A Preliminary Study of Trifocal Distraction Osteogenesis for Reconstruction of Segmental Mandibular Defects

Objective: to investigate the reconstruction of mandibular segmental defects. Methods: We applied internal trifocal distractor to reconstruct the mandibular segmental defects of a canine model at the same stage after the mandibular was resected. The regenerating bone was examined by X-ray, CT and histological method during stages of distraction osteogenesis. Two bone transport disk which was about 1.5 cm in width and 2cm in high was made at the each end of the mandibular defect by osteotomy.After 8 days of latency period, trifocal DO was started at a rate of 0.5mm two times per day at each distraction region. The total distraction distance was 2mm perday. Distraction was continued for 15 days. Results:the mandibular defect was successful reconstructed for 30mm in length in 15 days without any complication. HE stain showed osteoblasts in the distraction region, and new bone formation behind the transport disk. With active osteogenesis, the island trabeculae were interspersed among osteoid stroma and were aligned parallel to the distraction force. Immunohistochemical stain showed that the BMP-2 and VEGF expressed stronger at 12 weeks in the distraction region. Scanning electron microscope(SEM) showed that the new bone matrix contained coarse fibers and the osteocytes within the matrix were larger than normal bone. X-ray showed the distractor fixed firmly and both the distal and near transport reached their targets simultaneously. The new bone formation was oriented in columns directed parallel to the force of distraction. Compression osteosynthesis occured at the region of transport disk union with frequent thin intervening bands of fibrous tissue. The high-density bone bridge was seen at the middle part. At 12 weeks after distraction the entire regenerate bone showed near normal calcification and density. Conclusions: Mandibular segmental defect can be reconstructed successfully by trifocal distraction osteogenesis.