Total hip arthroplasty for the treatment of ankylosed hips - A five to twenty-one-year follow-up study

Background: The purpose of the present retrospective study was to report the long-term results of total hip arthroplasty following a hip fusion. Special attention was paid to the resulting function of both the involved joint and the neighboring joints, as pain in the lower back or knee was the usual indication for conversion. The factors that were likely to influence the functional outcome were analyzed. Methods: Forty-five consecutive total hip arthroplasties were performed in forty-five patients from 1969 through 1993. The mean age of the patients at the time of the operation was 55.8 years (range, twenty-eight to eighty years). Ankylosis of the hip had been spontaneous in twenty patients and postoperative in twenty-five patients. The mean duration of the ankylosis had been thirty-six years (range, three to sixty-five years). The mean duration of follow-up was 8.5 years (range, five to twenty-one years). No patient was lost to follow-up. Results: The mean hip score, according to the scale of Merle d'Aubigne, was 16.5 +/- 1.5 points at the latest follow-up evaluation. Hip function was considered to be satisfactory for forty-one (91%) of the forty-five patients. The definitive score for walking ability was not achieved by the one-year evaluation; it improved notably for two to three years and then it remained stable. At the time of the latest follow-up, the mean are of flexion was 88 degrees (range, 30 degrees to 130 degrees). Forty-three (96%) of the forty-five patients had no pain in the involved joint. The only factor that was predictive of the final functional result with regard to walking ability was the intraoperative status of the gluteal muscles. Most patients had effective pain relief in the neighboring joints. The cumulative survival rate at eight years, with revision as the end point, was 96.7% (95% confidence interval, 90.2% to 100%). Conclusions: The long-term effectiveness of total hip arthroplasty for the treatment of an ankylosed hip was clearly demonstrated in both the involved and the neighboring joints in the present study. However, the preoperative and intraoperative status of the gluteal muscles should be carefully evaluated when this procedure is being considered, as this was the only factor that was predictive of the final walking ability.