Improved wear resistance of orthopaedic UHMWPE by reinforcement with zirconium particles

A considerable number of total-joint replacement devices used in orthopaedic medicine involve articulation between a metallic alloy and ultra-high molecular weight polyethylene (UHMWPE). Though this polymer has excellent wear resistance, the wear particulate that is produced leads to the limited lifetime of the devices—osteolytic bone loss. Crosslinking has been shown to reduce the wear rate of UHMWPE, but can cause a reduction in various mechanical properties such as impact toughness. Previous work by the authors has shown that UHMWPE-based composites have wear resistance comparable to the irradiation-crosslinked polymer. However, the selection of the reinforcing material is complicated both by understanding the mechanical behavior of the filler and also by biocompatibility considerations. Zirconium has been shown to have excellent corrosion resistance and biocompatibility, and the authors have used the material as a reinforcing filler in UHMWPE with promising results. Compression-molded UHMWPE composites with up to 20 wt.% of microsized zirconium particles were investigated with regards to wear behavior and impact toughness. These composites showed a significant reduction in wear compared to unfilled polymer while still maintaining impact toughness. These results reinforce the paradigm of using polymer composites for orthopaedic applications and may provide a viable alternative to the property tradeoffs encountered with irradiation crosslinking.