[Prospective study on the prevention of heterotopic ossification after total hip replacement. Non-steroidal anti-inflammatory agents versus radiation therapy].

PURPOSE

Two prospective trials were undertaken to assess the comparative efficacy of early postoperative irradiation with different radiation doses versus the postoperative use of nonsteroidal antiinflammatory drugs (NSAID) for prevention of heterotopic ossification (HO) following prothetic total hip replacement (THP).

PATIENTS AND METHOD

Between 1992 and 1994 585 patients received THP. These patients were randomed in two longitudinal studies each with 3 treatment arms comparing postoperative irradiation with 4 x 3 Gy (101 patients), 1 x 5 Gy (93 patients), 1 x 7 Gy (95 patients) and the postoperative use of the NSAID indometacin for 7 days (113 patients) respectively for 14 days (90 patients) und acetyl salicyl acid (ASS) for 14 days (93 patients). Heterotopic ossification was scored according to the Brooker grading system. One hundred patients receiving no prophylactic therapy after total hip arthroplasty between 1988 and 1992 were analysed and defined as historical control group.

RESULTS

Incidence of heterotopic ossification was 5% in the 4 x 3 Gy group (Brooker grade I 5%, grade II 0%, grade III 0%), 30.5% in the 1 x 5 Gy group (Brooker grade I 24.7%, grade II 4.1%, grade III 1.0%) and 10.5% in the 1 x 7 Gy group (Brooker grade I 10.5%, grade II 0%, grade III 0%). 15.9% of the indometacin-7 days-group developed heterotopic ossification (Brooker grade I 8%, grade II 6.2%, grade III 1.7%, grade IV 0%), 12.2% of the indometacin-14 days-group (Brooker grade I 8.9%, grade II 2.2%, grade III 1.1%) and 37.5% of the ASS-group (Brooker grade I 27.9%, grade II 4.3%, grade III 5.3%). The lowest incidence of heterotopic ossification was found for the 4 xx 3 Gy and the 1 x 7 Gy group, but no significant difference between these two different treatments was observed.

CONCLUSION

Prophylactic irradiation of the operative site after hip replacement is more effective than the use of NSAID. Because no significant difference between the fractionated ingle dose irradiation was found and the latter is more comfortable for patients and more economical, irradiation with single 7 Gy fraction should be preferred.