Abstract
Metal ion release is a concern with all metal-on-metal (MOM) hip replacements. The Cormet Resurfacing Hip replacement, in use since 1997, has been validated in vivo and in vitro. In addition to clinical follow-up, extensive wear testing has been carried out under standard and severe conditions. A 6-year study on the serum metal ion levels in patients has also been done.
Between September 1997 and November 2003, 383 primary total hip resurfacings were performed in five centres. The mean age of the 196 men (23 bilateral procedures) and 146 women (18 bilateral procedures) was 55.4 years (24 to 73). Mean follow-up was 17 months (3 to 84). At the latest review the mean modified Harris hip score (truncated format) was 77.9 out of 91 (mean 86%), with a range of 49 to 91. The Kaplan Meier survivorship rate was 96% at 7 years.
Wear testing has shown that heat treatments do not affect the wear of cast high carbon cobalt chrome alloys and that larger bearings (56-mm and 40-mm diameter) have lower wear rates than conventional 28-mm bearings. Metal ion levels rose initially, then decreased over time.
Metal ion release does not appear to be a major long-term concern and medium-term clinical results are very encouraging.
Secretary: Dr H.J.S. Colyn, Editor: Professor M.B.E. Sweet. Correspondence should be addressed to SAOA, Box 47363, Parklands, Johannesburg, 2121, South Africa.
