Preoperative vs. postoperative radiation prophylaxis of heterotopic ossification: a rural community hospital's experience.

Abstract

In vivo data employing a rat model, suggest equivalent suppression of ectopic bone formation by single-fraction irradiation given either pre (< or = 4 h)- or post (< or = 24 h)-surgery. Two subsequent randomized clinical trials, from tertiary academic centers with robust experience in heterotopic bone prophylaxis, have reached similar conclusions. To assess the transferability of the above data to the community setting we reviewed our rural community hospital experience with pre- and postoperative radiation prophylaxis. Between 11/90 and 6/96, 16 surgerized hips with high risk of heterotopic bone formation received 7.00-8.00 Gy in one fraction either preoperatively (< or = 4 h) (n = 9) or postoperatively (< or = 3 days for six hips; day 7 for one hip) (n = 7). Initial patients were routinely treated postoperatively. In late 1992, treatment preference was switched to preoperative irradiation in response to evolving data. The two groups were similar with respect to age, sex, nature of surgery, presurgical Brooker and Harris scores, and in U. of Rochester risk classification distribution. Irradiation was given via 4-20 MV photons through equally weighted AP:PA portals to the periacetabular tissues and proximal one third to one-half of the femoral component. Radiation dose, energy, portal, and blocking design were all similar for the two groups. Hip radiographs were obtained immediately postsurgery and at last follow-up: Delta grades (Brooker grade at follow-up--Brooker grade immediately postsurgery) were computed. Harris scale scores of hip function and movement were assigned via personal interviews and examinations performed prior to irradiation and at last follow-up. All 16 hips are evaluable. Follow-up interval among the post-operative group (mean = 39.8 months; range 18.6-65.8) was significantly longer than among the preoperative group (mean = 20.4 months; range 8.6-41.3) (p < 0.02). The mean Delta grade among the postoperative and preoperative groups was identical (-0.02). Similarly, improvement in Harris scale scores, from preirradiation to last follow-up, were nonsignificantly different among postoperative (+43.3) and preoperative (+44.8) groups. There was one postoperative infection in either group; there was no acute or late toxicity attributable to irradiation. As heterotopic bone formation is complete within 6 months, the data for both treatment groups may be considered mature. Our community generated results parallel those derived from tertiary care centers. Single-fraction radiation prophylaxis of heterotopic ossification may be given with similar efficacy either < or = 4 h pre- or < or = 24 h postsurgery. For reasons of minimizing patient discomfort, postsurgical movement and radiation staff resource utilization, we prefer and recommend preoperative radiation prophylaxis.