Anisometry of Medial Patellofemoral Ligament Reconstruction in the Setting of Patella Alta and Increased Tibial Tubercle-Trochlear Groove (TT-TG) Distance

Objectives:Medial patellofemoral ligament (MPFL) reconstruction is a common procedure to treat recurrent patellofemoral instability. However, the effects of an elevated tibial tubercle-trochlear groove (TT-TG) distance and patella alta, as measured by the Caton-Deschamps (C/D) ratio, on MPFL isometry remain unclear. We hypothesized that increased lateralization and proximalization of the tibial tubercle (TT) will have increasingly adverse effects on the isometry of the MPFL.Methods:Ten fresh-frozen cadaveric knees were placed on a custom testing fixture, with a fixed femur and tibia mobile through 120 degrees of flexion. The quadriceps tendon was loaded with 10.8 N in an anatomic direction using a weighted pulley system. A 0.2 N patellar lateral displacement load was used to simulate an intact lateral retinaculum to avoid over-medializing the patella. A tunnel was drilled under fluoroscopic guidance from Schottle’s point on the medial distal femur through the lateral cortex. A suture anchor was placed at ...