A hip joint simulator study using new and physiologically scratched femoral heads with ultra-high molecular weight polyethylene acetabular cups

This study validates a hip joint simulator configuration as compared with o ther machines and clinical wear rates using smooth metal and ceramic femora l heads and ultra-high molecular weight polyethylene (UIIMWPE) acetabular c ups. Secondly the wear rate of UHMWPE cups is measured in the simulator wit h deliberately scratched cobalt-chrome heads to represent the type of mild and severe scratch damage found on retrieved heads. Finally, the scratching processes are described and the resulting scratches compared with those fo und in retrieved cobalt-chrome heads. For smooth cobalt-chrome and zirconia heads the wear rates were found to be statistically similar to other simulator machines and within the normal ra nge found from clinical studies. An increased wear rate was found with coba lt-chrome heads scratched using either the diamond stylus or the bead cobal t-chrome but the greatest increase was with the diamond scratched heads whi ch generated scratches of similar dimensions to those on retrieved heads. A greater than twofold increase in wear rate is reported for these heads whe n compared with smooth heads. This increased wear rate is, however, still w ithin the limits of data from clinical wear studies.