Patellar component positioning in total knee arthroplasty.

Five human anatomic specimen knees were used to determine the effect of patellar component position on patellofemoral kinematics, contact pressures, and contact areas after total knee arthroplasty using a polyethylene, domed patellar component. Each patellar component was positioned at the anatomic center of the resected patellar surface and then repositioned 5 mm proximally, distally, medially, and laterally. Patellar tilt was greatest with medial positioning of the patellar component and least with central and lateral positioning. At higher knee flexion angles, patellofemoral joint contact pressures increased at the medial facet with the medialized component and at the lateral facet for the lateralized component. The centralized component had the most evenly balanced patellar facet contact pressures. Distally positioned patellar components resulted in decreased patellar component loading at higher knee flexion angles. Central positioning of the patellar component results in optimal patellofemoral mechanics when maximal coverage of the resected patella is desired.