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Stukenborg-Colsman C., Ostermeier S., Hurschler C., Wirth C. J.
Orthopaedic Department Hannover Medical School, Hannover, Germany
Recent knee prosthesis designs have incorporated mobile-bearing inlays. They are intended to allow higher conformity of the tibiofemoral joint than is possible in fixed inlay designs, thereby reducing contact stress without decrea-sing the knee’s range of motion. We compared the kinematics of a mobile- and fixed-bearing design by measuring the tibiofemoral contact stresses, load bearing contact area and motion of the mobile-bearing inlay under dynamic loading conditions. Stresses and motion were also measured with the tibial component aligned normally, as well as in internally and externally rotated positions. The average peak contact stresses measured on the fixed-bearing design were greater than those on the mobile-bearing design. The test results correlate to radiographic measurements of in vivo movements of mobile bearing inlays showing “paradoxical” movement of the mobile inlay compared to physiologic meniscal movement.