牵张方向对下颌骨牵张成骨应力分布与位移影响的生物力学分析

目的 建立优化的下颌骨牵张成骨的三维有限元模型以研究下颌骨体部模拟牵张成骨时牵张方向对下颌骨体部牵张成骨的影响.方法 测量不同加载条件下,下颌骨的VonMises应力、位移.结果 可以看出当牵张器平行于下颌骨体放置时,模型中的最大应力是牵张器平行于矢状轴模型中最大应力的2倍.Von Mises应力集中主要发生在加载部位(牵张器与骨的结合点)和髁状突的颈部前下方区域,可能导致局部骨质吸收,从而造成螺钉松动,影响牵张器的稳固性.当模型的加载位移增加时,最大应力与加载位移值成线性关系.平行于下颌骨体组模型存在明显的侧方力,牵引装置牢固固定在下颌骨体部表面,牵引装置所产生的反作用力使它的后臂产生向外侧位移,这种装置-骨界面效应,可导致近中骨段颊侧移位,从而使牵张后的下颌骨形态发生变化,导致咬合关系错乱,面形改变,颞颌关节滑动轨迹的变化可能导致关节功能的紊乱.牵引装置平行于矢状轴放置时,这种反作用力可降至最低程度.结论 牵张器平行于矢状轴优于平行于下颌骨体,此项研究为牵张器在临床应用中的放置位置和牵引方向提供了理论依据.

Stress distribution and displacement in two different distraction directions on mandibular body

Objective To investigate the influence of two different distraction orientations on mandibular distraction osteogenesis.Methods A three-dimensional finite element model of mandibular distraction osteogenesis was established.Von Mises stress and the displacement under different loads were measured.Results The maximum stress when the distraction device was parallel to the mandibular corpus was two times of that when the distraction device was parallel to the sagittal axis.Von Mises stress concentration mainly occurred in the loading position and the anterior and inferior part of condyle.When the displacement increased in the model,the maximum stress and displacement showed a linear relation.The device was firmly fixed on the surface of mandibular body.The counterforce produced by the device made lateral displacement in tail.The interfacial effect could lead buccal displacement of mesial part.Accordingly,the change in the shape of the mandibular body would happen.The reaction force could be reduced to a minimum degree when the distraction device was parallel to the sagittal axis.Conclusion Distraction device parallel to the sagittal axis was preferred.It provided information for the position of distraction device and distraction orientations.