Lenke-Silva Ⅵ型退行性脊柱侧凸不同内固定方式的生物力学分析及活动度研究

Biomechanical analysis and activity study of Lenke-Silva type Ⅵ degenerative scoliosis with different internal fixation methods

目的:建立退行性脊柱侧凸矫正术后三维有限元模型并对其进行仿真分析,得出钉-棒系统的应力分布情况,根据钛合金钉棒的屈服强度确定患者术后活动度.方法:选取4例已完成矫形手术但钉棒并未取出的患者,分别采取了不同内固定方案(A方案,T10~S1共17枚螺钉固定,横向连接位于矫形区上方;B方案,L2~S1共12枚螺钉固定;C方案,T10~S1共14枚螺钉固定,横向连接位于矫形区下方;D方案,T10~S1共19枚螺钉固定,卫星棒跨L1~S1固定加强,横向连接位于矫形区上方).分别对4例患者的脊柱进行CT扫描,通过CT图像建立完整的三维有限元模型,对三维模型进行加载,模拟人体前屈后仰、左右弯曲、左右旋转六种工况,分析各个工况下钉-棒系统应力分布.对钉棒进行敏感度分析,并根据钛合金钉棒的屈服强度及敏感度曲线确定患者术后的活动度.结果:成功建立了退行性脊柱侧凸矫正术后三维有限元模型,钉棒所受应力集中于钉尾与钉身交界处以及钉尾与矫形棒连接处.A、B、C、D四种内固定方案前屈后仰的活动度分别约为22°、30°、45°、30°;左右弯曲分别约为19°、28°、34°、32°;左右旋转分别约为21°、20°、42°、24°.结论:退行性脊柱侧凸矫正术后有限元模型的建立及应力分析能为退行性脊柱侧凸生物力学研究提供借鉴意义,并为手术方案的制定及患者术后活动度预测提供一定的理论基础.

Objectives:A three-dimensional finite element model after degenerative scoliosis correction was established and simulated analysis was performed to obtain the stress distribution of the nail-rod system.The patient’s postoperative activity was determined based on the yield strength of the titanium alloy nail rod.Methods:Four patients who had undergone orthopedic surgery but the nail rods were not removed were selected.Four patients underwent A,B,C and D internal fixation schemes.Innovative solution of satellite rod technology,A,T10-S117 screws were fixed,the horizontal connection was located above the orthopedic area;B,L2-S112 screws were fixed;C,T10-S114 screws were fixed,the horizontal connection was located below the orthopedic area;D,T10-S119 screws were fixed,the satellite rod was fixed and strengthened across L1-S1,and the horizontal connection was located above the orthopedic area.CT scans were performed on the spine of 4 patients,and a complete three-dimensional finite element model was established based on the CT images.The three-dimensional model was loaded to simulate six conditions:forward-backward bending,leftright bending and left-right rotation.Stress distribution of the nail-rod system.The sensitivity analysis was performed on the nail rod,and the postoperative mobility of the patient was determined according to the yield strength and sensitivity curve of the titanium alloy nail rod.Results:A three-dimensional finite element model after degenerative scoliosis correction was successfully established,the stress on the nail rod was concentrated at the junction of the nail tail and the nail body and the junction of the nail tail and the orthopedic rod.The activities of the four schemes(A,B,C and D)under the six operating conditions were as follows,forward-backward bending was 22°,30°,45°,30°;left-right bending was 19°,28°,34°,32°;leftright rotation was 21°,20°,42°,24°,respectively.Conclusions:The establishment of finite element model and stress analysis after degenerative scoliosis correction can provide reference for the biomechanical research of degenerative scoliosis,and provide a certain theoretical basis for the formulation of surgical plans and postoperative mobility of patients.