| Ultra-high molecular weight polyethylene (UHMWPE) is the current gold standard for bearing materials used in total joint arthroplasty. High-dose radiation is commonly used to crosslink UHMWPE, thereby improving its wear resistance. A subsequent remelting step eliminates trapped residual free radicals to promote oxidative stability on the shelf, and to prevent material degradation over the long term.;Radiation crosslinking of UHMWPE improves its wear resistance at the tradeoff of reduced mechanical properties. By altering microstructure and molecular entanglements, Equal Channel Angular Processing (ECAP) has shown promise in producing UHMWPE with superior mechanical properties compared to that of commercially crosslinked UHMWPEs, with comparable unidirectional wear resistance. In order to extend this application to multidirectional wear scenarios, low-dose irradiation and remelting following ECAP has been proposed.;Assessment of clinically retrieved, highly-crosslinked UHMWPE devices shows signs of unanticipated oxidation occurring in vivo, despite the absence of free radicals prior to implantation. These findings warrant further investigation into possible factors impacting this phenomenon along with its clinical implications.;The overall objective of this work is to quantify the influence of irradiation dose and source on UHMWPE's oxidative stability, along with the effects of oxidation on the ultimate mechanical properties, including strength, ductility, and toughness. This investigation examines these effects on conventionally processed crosslinked polyethylene, and the proposed crosslinked ECAP processing method. Oxidation dependence on consolidation is demonstrated, and an oxidation mechanism involving chain unsaturations is proposed. |
