| Background:Since correction the human mandible malformation with distraction osteogenesiswas reported by McCarthy in1992, this technology has been displayed its excellence in craniomaxillofacial surgery.Clinically, because of the long therapy cycle and retractor placed in oral cavity for a long time result in multiple complication,these would be the main hamper to further clinical application. Therefore, how to promote new bone formation, shorten treatment period and reduce the complications, has become a hot spot and challenge in craniomaxillofacial surgery research.Objective:To observe the effect on newborn bone mineral density and bone strength produced by hyperbaric oxygen in distraction area. Exploring a simple and practical method promote new bone formation in distraction gap. In order to shorten the course of treatment,reduce complication.Methods:60New-Zealand rabbits were employed, mandibles were osteotomy bilaterly under general anaesthesia, the retractor were fixed by titanium screws at the ends of bone gap. Establishing animal model of distraction osteogenesis. The rabbits were randomly divided into4groups:All groups were underwent three days incubation period, the distraction was launched at the fourth day.Group A:at the speed of1.6mm per day (with the speed of0.8mm every time,twice per day),last for5days; Group B:at the speed of1.6mm per day(with the speed of0.4mm every time,twice per day), last for5days; Group C:at the speed of0.8mm per day(with the speed of0.4mm every time,twice per day),last for10days,group D:at the speed of0.8mm per day(with the speed of0.4mm every time,twice per day),last for10days. Under the pressure of0.2Mpa, group A and group C were treated by hyperbaric oxygen which consume90mins and once per day. Group B and D only distracted without hyperbaric oxygen therapy, Five rabbits of each group were sacrificed at lwk,2wk,4wk of consolidation respectively. The mandibles were harvested and the left subject to X-ray examination for bone healing, and quantitative computed tomography (QCT) dectection for the density of newly formed bone in the distraction gap. The biomechanical properties of the new generation bone at4th week of consolidation were detected by three point bending test. The newly formed tissue in the distraction area of the right mandible was harvested for histology examination and histomorphometry analysis.Results:All experiment animals underwent operation and survived, the distraction devices fixed good. when the hauling ended, the rabbits mandible were forward prominent and the occlusions were disorder. The hyperbaric oxygen therapy group(A、C group)compared with group(B、D) the surgery region swelling abated quickly. In general observation all experimenal animals had bony callus. With the fixation period extending,the bone mineral density of every group increased.(p<0.05).At the time of7days fixation,there was no significant difference between every groups.In the rest of groups, the BMD of HBOT groups(A、C) was higher than blank control groups(B、D).At the time of28days fixation,the anti-pressure strength of newbone reach40-50%of normal bone. The BMD OF the quick diatraction group joint HBOT reachl.26±0.08N/mm2,this result very close to the group D. The BMD of the quick diatraction group without HBOT was0.96±0.04N/mm2), compared with group(A、C、D),there could be seen significant difference.(p<0.01)。 The result of elastic modulus of group (A and B) reach20-30%of normal bone at the time of28days fixation, there was a significant difference between A and B.(p<0.05). The result of elastic modulus of group (C and D) reach30-60%of normal bone, there was a significant difference between group C and D (P<0.05). There was no significant difference between group A (1.6mm/d+HBOT) and D(0.8mm/d, without HBOT)(P>0.05). The result of new formed bone of maximum damage energy was close to the former result. There was a significant difference between A and B (P<0.05), there was a significant difference between C and D (P<0.05). There was no significant difference between A (1.6mm/d+HBOT) and D (0.8mm/d, without HBOT)(P>0.05)Conclusion:HBOT can improve bone mineral density and bone strength of the new formed bone in the distraction gap distracted by the different rate. It presentated that HBOT may promote new bone formation and mineralization of distraction gap, the mechanism maybe the following:HBOT accelerated clearance angiogenesis, increase local oxygen and promote growth factor synthesis in the distraction gap. It implied that HBOT is an effective way to promote the mandibular DO. |
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