腰椎椎弓根壁侧置钉内固定方式及生物力学三维有限元分析

目的：建立L4，L5三维有限元模型，并分别行椎弓根常规置钉及壁侧置钉两种内固定方式，用三维有限元法分析固定后椎体及螺钉的应力分布特点。方法选取正常成年人L3～L5节段的多层螺旋CT扫描的薄层原始数据（DICOM格式），利用Mimic等软件建立人正常L4，L5三维有限元模型，并建立L4，L5椎弓根螺钉内固定模型。并于L4上表面施加500N预载荷，再施加8N· m的力矩模拟腰椎垂直压应力、前屈、旋转等生理活动，观察不同情况下两种模型中椎体螺钉应力分布情况。结果由应力分布图可知，在各种载荷下，两种模型的螺钉应力从钉尖至钉棒连接处逐渐减少，螺钉根部附近应力最小。3种载荷之间比较，垂直压缩时螺钉应力最大。椎弓根壁侧置钉内固定方式较常规置钉内固定方式的螺钉应力明显减小。结论模拟两种内固定方式正常生理活动时，椎弓根常规置螺钉内固定模型中椎弓根螺钉的应力主要集中在与椎体交界界面处，而椎弓根壁侧置螺钉内固定模型中螺钉的应力基本分散在钉体上，一部分应力分布在椎弓根皮质上，增加了椎弓根螺钉的抗拔出力，从而增加固定的可靠性，减少发生内固定螺钉断裂等风险。

Lumbar Pedicle Screw Fixation Side-Wall Method and Finite Element Analysis of Biomechanical

Objective To establish L 4 ,L5 dimensional finite element model ,and two kinds of L 4 ,L5 pedicle screw placement were performed ,and to analysis the stress distribution characteristics of vertebral body and screw with three dimensional finite element method .Methods A normal adult L 3 ~L5 segment of multislice CT scans the thin layer of raw data（DICOM format） were chosen.Using software such as the Mimic people,normal L4,L5,three-dimensional fi-nite element model was set up ,and the model of the L 4 ,L5 pedicle screw internal fixation was established .500 N was ap-plied on the surface of L 4 ,and plus 8N· m to simulate torque lumbar vertical compressive stress ,bending forward and ro-tating,such as physical activity Different situations two vertebral bolt stress distribution in the model were observed .Re-sults From the stress distribution under various loads ,screws gradually reduced the stress of the two models to the nail from the nail tip rod joints,and screws near the roots shared a minimum of stress .Compared among the three loads,the vertical compressive stress screws was maximum .Compared with the conventional set screw stress of pedicle screw fixa-tion methods side-wall nail fixation significantly reduced .Conclusion Two simulated within the normal physiological ac-tivity after fixation,the pedicle screw fixation device model conventional pedicle screw with the vertebrae in the stress is prone to the junction interface .Stress fixed model pedicle screw side-wall screws scattered on basic staples body part stress distribution on the pedicle cortex ,increased resistance to pull-out strength of pedicle screws ,thereby increasing the reliability of fixed and reducing the risk of fracture fixation screws .