Similar effects of rofecoxib and indomethacin on the incidence of heterotopic ossification after hip arthroplasty.

BACKGROUND Although indomethacin is effective in preventing heterotopic ossification (HO) after primary total hip arthroplasty, side effects are frequently observed. In the last decade a new class of drugs--the COX-2 selective nonsteroidal anti-inflammatory drugs--has been developed. To investigate the effect of these COX-2 selective NSAIDs on heterotopic ossification (HO) after primary total hip arthroplasty (THA), we conducted a randomized controlled trial using either indomethacin or rofecoxib for 7 days. METHODS 186 patients received either indomethacin 3 times daily, or rofecoxib twice, and 1 placebo, daily for 7 days. HO was graded according to the 1-year postoperative radiographs according to the Brooker classification. RESULTS 12 of the 186 patients included discontinued their medication before the end of the trial due to side effects. The remaining 174 patients were included in the analysis. In the indomethacin group (n = 89), 77 patients (87%) showed no HO, 9 showed HO of grade 1 and 3 showed HO of grade 2 according to the Brooker classification. In the rofecoxib group (n = 85) 73 patients (86%) showed no ossification, 9 showed grade 1, and 3 showed grade 2. INTERPRETATION The prophylactic effect of rofecoxib for 7 days in preventing heterotopic ossification after primary total hip arthroplasty is comparable to the effect of indomethacin given for 7 days. These results indicate that the development of HO follows a COX-2 pathway.