Research regarding the posterolateral corner (PLC) of the knee has significantly improved our understanding of the anatomy and biomechanics it encompasses, yielding vital information regarding the three major stabilizing structures of the PLC: the fibular (lateral) collateral ligament (FCL), the popliteus tendon (PLT), and the popliteofibular ligament (PFL) (shown in Fig. 18.1 ). This greater understanding has allowed for a substantial advancement in the treatment options available for injury to the PLC, and the subsequent patient outcomes that result. Because of the youth of such treatment protocols, there are a substantial number of complications that can occur during any phase of treatment that may compromise patients’ ability to recover from such injuries.
Complications in treating PLC injuries vary from misdiagnosis during the preoperative stage to intraoperative issues dependent on the selected surgical procedure and postoperative issues in rehabilitation following surgery. Several anatomy, biomechanics, and clinical outcomes studies in the literature have detailed solutions to avoid such complications so that outcomes for these injuries may be improved.
Preoperative issues involving PLC injuries mainly stem from misdiagnosis in which PLC injuries are overlooked and subsequently unaddressed at the time of treatment for differing injuries. PLC injuries most frequently occur in concomitance with anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) injuries, with isolated injuries only occurring in 28% of all PLC injuries. Failure of detecting and subsequently treating a PLC injury in conditions of multiligamentous surgical management has been shown to compromise concurrent cruciate ligament reconstruction procedures, resulting in failure of the cruciate ligament reconstruction graft stemming from the failure to restore native biomechanics to the knee. , , Additionally, reports of degenerative changes, persistent instability, and poor functional outcomes commonly occur upon nonoperative treatment of grade III PLC injuries. ,
To test for the various possible injuries to the PLC, a study by LaPrade et al. found that, based on varus stress radiographs, isolated FCL injuries increased the lateral compartment opening by approximately 2.7 mm, whereas a complete PLC injury (Grade III) led to 4.0 mm of increased gapping, and a combined PLC and ACL injury further increased gapping to 5.3 mm relative to the intact state. If stress radiographs are inconclusive for a diagnosis, MRI further provides a validated means for effectively identifying posterolateral complex knee injuries. , If detection of the PLC is overlooked or clouded by edema/swelling in imaging, associated lesions may suggest referral for a more in-depth recheck of the PLC structures and/or confirmation during an examination under anesthesia.
Association With Bone Bruises
In a study by Geeslin et al., patients with grade III PLC injuries, either isolated or combined, commonly displayed bone bruises of the medial compartment. The most commonly associated bone bruise with isolated PLC injuries was of the anteromedial femoral condyle, and of these patients, one in five additionally displayed an anteromedial tibial plateau fracture. In nearly all of the patients with a multiligamentous injury involving the PLC, ACL, and PCL, posteromedial tibial plateau bone bruises were found, indicating that this bone bruise location has a strong association with PLC injuries involving ACL and PCL, and may provide a supplementary method for detection of PLC injuries.
Grade III Nonoperative Treatment Issues
In the orthopedic community, it is commonly accepted that failure to address grade III PLC injuries leads to patients developing functional limitations and osteoarthritis. Patients enduring grade II PLC injuries have been shown to tolerate mild to moderate persistent lateral pain, but with grade II injuries, patients often display anterior and anterolateral instability in addition to lateral instability. More recent studies have provided a greater understanding of the unique osseous anatomic structure of the PLC attachment points and why nonoperative treatment may not yield similar outcomes as nonoperative treatment of MCL injuries of the same severity/grade.
As stated earlier, the loss of the PLC structures can have detrimental outcomes upon other structures of the knee. In cases of multiligamentous injuries and subsequent reconstruction procedures involving the PLC complex with either cruciate ligament, the absence of the PLC has been shown to make the cruciate reconstructions highly vulnerable to failure. A cadaveric study by LaPrade et al. compared the force application upon ACL reconstructed grafts with either an intact or sectioned PLC, and the results displayed a significant increase of forces in knees with sectioned PLCs. Forces upon ACL reconstruction grafts significantly increased during both varus loading and combined varus–internal rotational loading at 0 and 30 degrees of knee flexion. The subsequent study, which was performed in a similar manner but substituted force analysis of PCL reconstructed grafts, found relatively identical results; significant increases of forces upon PCL reconstructed grafts were present for both varus loading and for coupled posterolateral rotational loading at all tested knee flexion angles.
Repair Versus Reconstruction
Invasive surgical procedures always have the potential to be accompanied by the common surgical complications of infection and wound dehiscence, but during PLC treatment, there is a greater potential for these occurrences. A severe complication worth avoiding is foot drop, occurring upon laceration or compression of the peroneal nerve, which courses parallel and inferior to the biceps femoris tendon. Then there are numerous complications that may occur which vary by the type of procedure that is chosen between repair or reconstruction, and the subsequent difficulty in achieving the native characteristics of the PLC relative to its anatomic attachments in these procedures.
Although subjective outcomes after different surgical techniques are relatively similar, newly developed reconstruction procedures have yielded significant improvements in failure rates relative to repair. Geeslin et al. reported a failure rate of 9% from a reconstruction-focused approach of acute grade III PLC injuries with concurrent reconstruction of cruciate injuries relative to 38% from a repair approach with staged cruciate reconstruction, whereas Levy et al. similarly reported a 6% failure rate in the reconstruction group compared with 40% in the repair group. The difference in these failure rates may derive from a surgeon’s preference in staging the operation or from subtle deviations between surgical techniques, but anatomic literature suggests this failure is instigated by the anatomic discrepancies amongst the medial and lateral compartments. The stability of the medial compartment stems from its innate characteristics, including its convex femoral condyle and the concave tibial plateau, whereas contrarily the lateral compartment articulates between two convex surfaces, creating a far less stable construct. This unstable nature necessitates the use of reconstruction grafts to provide greater stability for the compartment as opposed to the repair techniques.
Guidelines for Anatomic Reconstruction
The recent procedure for anatomic reconstruction of the PLC ( Fig. 18.2 ) yields better outcomes but is of greater difficulty than previously described surgical treatments, carrying with it potential pitfalls for those who proceed with lack of experience; a technique overview by Cruz et al. details these. The splitting of the iliotibial band should be placed anterior to the FCL attachment as opposed to posterior, as the former would hinder visualization. Knowing the proximity of the peroneal nerve distal to the champagne glass drop-off on the fibular head is vital when handling the scalpel, ensuring that the blade is always faced toward bone.