Quality of the surface finish of the head of the femoral component and the wear rate of the socket in long-term results of the Charnley low-friction arthroplasty.

Four Charnley femoral stems, removed on average 20 years after implantation, were examined for the quality of surface finish of the head. The average roughness was 0.031 microns (range 0.008-0.102 microns) as compared with 0.019 microns (range 0.008-0.031 microns) for the current production models and 0.05 microns as recommended by the British Standard and the International Standards Organization. The average socket penetration rate was 0.022 mm/year and there was no radiological or operative evidence of socket loosening. The findings emphasize the importance of achieving and maintaining good surface finish of the head of the femoral component. A suggestion is also made that the orientation of the asperities may be important.