以三维有限元模型分析短节段腰椎椎弓根螺钉系统固定后螺钉应力的分布  

Stress distribution of lumbar pedicle screws following short-segment fixation based on three-dimensional finite element model

作　　者：敖俊[1] 方国芳[1] 冯伟[1] 张辉[1] 于博[1] 薛忠林[1] 靳安民[1] 

机构地区：[1]南方医科大学珠江医院骨科,广东省广州市510282

出　　处：《中国组织工程研究与临床康复》2008年第39期7601-7604,共4页Journal of Clinical Rehabilitative Tissue Engineering Research

摘　　要：背景：作者未查及生理负荷状态或接近生理负荷状态下下腰椎非融合状态时螺钉应力分布的文献报道。目的：建立L3-5节段三维有限元模型，观察前路L4/5椎弓根螺钉内固定后的应力特点。设计、时间及地点：三维有限元模型的生物力学分析，于2008—01／06在南方医科大学珠江医院骨科实验室完成。材料：采集1名32岁男性青年自愿者的正常腰椎螺旋CT层厚0．625mm的连续水平扫描图像。方法：将CT扫描所得的数据以Dicom格式转入计算机，借助Mimics 11．1软件，建立L3-5节段的几何模型。将几何模型转入Simpleware2．1软件，同时将椎弓根螺钉系统以STL格式转入Simpleware软件进行匹配，模拟L4/5椎间椎弓根螺钉内固定，从而建立有限元模型，导入Abaqus 6．51进行分析，在L3上表面施加500N压力模拟轴向压缩、再施加15N·m的力矩模拟腰椎前屈、后伸、侧屈和旋转等各种生理载荷，观察不同载荷下螺钉的应力分布。主要观察指标：椎弓根螺钉在轴向压缩、前屈、后伸、侧屈和旋转等各种生理载荷下的应力云图和峰值。结果：椎弓根螺钉在下方螺钉钉尾部应力集中明显：在各种加载运动模式中，下方螺钉钉尾部应力值在轴向压缩载荷下最小，在旋转时最大。结论：在模拟正常腰椎活动情况下，仅予以腰椎椎弓根螺钉系统固定情况下，螺钉疲劳断裂的部位易发生在下方螺钉钉尾部，融合相应节段可减少因螺钉应力集中引起的螺钉疲劳断裂。BACKGROUND： No reports are found about screw stress distribution of nonfused low lumbar vertebra condition under or near physiological stress. OBJECTIVE： To develop a L3-5 segment three-dimensional （3D） finite element model and to evaluate the stress of screw in posterior lumbar internal fixation. DESIGN, TIME AND SETTING： Biomechanical analysis of 3D finite element model was performed at the laboratory of Department of Orthopaedics, Zhujiang Hospital of Southern Medical University from January to June 2008. MATERIALS： Continuous horizontal scanning images of normal lumbar vertebra from a 32-year-old male volunteer were collected by spiral CT （0.625 mm thickness）. METHODS： The geometrical model was created by Mimics 11.1 based on CT data of L34 segment. The models were imported into the Simpleware 2.1 and pedicle screw fixation system was shifted in with STL format to establish 3D finite element models of posterior lumbar internal fixation. The 3D finite element models were imported into Abaqus 6.51 and analyzed. 500 N pressure was loaded on the upper surface of L3, and 15 N · m moments was loaded to simulate lumbar axial compression, anteflexion, extension, lateral bending and rotation. The stress of the pedicle screws was recorded. MAIN OUTCOME MEASURES： Stress images and peak stress of pedicle screws under lumbar axial compression, anteflexion extension, lateral bending and rotation. RESULTS： Most of stress concentrated on the tail part of the low screws. Under different loadings of low pedicle screws, the stress was minimal under axial compression and maximal under axial rotation. CONCLUSION： Under the condition of pedicle screws fixation, stress concentration presents at tail parts of screws, coincident with frequent pedicle screw breakage after operation. Lumbar vertebra fusion in operation could reduce stress-induced screw breakage.

关 键 词：腰椎 椎弓根螺钉固定 生物力学 有限元分析 

分 类 号：R318[医药卫生—生物医学工程]