The effect of displacement control input parameters on tibiofemoral prosthetic knee wear

The mechanisms of UHMWPE wear at the tibiofemoral articulation of a total knee replacement are potentially highly dependent on the cyclic direction of motion, the relative amounts of rolling versus sliding, and the loading of the contacting surfaces as previously described for hip components 3]. The simulated wear rate, for a standard test protocol utilizing the Insall-Burstein^®1 II Modular Knee System (IB-II) knee prosthesis, for normal walking gait was found to be 17.0 mg/10⁶ cycles on a Boston AMTI knee simulator. When the anterior/posterior (A/P) translation input was reduced by 50%, the wear rate was reduced approximately 37% to 10.6 mg/10⁶ cycles. Eliminating either the A/P translation or tibial rotation reduced the wear rate to 1.7 mg/10⁶ cycles and 0.69 mg/10⁶ cycles, respectively. These results cannot be explained by sliding distance effects alone and suggest that the UHMWPE wear rate is sensitive to other parameters, such as the magnitude of multidirectional shear motion and the ratio of rolling/sliding contact kinematics in combination with the applied load.