2种牵张方向对下颌骨体部牵张成骨应力分布与位移的影响

The effect of stress distribution and displacement by two kinds of different distract directions on mandibu-lar body

目的建立下颌骨牵张成骨三维有限元模型,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。方法建立下颌骨牵张成骨三维有限元模型,测量不同牵张位移加载条件下,下颌骨的Von Mises应力、骨结合点位移。结果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)和髁突的颈部前下方区域,由于这2处有应力集中,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。结论平行于下颌骨体组模型存在明显的侧方力,牵引装置所产生的反作用力使它的后臂产生向外侧位移。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,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。

Objective To establish a three-dimensional finite element model of mandibular distraction osteogenesis （DO） in order to study the influence of distraction orientations to mandibular DO. Methods By using the two finite element models, Von Mises stress and the displacement under different loads were measured. Results The maximum stress in the distract equipment paralleled to the mandibular corpus was two times of that when the distract equipment paralleled to the sagittal axis. Von Mises stress concentration mainly occurred in the loading position and the condylar ante inferior. This phenomenon may lead to partial bone resorption, consequently lead to screw loose and affect the stability of distraction device. When the displacement increased in the model, the maximum stress and displacement showed linear relation. Conclusion The counterforce produced by the device makes lateral displacement in tail. The reaction force could be reduced to a minimum degree when the traction device parallel to the sagittal axis. This study provides theoretical basis for the position of distract equipment and distraction orientations in clinical application.