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Title: In vivo kinematics of mobile-bearing total knee arthroplasty during deep knee bending under weight-bearing conditions. Author: Futai K, Tomita T, Yamazaki T, Tamaki M, Yoshikawa H, Sugamoto K. Journal: Knee Surg Sports Traumatol Arthrosc; 2011 Jun; 19(6):914-20. PubMed ID: 20845031. Abstract: 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° relative to the tibial component. From 80° to 120°, 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°, and the polyethylene insert had also rotated 8.2°±6.2° externally on the tibial tray. CONCLUSION: The present results demonstrated that mobile-bearing mechanisms with this prosthesis might reduce articular contact stress in vivo.[Abstract] [Full Text] [Related] [New Search]