不同载荷条件下颈脊髓过伸损伤的应力分布特征

目的 利用有限元法研究不同载荷条件下颈脊髓过伸损伤时脊髓内不同区域的应力分布特征. 方法 利用颈脊髓的三维有限元模型(此模型由8484个节点和14 297个单元组成),进入Ansys前处理器,设置边界条件和不同大小的载荷配置:第Ⅰ种载荷配置:后伸载荷0.0015 N,压缩载荷1N;第Ⅱ种载荷配置:后伸载荷0.0030 N,压缩载荷2 N;第Ⅲ种载荷配置:后伸载荷0.0045 N,压缩载荷3N;第Ⅳ种载荷配置:后伸载荷0.0060 N,压缩载荷4 N;第Ⅴ种载荷配置:后伸载荷0.0075 N,压缩载荷5N.模拟不同损伤情况,进入求解模块,进行过伸损伤负载模拟计算,最后进入Ansys后处理器,读取并分析颈脊髓横断面9个不同功能区域(颈脊髓白质前索、侧索外侧部、侧索内侧部、后索外侧部、后索内侧部、灰质前角、前角底部、后角尖和头部及后角颈部)的应力分析结果. 结果 颈脊髓损伤断面应力云图提示应力主要集中于灰质前角、后角和白质前索、侧索内侧和后索外侧内,并且其平均应力依次减小.随着施加载荷的增大,灰白质内各个部位的应力均明显增加,灰质前角内的应力增幅最大.灰质前角和白质侧索的应力增幅值比较差异有统计学意义(P<0.05),后角和白质前索分别与后索应力增幅值比较差异均有统计学意义(P<0.05),后角和白质前索应力增幅值比较差异无统计学意义(P>0.05). 结论 轻度颈脊髓过伸损伤主要造成白质前索和灰质前后角损伤,表现为以上肢为主的运动和感觉异常.随着损伤载荷加大,应力分布向相邻白质扩展,载荷加大后前角支配手内肌的神经元细胞较其他部位损伤更严重.

Effects of different loading conditions on the stress features of hyperextension injury to the cervical spinal cord

Objective To investigate the mechanical responses by the cervical spinal cord to the hyperextension injury under different loading conditions. Methods A three dimensional finite element model of the cervical spinal cord was built and imported into the preprocessor of the Ansys software for assigning boundary and different loading conditions. Then the extension and pinching conditions were simulated after the solution module was entered. The stress results of 9 different anatomical regions in the cross-section of the cervical spinal cord were read and analyzed in the postprocessor of the Ansys software. Results The localized stress mainly occurred at the anterior horn and posterior horn in the gray matter, the anterior funiculus, the medial part of the lateral funiculus, and the lateral part of the posterior funiculus, with the average magnitude decreasing successively. The magnitude of the stress increased with the severity of the cervical spine injury. The maximum stress increment occurrred at the anterior horn. Significant differences in the stress increment were observed between the anterior horn and the lateral funiculus( P<0. 05). Compared with the posterior funiculus, the stress increment at the posterior horn and the anterior funiculus showed a statistical difference( P<0.05) . There was no statistical difference between the posterior horn and the anterior funiculus( P>0. 05). Conclusions The cervical hyperextension injury mainly leads to injury to the motor neuron of the anterior horn. More damage to the motor neuron dominating the intrinsic muscle of hand can lead to poorer prognosis. A greater injury load may cause stress to distribute onto more adjacent white matter.