Heterotopic ossification as a complication of acetabular fracture. Prophylaxis with low-dose irradiation.

In a retrospective review of thirty-seven patients who had operative treatment for thirty-eight complex acetabular fractures, postoperative low-dose irradiation was administered to seventeen patients (eighteen fractures) to suppress heterotopic ossification. All of the patients had been operated on through either an extended iliofemoral incision or a modified extended iliofemoral incision. The prophylactic radiation was administered using a low-dose protocol; most of the patients received 1,000 rads in 200-rad increments, starting on the third post-operative day. The incidence of heterotopic ossification in the eighteen irradiated limbs was much lower than in the twenty patients who comprised the control group (50 per cent compared with 90 per cent). Only two of the irradiated limbs had Class-3 heterotopic ossification as described by Brooker et al., and no patient had Class-4 (ankylosis of the hip). Of the twenty control-group patients, ten had severe heterotopic ossification: Class 3 in seven and Class 4 in three. The difference in the incidence of severe (Class-3 or 4) heterotopic ossification between the two groups of patients was significant (p less than 0.01).