枢椎有限元模型的建立及齿状突骨折的三维有限元分析

 目的建立枢椎有限元模型，探索不同受力状态下齿状突发生Ⅱ、Ⅲ型骨折的趋势。方法用64层螺旋CT对健康成人进行颈部扫描，利用MIMICS软件重建枢椎的面模型及优化网格,而后导入有限元分析软件ANSYS中，生成体网格，即生成枢椎有限元模型。模型加载，force/moment200N分别施于枢椎齿状突中部、尖部、底部及侧方节点。结果force/moment施于齿状突中部节点时应力集中分布在齿状突基底部及中下部；施于尖部时应力集中于齿状突基底部及双侧上关节突；施于底部时应力集中于齿状突基底部及双侧上关节突；施于侧部时应力集中于枢椎齿状突基底部两侧。结论所建立的枢椎有限元模型可有效用于模拟生物力学分析。颈椎在旋转状态下遭受暴力更易产生Ⅱ型齿状突骨折，后伸及前屈时则易发生Ⅲ型骨折。

Establishment of Odontoid Finite Element Model and Three Dimensional Finite Element Analysis of Odontoid Fractures

Objective To establish the finite element model of the axis and analyse different type of the odontoid fracture by different force.Methods One intact health adult cervical vertebrae was scanned by 64-slice CT,and saved as DICOM format.View the CT images in the PACS system,then export DICOM format of the stored data.Reconstruct the axis surface model in use of Mimics software,meshing and optimizing,and import the surface model of the axis to the finite elements analysis software ANSYS in ANSYS element lis format.Set element type,real constants,and material props and the finite element model of axis was built.Give load to the model,containing displacement on the lower surface of the vertebrae body,on the lower surface of the spinous process and on the surface of the bilateral inferior articular process.50N pressure was also given to the surface of the bilateral superior articular process.Then Force/moment was applied to nodes on the middle,tip,bottom and side of the odontoid.Results: As the Force/moment was applied to nodes on the middle,stress is concentrated in the lower part and the bottom of the odontoid,the typeⅡ fracture tend to occur.The maximum stress value is 135.934MPa,which verified the odontoid model:As on the tip or the bottom,the maximum stress is 137.610MPa and 143.411MPa,both greater than the neutral state (135.934MPa):As on the side,the maximum stress value is 148.499MPa,which is the greatest in the four states.Conclusion: The biomechanics behavior of the axis finite element model can be used for further analysis.In the rotation state,fracture of the odontoid tend to occur.Stress concentrated in the bottom of the odontoid and result in the Ⅱ type of fracture.Hyperextention injury lead to type Ⅲ fracture because of the concentrated stress in the lower part and bottom of the Odontoid.In the flexor state,stress concentrated in the bottom of the odontoid and the bilateral superior articular process of the axis and result in type Ⅲ fracture.