植入人工腰椎间盘后小关节应力分布的有限元分析(英文)

Finite element analysis of the stress distribution in small joint after the implantation of artificial lumbar intervertebral disk

背景:目前所使用的人工椎间盘结构、材料特性及生物学特性等与正常生理的椎间盘有着很大区别,因此,人工椎间盘植入后相应脊柱节段的应力传导将发生一定的变化。目的:通过三维有限元的方法研究正常椎间盘、髓核摘除、人工腰椎间盘三组小关节的应力分布,探讨人工腰椎间盘植入对小关节应力分布的影响。设计:观察对比实验。单位:中山大学附属第三医院骨科、附属第二医院骨科及南方医科大学生物力学实验室。对象:以健康人意外死亡的无任何脊柱疾患的脊柱标本(家属志愿捐献)建立起脊柱运动节段的有关正常椎间盘、人工椎间盘、髓核摘除的三种三维有限元模型作为实验对象。方法:利用有限元软件MSC.MARK,建立正常椎间盘模型,高度为10.00mm,横截面积1300.00mm2,髓核横截面积495.80mm2;髓核摘除模型,将髓核内压取值为零;人工腰椎间盘及L4-5运动节段的三维模型,小关节高度10.53mm,宽度13.37mm,关节面面积135.00mm2。然后模拟腰椎节段的运动,进行小关节应力分布的比较研究。主要观察指标:上述三种椎间盘的运动节段模型在6种运动状态下小关节应力大小的比较。结果:髓核摘除组小关节的上边缘部、后中部、下边缘部和前中部在前屈、后伸、压缩、侧屈、旋转状态应力最大,人工腰椎间盘组的小关节的应力比正常椎间盘高,但明显小于髓核摘除组,但正中部在旋转状态下,人工腰椎间盘小关节的中心部位承受的应力最大。结论:人工腰椎间盘植入后与髓核摘除组相比可降低小关节的应力,但仍高于正常的腰椎间盘组;人工腰椎间盘组的抗旋转能力明显低于正常腰椎间盘组和髓核摘除术后组,由此可见,目前的人工腰椎间盘具有腰椎间盘大部分的力学功能,与真正的腰椎间盘仍有差别。

BACKGROUND： Presently-used artificial intervertebral disk is different greatly from the normal physiological intervertebral disk in structure, material and biological properties and so on. Therefore, stress conduction at corresponding spinal section will have a certain change after the implantation of artificial intervertebral disk. OBJECTIVE： To investigate the stress distribution in small joints of norreal intervertebral disk group, vertebral extirpation group and artificial lumbar intervertebral disk group with three-dimensional element method in order to discuss exploratorily the influence of the implantation of artificial lumbar intervertebral disk on the stress distribution in small joints. DESIGN： Observative and comparison experiment. SETTING： Orthopedic Department, Third Affiliated Hospital and Second Affiliated Hospital, Sun Yat-sen University; Biomechanical Laboratory in Southern Medical University. PARTICIPANTS： Spinal specimen collected from the healthy people who died in accidenct without any spinal illness （donated by their family member） was used to establish three kinds of three-dimensional element models of normal intervertebral disk, artificial intervertebral disk and vertebral extirpation as experimental subjects. METHODS： Finite element MSC.MARK software was used to establish normal intervertebral disk model with height of 10.00 mm, cross sectional area of 1300.00 mm^2, and vertebral pulp cross sectional area of 495.8 mm^2; in the model of vertebral pulp extirpation,the intrinsic pressure of vertebral pulp was zero; and in the three dimensional models of artificial lumbar intervertebral disk and L4-5 movement segment, the small joints were about 10.53 mm high with width of 13.37 mm and auricular area of 135 mm^2. Then lumbar movement was simulated for the study of the stress distribution in small joint. MAIN OUTCOME MEASURES： Comparison of the stress in small joints under 6 kinds of states in the above three kinds of intervertebral disk movement model. RESULTS：In vertebral pulp extirpation group, the stress was proved to be the highest at superior edge, posterior middle part, lower edge and anterior middle part of small joints under anteflexion, backward extension, compression, lateroflexion and revolving states, moreover, small joint stress in artificial lumbar intervertebral disk was higher than that in normal intervertebral disk, but obviously lower than that in vertebral pulp extirpation group; however, the small joint of the middle part of artificial lumbar intervertebral disk bore the highest stress under revolving states. CONCLUSION： In contrast with vertebral pulp extirpation group, the small joint stress could be reduced after the implantant of artificial lumbar intervertebral disk, but was still higher than that of normal lumbar intervertebral disk group and the anti-verticity in artificial lumbar intervertebral disk group was markedly lower than that of normal lumbar intervertebral disk group and vertebral pulp ablation group, thus indicating that although presently-used artificial lumbar intervertebral disk possesses most of mechanical functions of normal lumbar intervertebral disk, but is still different from true lumbar intervertebrad disk.