枢椎齿突Ⅱ型骨折中空螺钉固定的三维有限元分析

Finite element analysis of magnesium alloy hollow screw for treatment of type Ⅱ fractures of the odontoid process

目的建立枢椎齿突Ⅱ型骨折螺钉固定的三维有限元模型,分析不同材料螺钉内固定对齿突Ⅱ型骨折术后稳定性的影响。方法通过CT扫描获取枢椎的空间结构信息,建立其三维有限元模型。模拟齿突骨折螺钉固定术后的受力情况,比较镁合金、钛合金两种材料螺钉固定下骨折端前后位移和骨折面及螺钉所承受的应力大小。结果 (1)所建枢椎有限元模型外形逼真,几何相似性好,共包含为32929个四面体单元、59265个结点;(2)头部后伸、前屈活动时,钛合金螺钉最大应力分别为42.3MPa、62.8 MPa,上骨折端最大位移分别为0.028mm、0.040 mm,;镁合金螺钉最大应力分别为33.6 MPa、52.1MPa,上骨折端最大位移分别为0.036mm、0.056mm。结论应用CT扫描获取枢椎空间结构信息建立的枢椎模型可用于生物力学实验,两种材料的螺钉固定枢椎齿突II型骨折时其最大应力均小于其材料的屈服强度,骨折端应力镁合金组大于钛合金组。

Objective To set up the finite element（FE） model of type II odontoid fracture screw fixation and analyze the stability of fixation on postoperative type 1I odontoid fracture using different material. Methods Aflantoaxial spatial structure information was obtained through CT scanning and 3D finite element model was established. Simulation of stress situation after screw fixation of odontoid fi：actures was performed; Then comparison of the displacement of the fracture surfaces and stress the fracture surfaces and the screw should take after fixation with screws using two materials（the magnesium alloy and the titanium alloy） were measured; the results were analyzed by t test statistical analysis. Results （ 1 ）The finite element model of the axis that consists of 32929 elements and 59265 nodes is of object-like appearance and excellent geometric similarity; （ 2 ） under the circumstance of head extension and flexion, the maximum stress of the titanium alloy screws were 42.3MPa and 62.8 MPa, and the maximum displacement of fracture ends were 0.028ram and 0.040mm respectively; the maximum stress of the magnesium alloy screws was 33.6 MPa and 52.1 MPa and the maximum displacement of fracture ends was 0.036mm and 0.056mm, respectively. Conclusion Information of the spatial structure of the axis obtained through CT scanning and utilized for model building can be used in biomechanical experiment; the maximum stress of the screws with two type of materials used for fixation of the pattern-II odontoid fracture is smaller than the yield strength Of the material; the stress the fracture ends in the magnesium alloy group was higher than that of the titanium alloy group.