Distraction Osteogenesis after Membranous Onlay Bone Graft in a Dog Model

ABSTRACT

The purpose of this study was to investigate the possibility of distraction osteogenesis in membranous onlay bone graft on the mandible and to clarify the histology of bone repair during distraction osteogenesis in the membranous onlay bone in a dog model. Four dogs, 5 months of age at the beginning of the experiment, were used for this study. The zygomatic arch was exposed in the subperiosteal plane and the full-thickness zygomatic arch was harvested to 3 centimeters in length. The lateral surface of the mandibular body was exposed in the subperiosteal plane and the membranous onlay bone graft was performed with firm contact using screws. The osteotomy on the membranous onlay bone graft and underlying mandibular body was carried down week 1 in dog 1, week 2 in dog 2, week 3 in dog 3, and week 4 in dog 4 after membranous onlay bone graft. The external distraction device was applied to the mandibular body. Mandibular distraction was started 7 days after the operation at a rate of 1mm per day for a total of 10 mm distraction over 10 days. After completion of distraction, the distraction device was left in place for 6 weeks bony consolidation of the distracted area. Radiographs were carried out at 2 weeks, 4 weeks and 6 weeks after distraction. New bone between the native underlying mandibular segments was generated in the distracted zone in all dogs. The new bone between the native underlying mandibular segments was generated in the distracted zone in all dogs. The new bone between segments of membranous onlay bone graft was not generated in dog 1, but it was generated in dogs 2, 3 and 4. However, in dog 2 and 3, the new bone between segments of the distracted membranous onlay bone graft presented less firmness with fibrous tissue than that of the native underlying mandibular segment. Histologically, the distracted gap between segments of the membranous onlay bone graft was composed of much fibrous tissue in the central zone while activated osteoblastic cells formed new bone in the margins of the distracted gap in dogs 2 and 3. In dog 4, there were abundant osteoblastic activities in the distracted gap and the new bone appeared as nearly-normal cortical bone. In conclusion, these findings suggested that membranous onlay bone graft had an osteogenic capacity and that distraction osteogenesis was possible in membranous onlay bone graft.