[Long-term review of homogeneous and consecutive series of 100 "Charnley"-type total hip prostheses].

PURPOSE OF THE STUDY

Long-term studies of total hip replacements often give diverse results because the series studied are not homogeneous. We report the long-term result in a homogeneous, consecutive series of 100 Charnley total hip replacements for idiopathic hip osteoarthritis in patient without previous surgery, by the same operator.

MATERIALS

Of 200 patients with 223 Charnley or Charnley-Kerboull total hip prostheses, implanted more than 13 years earlier, 94 patients with 104 implants were alive at the time of the study. Ninety of them (95.7 per cent) with 100 implants were clinically and radiographically examined. Mean 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'Aubigné's criteria. Immediate postoperative x-rays 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 analysed. For the femur, the position of the implant, radiolucent line and loosening, changes in the calcar and cortical bone were analysed.

RESULTS

Two femoral implants had to be replaced because of implant fracture. The acetabulum became loose in 3 cases and the femur in 2, but did not require revision at the time of examination. Mean acetabular wear 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 was marked (p < 0.001). Thinning of cortical bone was more frequent in women (p < 0.05), sedentary subjects (p < 0.001) and those in poor general condition (p < 0.05) and was less frequently associated with acetabular wear (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 Charnley's total hip prostheses. Acetabular wear gave most cause for concern. It was linked with the weight and activity of the patients and with 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 occurred in light-weight, osteoporotic patients whose prosthesis did not entirely fill the medullary canal.

CONCLUSION

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.