OBJECTIVESTo measure the linear polyethylene wear with use of a computer-assisted two-dimensional method, and to evaluate the relationship between wear and long-term clinic-radiological findings.

METHODSBetween December 1991 and December 1995, the senior author performed 40 primary total hip arthroplasties with use of H/G porous-coated acetabular component. Radiographs of 40 H/G cementless total hip arthroplasties were examined for osteolysis, radiolucent line, cup migration and so on. To measure the linear polyethylene wear, migration in the femoral head center relative to the cup shell center was calculated on digitized consecutive radiographs with special computer software program.

RESULTSThe minimum follow-up was 10 years. Total linear wear was 2-8 mm, the mean rate of linear polyethylene wear was (0.32+/-0.31) mm/year. Twelve acetabular components (30%) were revised at an average follow-up point of 12 years. Three types of polyethylene liner failure were identified: wear-through of the polyethylene liner with resultant metallosis (5 hips), excessive wear necessitating revision (5 hips), and polyethylene liner dissociation without gross evidence of wear (2 hips).

CONCLUSIONSHigh wear rates and femoral and acetabular osteolysis have been and still are the main problems in uncemented total hip replacement. There is clear relationship between wear and acetabular osteolysis or loosening of the prostheses. The poor long-term results with these uncemented total hip arthroplasties illustrate the necessity of regular radiographic evaluation in order to detect osteolysis and liner failure, which are both generally asymptomatic until catastrophic failure appears.