Posterolateral Knee
PURPOSE: The posterolateral corner of the Knee is a growing area of concern, but its effect on an ACL Reconstruction procedure is not well understood. It is hypothesized that increasing ACL graft tension will increase the amount of external rotation of the tibia if the posterolateral structures are not repaired. The goal of this study is to evaluate the effect of the sequential sectioning of the posterolateral structures on tibiofemoral orientation with increasing ACL graft set force METHOD: Eight fresh frozen cadaveric knees were used in this study. Each knee was reconstructed using the central third of the patellar tendon similarly to the clinical procedure except that the distal fixation on the tibia was an external tensioning device. The knee was secured in a joint testing machine that allowed the five other degrees of motion free to move. An instrumented spatial linkage (ISL) was used to measure the motion of the tibia with respect to the femur. The graft force was set at 30° of knee flexion using the tensioning device. Measurements were taken with 67 N anterior tibial force at zero graft force and increasing forces up to 100 N. The fibular collateral ligament, popliteofibular ligament, and the popliteal tendon were cut sequentially and ISL measurements were taken at each state. RESULTS: The lack of posterolateral structures was found to have a significant effect on the position of the tibia with respect to the femur with increasing ACL graft set force. External rotation increased significantly with ACL graft force comparing the intact reconstructed knee to the state with all posterolateral structures cut (p =0.02) CONCLUSION: Deficiency of the posterolateral structures of the knee significantly affects the relative position of the tibia with respect to the femur in external rotation with increasing graft set force. To prevent this excessive increase in external rotation in the clinical situation, it is recommended that associated posterolateral corner injuries be repaired or reconstructed prior to fixation of the ACL graft.
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