后纵韧带硬化对颈椎力学影响的三维有限元分析

Biomechanics influence in ossification of the posterior longitudinal ligament: a finite element model of cervical spine

目的利用三维有限元分析探讨后纵韧带(posterior longitudinal ligament,PLL)硬化后对颈椎生物力学的影响,分析探讨其可能引起的颈部稳定性改变。方法对1位健康成年男性进行颈部CT及MR扫描,获取C1—C7节段的断层图片,采用MIMICS(Version 12)软件对颈椎图像进行三维重建,用HYPERMESH 10.0软件对三维几何进行网格划分,后处理计算软件为LS-DYNA3D 971。模型开发和模拟计算在Dell Power Edge 12G M420刀片式服务器上进行,并固定C7,对C1进行前屈、仰伸及轴向旋转运动,加载力矩为3 N·m。比较在前屈、仰伸及旋转运动下,正常以及PLL硬化后颈椎有限元模型的生物力学改变对颈部稳定性的影响。结果颈椎前屈运动中,PLL硬化后椎间盘纤维环最大应力减小6%。颈椎仰伸运动中,PLL硬化后髓核最大应力降低约11%,椎小关节最大应力增大约15.7%。颈椎旋转运动中,PLL硬化椎间盘纤维环最大应力降低24%,最大应力集中在C4/5纤维环旋转方向侧;髓核最大应力降低25%,且最大应力位置由C2/3髓核上方下移至C6/7髓核下方;椎小关节最大应力下降10%。结论 PLL硬化后,前屈及旋转运动使PLL承载更多的力,可能加重已有病变或引起继发损伤;仰伸运动会使最大受力部位转移到椎小关节,导致继发性椎小关节损伤的可能性增加。

Objective To investigate cervical biomechanics and secondary pathological changes of the calcific posterior longitudinal ligament by 3D finite element analysis.Methods Sectional images of cervical spine（C1—C7）were obtained from CT scans of a healthy adult male.The FEM of cervical spine（C1—C7）was developed with the cervical spine CT images by the 3D reconstruction with MIMICS（Version 12）and mesh with HYPERMESH 10.0 software and post-processing software for the calculation of LS-DYNA3D 971（LSTC,USA）.Model development andsimulation were performed on the Dell Power Edge 12G M420 blade servers,which C7 was fixed,and the loading moment were 3 N·m in flexion,extension and axial rotation motions respectively.Compared with the normal by changing the parameters of the posterior longitudinal ligament material properties in lateral bending,flexion,axial rotation motion.Results After changing the parameters of the posterior longitudinal ligament material properties,in flexion,the maximum stress of the intervertebral disc decreased by 6%.In extension the maximum stress of the nucleus decreased by 11%,the maximum stress of facet joints increased by 15.7%.In rotation,respectively,the maximum stress of intervertebral disc reduced by 24%,the maximum stress concentrated at the direction of rotation in C4/5 fiber ring;the maximum stress of the nucleus reduced by 25%,and the position transferred from C2/3 to C6/7,the maximum stress of the facet joints decreased by 10%.Conclusions We can know that after the PLL harden the distribution of the mechanical system will be changed by using FEM.In flexion and rotation movement the PLL will carry more power after hardening,which may exacerbate existing disease or cause secondary injury.Moreover,the maximum stress position in extension is transferred to vertebral small joints,which increases the possibility of secondary injury to vertebra small joint.