[Periprosthetic ossifications of the hip: role of the duration of postoperative indomethacin therapy in the prevention of ossifications and role of screwed acetabulum in the occurrence of ossification].

After showing, as many others did, in an article published in 1987, that indomethacin administered immediately after surgery and for about 3 weeks at a dose of 75 mg/day effectively protected THA against heterotopic ossification, the authors have searched whether treatment duration could be reduced, and to investigate the existence of risk factors other than those classically known. They studied the prevalence of heterotopic ossification in two groups of THA with known risks of ossification, one with one-week prophylaxis, the other with two-week prophylaxis using Indomethacin. The results obtained were compared with a third group of THA performed during the same period, which presented no known risk of ossification and were not treated with indomethacin, and with the THAs of the initial study, where indomethacin had been administered for 3 weeks. Occurrence of heterotopic ossification was equally prevented by an 8-day course and by a longer one. No etiological, radiological or pathological risk factor other than those described in 1987 were fund (with all due caution given to hips re-operated on that had not ossified the first time): in contrast, the type or acetabular cup appears to have some influence on the occurrence of HO: uncemented prosthesis clearly favours ossification.