下颌骨双侧升支矢状劈开双皮质螺钉内固定的生物力学分析

Biomechanical analysis of mandibular bilateral sagittal split ramus osteotomy with bicortical screws internal fixation

目的:对下颌骨升支矢状劈开不同方式双皮质固位螺钉内固定进行三维有限元分析,为临床提供理论指导。方法:建立下颌骨升支矢状劈开6种双皮质螺钉固定方式的三维有限元模型;计算不同固定方法在3种咬合情况下颌骨的应力、内固定系统的应力以及骨劈开处的位移,对比这些固定方式的固定效果以及不同咬合情况对固定稳定性的影响。结果:在相同咬合情况下,颌骨的应力、内固定系统的应力以及劈开处的位移的大小情况如下:单纯上缘固定大于倒"L"型固定;直径2.0mm大于直径2.7mm螺钉固定;倒"L"型60°大于倒"L"型90°和120°固定;间距2.0cm大于间距3.0cm固定。相同固定方式情况下,颌骨的应力、内固定系统的应力以及劈开处的位移从大到小排列顺序为:前牙咬合、前磨牙咬合、磨牙咬合。结论:双皮质固位螺钉内固定的排列方式,如:间距、角度、位置和内固定系统的规格均对固定稳定性有不同程度的影响;前牙咬合对固定的不良影响最大,应尽量避免。

Objective： To study the mandibular bilateral sagittal split ramus osteotomy （BSSRO） with bicortical screws rigid internal fixation（RIF） with the three-dimensional finite element method, and supply directions for clinic practice. Methods： CT scanned technology and the finite element software （Ansys） were used to establish the three-dimensional finite element model of BSSRO with bicortical screws RIF. The stress distribution of the mandible and the RIF and the displacement of split mandible were calculated under three kind of occlusion situation. Results： Under the same kind of occlusion situation, the stress and displacement of the split mandible with single upper screws fixation was higher than that with the reverse ＂L＂ screws fixation, the stress and displacement of the split mandible with 2.0 mm diameter screws fixation was higher than that with 2.7 mm diameter screws fixation. With the same kind of fixation method, the stress and the displacemen of the mandible under the incisor occlusion was the highest. Conclusion：The fixation distance, position, distribution angle of the bicortical screws all have effects on the fixation stability. The patient should avoid the incisor occlusion after the surgery.