Radiation prophylaxis for heterotopic ossification about the hip joint--a multicenter study

Prophylactic radiotherapy (RT) can prevent ectopic bone formation about the hip after total hip arthroplasty. The German Cooperative Group on Radiotherapy for Benign Diseases conducted a patterns of care study about this indication addressing the involved institutions, RT dose concepts, clinical handling, and treatment outcome of prophylactic RT about the hip joint.

In 1999, a patterns of care study was conducted in all German institutions to analyze the accrual pattern, number of patients, and different indications for the use and performance of prophylactic RT about the hip. The applied RT concepts of prophylactic RT were evaluated with regard to the RT technique, timing of RT (pre- or postoperative), RT dose prescription (median, range of single and total doses), and treatment outcome. All institutions were asked about the radiologic and functional failure rates at least 1 year after the completion of RT using the established radiologic (Brooker) and functional (Harris) scores with objective and subjective evaluation components.

One hundred fourteen institutions reported their clinical experience with prophylactic RT for the prevention of heterotopic ossification about the hip joint: 70 community hospitals, 23 university hospitals, and 21 private RT practices. In 1999, 5677 patients (5989 hips) had received prophylactic RT. The median number per institution was 36 patients (range 8-240). The interdisciplinary referral included orthopedic surgery (89 institutions; 3763 patients), trauma surgery (82 institutions; 1611 patients), or other disciplines (8 institutions; 298 patients). Preoperative RT was applied in 53 institutions 0.5-24 h before surgery, and postoperative RT was applied in 54 institutions 1-120 h after surgery. Most patients received 1 x 7 Gy either pre- or postoperatively. The total dose range was 5-10 Gy (preoperative RT) or 5-16 Gy (postoperative RT); the median total RT dose of both RT concepts was 7 Gy. Cobalt-60 (n = 15), linear accelerators (n = 95), and a few lower energy units (n = 4) were used. Bony structures or prostheses were shielded with standard blocks in 31 and with individual blocks in 27 institutions. Long-term clinical evaluation was available in 30 institutions from 4377 hips. Of those, 475 (11%) developed radiologic failures according to Brooker's criteria. Functional hip evaluation was available in 5 institutions from 685 hips. Of those, 34 (5%) had functional failures according to the criteria of Harris. No difference in outcome was found between pre- and postoperative RT, but was with regard to the patient's referral and the timing of RT. The patients who were treated >8 h before surgery or >72 h after surgery experienced a higher radiologic failure rate; radiologic failures were an important precondition for functional failures (p <0.05).

This patterns of care study comprises the largest number of cases reported for prophylactic hip RT to date. The results reveal that both preoperative (within 24 h) and postoperative RT (within 72 h) are effective in preventing heterotopic ossification after hip surgery. Both RT concepts achieved a similar low radiologic and functional failure rate. Single-dose RT concepts, especially, can be recommended as an excellent treatment alternative for patients with contraindications to long-term steroid or nonsteroidal anti-inflammatory agents, and this approach has become standard in most German RT institutions.