Patellar component positioning in total knee arthroplasty

Five human anatomic specimen knees were used to determine the effect of pat ellar component position on patellofemoral kinematics, contact pressures, a nd 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 proximal ly, distally, medially, and laterally. Patellar tilt was greatest with medi al positioning of the patellar component and least with central and lateral positioning. At higher knee flexion angles, patellofemoral joint contact p ressures 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 po sitioned patellar components resulted in decreased patellar component loadi ng at higher knee flexion angles. Central positioning of the patellar compo nent results in optimal patellofemoral mechanics when maximal coverage of t he resected patella is desired.