Six-year results of a cementless stem with prophylaxis against heterotopic bone.

The hypothesis of a possibly diminished bony ingrowth revealed by the development of radiolucency or a radiodense line with time around a cementless femoral stem subsequent to indomethacin administration for prevention of heterotopic ossification was investigated. Eighty prospective patients with indomethacin prophylaxis were compared with 82 patients without indomethacin prophylaxis chosen retrospectively. The same cementless implant was used in all cases, and patients were observed clinically and radiologically for a minimum of 6 years. The mean postoperative Harris hip score at 6 years was 91 versus 88 points, respectively, and there were significantly more excellent results (Harris hip score > 90) in the indomethacin group. None of the patients underwent revision surgery. Radiologic signs such as loss of bone density and radiodense lines were observed around the shoulder of the prosthesis in a similar percentage in both groups. Significant subsidence of the stem was observed in one instance in the indomethacin group and in three instances in the control group. The results of this study are a strong indication that indomethacin does not influence the development of radiolucency or other radiologic changes around a cementless stem after 6 years.