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.