Howse II cemented titanium metal-backed acetabular cups

We report a retrospective clinical and radiographic review of 107 consecutive primary total hip replacements, using the cemented Howse II prosthesis. The review concentrates on the long-term performance of the acetabular cup, which was designed with a cylindrical titanium metal backing and a polyethylene liner. In all the hips in the series, this cup was used with a modular titanium straight femoral stem and a 32-mm diameter titanium head. At a mean follow-up of 9.8 (7-11) years, 28 hips had already been revised and 10 others were recognized as clinical or radiographic failures. The indication for revision in 26 of the hips was aseptic loosening and the mean time to revision was 7.2 (3.7-10.9) years This metal-backed cup has only 42% survival at 10 years, which seems to be related to certain of its design features. These include an inadequate thickness of polyethylene sterilized by gamma irradiation in air, a lack of mechanical bonding between the liner and its metal shell, and the high wear rate from the use of a 32-mm titanium femoral head.