椎弓根螺钉及融合器应力分布在腰椎滑脱后路骨融合模型的三维有限元分析

背景：目前在脊柱外科的有限元分析多见于正常的腰椎模型，对术后病理状态的模型未见深入研究。目的：建立L4/5滑脱不同融合术式的有限元模型，通过此模型对椎弓根螺钉和融合器上的应力分布及模型稳定性有无显著性差异进行生物力学评价。方法：采集1名腰椎滑脱男性的腰椎螺旋CT数据借助mimics 10.01 软件，建立L4/5三维模型。将模型导入abaqus6.51软件，对模型进行网格划分，赋予材料属性。再分别建立椎弓根螺钉和融合器的有限元模型，然后根据临床术式组合成不同后路融合模型。设定边界条件在上述模型上分别施加垂直压缩载荷以及前屈、后伸、左屈、右旋等力矩载荷，并测定各种载荷下椎弓根螺钉、融合器上的应力及模型的位移，结果在SPSS13.0软件上进行统计学分析。结果与结论：①两种模型在各种载荷中应力多集中在椎弓根螺钉与钛棒连接处，轴向压缩载荷下最小，在旋转时最大，融合器应力集中分布在前段及后断。②对比在5种载荷下两种模型位移后路椎体间融合组均小于后外侧融合(P < 0.05)。实验建立了L4椎体滑脱后路不同融合术式的有限元模型，模型加载后的应力分布和位移具有临床意义，椎体间融合的稳定性优于椎弓根螺钉内固定加后外侧植骨融合。

Stress distribution on pedicle screw and cage in posterior fusion surgery of lumbar spondylolysis: A three-dimensional finite element analysis

BACKGROUND: Nowadays, most of three-dimensional finite analysis concern normal lumbar vertebra models in spinal surgery. Few researches have been conducted regarding models of postoperative pathological state.OBJECTIVE: To develop a three-dimensional finite element model of posterior fusion surgery of L4-5 spondylolysis to evaluate the stability and the stress distributions of pedicle screw and cage in different models.METHODS: The L4-5 motion segment data were obtained from CT scans of the lumbar spine of an adult man with spondylolysis. The three-dimensional finite element model of L4-5 spondylolysis was established by abaqus6. 51. The models were subjected to gridding and attribute assignment. The finite element models of pedicle screw and cage were also established, and various posterior fusion models of different approaches were created according to the clinical operation types. The boundary was set, and the models were subjected to different forces including axial compressive, anterior bending, posterior extension, left bending, and right rotation. The von Mises stress, displacement of the fusion segments on the pedicle screw and cages were recorded. All the measuring data were analyzed by SPSS 13.0.RESULTS AND CONCLUSION: All the stress mostly concentrated in the joint position of the arch bar and screw fixed. The stress was minimal under axial compression and maximal under axial rotation. The stress of the Cage mainly located in the anterior part and posterior parts. The displacement of posterior fusion was less than the lateral fusion (P < 0.05). A three-dimensional finite element model of different posterior fusion methods for L4 spondylolysis was established, and the stress distribution and displacement was clinically significant under loading. The stability of lumbar interbody fusion was better than pedicle screw fixation plus lateral fusion.