Experimental Study On Bone Metabolism Of Nonvascular Transport Distraction Osteogenesis

Objective:To investigate the feasibility of the surgical model of nonvascular transport distraction osteogenesis (NTDO) for reconstructing extensive canine mandibular marginal partial defects, and to further study its possible bio-mechanisms of osteogenesis by bone metabolism.Methods:8 mongrel dogs were randomly divided into four groups with two of each group according to different consolidation periods of 2,4,8andl4weeks and conducted osteotomies in the inferior half of right mandibular bodies to form a 10.0-mm in length by 10.0-mm 10.0-mm segmental skeletal defects. Then a 20.0-mm in length by 10.0-mm in height marginal partial 10.0-mm free nonvascularized bony transport discs were prepared at the mesial stumps of mandibles and custom-made internal distractors were installed in place as designed. After 5-day latency period distractors were initiated and activated at lmm/d. All animals were sacrificed after different consolidation periods. The regenerated bone specimens harvested from distracted mandibles were assessed with macromorphological, SEM and X-electron dispersive spectroscopy examination, respectively.Results:1. Specimens macrography All the subjects completed the process of distraction osteogenesis, wound healled, the dog's mandibular defect repaired successfully. As can be seen from 2 weeks of growth in fixed time, the edge of new bone around transportdisk, and then the lingual side, lower edge and the buccal side plate surrounded the transportdisk gradually, transportdisk drive narrowing around the new bone and eventually it replaced by the new bone completely, the same bone marrow, it is difficult to distinguish boundaries; with new bone constantly thickening inside the stretch region, mandibular continuity restored to 14 weeks.2. SEM New bone formed in 2 weeks inside the stretch region, and a large number of collagen fibers growth in the direction along the stretch, with a fixed time, the calcium salt particles continuously deposited along the collagen fiber orientation, the new bone matures, in 14 weeks it has become lamellar bone with mature Haversian systems with. 3. X-ray electron dispersive spectroscopy From 2 weeks the new bone distraction gap of calcium level gradually to near normal tissue,14 weeks, it close to the 85%normal level of bone tissue calcification. The new bone around the disk delivery,its calcification of bone tissue gradually to near normal from 2 weeks,0-4 weeks for the transfer of the fastest disk around a new period of osteocalcin, and new bone is to start close to the periosteum of the lingual side in the calcification.Conclusion:We successfully replicated the non-vascularized Transport Distraction dog mandible bone repair model, periosteal stripping the delivery of the same disk can get high-quality gap distraction osteogenesis, distraction factors, adding free bone graft,can be replaced by creeping substitution by new bone, that the non-vascularized bone transport disc distraction osteogenesis repair process is mainly accompanied by the results of the combined effect of creeping substitution.