Nanometre size wear debris generated from crosslinked and non-crosslinked ultra high molecular weight polyethylene in artificial joints

Ultra high molecular weight polyethylene (UHMWPE) wear debris is a major cause of long term failure of total joint replacements. Recently, crosslinking has been introduced in order to reduce the wear of UHMWPE. In this study the wear and wear debris of non-crosslinked and two crosslinked UHMWPEʹs were compared. In particular this study has focused on the characterisation of nanometre size wear debris. The UHMWPEʹs were tested in a multidirectional pin on plate wear simulator against smooth and scratched counterfaces. The wear particles were isolated and imaged using a field emission gun scanning electron microscope (FEGSEM) at high resolution. The use of FEGSEM revealed nanometre size particles (less than 0.1 μm) for the first time. No significant difference was found in the percentage number and percentage volume of the particles in different size ranges from any of the materials against any of the counterfaces. The specific biological activity (biological activity per unit value, SBA) was highest for the highly crosslinked material tested on the smooth counterfaces. The functional biological activity (FBA) which takes into account the wear volume and SBA showed that the highly crosslinked UHMWPE had a lower FBA for debris from both the smooth and scratched counterfaces.