Reconstruction of the Posterolateral Corner After Sequential Sectioning Restores Knee Kinematics

BACKGROUND: Various surgical techniques to treat posterolateral knee instability have been described. To date, the recommended treatment is an anatomic form of reconstruction in which the 3 key structures of the posterolateral corner (PLC) are addressed: the popliteofibular ligament, the popliteus tendon, and the lateral collateral ligament. PURPOSE/HYPOTHESIS: The purpose of this study was to identify the role of each key structure of the PLC in kinematics of the knee and to biomechanically analyze a single-graft, fibular-based reconstruction that replicates the femoral insertions of the lateral collateral ligament and popliteus to repair the PLC. The hypothesis was that knee kinematics can be reasonably restored using a single graft with a 2-strand “modified Larson” technique. STUDY DESIGN: Descriptive laboratory study. METHODS: Eight fresh-frozen cadaveric knees were used in this study. We conducted sequential sectioning of the popliteofibular ligament (PFL) and then subsequently the popliteal tendon (PT), the lateral collateral ligament (LCL), and the anterior cruciate ligament (ACL). We then reconstructed the ACL first and then the posterolateral corner using the modified Larson technique. A surgical navigation system was used to measure varus laxity and external rotation at 0°, 30°, 60°, and 90° with a 9.8-N·m varus stress and 5-N·m external rotation force applied to the tibia. RESULTS: In extension, varus laxity increased only after the sectioning of the lateral collateral ligament. At 30° of flexion, external rotation in varus and translation of the lateral tibial plateau increased after the isolated popliteofibular ligament section. From 60° to 90° of flexion, translation and mobility of the lateral plateau section increased after sectioning of the PFL. After reconstruction, we observed a restoration of external varus rotation in extension and translation of the lateral tibial plateau at 90° of flexion. This technique provided kinematics similar to the normal knee. CONCLUSION: The PFL has a key role between 30° and 90° of flexion, and the lateral collateral ligament plays a role in extension. Reconstruction with the modified Larson technique restores these 2 complementary stabilizers of the knee. CLINICAL RELEVANCE: Although there are many different techniques to reconstruct the PLC-deficient knee, this study indicates that a single-graft, fibular-based reconstruction of the LCL and PT may restore varus and external rotation laxity to the knee.