Charnley THR (total hip replacement) had been performed in 64 hips of 52 patients in Chiba University Hospital from 1971 to 1986, who were serondary osteoarthritis due to congenital dysplasia or dislocation of the hip. We investigated clinical and radiographical results on 48 hips in 39 patients, with an average follow-up of 11 years and 10 months. The clinical results were evaluated according to JOA (Japanese Orthopaedic Association) hip score. The averave JOA hip score was 49 points preoperatively, and it showed over 80 points until 8 years after operation. Then, it deteriorated gradually, and was 72 points after 15 years from operation. On the radiographic evaluation, the socket loosening was seen in 13 hips (29 %) and the stem loosening in 10 hips (22 %). Wear of the socket more than 1mm was seen in 11 hips (27 %). After 12 years, the averave wear of 16 hips was 2.0mm and the average wear per year was 0.17mm. Survival analysis was performed using the method of Kaplan-Meier. In the analysis, we chose radiographic criteria of loosening as our definition of failure. Survival rate was 75.6 0x1.36cfp-890fter 5 years, 54.9 -0x1.db55b085084p-148fter 10 years, and 29.9 -0x1.6652fp-138fter 15 years respectively.
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