Lengthening of the mandible by distraction osteogenesis: experimental work in rabbits

The purpose of this experimental work was to lengthen the mandible in rabbits by means of distraction osteogenesis. The excellent results on the lengthening of the extremities with the Ilizarov technique and the unpredictable results in the mobilization of the facial bones by means of osteotomies and grafts are reasons for the application of the gradual distraction method in mandibular lengthening. Bone lengthening was first performed in 1905; but Ilizarov rekindled interest in 1951 when he induced bone neoformation in the extremities by the distraction technique using multiplanar wires and external circular fixators. We lengthened the mandible in 12 New Zealand adult rabbits using different mountings of the Ilizarov apparatus by means of two fixation techniques: transfixion and nontransfixion. In the transfixion group (6 rabbits), the two wires were passed through both mandibular rami. In this group, a 2-cm lengthening was obtained. In the nontransfixion group (6 rabbits), only one mandibular ramus was included with the transfixion wires. In this group, 1-cm lengthening was achieved. Unilateral lengthening was obtained with the nontransfixion technique and the lengthening of both rami with the transfixion technique. The results were evaluated by clinical periodic postoperative radiographs and histological studies of newly formed bone and surrounding soft tissues (masticatory muscles, arteries, and so on). The results demonstrated that lengthening of the mandible is obtained by means of a mature and normal new bone that is produced in the osteotomized area.