Trochlear Contact Pressures after Anteromedialization of the Tibial Tubercle

Abstract

BackgroundAnteromedialization is recommended for cartilage restoration of patellofemoral defects, with the presumption that it decreases contact pressures across the trochlea. No study has evaluated pressures on the trochlear side of the patellofemoral joint after anteromedialization of the tibial tubercle.HypothesisAnteromedialization of the tibial tubercle decreases contact pressure across the trochlea.Study DesignControlled laboratory study.MethodsTen cadaveric knees were tested by placing an electroresistive pressure sensor on the femoral side of the patellofemoral joint. A validated model of nonweightbearing resisted extension was simulated by loading the extensor mechanism at 89.1 N and 178.2 N. Knees were tested 3 times per load at 30°, 60°, 90°, and 105°. The center of force and pressure across the patellofemoral articulation were compared before and after a reproducible and consistent anteromedialization.ResultsThe mean center of force shifted medially after anteromedialization at 89.1 N and 178.2 N. At 89.1 N, the mean total contact pressure decreased significantly (P <. 05) at all angles, and at 178.2 N, it decreased significantly at 30°, 60°, and 90° of knee flexion. The mean lateral trochlear contact pressure decreased significantly (P <. 05) at all flexion angles at both 89.1 N and 178.2 N. The mean central trochlear contact pressure decreased significantly (P <. 05) at 30° with the 89.1-N and 178.2-N loads but increased significantly (P <. 05) at 90° with the 89.1-N load. The mean medial trochlear contact pressure increased significantly (P <. 05) at all flexion angles at 89.1 N and 178.2 N.ConclusionAnteromedialization shifts the contact force to the medial trochlea and decreases the mean total contact pressure.Clinical RelevanceAnteromedialization decreases the mean total contact pressure while shifting contact pressure toward the medial trochlea. This study suggests that anteromedialization is appropriate for unloading the lateral trochlea. However, this procedure appears to have minimal benefit on central chondral defects, and it may actually increase the load in patients with medial defects.