PREOPERATIVE VERSUS POSTOPERATIVE RADIOTHERAPY FOR PREVENTION OF HETEROTOPIC OSSIFICATION (H0) - FIRST RESULTS OF A RANDOMIZED TRIAL IN HIGH-RISK PATIENTS

Purpose: In vivo data support the effectiveness of pre- and postoperat ive radiotherapy in suppressing the development of heterotopic ossific ation after hip surgery. In June 1992 a prospectively randomized trial was initiated to assess the comparative efficacy of pre- vs. postoper ative prophylactic radiotherapy in patients with high risk to develop heterotopic ossification after hip surgery. Methods and Material: Betw een June 1992 and September 1993 a total of 84 eligible patients with high risk profile for the developement of heterotopic ossification wer e entered in the study. They were randomized to receive radiotherapy e ither preoperatively (< 4 h before surgery) or according to a ''standa rd protocol'' postoperatively (< 72 h after surgery). A single 7 Gy fr action was administered to the preoperative group, while the postopera tive group received a previously tested scheme of five fractions of 3. 5 Gy (total dose 17.5 Gy). The treatment portal encompassed the soft t issues between the periacetabular region of the pelvis and the intertr ochanteric portion of the femur. Important patient variables (age, sex , prior surgery) and predisposing risk factors were equally distribute d between both treatment arms. X rays of the irradiated hips were obta ined 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 ov erall functional status of the hip. If the Brooker grade and Harris sc ore 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 proph ylaxis was achieved in 41 (93%) hips. Two ''radiological failures'' we re observed in the preoperative group and one in the postoperative gro up. Neither the pre- nor the postoperative interval affected the proph ylactic efficacy. There were no increased intra- and postoperative com plications seen in the preoperative group. The interval of partial str ain (50% body weight) to the operated hip was longer in the preoperati ve group (19 days +/- 27) as compared to the postoperative group (8 da ys +/- 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 fai lures''). 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 aspect s 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 wi thin 4 h prior to elective hip surgery and total hip arthroplasty appe ars to be equally effective to currently accepted postoperative radiot herapy regimens in prevention of clinically significant heterotopic os sification about the hip. Improved patient comfort, ease of treatment management, and avoidance of possible postoperative complications asso ciated with moving and positioning the patient in the immediate postop erative period are the major advantages of the preoperative radiothera py concept.