MANDIBULAR LENGTHENING BY EXTERNAL DISTRACTION - AN EXPERIMENTAL-STUDY IN THE RABBIT

Objective: To observe the development of bone at different times during the period of mandibular lengthening by external distraction using Ilizarov's transosseous osteosynthesis technique. Materials and Methods: Fifteen rabbits, 2 to 3 kg in weight, were used for this experiment. The left side of the mandible was exposed and a corticotomy was performed with a water-cooled drill. After 12 hours, distraction was started and continued 1 mm per day for 2 weeks. Plain radiography and three-phase bone scan scintigraphy were performed on the Ist, 7th, and 14th postoperative days. The mandibles were then either removed for immediate histologic evaluation or after 2, 5, or 8 weeks of postdistraction fixation. Results: Elongation of up to 11 mm was achieved. Radiographic and scintigraphic evaluation suggested a residual inflammation on the 7th day and definite ossification on the 14th day. Histologic observations of the distraction site showed a gradual change from an amorphous matrix to a fibrous matrix and, finally, an osseous-like tissue. Conclusion: Bone lengthening by gradual distraction is commonly used in tubular bones. To achieve mandibular lengthening it is necessary to resolve many problems. Morphologic, radiographic, scintigraphic, and histologic observations confirm that mandibular lengthening by external distraction is possible, with the formation of new bone tissue.