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

Objective: To observe the development of bone at different times durin g the period of mandibular lengthening by external distraction using I lizarov'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 perfo rmed with a water-cooled drill. After 12 hours, distraction was starte d 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 immedia te histologic evaluation or after 2, 5, or 8 weeks of postdistraction fixation. Results: Elongation of up to 11 mm was achieved. Radiographi c and scintigraphic evaluation suggested a residual inflammation on th e 7th day and definite ossification on the 14th day. Histologic observ ations of the distraction site showed a gradual change from an amorpho us matrix to a fibrous matrix and, finally, an osseous-like tissue. Co nclusion: Bone lengthening by gradual distraction is commonly used in tubular bones. To achieve mandibular lengthening it is necessary to re solve many problems. Morphologic, radiographic, scintigraphic, and his tologic observations confirm that mandibular lengthening by external d istraction is possible, with the formation of new bone tissue.