Indomethacin for 3 days is not effective as prophylaxis for heterotopic ossification after primary total hip arthroplasty

Although indomethacin is effective in preventing heterotopic ossification ( HO) after total hip arthroplasty (THA) when used for 8 to 14 days, side eff ects are frequently observed. We conducted a prospective, nonrandomized pil ot study of prophylaxis for HO in THA using indomethacin for 3 days. We use d a 2-stage design for phase 2 clinical data, based on earlier studies in o ur department. Our study group consisted of 19 patients, of whom 14 (74%) d eveloped HO; 7 (37%) showed grade I, 4 (21%) grade II, and 3 (15.8%) grade III according to the Brooker classification. We compared these results with 2 historic control groups: one group received indomethacin for 7 days, and the other group received no prophylaxis. We did not see any reduction of t he ossification relative to the group that received no prophylaxis. Indomet hacin for 3 days seems not to be sufficient to prevent HO.