In vivo kinematics of mobile-bearing total knee arthroplasty during deep knee bending under weight-bearing conditions.

摘要

PURPOSE: Little is known about the in vivo kinematics of mobile-bearing total knee arthroplasty, especially at deep knee flexion under weight-bearing conditions. METHODS: In vivo knee kinematics was analyzed for 12 patients (13 knees) implanted with PFC-Sigma Rotating Platform-Flex (RP-F) prostheses. Under fluoroscopic surveillance, each patient performed weight-bearing deep knee bending. Motion between each component was analyzed using a two- to three-dimensional registration technique, which uses computer-assisted design models to reproduce the spatial positions of the femoral and tibial components and a polyethylene insert (implanted with four tantalum beads) from single-view fluoroscopic images. RESULTS: External rotation of the femoral component on the tibial tray was mostly caused by rotation of the polyethylene insert on the tibial tray. The femoral component typically exhibited a central pivot pattern from extension to 80 degrees relative to the tibial component. From 80 degrees to 120 degrees , bilateral condyles moved backward. In an upright standing position, the femoral component had already rotated externally relative to the tibial component by 7.8+/-7.5 degrees , and the polyethylene insert had also rotated 8.2 degrees +/-6.2 degrees externally on the tibial tray. CONCLUSION: The present results demonstrated that mobile-bearing mechanisms with this prosthesis might reduce articular contact stress in vivo.