Preoperative versus postoperative radiotherapy for prevention of heterotopic ossification (HO): first results of a randomized trial in high-risk patients.

PURPOSE

In vivo data support the effectiveness of pre- and postoperative radiotherapy in suppressing the development of heterotopic ossification after hip surgery. In June 1992 a prospectively randomized trial was initiated to assess the comparative efficacy of pre- vs. postoperative prophylactic radiotherapy in patients with high risk to develop heterotopic ossification after hip surgery.

METHODS AND MATERIAL

Between June 1992 and September 1993 a total of 84 eligible patients with high risk profile for the development of heterotopic ossification were entered in the study. They were randomized to receive radiotherapy either preoperatively (< 4 h before surgery) or according to a "standard protocol" postoperatively (< 72 h after surgery). A single 7 Gy fraction was administered to the preoperative group, while the postoperative group received a previously tested scheme of five fractions of 3.5 Gy (total dose 17.5 Gy). The treatment portal encompassed the soft tissues between the periacetabular region of the pelvis and the intertrochanteric portion of the femur. Important patient variables (age, sex, prior surgery) and predisposing risk factors were equally distributed between both treatment arms. X rays of the irradiated hips were obtained prior and immediately after surgery as well as at 6 months after surgery. The modified Brooker grading was used to score the extent of heterotopic ossification. The Harris score was applied to judge the overall functional status of the hip. If the Brooker grade and Harris score decreased from the immediate postoperative or preoperative status respectively to the follow-up situation, the case was considered as a "treatment failure."

RESULTS

At a minimum 6 months follow-up after hip surgery 44 patients were available for evaluation. Effective prophylaxis was achieved in 41 (93%) hips. Two "radiological failures" were observed in the preoperative group and one in the postoperative group. Neither the pre- nor the postoperative interval affected the prophylactic efficacy. There were no increased intra- and postoperative complications seen in the preoperative group. The interval of partial strain (50% body weight) to the operated hip was longer in the preoperative group (19 days +/- 27) as compared to the postoperative group (8 days +/- 13), however the interval to full strain (100% body weight) was equal in both groups. The functional status (Harris Score change) of the operated hip decreased only in two (5%) patients ("functional failures"). The overall change was better in the postoperative group (42.7 +/- 17.1) as compared to the preoperative group (34.3 +/- 13.7) (p = 0.08, NS) as well as with regard to the criteria "limp" (p = 0.05) and "use of walking support" (p = 0.10, NS). In in all other aspects no differences were observed between both treatment arms. Therefore, the preliminary results for preoperative radiotherapy are similar to historical results obtained with postoperative radiotherapy regimens.

CONCLUSION

Preoperative radiotherapy of the operative site applied within 4 h prior to elective hip surgery and total hip arthroplasty appears to be equally effective to currently accepted postoperative radiotherapy regimens in prevention of clinically significant heterotopic ossification about the hip. Improved patient comfort, ease of treatment management, and avoidance of possible postoperative complications associated with moving and positioning the patient in the immediate postoperative period are the major advantages of the preoperative radiotherapy concept.