新型无尾帽自锁式椎弓根钉的设计与有限元力学分析

Design and finite element analysis of a new tailcap-free self-locking pedicle screw

目的设计新型无尾帽自锁式椎弓根钉,建立腰椎后路融合新型椎弓根钉内固定有限元模型并进行力学分析。方法在传统椎弓根钉设计基础上,对尾帽旋转锁定方式进行优化,无尾帽自锁式椎弓根钉锁紧部分设计为螺钉座及紧固座,在固定连接棒的操作中实现外力提拉一步锁定。建立L_(4、5)后路椎间融合新型椎弓根钉内固定有限元模型,分析腰椎前屈、后伸、侧弯、旋转时椎弓根钉的受力情况。结果新型椎弓根钉内固定最大应力值:前屈2.92×10^(7 )N/m^2,后伸2.97×10~7N/m^2,侧弯3.12×10~7N/m^2,旋转2.89×10~7N/m^2。在前屈、后伸、侧弯及旋转情况下应力集中在螺钉中部及钉棒交界处,以钉棒交界处最为显著。不同工况下腰椎各方向活动度均下降,以屈伸活动时最为显著。结论新型无尾帽自锁式椎弓根钉摒弃了传统椎弓根钉尾帽垂直加压锁定方式,零切迹、一体式锁定设计体现出良好的手术操作便利性,具有良好的临床应用前景。此外,有限元分析新型椎弓根钉受力特点可以为后期生物力学测试及疲劳试验提供数据支持。

ObjectiveTo design a new type of tail-capless self-locking pedicle screw,set up the finite element model of posterior lumbar integrating the new pedicle screw internal fixation and conduct the mechanical analysis.Methods Based on the traditional pedicle screw design,the rotation locking mode of the tail cap was optimized.The locking part of tail-capless self-locking pedicle screw was designed with screw seat and fastening seat,which achieved one-step locking by external lifting force in fixing the connecting rod.The finite element model of L4and L5posterior lumbar integrating the new pedicle screw internal fixation was established to analyze the stress of lumbar pedicle screw during anterior flexion,posterior extension,lateral flexion and rotation.ResultsThe maximum stress values of the new pedicle screw internal fixation were2.92×10^7N/m^2 during anterior flexion,2.97×10^7N/m^2 for posterior extension,3.12×10^7N/m^2 for lateral flexion,and 2.89×10^7N/m^2 during rotation respectively.In the cases of anterior flexion,posterior extension,lateral flexion and rotation,the stress was concentrated in the middle of the screw and the junction of the screw and rod,most concentrated in the junction of the screw rod.The activity of lumbar spine decreased in all directions under different operating conditions,demonstrating significant decrease shown during flexion and extension.Conclusion The new type of tail-capless self-locking pedicle screw no longer adopts the tail cap vertical condensation locking mode of traditional pedicle screw,and the zero-notch integrated locking design reflects good convenience for surgical operation and has a broad prospect of clinical application.In addition,finite element analysis about the stress characteristics of the new pedicle screw can provide data support for the later biomechanical test and fatigue test.