齿状突骨折的两种内固定方式有限元分析

Finite element analysis of two internal fixation methods for odontoid fractures

目的采用有限元分析方法分析寰椎后弓交叉螺钉结合枢椎椎板螺钉内固定与寰枢椎椎弓根钉内固定治疗齿状突骨折的力学特性。方法选取1名健康成年男性志愿者进行上颈椎CT扫描,获取数据建立正常上颈椎模型(正常组)与齿状突骨折模型(骨折组),模拟手术完成寰枢椎椎弓根钉内固定模型(寰枢椎内固定组)与寰椎后弓交叉螺钉结合枢椎椎板螺钉内固定模型(新型内固定组),同时对枕骨上端施加1.5 N·m的6个自由度方向力偶,测量各组在各个工况下的C_(0~2)活动度,测量寰枢椎内固定组与新型内固定组内固定系统在各个工况下的最大应力。结果骨折组各个工况下的C_(0~2)活动度都较正常组大,寰枢椎内固定组与新型内固定组C_(0~2)活动度较骨折组与正常组显著降低。寰枢椎内固定组与新型内固定组在螺钉的根部及连接棒区存在较大的应力,前屈时内固定承受更大的应力。结论寰枢椎椎弓根钉内固定与寰椎后弓交叉螺钉结合枢椎椎板螺钉内固定均能明显限制寰枢椎各方向的活动度,两种内固定方式螺钉根部及连接棒处应力更为集中。

Objective To analyze the mechanical characteristics of the atlas posterior arch cross screw combined with axiallaminar screw internal fixation and atlantoaxial pedicle screw internal fixation for the treatment of odontoid fractures with the fi-nite element analysis method was used.Methods Finite element models of normal upper cervical spine(normal group)werebuilt from one healthy male adult volunteer on CT scan,then odontoid fractures models(fracture group)were established.Fur-ther,2 different posterior C_(1~2) fixation techniques including C_(1) posterior arch screws plus C_(2) laminar screws system(new type in-ternal fixation group)and C_(1) pedicle screw plus C_(2) pedicle screw system(atlantoaxial fixation group)were loaded on the model.A force couple(1.5 N·m)was applied to measure the C_(0~2) range of motion(ROM)and the maximum stress of the internal fixationsystem in the each group.Results ROM of C_(1~2) in fracture group increased significantly than normal group.The finite elementanalysis showed that atlantoaxial fixation group and new type internal fixation group could reduce the ROM of C_(1~2) effectively than normal group and fracture group.The atlantoaxial internal fixation group and the new internal fixation group have greaterstress at the root of the screw and the connecting rod area,and the internal fixation bears greater stress during flexion.Conclusion C_(1) posterior arch screws plus C_(2) laminar screws system and C_(1) pedicle screw plus C_(2) pedicle screw system could controlthe ROM of atlantoaxis in all directions.The stress is more focused on the basic of the screws and the rods.