Prophylaxis with indomethacin for heterotopic ossification after Chiari osteotomy of the pelvis.

One hundred patients who had painful dysplasia of the hip were treated with a Chiari osteotomy of the pelvis, and the postoperative radiographs were reviewed for the development of heterotopic ossification. Sixty patients did not receive indomethacin postoperatively, and eighteen (30 per cent) had heterotopic ossification of at least class 1; forty patients received indomethacin for two weeks postoperatively, and only three (8 per cent) of them had heterotopic ossification. This difference was significant (p < 0.025). No class-3 or 4 heterotopic ossification was seen in the patients who were given indomethacin. The prevalence of side-effects was relatively low, and no delayed union of the osteotomy was observed in any patient. We concluded that indomethacin, in the dosage schedule and regimen that we used, provides effective prophylaxis for heterotopic ossification after a Chiari pelvic osteotomy.