Kinematic Difference Between Various Geometric Centers and Contact Points for Tri-Condylar Bi-Surface Knee System

The purpose of the study was to analyze the motion of contact points (CPs), lowest points (LPs), and component facet centers of tri-condylar implants. In vivo knee kinematics was assessed for 43 knees implanted with a multi-radii femoral component during deep knee bend activity, using a model fitting approach. Both LPs had the similar positions to the corresponding geometric centers of the femoral component, and the LP and geometric center angles represented the same component rotation angle defined by Grood and Suntay. Antero-posterior translation of both CPs was significantly overestimated, compared to LPs, and the CP angle showed significant differences from other rotation angles. In conclusion LPs seemed better to evaluate kinematics than CPs because polyethylene congruity had considerable effects on CP analysis.