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 effects are frequently observed. We conducted a prospective, nonrandomized pilot study of prophylaxis for HO in THA using indomethacin for 3 days. We used a 2-stage design for phase 2 clinical data, based on earlier studies in our department. Our study group consisted of 19 patients, of whom 14 (74%) developed 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 the ossification relative to the group that received no prophylaxis. Indomethacin for 3 days seems not to be sufficient to prevent HO.