LONG-TERM BEHAVIOR OF THE CHARNLEY OFFSET-BORE ACETABULAR CUP

We report the long-term radiological results of 58 total hip arthropla sties (THA) using the Charnley offset-bore acetabular socket. Wear was measured at four sites and radiolucent lines and possible migration w ere recorded. Four cups were retrieved at revision and were examined u sing light microscopy, SEM and X-ray microanalysis. At a mean follow-u p of seven years the mean wear in the DeLee and Charnley zone I was 0. 4 mm and in zone II 0.26 mm. The wear rate was 0.06 and 0.04 mm/year, respectively. Progression of radiolucent lines was seen in five cases (8.6%). Three sockets (5.2%) were revised because of aseptic migration at a mean follow-up of 9.8 years and one socket for infection at two years. The offset-bore acetabular cup had excellent wear behaviour and a low migration and revision rate. We recommend that it should be con sidered in THA since the use of small cups is increasing, particularly in revision cases.