腰椎单侧椎弓根螺钉固定的三维有限元分析

Three-dimensional finite element analyses of unilateral pedicle screws fixation in lumbar spine

中文关键词:  腰椎  有限元模型  椎弓根螺钉  单侧固定  椎间融合

英文关键词:Lumbar spine  Finite element model  Pedicle screw  Unilateral fixation  Lumbar fusion

中文摘要:

  【摘要】　目的：建立人正常L3~L5节段三维有限元模型，分析腰椎单侧椎弓根螺钉固定融合的生物力学特性。方法：基于人正常L3～L5节段的CT扫描数据，利用Geomagic Studio 9.0、Simpleware　2.0、Abaqus 6.7软件建立人正常L3～L5三维有限元模型（INT），并在此基础上分别建立L4/5单侧椎弓根螺钉内固定加后外侧植骨融合模型（M1）、单侧椎弓根螺钉内固定加单枚融合器置入模型（M2）及双侧椎弓根螺钉内固定加单枚融合器置入模型（M3）。在L3上表面施加500N预载荷，再施加10N·m的力矩模拟腰椎前屈、后伸、侧屈及旋转等生理活动，观察不同工况下L4-L5节段角位移、椎弓根螺钉及融合器应力分布情况。结果：各工况下M1、M2、M3角位移均较INT减少，M3减少最明显；除右屈和后伸外，其他工况下M2与M3的角位移减少程度相当，而M1在左、右侧屈及左、右旋转时稳定性较差。M1的螺钉应力峰值明显高于M2和M3，尤以左屈及后伸载荷时螺钉应力峰值最大，M2螺钉应力峰值高于M3，M2椎间融合器的应力峰值在各种工况下均高于M3。结论：单侧椎弓根螺钉固定不能很好地控制侧屈和旋转载荷，椎弓根螺钉承受较大的应力；附加单枚融合器置入可以重建融合节段的稳定性，明显减少螺钉的应力。

英文摘要:

  【Abstract】　Objective：To construct a normal L3-L5 spinal segment model by using finite element method and investigate the biomechanical characteristics of unilateral pedicle screws fixation.Method：A three-dimensional finite element model of an intact L3-L5 segment was constructed by using computed tomography scans of a healthy male.The commercially available finite element program Geomagic Studio 9.0，Simpleware　2.0 and Abaqus 6.7 were applied to model.Based on the intact L3-L5 model（INT），new models were generated by simulating unilateral pedicle screws fixation and posterolateral fusion model（M1），unilateral pedicle screws fixation with a single cage insertion model（M2），and bilateral pedicle screws fixation with a single cage insertion model（M3）.500N preload was added on the superior surface of the L3 vertebral body，followed by load of 10N·m torque to simulate L4/5 flexion-extension，lateral bending and axial rotation，the L4/5 angular variation and stress distribution in pedicle screw and cage under different load were documented.Result：The angular variation in M1，M2，and M3 decreased significantly compared with normal，the angular variation in M3 showed similar with that in M2 under all direction except right lateral bending and extension，and M1 showed less stability under lateral bending and axial rotation.The pedicle peak stress in M1 was markedly higher than that in M2 and M3，especially high on left lateral bending and extension.The pedicle peak stress in M2 was markedly higher than that in M3，and the cage peak stress in M2 was higher than that in M3 on all direction.Conclusion：Unilateral pedicle screws fixation cannot provide sufficient stability in lateral bending and axial rotation，pedicle screws endure more stress.Unilateral pedicle screws plus cage instrumentation can restore the stability as well as share the stress of pedicle screws.