后路椎弓根螺钉系统治疗特发性腰椎侧凸的有限元分析

目的通过有限元计算与刚体动力学相结合的方法,模拟后路椎弓根螺钉系统治疗脊柱侧凸的矫形过程,研究矫形过程中的生物力学特性,探讨不同矫形策略对临床结果的影响,为脊柱侧凸的手术规划提供依据。方法通过病体腰椎CT切片进行三维几何重构,利用ANSYS有限元软件建立了右凸40o腰椎L1-L5和椎弓根螺钉器械的三维有限元模型,联合ADAMS刚体动力学软件模拟了矫形手术中的反旋转与回弹,得到了矫形全过程中植入物所受载荷以及脊椎的应力应变场。结果不同矫形手术过程中,植入器械承受的最大反力范围约为1961099N,椎骨的极少数单元应力超过强度极限120MPa。结论后路椎弓根螺钉系统矫正腰椎侧凸具有较好的治疗效果,脊椎骨性结构的应力水平整体较低。在满足矫形效果的前提下,临床上可考虑选择不同的矫形策略,以减少需植入螺钉的腰椎节段数量并提高手术质量。

Finite element analysis of lumbar spine scoliosis surgical correction by posterior pedicle screw instrumentation

Objective To investigate the effect of posterior pedicle screw instrumentation and determine the impact of alternative surgical strategies to provide guidance for the operation planning. Methods A detailed three-dimensional finite element model of a 40° scoliotic lumbar with pedicle screw instrument were constructed by using the commercial finite element software ANSYS. The geometry of the model was extracted from a computed tomography reconstruction. The correction process including rod rotation and spring-back was simulated with rigid body dynamic software ADAMS. Reaction loads on implant as well as stress distribution of lumbar spine were acquired through the correction simulation. Results The maximal reaction forces were in the range of 196-1099 N. Few bony elements around the screw exceeded the ultimate strength of 120 MPa. Conclusions Idiopathic scoliosis could be well treated by posterior pedicle screw instrumentation with the safety of vertebrae ensured. Different surgical strategies could be considered to conserve implanted lumbar spine level and to improve the surgical quality.