ROLE OF CYCLIC PLASTIC-DEFORMATION IN THE WEAR OF UHMWPE ACETABULAR CUPS

The mechanisms of wear in ultra-high-molecular-weight polyethylene (UH MWPE) acetabular cups were investigated on both laboratory simulator-t ested cups and a clinically retrieved component. Two different levels of wear process were identified: one characterized by the formation an d detachment of platelet-like flakes from initial machining marks, and the other by the formation of fine ripples and fibrils by repeated pa sses of microscopic asperities on the femoral head. Both wear processe s could be described by a criterion of critical plastic strain. A theo retical model was developed to account for the generation of the micro scopic wear particles based on such a critical strain criterion. Its p redictions of the dependence of the UHMWPE wear rate on surface roughn ess and applied load were in excellent agreement with previously publi shed experimental correlations. (C) 1995 John Wiley and Sons, Inc.