上颈椎三维非线性有限元模型的建立及其有效性验证

Development and validation of a nonlinear finite element model of the upper cervical spine

目的建立具有详细解剖结构的上颈椎三维非线性有限元模型并验证其有效性。方法对健康成年男性志愿者进行CT扫描,获得枕骨底(C0)到C3的体层图像,将数据导入Mimics软件进行上颈椎骨质的三维模型重建,用Freeform软件进行模型修改,导入有限元软件Ansys9.0进行分析计算。模型中韧带以非线性的弹性元素建模,分为弹性区和中性区,分别定义元素性质,韧带的起止点及横截面积根据文献确定,寰椎横韧带坚韧、弹性低,定义为固体元素性质,同时便于对齿状突横韧带关节进行受力分析。寰枕关节、寰枢关节、C2,3关节突关节、寰椎齿状突关节、齿状突横韧带关节均定为有摩擦系数的表面滑动接触关节。使模型C3椎体下缘固定,在枕骨底施加40N的预载荷和1.5N·m的力矩作用下使其产生前屈、后伸、旋转、侧屈运动,将模型的活动度(ROM)与Panjabi测得正常上颈椎的实验数据对比进行验证。结果建立了具有详细解剖结构的上颈椎三维非线性有限元模型,整个模型有229047个节点和152475个单元,模型运动范围与Panjabi的数据相符合。结论建立的上颈椎模型具有较高的真实性,可以用于生物力学分析实验。

Objective To develop and validate an anatomic detailed finite element model of the upper cervical spine. Methods The upper cervical spine （ C0-3 ） geometries were determined from CT images of a 28-year old healthy man. The finite element model was constructed by the combination of software Mimics 8.1 and Freeform. The meshed model was acquired and finished with Ansys 9.0. The ligaments were added to the model based on data from the literature. The transverse ligament was modeled with solid elements so that the odontoid-transverse ligament joint could be modeled. The other ligaments were modeled with tension-only spring elements with bilinear modulus of elasticity data according to neutral and elastic zones. Sliding contact definitions with friction were used for all the facet joints. To validate the C0-3 finite element model, the predicted kinematic data, in term of the range of motion （ROM）, under different static loading configurations were analyzed and compared against the experimental data by Panjabi et al. In the analysis, the weight of the skull was simulated by applying vertical load of 40 N on the occiput, and the inferior surface of the C3 vertebral body was fully constrained. Pure moment loading of 1.5 N · m was applied to the occiput along the various anatomical planes to simulate various movements of the cervical spine under flexion, extension, axial rotation and lateral bending configurations. Results The model consists of 229047 nodes and 152475 elements, and correlated well with the results by Panjabi et al. Conclusion The anatomic detailed finite element model of the upper cervical spine realistically simulates the complex kinematics of the craniocervical region which can simulate the natural condition and facilitate the further biomechanical research.