Effect of radiation on segmental distraction osteogenesis in rabbits

Objective: To determine whether consolidation can occur during radiotherapy after segmental distraction osteogenesis. Segmental distraction osteogenesis has potential as a reconstructive option after oncologic resection of the mandible. However, postoperative radiotherapy has potentially deleterious effects on bone consolidation after distraction osteogenesis. Methods: Tibial defects of 1.0 cm were created in 5 New Zealand white rabbits. After a 6-day latency phase, a 1.0-cm distraction segment was created in 0.3-mm increments every 12 hours. Within 24 hours of the distraction completion, the tibia received the biologic equivalent of 6000 rad (60 Gy). After 6 weeks of consolidation, the animals were humanely killed. Bone was analyzed radiographically, grossly (at autopsy), and histomorphometrically. Results: Four rabbits completed the 6-week consolidation period. All specimens had evidence of calcified bone in the segmental defect on radiographic analysis. At autopsy, the volume of new bone equaled that of the removed segment. On histologic examination, the volume of new trabecular bone was similar to adjacent cortical bone. Conclusions: Consolidation of segmental distraction osteogenesis defects can occur in rabbit tibia during external beam radiotherapy. To our knowledge, this study is the first to demonstrate successful consolidation of segmental distraction osteogenesis during external beam radiotherapy.