放射照射后牵张下颌骨成骨犬实验动物模型的建立

目的：建立放射照射后牵张下颌骨成骨犬实验动物模型。方法：选取成年中国犬12只，实验组10只以60 Co 颊舌向照射下颌骨后部标定区域，照射方法为22．8 Gy、5．7 Gy／次，共4次（生物等效剂量为50 Gy／25次）。对照组2只不照射。照射完成后3个月，在动物下颌第五和第六臼齿间行骨皮质切开术，植入骨牵张器，经过1周的延迟期，2次／d，每次0．5 mm 的速率连续牵张下颌骨10 d，然后固定8周。处死动物，以放射学，组织学和 SPECT 方法对牵张区新骨进行检查，对下牙槽神经进行组织学检查。结果：除实验组1只动物因麻醉意外死亡，其他动物都完成了实验。实验组和对照组新骨形成无明显差异。SPECT 显示实验组成骨活跃。观察到下牙槽神经修复性组织学变化。结论：放射照射后牵张犬下颌骨可形成新骨。

Establishment of an animal model of distraction osteogenesis in the irradiated dog mandible

Objective:To establish an animal model of bone distraction in the irradiated dog mandible.Methods:1 0 Chinese dogs were used.8 dogs received a unilateral irradiation of 60 Co(Group R)in the mandible with a total dose of 22.8 Gy in four 5.7 Gy frac-tions (biologically equivalent to 50 Gy/25 fractions).The other 2 dogs without irradiation served as the controls(Group C).Bilateral corticotomy was made 3 months after completion of irradiation.After a 1 -week latency period,bone distraction was activated at a rate of 0.5 mm twice daily for 1 0 days,followed by a consolidation phase of 8 weeks.New bone was evaluated by radiographic,histological and single photon emission computed tomography(SPECT)analysis.Results:One dog was excluded from the study due to anaesthetic death in group R.After 8 weeks of consolidation,no difference was found between the percent area of new bone of both groups.New bone was more mature and organized in Group C than that in Group R.SPECT analyses showed that there was active osteogenic activity in Group R.Conclusion:Distraction osteogenesis can be achieved in the irradiated dog mandible.