Rolling sliding wear of UHMWPE for knee bearing applications

Wear of ultra high molecular weight polyethylene (UHMWPE) for total joint replacements is an important study area due not only to the potential for device failure, but also to the biological activity of the wear debris. Although relationships between wear rate and material treatment have been determined by other researchers, the micromechanism responsible for wear in a linear reciprocation is not well understood. This mechanism is important for wear analyses of rotating platform knee devices and highly conforming knee devices. A rolling sliding tribotest was performed to determine the wear rates of materials with clinically relevant thermal and radiation histories. Microstructure analysis coupled with tensile testing revealed that crystallite morphology has a direct effect on wear rate. A delamination mechanism of wear is proposed in which incremental plastic flow results in crack nucleation at the edge of crystallites. This mechanism is shown to be an excellent predictor of wear rate and is in accord with microstructural observations by other researchers.