A biomechanical analysis of four medial patellofemoral ligament reconstruction techniques

Implant free medial patellofemoral ligament reconstruction is an increasingly popular technique to address patellar instability. There remains sparse literature on the biomechanical differences between the most common femoral attachment fixation points including Schottle's point, superficial medial collateral ligament, and adductor magnus tendon. This study compared these reconstruction techniques as well as a novel triangle reconstruction integrating both superficial medial collateral ligament and adductor magnus tendon.

Eight cadaveric knees were tested in a muscle activated knee simulator which mimicked a standing, shallow knee bend movement. Patella lateral displacement, external rotation and flexion were measured with and without a lateral load applied under the following conditions: 1) intact, 2) medial patellofemoral ligament cut, 3) Schottle's point reconstruction, 4) adductor magnus tendon reconstruction, 5) superficial medial collateral ligament reconstruction, 6) triangle reconstruction. Differences were analyzed using a repeated measures analysis of variance at 20, 30, 45 and 60 degrees of knee flexion.

All reconstruction techniques had significantly less lateral displacement compared to the cut condition when a lateral load was applied. Between reconstruction conditions, there was significantly less lateral displacement using Schottle's point and superficial medial collateral ligament as compared to adductor magnus tendon (p < 0.05). All reconstruction techniques had a trend towards medial constraint as compared to intact.

An over constrained position of the patella through early flexion of the knee may increase the likelihood of secondary patellofemoral arthritis. Although there were differences in magnitude of displacement/constraint, further studies are needed to assess clinical differences regarding constraint.