轴向载荷下不同体位C5-6节段生物力学的有限元分析

Finite element analysis of C5-6 segment biomechanics under axial loads in different postures

中文关键词:  颈椎  体位  轴向压缩  生物力学  有限元分析

英文关键词:Cervical spine  Posture  Axial compressive force  Biomechanics  Finite element analysis

中文摘要:

  【摘要】 目的：探究不同体位C5-6节段在轴向载荷作用下的生物力学特点。方法：基于一名28岁健康男性志愿者CT数据，构建C5-6节段三维有限元模型，并通过模型活动度（range of motion，ROM）与既往研究进行对比来验证模型有效性。模拟前屈、后伸、左侧屈、右侧屈、左旋、右旋及中立位7种体位下的力学特点，于上终板施加7000N轴向载荷，分析不同体位下C5、C6椎体及椎间盘等效应力/等效应变、最小主应力/最小主应变及剪切应力/剪切应变分布，并采用Kruskal-Wallis检验评估体位间差异。结果：在轴向载荷作用下，C5椎体等效应力峰值中的最大值（370.09MPa），位于后伸体位左侧椎弓根与椎体连接处，最小值（289.30MPa），位于中立体位右侧上椎体钩前部；等效应变峰值中的最大值（0.132）位于左侧屈体位左侧椎体钩前部，最小值（0.094）位于左旋体位同一区域，且等效应力集中于椎体、椎弓根、横突孔周围及终板，等效应变则集中于终板及椎体钩。C6椎体等效应力峰值中的最大值（305.94MPa）与等效应变峰值中的最大值（0.159）均位于后伸体位椎体下终板右后外侧缘，等效应力峰值中的最小值（167.14MPa）和等效应变峰值中的最小值（0.094）均出现于前屈体位同一区域，等效应力和等效应变主要集中于椎体、横突孔周围及终板；椎间盘等效应力峰值中的最大值（53.47MPa）与等效应变峰值中的最大值（16.346）均位于前屈体位前外侧缘中部，等效应力峰值中的最小值和等效应变峰值中的最小值均位于后伸体位右侧外侧缘，等效应力和等效应变集中分布于外侧缘。C5椎体最小主应力峰值中的最大值（388.81MPa），位于后伸体位左侧椎弓根，最小值（309.76MPa），位于中立体位右侧终板前外侧；最小主应变峰值中的最大值（0.104）位于左侧屈体位左侧椎弓根中前部，最小值（0.075）位于中立体位同一区域，最小主应力集中于终板、椎弓根及椎体，最小主应变集中于上终板、椎体钩及椎弓根；C6椎体最小主应力和最小主应变峰值中的最大值分别为1281.90MPa和0.184，均位于右侧屈体位椎体下终板右后外侧缘，峰值中的最小值分别为808.12MPa和0.116，均位于前屈体位同一区域，最小主应力和最小主应变主要集中于终板、椎弓根及椎体；椎间盘最小主应力和最小主应变峰值中的最大值分别为83.91MPa和16.895，均位于前屈体位椎间盘前外侧缘中部，峰值中的最小值分别为65.06MPa和12.791，均位于后伸体位椎间盘右侧外侧缘，最小主应力和最小主应变均集中分布于外侧缘。C5椎体剪切应力峰值中的最大值（206.07MPa）位于后伸体位左侧椎弓根，最小值（155.76MPa）位于前屈体位右侧椎体上部分前侧；剪切应变峰值中的最大值（0.213）位于左侧屈体位左侧椎体钩前部，最小值（0.150）位于左旋体位同一区域，且剪切应力和剪切应变集中于上终板、椎体钩及椎弓根。C6椎体剪切应力峰值中的最大值（664.36MPa）和剪切应变峰值中的最大值（0.230）均位于右侧屈体位椎体下终板右后外侧缘，剪切应力峰值中的最小值（422.40MPa）和剪切应变峰值中的最小值（0.136）均位于前屈体位同一区域，剪切应力和剪切应变主要集中于下终板及椎弓根。椎间盘剪切应力峰值中的最大值（30.30MPa）位于前屈体位椎间盘前外侧缘中部靠左，峰值中的最小值（22.60MPa）位于后伸体位椎间盘右侧外侧缘；剪切应变峰值中的最大值（24.954）位于前屈体位椎间盘前外侧缘中部，峰值中的最小值（18.608）位于后伸体位椎间盘右侧外侧缘，剪切应力和剪切应变集中于外侧缘。结论：C5-6节段在轴向压缩载荷作用时不同体位椎体和椎间盘的应力应变分布存在差异，后伸时椎体应力最大且集中于后部区域，前屈时椎间盘前外侧应变集中，侧屈时同侧椎体应力增加。

英文摘要:

  【Abstract】 Objectives: To investigate the biomechanical characteristics of the C5-6 segment under axial compressive load in different postures. Methods: A three-dimensional finite element model of the C5-6 segment was constructed based on the CT data of a 28-year-old healthy male volunteer, and the validity of the model was verified by comparing the range of motion(ROM) of the model with previous studies. Seven postures, including flexion, extension, left lateral bending, right lateral bending, left rotation, right rotation and neutral position, were simulated, and an axial compressive load of 7000N was applied on the superior endplate. The distributions of equivalent stress/equivalent strain, minimum principal stress/minimum principal strain, shear stress/shear strain in the C5, C6 vertebral bodies and intervertebral discs under different postures were analyzed, and the Kruskal-Wallis test was used to evaluate the differences between different postures. Results: Under axial load, the maximum value of the peak equivalent stress of the C5 vertebral body was 370.09MPa, located at the junction of the left pedicle and the vertebral body in the extension posture, and the minimum value was 289.30MPa, located at the anterior part of the right uncinate process of the upper vertebral body in the neutral posture. The maximum value of the peak equivalent strain was 0.132, located at the anterior part of the left uncinate process in the left lateral bending posture, and the minimum value was 0.094, located at the same region in the left rotation posture. The equivalent stress of the C5 vertebral body was mainly concentrated in the vertebral body, pedicle, around the transverse foramen and endplate, while the equivalent strain was mainly concentrated in the endplate and uncinate process. For the C6 vertebral body, both the maximum value of the peak equivalent stress(305.94MPa) and the maximum value of the peak equivalent strain(0.159) were located at the right posterolateral edge of the inferior endplate of the vertebral body in the extension posture; the minimum value of the peak equivalent stress(167.14MPa) and the minimum value of the peak equivalent strain(0.094) both appeared at the same region in the flexion posture. The equivalent stress and equivalent strain of the C6 vertebral body were mainly concentrated in the vertebral body, around the transverse foramen and endplate. For the intervertebral disc, both the maximum value of the peak equivalent stress(53.47MPa) and the maximum value of the peak equivalent strain(16.346) were located at the middle of the anterolateral edge in the flexion posture; the minimum values of the peak equivalent stress and peak equivalent strain were both located at the right lateral edge in the extension posture, and the equivalent stress and equivalent strain of the intervertebral disc were mainly concentrated at the lateral edge. The maximum value of the peak minimum principal stress of the C5 vertebral body was 388.81MPa, located at the left pedicle in the extension posture, and the minimum value was 309.76MPa, located at the anterolateral part of the right endplate in the neutral posture. The maximum value of the peak minimum principal strain was 0.104, located at the anteromedial part of the left pedicle in the left lateral bending posture, and the minimum value was 0.075, located at the same region in the neutral posture. The minimum principal stress of the C5 vertebral body was mainly concentrated in the endplate, pedicle and vertebral body, and the minimum principal strain was mainly concentrated in the superior endplate, uncinate process and pedicle. For the C6 vertebral body, the maximum values of the peak minimum principal stress and peak minimum principal strain were 1281.90MPa and 0.184, respectively, both located at the right posterolateral edge of the inferior endplate of the vertebral body in the right lateral bending posture; the minimum values of the peak values were 808.12MPa and 0.116, respectively, both located at the same region in the flexion posture. The minimum principal stress and minimum principal strain of the C6 vertebral body were mainly concentrated in the endplate, pedicle and vertebral body. For the intervertebral disc, the maximum values of the peak minimum principal stress and peak minimum principal strain were 83.91MPa and 16.895, respectively, both located at the middle of the anterolateral edge of the intervertebral disc in the flexion posture; the minimum values of the peak values were 65.06MPa and 12.791, respectively, both located at the right lateral edge of the intervertebral disc in the extension posture. The minimum principal stress and minimum principal strain of the intervertebral disc were both concentrated at the lateral edge. The maximum value of the peak shear stress of the C5 vertebral body was 206.07MPa, located at the left pedicle in the extension posture, and the minimum value was 155.76MPa, located at the anterior part of the upper right vertebral body in the flexion posture. The maximum value of the peak shear strain was 0.213, located at the anterior part of the left uncinate process in the left lateral bending posture, and the minimum value was 0.150, located at the same region in the left rotation posture. The shear stress and shear strain of the C5 vertebral body were concentrated in the superior endplate, uncinate process and pedicle. For the C6 vertebral body, both the maximum value of the peak shear stress(664.36MPa) and the maximum value of the peak shear strain(0.230) were located at the right posterolateral edge of the inferior endplate of the vertebral body in the right lateral bending posture; the minimum value of the peak shear stress(422.40MPa) and the minimum value of the peak shear strain(0.136) both appeared at the same region in the flexion posture. The shear stress and shear strain of the C6 vertebral body were mainly concentrated in the inferior endplate and pedicle. The maximum value of the peak shear stress of the intervertebral disc was 30.30MPa, located at the left middle part of the anterolateral edge of the intervertebral disc in the flexion posture, and the minimum value was 22.60MPa, located at the right lateral edge of the intervertebral disc in the extension posture. The maximum value of the peak shear strain was 24.954, located at the middle of the anterolateral edge of the intervertebral disc in the flexion posture, and the minimum value was 18.608, located at the right lateral edge of the intervertebral disc in the extension posture. The shear stress and shear strain of the intervertebral disc were concentrated at the lateral edge. Conclusions: Under axial compressive load, there are significant differences in the stress and strain distributions of the vertebral bodies and intervertebral disc of the C5-6 segment in different postures. The vertebral body stress is the largest and concentrated in the posterior region in the extension posture; the anterolateral strain of the intervertebral disc is concentrated in the flexion posture; and the ipsilateral vertebral body stress is increased in the lateral bending posture.