Session I - Pelvis

Indomethacin vs. Localized Irradiation for the Prevention of Heterotopic Ossification Following Acetabulum Fractures: A 7-Year Prospective Randomized Trial of 182 Patients

Timothy A. Burd, MD; Jeffrey O. Anglen, MD, University of Missouri at Columbia Hospital & Clinics, Columbia, MO

Purpose: A serious complication to patients who undergo acetabulum fracture surgery is the formation of heterotopic ossification (HO). Local radiation therapy and indomethacin are effective in the prophylaxis of heterotopic bone formation. The purpose of this study is to determine whether local radiation therapy or indomethacin is more effective in preventing heterotopic bone formation following operations for acetabulum fractures in a prospective, randomized trial. Our hypothesis was that local irradiation is more effective in the prophylaxis of HO than oral indomethacin therapy.

Methods: From July 1992 to June 1999, 224 acetabulum fractures were treated surgically with open reduction and internal fixation by the senior author. One hundred and eighty-two patients underwent a Kocher-Langenbeck, extended iliofemoral, or combined anterior and posterior approaches to the acetabulum. Seventy-eight patients received 800cGy local radiation therapy within 72 hours of surgery, and 72 patients received a 6-week course of indomethacin, 25 mg p.o. t.i.d. beginning within 24 hours of surgery. Sixteen patients who were randomized were medically too unstable to undergo treatment but were included in the study. An additional 16 patients did not have adequate follow-up (>10 weeks). Average follow up was 14.3 months. The extent of HO was assessed using the Brooker classification.

Results: There was no significant difference with regard to age (P = 0.29), GCS (P = 0.10), operative time (P = 0.21), EBL (P = 0.65), follow-up (P = 0.73), head injuries (P = 0.66), and osteonecrosis (P = 0.64). Injury severity score appeared to be the only significant covariate among groups (P = 0.019). Significant HO (Brooker grades III-IV) occurred in 8 cases (11.1%) in the indomethacin group and 3 cases (3.8%) of in the radiation therapy group (95% confidence interval [-2.5%, 16.7%]). All 16 patients "too sick" to receive treatment had HO with 37.5% incurring significant ectopic bone formation. The overall incidence of significant (Grade III or IV) heterotopic ossification in the treated groups was 7.3% (11/150) and 37.5% in the non-treated group (6/16).

Fracture type and incidence of HO demonstrated no significant relationship (P = 0.296). In addition, we found no association between posterior hip dislocation and frequency of heterotopic ossification (P = 0.306). Ranges of motion were found to be not related to the degree of HO except in forward flexion (forward flexion, P = 0.011; external rotation, P = 0.220; internal rotation, P = 0.062; and abduction, P = 0.132). A significant difference in cost of treatment was noted in that a 6-week course of indomethacin costs approximately $12, whereas a single dose of 800 cGy radiation costs approximately $2,400, 200 times more costly.

Conclusions: Both focal radiation therapy and indomethacin are effective modalities in the prophylaxis of heterotopic ossification following acetabular surgery through posterior and extensile approaches. These results suggest that there is no significant difference between the 2 treatment modalities with respect to prevention of HO. Prophylaxis against HO after acetabular surgery should be tailored to the patient's overall condition, accessibility to a radiation therapy facility, and the ability to remain compliant and tolerant of a 6-week course of indomethacin.