Wear of conventional and cross-linked ultra-high-molecular-weight polyethylene acetabular cups against polished and roughened CoCr femoral heads in a biaxial hip simulator

The wear of acetabular cups made from conventional γ‐sterilized, and electron‐beam cross‐linked ultra‐high‐molecular‐weight polyethylene was studied with a biaxial hip wear simulator. The femoral heads were either polished or roughened so that they represented the type of roughening and the value of surface roughness (Ra = 0.14–0.18 μm) observed in the roughest explanted femoral heads. The lubricant was diluted calf serum, and the test length 3 million cycles. The mean wear rate and standard deviation of conventional polyethylene cups against polished and against roughened heads was 11.6 ± 0.07 and 64.4 ± 10.1 mg per 1 million cycles, respectively. The latter value closely corresponds to that measured from explanted Charnley prostheses. Against polished heads, cross‐linked polyethylene cups showed net weight gain, whereas against roughened heads, their mean wear rate was 2.4 ± 0.3 mg per 1 million cycles. The mean equivalent circle diameters of polyethylene wear particles produced in the above four categories were: conventional/roughened 0.32 μm, cross‐linked/roughened 0.29 μm, conventional/polished 0.28 μm, cross‐linked/polished 0.23 μm. The size ranges and shapes were close to those seen in particles isolated from tissue samples. In conclusion, the tests indicated that electron‐beam irradiation effectively reduces the harmful polyethylene wear particle production in total hip arthroplasty. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 848–853, 2002