Analysis of 118 second-generation metal-on-metal retrieved hip implants

Osteolysis is due to particulate wear debris and is responsible for the long-term failure of total hip replacements. It has stimulated the development of alternative joint surfaces such as metal-on-metal or ceramic-on-ceramic implants, Since 1988 the second-generation metal-on-metal implant Metasul has been used in over 60 000 hips. Analysis of 118 retrieved specimens of the head or cup showed rates of wear of approximately 25 mu m for the whole articulation per year in the first year, decreasing to about 5 mu m per year after the third, Metal surfaces have a 'self-polishing' capacity. Scratches are worn out by further joint movement, Volumetric wear was decreased some 60-fold compared with that of metal-on-polyethylene implants, suggesting that second-generation metal-on-metal prostheses may considerably reduce osteolysis.