以三维有限元分析两种方法L_(4/5)椎间融合后的螺钉应力

Three-dimensional finite element analysis of pedicle screw stress following two intervertebral fusion treatments in L_(4/5) segment

背景:作者未查及使用三维有限元方法分析椎弓根螺钉内固定并自体髂骨植骨或椎间融合器植骨后螺钉应力情况的相关报道。目的:在L4～L5节段有限元模型上建立椎弓根螺钉内固定并椎间双枚椎间融合器置入和椎弓根螺钉内固定并椎间自体髂骨植骨的模型,分析两种不同方法植骨后螺钉的应力分布情况。方法:选择1名健康男性,年龄20岁,借助CT扫描和有限元软件,建立L4～L5节段的三维有限元模型。在验证有效的模型上建立后路椎弓根钉棒系统内固定+双枚椎间融合器植骨模型(模型A)和后路椎弓根钉棒系统内固定+椎间自体髂骨植骨有限元模型(模型B),然后在各模型上分别施加载荷,观察螺钉应力分布情况。结果与结论:建立两种不同后路内固定并植骨融合术式三维有限元模型,在不同载荷情况下,发现模型B螺钉应力值均大于模型A,且差异具有显著性意义(P<0.05),差值最大部位为螺钉尾部。结果提示后路椎弓根钉棒系统内固定+椎间自体髂骨植骨后更容易出现椎弓根螺钉断裂情况。

BACKGROUND： No reports regarding three-dimensional （3-D） finite element analysis of pedicle screws stress following autologous lilac crest interbody fusion combined with internal pedicle screw fixation or lumbar vertebra grating can be searched by the authors. OBJECTIVE： To compare the stress distribution of lumbar pedicle screws of two surgical approaches, double fusion cage versus autologous lilac crest interbody fusion combined with internal pedicle screw fixation in lumbar L4-5 segment models. METHODS： Continuous horizontal scanning images of normal lumbar vertebra from a 20-year-old male volunteer that were collected by spiral CT and constructed for L45 segment models. 3-D finite element models of posterior lumbar internal fixation with double cage （model A） or autologeus lilac crest interbody fusion （model B） were constructed. Pressure was loaded on the upper surface of L4 to simulate lumbar compressions. The stress of the pedicle screws and cage were recorded and compared. RESULTS AND CONCLUSION： 3-D finite element model of L4 5 segment internal pedicle screw fixation with two surgical approaches were validated. In every motion state, the stress of screw fixation of model B was obviously greater than that of model A （P〈0.05）, and the maximum difference value located at end part of screw. The screw fixation of model B is more inclined to be fractured than model A.