Introduction
The medial collateral ligament (MCL) is one of the most frequently injured ligaments of the knee. Earlier studies tended to focus primarily on injury to the MCL; however, recent anatomical and biomechanical work has outlined the importance of the posterior oblique ligament (POL) and the posterior medial capsule (PMC). Although a majority of MCL injuries occur in isolation, complete ruptures are frequently associated with injuries involving the posteromedial structures and cruciate ligaments. Failure to identify and address these associated injuries may lead to persistent instability. Several reparative and reconstructive techniques have been proposed, with the most recent focusing on anatomical reconstruction. This chapter aims to outline the management of MCL injuries and highlight the complications associated with each step.
Anatomy
Traditionally, the medial side of the knee has been described as containing a superficial layer, a middle layer, and a deep layer. More recently, the work of LaPrade and associates has detailed the three most important stabilizers of the medial knee: the POL, the superficial medial collateral ligament (sMCL), and the deep medial collateral ligament (dMCL) ( Fig. 17.1 ). , , The sMCL is the largest structure of the medial knee, measuring 10 to 12 cm in total length. The femoral attachment is described as 3.2 mm proximal and 4.8 mm posterior to the medial epicondyle. Two separate tibial attachment sites are identified. The distal attachment site is 6 cm distal to the joint line attaching to bone, and the proximal attachment site is to soft tissue located over the semimembranosus tendon. The dMCL is identified as a thickening of the medial joint capsule distinct from and deep to the sMCL. The dMCL is comprised of the meniscotibial and the meniscofemoral components. The POL is a separate structure from the sMCL, consisting of three fascial extensions off of the semimembranosus that merge with the posteromedial joint capsule. The central extension has been proposed to be the most important because it is the largest and thickest. , , The femoral POL insertion site is described as attaching 7.7 mm distal and 2.9 mm anterior to the gastrocnemius tubercle. The tibial insertion site of the POL is described as fanlike, primarily attaching to the posteromedial aspect of the medial meniscus, the meniscotibial portion of the posteromedial capsule, and the posteromedial part of the tibia ( Fig. 17.2 ).
The biomechanics of the sMCL can be attributed to the distinct proximal and distal and divisions. The proximal division is the primary stabilizer to valgus motion at all knee flexion angles, whereas the distal division resists valgus loading at increased knee flexion angles. The sMCL is also an important restraint to external rotation, as well as a secondary stabilizer against anterior and posterior tibial translation in the cruciate-deficient knee. The dMCL has been reported to provide secondary valgus stability, which becomes significant during sMCL injuries. The POL provides restraint to valgus loads, as well as internal rotation with knee flexion angles between 0 and 30 degrees. Reconstruction techniques should aim at anatomic recreation of these structures to restore the important load sharing characteristics ( Fig. 17.3 ).
Preoperative Complications
The prevention of any complication starts with a thorough history and physical examination. Patients experiencing medial-sided knee injuries typically present with either a history of high-energy trauma or a valgus stress injury. It is not uncommon for the patient who experiences a high-energy trauma to have associated multiligamentous injuries that must be taken into consideration during preoperative planning. Isolated grade III MCL injuries are extremely rare and have been reported in the literature at a rate of 0.02%. Concomitant ACL injuries have been reported at rates as high as 95% in the setting of grade III MCL injuries. , In the nontraumatic setting, the patient may report a valgus force to the knee. Athletes will typically report an impact to the lateral knee with the foot planted. Pain and swelling to the medial knee along with a feeling of instability in the coronal plane is commonly reported.
A detailed and thorough physical examination is necessary to assess the grade of the MCL injury and to rule out any concomitant injuries ( Fig. 17.4 ). If the patient is able to walk, a gait evaluation may clue the examiner in on existing ligamentous injuries. A vaulting-type gait owing to the quadriceps attempting to stabilize knee joint may be present. Inspection of the knee may or may not reveal an effusion. Localized edema may be mistaken for an effusion; however, the presence of an effusion may be indicative of coexisting intraarticular pathology. Following high-energy injuries, the examiner must look for skin dimpling that may indicate an irreducible knee dislocation. Bruising may be detected over the femoral or tibial attachment sites of the MCL. Palpation of the medial knee structures over their entire lengths can clue the examiner in on a femoral, midsubstance, or tibial-sided injury. Valgus stress testing is the cornerstone to making an appropriate diagnosis. , , , The knee is stressed at full extension and at 30 degrees of flexion. The sMCL is isolated in 30 degrees of knee flexion, and medial-sided gapping is usually graded on a scale of I to III. A grade I injury is classified as 0 to 5 mm of medial-sided opening and a grade II injury is a 5- to 10-mm opening, both with firm endpoints. A grade III injury is defined as greater than 10 mm of opening with no firm endpoint. Valgus opening with the knee in full extension signifies a grade III MCL injury with posteromedial corner or cruciate injury. , The integrity of the posteromedial capsule and POL is tested by applying an anteromedial rotation force with the knee flexed to 90 degrees and the foot externally rotated 10 to 15 degrees. Because of its function as a secondary restraint to external rotation, a positive dial test has been reported with complete injuries to the posteromedial corner structures. , , , The examiner must be thorough and take all examination findings into account when making an appropriate diagnosis. Failure to properly address all associated pathology may lead to persistent instability and surgical failure.
Imaging
Weight-bearing radiographs of the knee are typical with MCL injuries. Associated bony avulsions, osteochondral lesions, or joint malalignment may be seen. Valgus stress radiographs are a valuable objective means to assess medial joint space opening in suspected MCL injuries ( Fig. 17.5 ). LaPrade and associates found that, at knee flexion between 20 and 30 degrees, 3.2 mm of increased opening compared with the contralateral knee is needed for a grade III MCL injury. Complete sectioning of the medial structures increased medial gapping at 0 and 20 degrees of knee flexion to 6.8 and 9.8 mm, respectively. Further medial gapping was noted at 0 and 20 degrees with associated ACL and PCL sectioning. Magnetic resonance imaging (MRI) can be used to look at the continuity of the MCL fibers best appreciated on coronal sequences. , Edema is usually present at the femoral or tibial insertion sites depending on the location of the injury ( Figs. 17.6, 17.7, and 17.8 ). Bone bruising of the lateral femoral condyle and tibial plateau have been reported in up to 45% of patients with MCL injuries. Delineation of the posteromedial structures of the knee is difficult to assess with MRI and has not been described. Associated intraarticular injuries can be appreciated on MRI as well.
Intraoperative Complications
Nonoperative treatment of isolated grade I, II, and III femoral-sided MCL injuries have shown good results with functional rehabilitation, mostly owing to the inherent self-healing potential. Controversy certainly exists when it comes to surgical management of the MCL and posteromedial knee structures. Few indications for operative intervention of MCL injuries have been identified. Persistent valgus laxity or alignment following conservative treatment, associated knee dislocations with multiligamentous involvement, and involvement of the posteromedial corner structures have traditionally been treated more aggressively owing to inferior nonoperative results. Entrapment of the pes anserine between an avulsed ligament and the tibial insertion site (Stener-type lesion) has also been described as necessitating acute surgical intervention. Surgical treatment strategies include direct or augmented repair versus reconstruction using allograft or autograft tendon.
A variety of reparative techniques have been described, including direct suture repair, augmented suture repair, and repair with suture anchors or bone tunnels. Many early studies recommend primary repair for grade III MCL injuries. A recent systematic review identified just 16 reports of direct repair of MCL injuries throughout the literature. A majority of those studies focused on the sMCL and failed to address the remaining posteromedial structures. Overall, the authors found a 6% failure rate; however, indications and outcome reporting were highly variable. The authors concluded that, in the acute setting, MCL repair may be a viable option. Recent biomechanical results of augmented repair have been favorable. A cadaveric biomechanical study by Wijdicks and associates compared an anatomic augmented repair of an isolated grade III sMCL injury with anatomic semitendinosus autograft reconstruction. No significant differences were found with regard to rotational stability and medial joint space opening. In an attempt to decrease morbidity associated with reconstruction, repair augmentation using the internal brace technique has been recently described. , Cadaveric biomechanical data suggest the internal brace technique is more resistant to valgus loads than direct repair alone, and shows comparable results to allograft reconstruction. Clinical outcome data on augmented repair are currently lacking, however.
In the setting of an acute MCL with combined ACL injury, no clear differences have been shown between operative and nonoperative treatments. The timing of treatment remains controversial, with some authors suggesting that MCL repair should be done acutely with ACL reconstruction and others favoring an initial trial of nonoperative treatment with delayed ACL reconstruction. Those in favor of acute repair argue that it saves the patient time with rehabilitation and allows the patient to undergo a single rehabilitation process. , , , Those in favor of nonoperative MCL management with delayed ACL reconstruction argue superior range of motion (ROM) and faster strength gains. , The literature supports nonoperative treatment of acute MCL tears with concomitant ACL reconstruction; however, if healing fails to occur, undue stress may be placed on the ACL graft. Some authors suggest reassessing the integrity of the nonoperatively treated MCL at the time of delayed ACL reconstruction and plan for concomitant MCL reconstruction if persistent instability is noted.
In the setting of multiligamentous injuries, direct repair has shown inferior results. Stannard and associates directly compared a group of patients undergoing MCL repair with a group undergoing MCL reconstruction following a traumatic knee dislocation. , The failure rate was noted to be significantly higher (20% vs. 4%) in the repair group. Failure was defined as 2+ laxity in valgus stress or instability with an anterior drawer with the knee in external rotation. Overall, the literature suggests that in select patient populations, direct repair may have a role. The treating surgeon must be cautious of isolated MCL injuries when selecting repair as an operative technique. Failure to anatomically restore all facets of the posteromedial knee complex may lead to persistent instability and degenerative problems.
Indications favoring MCL reconstruction include chronic valgus laxity, associated multiligamentous injuries, and MCL tissue not amenable to repair. Multiple fixation strategies have been reported for reconstructing the medial knee structures, with no clear consensus. A recent systematic review identified 18 single-bundle techniques and 10 double-bundle techniques with only two anatomic reconstructions. Significant variation between graft types and fixation constructs exists throughout the current literature. Potential complications include nonanatomic fixation of the femoral or tibial insertion sites, improper graft tensioning, failure to reconstruct the POL or the PMC, injury to the sartorial branch of the saphenous nerve, and, in the setting of multiligamentous reconstruction, tunnel convergence. ,
Anatomic double-bundle reconstruction is an attempt to restore stability to the posteromedial knee by reconnecting the sMCL and POL to their respective anatomic insertion sites ( Fig. 17.9 ). LaPrade and colleagues championed this technique after rigorous biomechanical testing of ligament reconstructions based off of their detailed anatomical study. The goal was to create a reconstruction technique that could withstand aggressive early ROM. Nonanatomic techniques often fail to recreate normal anatomy, especially with regard to the femoral insertion. The medial epicondyle is often used errantly as a landmark for dual insertion of the sMCL and POL grafts. A recent systematic review found greater side-to-side laxity with nonanatomic fixation techniques compared with the anatomic technique described by LaPrade. In the technique paper, the authors suggest using intraoperative landmarks combined with fluoroscopy to identify the anatomical femoral insertion sites of the sMCL and POL ( Fig. 17.10 ). , During biomechanical testing of their anatomic reconstruction design, LaPrade and colleagues simulated early ROM and noted graft failure in all knees with a common single femoral tunnel. Tibial graft failure was noted when the sMCL tunnel was placed too anterior within the tibial insertion site. The authors attributed this failure to excessive stretch placed on the graft during early ROM in the more anterior position. After several variations of graft configurations, they concluded that early ROM could be initiated by restoring the anatomic relationships of the medial knee structures. ,
