腰椎椎弓根螺钉系统断裂的三维有限元分析

背景：椎弓根螺钉系统已是最为常用的脊柱内固定器械，但其钉棒断裂在临床上仍时有发生。 目的：利用三维有限元分析腰椎椎弓根螺钉系统在临床中断裂的并发症，以期提高手术成功率。 设计、时间及地点：三维有限元分析，于2007-11/2008-03在南方医科大学珠江医院完成。 对象：选择1名成年志愿者，年龄27岁，身高174 cm，体质量63 kg，经X射线检查排除脊柱疾病。 方法：建立腰椎椎弓根螺钉系统内固定的三维有限元模型，并分别施加压缩、前屈、后伸、侧屈及旋转5种生理载荷，对比分析不同载荷下螺钉、连接棒的应力分布。 主要观察指标：不同载荷下螺钉、连接棒各部分的应力。 结果：椎弓根螺钉系统各部分于垂直压缩下的应力远小于前屈、后伸、侧屈及旋转时所受压力。垂直压缩下应力主要集中在螺钉近棒段，而在前屈、后伸、侧屈及旋转时应力主要集中在连接棒上。 结论：椎弓根内固定系统设计及类型的选择，术中的规范操作，术后康复活动的指导及保护、适时取出内固定等对预防其断裂均十分重要。

Three-dimensional finite element analysis of the breakage of lumbar pedicle screw instrumentation

BACKGROUND: Pedicle screw instrumentation has been commonly used for spinal fixation, but screw and rod breakage is often reported in clinic. OBJECTIVE: To analyze the reasons for breakage of lumbar pedicle screw instrumentation in clinic by finite element analysis to raise operation efficiency. DESIGN, TIME AND SETTING: Three-dimensional finite element analysis was performed at the Zhujiang Hospital of Southern Medical University between November 2007 and March 2008. PARTICIPANTS: An adult volunteer, aged 27 years, 174 cm high, weighing 63 kg, was selected with no spinal disease confirmed by X-ray. METHODS: Three-dimensional finite element model of lumbar pedicle screw instrumentation was established. Loads including axial compressive, flexion, extension, lateral bending, and rotation forces were given to compare distribution of stress of the fixed segment. MAIN OUTCOME MEASURES: Stress of all parts of screw and rod under different loads. RESULTS: The stress of axial direction in various part of pedicle screw instrumentation was far smaller than the stress of flexion, extension, lateral bending, and rotation forces. The stress of axial direction mainly concentrated on the conjunction of screw-rod, while the stress of flexion, extension, lateral bending, and rotation forces mainly on the rod. CONCLUSION: Design and type of the instrumentation, standard operation, postoperative treatment and instrumentation extraction at the right moment are important factors for the breakage of pedicle screw.