Metal backing for the acetabular component of a total hip replacement,
initially designed to allow replacement of the polyethylene liner, has
since been universally accepted as a means of decreasing peak stresses at
the interfaces of bone and cement. We studied the results of 238 total hip
replacements that had been performed between 1980 and 1983 and that
differed only in that 138 of the acetabular components had a metal backing
and 100 were made of polyethylene only. Kaplan-Meier survival analysis,
with three different modes of failure (radiolucency, loosening, and
revision), showed a significant increase in the rate of failure of the
metal-backed acetabular cup compared with the all-polyethylene cup:
radiolucency, 39 compared with 23 per cent (p less than 0.0001); loosening,
4 compared with 2 per cent (p less than 0.0001); and revision, 6 compared
with 2 per cent (p less than 0.0034). It was concluded that metal backing
cannot be recommended for a cemented acetabular component of a total
hip-replacement system.