Study on long life of artificial joints by investigating optimal sliding surface geometry for improvement in wear resistance

The effective life of artificial joints is approximately 15 years. A smooth metal sliding surface is presumably the most suitable when manufacturing artificial joints; however, the relationship between the characteristics of metal sliding surface and ultra high molecular polyethylene (UHMWPE) wear has not been confirmed. Further, there is no apparent proof that a smooth surface is the optimal option for the improvement in the wear resistance of artificial joints. In this study, we investigated the mechanism of UHMWPE wear and proved that scratch marks caused by a sliding motion against the metal surface are the prime cause of UHMWPE wear. Furthermore, we used a micro-dimpled surface as an effective sliding surface to reduce the UHMWPE wear. A 2-axes pin-on-plate sliding test proved that the life of artificial joints can be extended to approximately 35 years by using a micro-dimpled surface with 1-μm deep dimples.