Long-term results of Charnley-Kerboull hip arthroplasty in patients younger than 50 years.

Two hundred eighty-seven Charnley-Kerboull low friction total hip arthroplasties were done between 1975 and 1990 in 222 patients younger than 50 years. The average age of the patients at the time of the index procedure was 40.1 years. The mean followup of the entire series was 14.5 +/- 5.1 years with a median of 13.9 years. Forty-five patients (52 hips) had a followup greater than 20 years. The mean preoperative Merle d'Aubigné hip functional score was 9.6 +/- 2.5 points versus 17.2 +/- 0.8 points at the latest followup. Twenty-five revisions were documented in this series; 17 were done for aseptic loosening. The mean wear rate was 0.12 +/- 0.21 mm per year. Considering 0.1 mm per year as the threshold for a normal wear rate, 196 hips had a normal or below normal wear rate (mean, 0.02 mm per year), whereas the remaining 91 hips had an abnormally high wear rate (mean, 0.28 mm per year). The overall survival rate at 20 years was 85.4% +/- 5% using revision of either component as the end point. The only predictive factor of loosening was a wear rate higher than 0.1 mm per year.