Purpose: A randomized trial was undertaken to assess the comparative efficacy of early postoperative irradiation with either 5 or 7 Gy vs. the use of nonsteroidal antiinflammatory drug (NSAID) for prevention of heterotopic ossification (HO) following prosthetic total hip replacement (THP).
Methods and materials: Between 1993 and 1994, 301 patients were randomized to receive postoperative irradiation (5 or 7 Gy) or NSAID. One hundred and thirteen patients were treated with NSAID (indomethacin 2 x 50 mg/day for 1 week), 93 patients were irradiated with a single 7 Gy fraction, 95 patients with a single 5 Gy fraction. The treatment volume included the soft tissues between the periacetabular region of pelvis and the intertrochanteric portion of the femur. X-rays of treated hips were obtained immediately and 6 months after surgery. 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 analyzed and defined as historical control group.
Results: Incidence of heterotopic ossification was 16.0% in NSAID-group (Brooker Score I: 8.0%; II: 6.2%; III: 1.8%; IV: 0%), 30.1% in 5 Gy group (Brooker Score I: 24.7%; II: 4.3%; III: 1.1%; IV: 0%), and 11.1% in 7 Gy group (Brooker Score I: 11.6%; II: 0%; III: 0%; IV: 0%). Regarding overall heterotopic ossification there was a significant difference between the NSAID group and the 5 Gy group (p < .015), respectively, between the 7 Gy group and the 5 Gy group (p < .0001). No significant difference was noted in the influence of overall HO between the NSAID and the 7 Gy group (p > 0.3). Analyzing the clinically significant HO (Brooker Score III and IV) patients irradiated with 7 Gy developed less HO than those treated with NSAID (p = 0.003). Incidence of HO was greater in the untreated historical control group (Brooker Score I: 26%; II: 15%; III: 19%; IV: 5%) than in all three prophylacticly treated groups.
Conclusion: Prophylactic irradiation of the operative site after hip replacement with single a 7 Gy fraction is the most effective postoperative treatment schedule in prevention of clinically significant heterotopic ossification. This therapy modality is more effective than irradiation with a single 5 Gy fraction or use of NSAID.