Background: Arthrodesis of the hip remains a viable treatment for severe unilateral arthritis after traumatic injury or infection in a young but otherwise healthy individual. The goal of the present study was to review the long-term clinical and radiographic results after conversion of a fused hip to a total hip arthroplasty and to identify the risk factors that would lead to a higher rate of failure.

Methods: We performed a retrospective review of the charts and radiographs of 187 patients (208 hips) who had conversion of a fused hip to a total hip arthroplasty. The mean duration of follow-up after the conversion to total hip arthroplasty was 9.2 years (range, two to twenty-six years).

Results: The mean age at time of the arthroplasty was fifty-one years. The mean time-interval between the arthrodesis and the conversion to a total hip arthroplasty was twenty-seven years. According to the information in the charts, at a mean duration of follow-up of 9.2 years after the total hip arthroplasty, 79% of hips were either pain-free or had minimal pain, 83% had good-to-excellent function, and 79% had good-to-excellent range of motion.

Complications, which included fifteen nerve palsies, occurred in twenty-four hips. Twenty-eight hips had heterotopic ossification, but it was not associated with a recurrence of ankylosis or a marked reduction of motion. Revision arthroplasty was performed in twelve hips. The probability of survival of the implant was 96.1% (95% confidence interval, 91.5% to 98.2%) at ten years, 89.9% (95% confidence interval, 85.3% to 96.1%) at fifteen years, and 72.8% (95% confidence interval, 36% to 90.6%) at twenty-six years.

Conclusions: Conversion of a fused hip to a total hip arthroplasty has a favorable outcome. However, the technically demanding nature of the procedure should not be underestimated. Patients should be cautioned with regard to the possibility of a higher rate of complications than that seen with primary total hip arthroplasty.