原位及复位融合腰椎滑脱的三维有限元分析

Three-dimensional finite element analysis of in situ and reductive interbody fusion of lumbar spondylolisthesis

背景:由于脊柱结构复杂,对复位或原位融合后融合的腰椎节段应力分布变化特点的精确生物力学分析一直是个难点。目的:通过建立L4/5节段退变性滑脱原位椎间融合椎弓根钉内固定和复位椎间融合椎弓根钉内固定的三维有限元模型来比较腰椎滑脱原位融合和复位融合两种手术方式在各种载荷下的生物力学变化及其对腰椎稳定的影响。方法:根据健康成年男性的下腰椎CT数据,利用mimics,Catia和Patran,Marc等软件建立起L4/5节段的三维有限元模型,利用此模型模拟退变性腰椎滑脱,在此基础上建立L4/5节段原位椎间融合椎弓根钉内固定和复位椎间融合内固定模型,分析两模型在各种载荷下的应力分布特点,并比较异同。结果与结论:L4/5节段退变性滑脱原位椎间融合椎弓根钉内固定和复位椎间融合椎弓根钉内固定三维有限元模型在前屈后伸侧屈旋转负荷下,该节段各部结构,包括椎体,椎弓根钉内固定器和椎间融合器上的应力变化没有显著差异。两模型都显示椎间融合器和椎弓根螺钉内固定器上分布的应力最大。结果表明退变性腰椎滑脱,行原位椎间融合内固定和复位椎间融合内固定后,复位与否对该节段生物力学没有显著影响。

BACKGROUND： Due to the complexity of the spinal structure, it is difficult to conduct the exact biomechanical analysis on the changes of the stress distribution characteristics of the lumbar segment after in situ and reductive interbody fusion. OBJECTIVE： To compare the biomechanical changes of in situ and reductive interbody fusion of lumbar spondylolisthesis under mechanical loads and the effect of those changes on the lumbar stability through developing the three-dimensional finite element models of L4/5 degenerative spondylolisthesis treated within situ and reductive interbody fusion pedicle screw internal fixation. METHODS： The three-dimensional finite element models of L4/5 segment of healthy male volunteers were established through analyzing the lower lumbar spine CT data and using the mimics, Catia, Patran and Marc softwares. Then the models were used to simulate the degenerative sPondylolisthesis and to establish the L4/5 segment in situ and reductive interbody fusion and pedicle screw internal fixation models. The stress distribution characteristics of these two models under different mechanic loads were analyzed and the difference was compared. RESULTS AND CONCLUSION： Under the loads of flexion, extension, right rotation and left bending, there was no significant difference of the stress on the vertebral body, pedicle screw fixator and interbody fusion cage between the L4/5 segment degenerateive spondylolisthesis in situ and reductive interbody fusion and pedicte screw internal fixation models. Both the two models manifested that the pedicle screw fixator and interbody fusion cage take the majority of the loads. After the in situ and reductive interbody fusion internal fixation for the degenerative spondylolisthesis of the L4/5 segment, reduction or not has no great biomechanical influence on the fusion segment.