Effect of graft fixation sequence on knee joint biomechanics in double-bundle anterior cruciate ligament reconstruction

Purpose To investigate the effect of graft fixation sequence in double-bundle anterior cruciate ligament (ACL) reconstruction on knee biomechanics. Methods Twelve mature porcine knees underwent double-bundle ACL reconstruction with a randomized fixation order of the two graft bundles. The knees were subjected to external loadings of (1) an 89 N anterior tibial load at 30°, 60° and 90° of knee flexion and (2) 4 N-m internal and external tibial torques at 30° and 60° of knee flexion for ACL intact, deficient and reconstructed states. Knee kinematics and in situ graft forces were measured under the applied loads. Results The anterior tibial translation of the two reconstructions was not different from each other but was significantly different from the intact ACL. There was no difference in internal and external rotations between the intact knees and the reconstructions. At lower flexion angles, the graft that was fixed last (whether anteromedial or posterolateral) tended to carry significantly higher in situ load under anterior tibial loading and tibial torques. Conclusion While a difference in knee kinematics may not be observable with different graft fixation sequences, fixation sequence can alter the in situ forces that the grafts bear under knee loading.