THE OUTCOME OF ACETABULAR COMPONENTS IN C HARNLEYS FETAL HIP-ARTHROPLASTY AFTER A MINIMUM OF 15-YEARS FOLLOW-UP

Purpose of the study The aim of this study was to appreciate the long term result of 309 acetabular components of total hip arthroplasty. Ma terials and methods All were performed using Charnley's prosthesis and cement, by one surgeon, between January 1972 and December 1975. Clini cal function was graded according to Postel-Merle-d'Aubigne's scoring system (PMA score). We mesured wear of polyethylene using a personal m ethod, on anteroposterior radiographs of the pelvis. Radiolucent line were appreciated by Delee and Charnley's criteria, migration by Massin 's criteria. Survivorship curves were calculated with radiolucent line s, as migration, on 15 years. We compared the effect of different para meters on wear and loosening of the sockets. Results At 15 years follo w-up, we found 51.5 per cent hips with the highest PMA score (18). Rev ision for socket loosening was 3.88 per cent, the same for dislocation s. Concerning 25 per cent of the sockets, wear of polyethylene was eva luated less than 0.065 mm a year, concerning 50 per cent of them, it w as evaluated less than 0.11 mm a year, at last concerning 75 per cent of them, it was evaluated less than 0.16 mm a year. No significant cor relation was established between the tilt of the acetabular component and the wear of polyethylene. We observed no radiolucent lines for 60 per cent of the implants, nor migration for 83 per cent of them. Stati stical analysis proved the influence of the wear on radiolucent lines and migration. Discussion and conclusion The analysis confirms a moder ate wear of polyethylene during 15 years. We introduce an original met hod for its measurement and its formulation. This method allows a trul y description of wear in long term results. This analysis confirms als o that several parameters intercede on loosening; these are different if one considers radiolucent lines or migration. We do think at last, that the best positionning of the socket in the A.P. view should appro ach 35 degrees.