In Vitro Comparison of Popliteus Tendon and Popliteofibular Ligament Reconstruction in an External Rotation Injury Model of the Knee

Abstract

Background: In posterolateral corner (PLC) injuries in which the lateral collateral ligament (LCL) is intact, there is controversy about whether reconstructing the popliteus tendon (POP), the popliteofibular ligament (PFL), or both structures (POP + PFL) is required to restore normal external tibial rotation. Hypothesis: Three reconstruction techniques, POP, PFL, and POP + PFL, are able to restore external tibial rotation to normal. Study Design: Controlled laboratory study. Methods: Six nonpaired human knees were tested under the following states: POP and PFL intact and sectioned. The 3 different surgical techniques were used to reconstruct the sectioned structures, and the knees were retested. Each knee was subjected to a 5-N·m external rotation torque and tested at 0°, 30°, 45°, 60°, 90°, and 120° of flexion. A navigation system was used to measure motion changes of the tibia with respect to the femur. Results: There were small but significant increases in external rotation after sectioning both the POP and PFL. Sectioning of either one of these structures alone produced smaller increases that were not significant. After comparing all of the tested reconstructed states to the intact state, there were significant differences at knee flexion angles from 30° to 90°. The PFL procedure restored external tibial rotation without significant differences compared with the intact knee at 30° to 90° of flexion. The POP and POP + PFL techniques significantly overconstrained external tibial rotation at all tested angles. Conclusion: In an LCL-intact PLC injury model, the POP and PFL function as a unit in resisting external rotation. All surgical procedures described and tested were able to reduce the increased external rotational laxity found in the sectioned state. The PFL reconstruction technique was able to restore external rotation to near normal. However, the techniques involving POP reconstruction overconstrained external rotation during laxity testing.