which is the primary restraint to internal rotation and the secondary valgus restraint; and the semimembranosus.^5,6

Surgical techniques for posteromedial knee reconstruction include direct repair,⁷ repair with augmentation,^8,9 advancement of the tibial insertion of the sMCL,¹⁰ and transfer of the pes anserine tendons.¹¹ In anatomical reconstruction of the posteromedial corner, which has been described before, the sMCL and the POL are reconstructed to reproduce the native motion and stability of the knee.¹² Clinically, repair and reconstruction have similar patient-reported outcomes and medial opening evaluations over the short term.

These approaches require large incisions and extensive dissection of soft tissue on the medial aspect of the knee.⁵ Given these drawbacks, it is reasonable to consider less invasive options. Minimally invasive surgery has the advantages of reduced scarring and blood loss, less disruption of surrounding tissue, faster recovery, and improved aesthetics.⁴

We conducted a study of a minimally invasive technique for reconstructing the posteromedial structures of the knee. We compared medial compartment stability measured on valgus stress radiographs in intact, sectioned, and reconstructed states in cadaveric knees. We hypothesized that a minimally invasive technique using autogenous hamstring graft in the appropriate anatomical location would return valgus stability to its nearly native state.

Materials and Methods

This study was conducted at the Buenos Aires British Hospital in Buenos Aires, Argentina, and at the University of Colorado Hospital in Aurora. Ten fresh-frozen cadaveric knees with no evidence of ligamentous injuries, osteoarthritis, or previous surgery were used. Mean donor age was 69.4 years (range, 45-87 years). Each specimen was maintained at room temperature for 24 hours before use. The femur was sectioned 20 cm proximal to the knee joint. The tibia was sectioned 12.5 cm distal to the knee joint.

Identification and Sectioning of Posteromedial Structures

Anatomical insertion sites of the sMCL, the deep MCL (dMCL), and the POL were identified on the tibia through an oblique 3-cm incision on the posteromedial aspect of the knee (Figures 1A-1C). A valgus stress radiograph with medial compartment gap measurement was obtained for each of the 10 knees before sectioning the medial stabilizing structures.

After intact-state evaluation, each knee’s sMCL, dMCL, and POL were sectioned at their tibial insertion. Valgus stress radiograph was repeated and medial compartment gap was remeasured for comparison of the sectioned state with the intact and reconstructed states.

Anatomical Reconstruction With Mini-Invasive Technique

After sectioning of medial stabilizing structures, minimally invasive reconstruction was performed through 2 small incisions on the medial aspect of each of the 10 knees, as follows. First, the semitendinosus tendon was identified through the oblique incision that had been used for sectioning. Then, an open-ended tendon stripper was placed around the circumference of the semitendinosus and was passed proximomedially, transecting the tendon at its musculotendinous junction. While the tendon stripper was being passed, care was taken to maintain the nearby tibial insertion of the sartorius fascia (Figures 1D-1F).

The proximal end of the semitendinosus tendon (~5 cm proximal to incision) was then cleared of all muscular and fatty soft-tissue remnants and whipstitched with No. 2 Vycril suture (Figure 2). Then, the medial epicondyle was visualized and identified under radiographic guidance. A 1-cm incision was made 10 mm posterior and 2 mm proximal to the epicondyle (midpoint of femoral attachment of sMCL and POL).¹² A 1.8-mm Kirschner wire was inserted into the femur at this location. A blunt awl was used for deep (under sartorius fascia) passage of the semitendinosus tendon, from distal to proximal, and the tendon was looped over the top of the wire and brought through the incision.

With the semitendinosus tendon looped around the wire, isometricity was tested by pulling the suture within the tendon and moving the knee through a full range of motion. The isometric point was confirmed by tendon migration of <2 mm.¹³ Migration was measured by marking the graft 2 mm from its insertion; the graft was then pulled to ensure correct isometric point position. An 18-mm cannulated spiked screw and washer (Arthrex) were then passed over the wire and partially secured to the femur—the attachment point for the proximal sMCL portion of the semitendinosus graft. The semitendinosus tendon was then secured beneath the spiked washer with the knee in 20° of flexion with neutral rotation, recreating the sMCL.

Posteriorly, the distal insertion site of the POL was identified at the posteromedial aspect of the tibia through the oblique incision previously described. A 7-mm tunnel was drilled starting posteromedial (10 mm under tibial articular surface) and exiting just distal and medial to the Gerdy tubercle.

The graft was passed subcutaneously and below the sartorius fascia from posterior to anterior and was secured with a 7-mm × 23-mm cannulated titanium screw. Fixation was performed at full extension with neutral rotation (Figures 3A-3C, 4). 

After final fixation, the medial knee was openly dissected to assess the inverted-V ligament reconstruction for anatomical placement and avoidance of crucial structures.

Stability Testing

Per International Knee Documentation Committee guidelines for stressing the medial compartment,¹⁴ valgus stress radiographs were obtained for all specimens at 0° and 20° of flexion in intact, sectioned, and reconstructed states.

For all radiographs, performed by Dr. Chahla, a 10-N valgus force (measured by dynamometer) was applied to an intramedullary rod placed in the femur while the tibia was firmly attached to a specially designed base¹⁵ (Figures 5A-5C). A situation of 1 df was recreated to allow only varus/valgus motion during testing. 

 

The medial gap formed by the femoral condyle and its corresponding tibial plateau (at site of maximal separation) was tested in all 3 state conditions (intact, sectioned, reconstructed). Distances were digitally measured with a picture archiving and communication system viewer (Imagecast; IDX Systems Corporation). Medial gap was measured by taking the shortest distance between the subchondral bone surface of the most distal aspect of the medial femoral condyle and the corresponding medial tibial plateau. Three independent examiners took all the measurements; each examiner was blinded to the others’ measurements.

Statistics

Paired Student t tests were used to compare the 3 conditions, and the Shapiro-Wilk test was used to check for a normally distributed population. Statistical significance was set at P < .05. Statistical analyses were performed with GraphPad software.

Results

In all 10 specimens, the sMCL, the dMCL, and the POL were successfully identified and sectioned through a medial oblique incision over the distal insertion of the structures.

During all valgus testing states, there was no loss of graft fixation, and there was no gross graft slippage. In addition, all grafts remained in continuity with no evidence of failure, and there were no failures or breakages of the proximal or distal screw.

After posteromedial sectioning, mean medial gap was statistically significantly larger (P = .0002) at full extension (11 mm vs 3.3 mm) and at 20° of flexion (12.6 mm vs 3.8 mm). There was no statistically significant difference between the value of the intact state and the value after minimally invasive reconstruction at 0° (P = .56) or 20° (P = .102) of flexion.

Each knee had a notable endpoint in valgus stress noted on clinical examination after reconstruction. All individual results are listed in the Table. Interobserver reliability for the measurements was almost perfect¹⁶ (κ = 0.86).

Discussion

In this article, we describe a minimally invasive technique for anatomical posteromedial reconstruction of the knee in a cadaveric model. This technique restores the knee’s native valgus stability without causing extensive damage to the surrounding soft tissues and thereby potentially prevents scar formation and reduces blood loss.

Superficial MCL injury, one of the most common knee ligament injuries, is often associated with POL injury.⁷ Although most sMCL injuries are treated nonoperatively, with good results,³ surgical treatment is needed for severe (grade III) instabilities, symptomatic chronic instabilities, and knee dislocations.^12,17 Most posteromedial reconstruction techniques require an extensive approach that causes damage to surrounding soft tissue,^6,7,9,10 which in turn may compromise healing and positive patient outcomes. Surgical techniques include direct repair with sutures or anchors,¹⁸ capsular procedures,¹⁹ augmentations,⁹ internal bracing,⁶ and complete reconstruction of the posteromedial corner.²⁰

LaPrade and Wijdicks¹² have previously described anatomical reconstruction of the posteromedial corner. In their technique, a split semitendinosus autograft is used to reconstruct the sMCL and the POL separately, using 4 implants and reproducing each ligament’s anatomical attachment site. In this proposed technique, the distal attachment of the semitendinosus insertion is left intact, and uses 1 attachment point on the distal femur and 1 on the proximal tibia, allowing use of only 2 implants. In addition, it is performed with a minimally invasive approach, reduces cost, limits surgical exposure, and with experience may shorten operative time. To reduce the graft failure rate, the technique of LaPrade and Wijdicks¹² positions the sMCL tibial attachment as posterior as possible, which can be performed with this minimally invasive approach as well.

To reduce the graft failure rate, the technique of LaPrade and Wijdicks¹² positions the sMCL as posterior as possible. Despite the potential for increased graft stress with an anterior position, as in our modified technique, our group of 10 knees had no graft fixation failures in isolated valgus stress testing in either extension or flexion. Our minimally invasive posteromedial knee reconstruction significantly improved knee stability over the sectioned state as well as medial compartment gapping with valgus stress. There was no significant difference in medial compartment gapping between the intact and reconstructed states.

Our technique was built on open procedures (described by Kim and colleagues¹³) that carefully identify the isometric point of the graft. In addition, it adopted the modification (proposed by Lind and colleagues²¹) in which a fixation point is added at the distal insertion of the POL instead of being sutured to the direct arm of the semitendinosus tendon.

Furthermore, our technique, despite being similar to those described by Dong and colleagues²² and Borden and colleagues,²³  has the advantages of minimally invasive surgery and reduced disruption of soft tissues. Dong and colleagues²² reported on 64 patients with a mean follow-up of 34 months; patients’ medial opening measurements were significantly decreased at follow-up and fell within the normal range. 

The present study had several limitations. First, the age of our specimens was higher than the mean age of patients with knee ligament injury, potentially leading to firmer or more fibrotic tendons less susceptible to elongation. Second, we did not evaluate the knees’ rotational stability, and anterior cruciate ligaments (ACLs) were intact. As most posteromedial injuries co-occur with ACL injuries, a more realistic situation would have been reproduced by assessing rotational stability while performing both ACL reconstruction and the proposed posteromedial reconstruction. Third, static specimen measurements do not reflect the dynamic function of the posteromedial corner. Prospective clinical studies are needed to assess the true effectiveness of the posteromedial corner in the clinical scenario.

Knowledge of the anatomy of the medial aspect of the knee is vital to reconstruction of the medial side of the knee. Our results suggest that a minimally invasive technique can restore valgus stability without the need for extensive dissection and disruption of surrounding soft tissues. More research is needed to determine the results of this technique in vivo.

Take-Home Points

• Injuries to the medial knee are the most common knee ligament injuries, and often occur in the athletic population.
• Complete posteromedial corner injuries require surgical treatment to restore joint stability and biomechanics.
• Biomechanical evidence has demonstrated an important load-sharing distribution between the sMCL and the POL.
• Valgus instability caused by a medial side injury, can lead to both ACL/posterior cruciate ligament reconstruction graft failure if the medial sided injury is not concurrently repaired or reconstructed.
• Anatomic posteromedial corner reconstruction yields excellent biomechanical and patient-reported outcomes.

Most injuries of the medial structures of the knee are treated conservatively.^1-3 In severe acute injuries and chronic symptomatic instabilities, however, surgical treatment is needed to restore knee stability and to prevent degenerative changes secondary to instability.⁴ Three structures involved in medial stability are the superficial medial collateral ligament (sMCL), which is the primary valgus restraint; the posterior oblique ligament (POL), which is the primary restraint to internal rotation and the secondary valgus restraint; and the semimembranosus.^5,6

Surgical techniques for posteromedial knee reconstruction include direct repair,⁷ repair with augmentation,^8,9 advancement of the tibial insertion of the sMCL,¹⁰ and transfer of the pes anserine tendons.¹¹ In anatomical reconstruction of the posteromedial corner, which has been described before, the sMCL and the POL are reconstructed to reproduce the native motion and stability of the knee.¹² Clinically, repair and reconstruction have similar patient-reported outcomes and medial opening evaluations over the short term.

These approaches require large incisions and extensive dissection of soft tissue on the medial aspect of the knee.⁵ Given these drawbacks, it is reasonable to consider less invasive options. Minimally invasive surgery has the advantages of reduced scarring and blood loss, less disruption of surrounding tissue, faster recovery, and improved aesthetics.⁴

We conducted a study of a minimally invasive technique for reconstructing the posteromedial structures of the knee. We compared medial compartment stability measured on valgus stress radiographs in intact, sectioned, and reconstructed states in cadaveric knees. We hypothesized that a minimally invasive technique using autogenous hamstring graft in the appropriate anatomical location would return valgus stability to its nearly native state.

Materials and Methods

This study was conducted at the Buenos Aires British Hospital in Buenos Aires, Argentina, and at the University of Colorado Hospital in Aurora. Ten fresh-frozen cadaveric knees with no evidence of ligamentous injuries, osteoarthritis, or previous surgery were used. Mean donor age was 69.4 years (range, 45-87 years). Each specimen was maintained at room temperature for 24 hours before use. The femur was sectioned 20 cm proximal to the knee joint. The tibia was sectioned 12.5 cm distal to the knee joint.

Identification and Sectioning of Posteromedial Structures

Anatomical insertion sites of the sMCL, the deep MCL (dMCL), and the POL were identified on the tibia through an oblique 3-cm incision on the posteromedial aspect of the knee (Figures 1A-1C). A valgus stress radiograph with medial compartment gap measurement was obtained for each of the 10 knees before sectioning the medial stabilizing structures.

After intact-state evaluation, each knee’s sMCL, dMCL, and POL were sectioned at their tibial insertion. Valgus stress radiograph was repeated and medial compartment gap was remeasured for comparison of the sectioned state with the intact and reconstructed states.

Anatomical Reconstruction With Mini-Invasive Technique

After sectioning of medial stabilizing structures, minimally invasive reconstruction was performed through 2 small incisions on the medial aspect of each of the 10 knees, as follows. First, the semitendinosus tendon was identified through the oblique incision that had been used for sectioning. Then, an open-ended tendon stripper was placed around the circumference of the semitendinosus and was passed proximomedially, transecting the tendon at its musculotendinous junction. While the tendon stripper was being passed, care was taken to maintain the nearby tibial insertion of the sartorius fascia (Figures 1D-1F).

The proximal end of the semitendinosus tendon (~5 cm proximal to incision) was then cleared of all muscular and fatty soft-tissue remnants and whipstitched with No. 2 Vycril suture (Figure 2). Then, the medial epicondyle was visualized and identified under radiographic guidance. A 1-cm incision was made 10 mm posterior and 2 mm proximal to the epicondyle (midpoint of femoral attachment of sMCL and POL).¹² A 1.8-mm Kirschner wire was inserted into the femur at this location. A blunt awl was used for deep (under sartorius fascia) passage of the semitendinosus tendon, from distal to proximal, and the tendon was looped over the top of the wire and brought through the incision.

With the semitendinosus tendon looped around the wire, isometricity was tested by pulling the suture within the tendon and moving the knee through a full range of motion. The isometric point was confirmed by tendon migration of <2 mm.¹³ Migration was measured by marking the graft 2 mm from its insertion; the graft was then pulled to ensure correct isometric point position. An 18-mm cannulated spiked screw and washer (Arthrex) were then passed over the wire and partially secured to the femur—the attachment point for the proximal sMCL portion of the semitendinosus graft. The semitendinosus tendon was then secured beneath the spiked washer with the knee in 20° of flexion with neutral rotation, recreating the sMCL.

Posteriorly, the distal insertion site of the POL was identified at the posteromedial aspect of the tibia through the oblique incision previously described. A 7-mm tunnel was drilled starting posteromedial (10 mm under tibial articular surface) and exiting just distal and medial to the Gerdy tubercle.

The graft was passed subcutaneously and below the sartorius fascia from posterior to anterior and was secured with a 7-mm × 23-mm cannulated titanium screw. Fixation was performed at full extension with neutral rotation (Figures 3A-3C, 4). 

After final fixation, the medial knee was openly dissected to assess the inverted-V ligament reconstruction for anatomical placement and avoidance of crucial structures.

Stability Testing

Per International Knee Documentation Committee guidelines for stressing the medial compartment,¹⁴ valgus stress radiographs were obtained for all specimens at 0° and 20° of flexion in intact, sectioned, and reconstructed states.

For all radiographs, performed by Dr. Chahla, a 10-N valgus force (measured by dynamometer) was applied to an intramedullary rod placed in the femur while the tibia was firmly attached to a specially designed base¹⁵ (Figures 5A-5C). A situation of 1 df was recreated to allow only varus/valgus motion during testing. 

 

The medial gap formed by the femoral condyle and its corresponding tibial plateau (at site of maximal separation) was tested in all 3 state conditions (intact, sectioned, reconstructed). Distances were digitally measured with a picture archiving and communication system viewer (Imagecast; IDX Systems Corporation). Medial gap was measured by taking the shortest distance between the subchondral bone surface of the most distal aspect of the medial femoral condyle and the corresponding medial tibial plateau. Three independent examiners took all the measurements; each examiner was blinded to the others’ measurements.

Statistics

Paired Student t tests were used to compare the 3 conditions, and the Shapiro-Wilk test was used to check for a normally distributed population. Statistical significance was set at P < .05. Statistical analyses were performed with GraphPad software.

Results

In all 10 specimens, the sMCL, the dMCL, and the POL were successfully identified and sectioned through a medial oblique incision over the distal insertion of the structures.

During all valgus testing states, there was no loss of graft fixation, and there was no gross graft slippage. In addition, all grafts remained in continuity with no evidence of failure, and there were no failures or breakages of the proximal or distal screw.

After posteromedial sectioning, mean medial gap was statistically significantly larger (P = .0002) at full extension (11 mm vs 3.3 mm) and at 20° of flexion (12.6 mm vs 3.8 mm). There was no statistically significant difference between the value of the intact state and the value after minimally invasive reconstruction at 0° (P = .56) or 20° (P = .102) of flexion.

Each knee had a notable endpoint in valgus stress noted on clinical examination after reconstruction. All individual results are listed in the Table. Interobserver reliability for the measurements was almost perfect¹⁶ (κ = 0.86).

Discussion

In this article, we describe a minimally invasive technique for anatomical posteromedial reconstruction of the knee in a cadaveric model. This technique restores the knee’s native valgus stability without causing extensive damage to the surrounding soft tissues and thereby potentially prevents scar formation and reduces blood loss.

Superficial MCL injury, one of the most common knee ligament injuries, is often associated with POL injury.⁷ Although most sMCL injuries are treated nonoperatively, with good results,³ surgical treatment is needed for severe (grade III) instabilities, symptomatic chronic instabilities, and knee dislocations.^12,17 Most posteromedial reconstruction techniques require an extensive approach that causes damage to surrounding soft tissue,^6,7,9,10 which in turn may compromise healing and positive patient outcomes. Surgical techniques include direct repair with sutures or anchors,¹⁸ capsular procedures,¹⁹ augmentations,⁹ internal bracing,⁶ and complete reconstruction of the posteromedial corner.²⁰

LaPrade and Wijdicks¹² have previously described anatomical reconstruction of the posteromedial corner. In their technique, a split semitendinosus autograft is used to reconstruct the sMCL and the POL separately, using 4 implants and reproducing each ligament’s anatomical attachment site. In this proposed technique, the distal attachment of the semitendinosus insertion is left intact, and uses 1 attachment point on the distal femur and 1 on the proximal tibia, allowing use of only 2 implants. In addition, it is performed with a minimally invasive approach, reduces cost, limits surgical exposure, and with experience may shorten operative time. To reduce the graft failure rate, the technique of LaPrade and Wijdicks¹² positions the sMCL tibial attachment as posterior as possible, which can be performed with this minimally invasive approach as well.

To reduce the graft failure rate, the technique of LaPrade and Wijdicks¹² positions the sMCL as posterior as possible. Despite the potential for increased graft stress with an anterior position, as in our modified technique, our group of 10 knees had no graft fixation failures in isolated valgus stress testing in either extension or flexion. Our minimally invasive posteromedial knee reconstruction significantly improved knee stability over the sectioned state as well as medial compartment gapping with valgus stress. There was no significant difference in medial compartment gapping between the intact and reconstructed states.

Our technique was built on open procedures (described by Kim and colleagues¹³) that carefully identify the isometric point of the graft. In addition, it adopted the modification (proposed by Lind and colleagues²¹) in which a fixation point is added at the distal insertion of the POL instead of being sutured to the direct arm of the semitendinosus tendon.

Furthermore, our technique, despite being similar to those described by Dong and colleagues²² and Borden and colleagues,²³  has the advantages of minimally invasive surgery and reduced disruption of soft tissues. Dong and colleagues²² reported on 64 patients with a mean follow-up of 34 months; patients’ medial opening measurements were significantly decreased at follow-up and fell within the normal range. 

The present study had several limitations. First, the age of our specimens was higher than the mean age of patients with knee ligament injury, potentially leading to firmer or more fibrotic tendons less susceptible to elongation. Second, we did not evaluate the knees’ rotational stability, and anterior cruciate ligaments (ACLs) were intact. As most posteromedial injuries co-occur with ACL injuries, a more realistic situation would have been reproduced by assessing rotational stability while performing both ACL reconstruction and the proposed posteromedial reconstruction. Third, static specimen measurements do not reflect the dynamic function of the posteromedial corner. Prospective clinical studies are needed to assess the true effectiveness of the posteromedial corner in the clinical scenario.

Knowledge of the anatomy of the medial aspect of the knee is vital to reconstruction of the medial side of the knee. Our results suggest that a minimally invasive technique can restore valgus stability without the need for extensive dissection and disruption of surrounding soft tissues. More research is needed to determine the results of this technique in vivo.