LONG-TERM REVIEW OF A HOMOGENEOUS, CONSEC UTIVE SERIES OF 100 CHARNLEYS TOTAL HIP PROSTHESES

Purpose of the study Long-term studies of total hip remplacements ofte n give diverse results because the series studied are not homogeneous. We report the long-term result in a homogeneous, consecutive series o f 100 Charnley total hip replacements for idiopathic hip osteoarthriti s in patient without previous surgery, by the same operator. Materials Of 200 patients with 223 Charnley or Charnley-Kerboull total hip pros theses, implanted more than 13 years earlier, 94 patients with 104 imp lants were alive at the time of the study. Ninety of them (95.7 per ce nt) with 100 implants were clinically and radiographically examined. M ean follow-up was 14 yr 8 mo and minimum follow-up was over 13 yr 6 mo . Methods Hip function was clinically assessed according to Merle d'Au bigne's criteria. Immediate postoperative xrays and x-rays at 1, 5 and 10 years and at maximum follow-up were examined. For the acetabulum, alignment, radiolucent line, loosening and wear of the socket were ana lysed. For the femur, the position of the implant, radiolucent line an d loosening, changes in the calcar and cortical bone were analysed. Re sults Two femoral implants had to be replaced because of implant fract ure. The acetabulum became loose in 3 cases and the femur in 2, but di d not require revision at the time of examination. Mean acetabular wea r was 0.93 mm (0-5 mm). Wear was greater if the subjects were active ( p<0.05) overweight (p<0.05) and if the acetabulum was vertical (p<0.05 ). Changes in calcar, generally lysis, were more frequent when wear wa s marked (p<0.001). Thinning of cortical bone was more frequent in wom en (p<0.05), sedentary subjects (p<0.001) and those in poor general co ndition (p<0.05) and was less frequently associated with acetabular we ar (p<0.01). Discussion This study is characterised by its homogeneity : same etiology, same operator, same implants. Functional outcome at a mean of 14 yr 8 mo after surgery was good, as in most series of Char nley's total hip prostheses. Acetabular wear gave most cause for conce rn. It was linked with the weight and activity of the patients and wit h socket alignment. This wear led to deterioration of the calcar, due to granulomas and not to stress shielding, In spite of the homogeneity of the series, no factor was found to account for cortical thickening , whereas cortical thinning occured in light-weight, osteoporotic pati ents whose prosthesis did not entirely fill the medullary canal. Concl usion Charnley's total hip prostheses are a good method for treatment of idiopathic hip osteoarthritis. Cement does not appear to be a major deterioration factor over time, unlike polyethylene sockets in which wear and its consequences are a matter for concern.