The histologic analysis of distraction osteogenesis of the mandible in rabbits.

The process of bone formation in mandibular lengthening by distraction was studied in 30 rabbits. The mandible was subjected to a corticotomy, held in a neutral position for 2 weeks, and then lengthened at 0.18 mm per 12 hours for 24 days using a unilateral external fixation device (Orthofix M-100). On completion of the distraction, x-ray analysis showed that the distracted gap was filled with callus organized into three zones, namely, two sclerotic zones with a central radiolucent zone. These zones became indistinguishable from the adjacent preexisting mandible at 10 weeks after distraction. Histologically, new bone, which was formed by both intramembranous and endochondral ossification, underwent remodeling and resulted in cortical bone by 8 to 10 weeks after completion of distraction.