Femoral Fixation Sites for Optimum Isometry of Posterolateral Reconstruction*

Background: Graft reconstructions of the lateral collateral ligament, popliteus tendon, and popliteofibular ligament are frequently performed in conjunction with a reconstruction of the posterior cruciate ligament to restore knee stabil-ity. The purpose of this study was to determine the femoral fixation sites resulting in the optimum isometry of popli-teus tendon, popliteofibular ligament, and lateral collateral ligament grafts in a knee with a reconstruction of the posterior cruciate ligament. Methods: Relative length changes (isometry measurements) were recorded between sutures fixed at femoral grid points and appropriate fibular or tibial graft tunnel sites; sites resulting in the least change in suture length as the knee was moved from 0 ° to 90 ° of flexion were identified as optimum isometric points. Bone blocks of Achilles ten-don grafts were fixed with the midpoint of the tissue’s leading edge adjacent to the optimum isometric point (opti-mum placement). Isometry measurements were repeated with a lateral collateral ligament graft placed in a fibular tunnel and with popliteus tendon and popliteofibular ligament grafts alternately placed in appropriate tibial and fibular tunnels. The graft isometry measurements were then repeated with the bone block centered over the femoral foot-print of the lateral collateral ligament or popliteus tendon. Results: For all reconstructions, there was no difference between the relative length changes of the suture placed at the optimum isometric point and the relative length changes of the graft with an optimally placed bone block. Th