一种新型后路寰枢椎固定系统的设计及有限元分析

Design and finite element analysis of a new posterior atlantoaxial fixation system

中文关键词:  寰枢椎失稳  内固定  有限元分析  生物力学

英文关键词:Atlantoaxial instability  Internal fixation  Finite element analysis  Biomechanics

中文摘要:

  【摘要】 目的：基于影像学参数设计一种新型后路寰枢椎固定系统，运用有限元方法评价该系统固定的生物力学稳定性。方法：运用医学影像存档与通信系统测量工具对后弓发育正常且结构完整的成人寰椎CT进行解剖学参数测量，依据寰椎影像学测量参数设计出一种符合寰椎解剖结构的新型后路寰枢椎固定系统。对1例健康志愿者上颈椎进行薄层CT扫描，对其CT图片数字图像处理，进行网格划分、设置材料属性及载荷与边界条件，建立正常上颈椎有限元模型（正常模型），并与已发表文献对比验证其有效性；在正常模型基础上通过修改材料属性及去除横韧带构建寰枢椎失稳有限元模型（失稳模型），加载新型后路寰枢椎内固定系统至失稳模型上建立新型后路寰枢椎固定系统固定有限元模型（新型模型）；运用Abaqus 2019对新型模型施加扭矩为1.5N·m，对该模型C0-C3节段屈伸、侧屈、旋转活动度进行计算分析，并与寰枢椎椎弓根螺钉固定有限元模型（椎弓根螺钉模型）对比。结果：设计出的新型后路寰枢椎固定系统符合寰椎的解剖结构，此系统由新型寰椎后弓钢板、连接棒及枢椎椎弓根螺钉组成。与以往文献对比，建立的正常模型验证有效。新型模型与正常模型相比减少了屈伸95.3%、侧屈92.6%、旋转99.0%的活动度，在各状态明显减少置入节段（C1-2）的活动度。有限元分析得出新型模型在屈伸、侧屈、旋转状态下C1-2节段活动度分别为1.10°、0.49°、0.59°，与椎弓根螺钉模型活动度相近；新型模型C2/3椎间盘最大应力在前屈、后伸、左侧屈、右侧屈、左旋转、右旋转状态下分别为3.71MPa、5.84MPa、3.09MPa、3.43MPa、2.65MPa、3.59MPa，与正常模型最大应力一致；新型后路寰枢椎固定系统固定的应力主要集中于枢椎椎弓根螺钉根部及连接棒。结论：新型后路寰枢椎固定系统固定具有良好的生物力学稳定性，可作为寰枢椎失稳内固定的补充方式。

英文摘要:

  【Abstract】 Objectives: A new posterior atlantoaxial fixation system was designed based on imaging parameters, and its biomechanical stability was evaluated by finite element analysis. Methods: Anatomy parameters for atlas CT were measured by image archiving and communication systems measuring tool, then a new posterior atlantoaxial fixation system conformed to atlas anatomical structure was designed based on the parameters. CT thin layer scan for upper cervical spine of healthy volunteers was performed, and digital image was processed for CT diagram, then mesh division was carried out and material property, loading and boundary conditions were set to establish the normal upper cervical spine finite element model(normal model), and the effectiveness was verified by comparing with the published literature. The atlantoaxial instability finite element model(instability model) was established based on normal model by modifying the material property and removing transverse ligament. Then new posterior atlantoaxial fixation system was loaded onto the instability model to establish the new posterior atlantoaxial fixation system fixed finite element model(new model). 1.5N·m torque was applied on the new model by Abaqus 2019, and the range of motion(ROM) for flexion and extension, lateral bending and axial rotation of C0-C3 segment was calculated, then comparison with atlantoaxial pedicle screw fixed finite element model(pedicle screw model) was performed. Results: The new posterior atlantoaxial fixation system conformed to the atlas anatomical structure, and the system was formed by new type of posterior atlas arch plate, connecting rod and axial pedicle screw. Compared with the published literature, the normal model we established was effective. Compared with the normal model, the new model decreased ROM by 95.3% in flexion and extension, 92.6% in lateral bending and 99.0% in axial rotation. The ROM of implanting segment (C1-2) decreased obviously under each status. Through finite element analysis, under flexion and extension, lateral bending and axial rotation, the ROM of C1-2 segment for new model were 1.10°, 0.49° and 0.59°, which were closed to the ROM of pedicle screw model. Under flexion, extension, left bending, right bending, left rotation and right rotation, the maximum stress of C2/3 intervertebral disc for new model were 3.71MPa, 5.84MPa, 3.09MPa, 3.43MPa, 2.65MPa and 3.59MPa, which were in accordance with the normal model. The stress of new posterior atlantoaxial fixation system mainly concentrated on the root of the axial pedicle screw and the connecting rod. Conclusions: The new posterior atlantoaxial fixation system owned good biomechanical stability and can be used as a supplement for atlantoaxial instability internal fixation.