目的 探究颈椎内镜下不同范围小关节切除对颈椎节段稳定性的影响，为临床手术提供生物力学理论基础。方法 基于CT数据建立颈椎C5-6正常有限元模型，并模拟颈椎内镜手术操作获得不同范围(0、25％、50％、75％、100％)单侧小关节切除椎板开窗模型(模型1～5)，分析比较各组模型节段活动度(range of motion，ROM)及椎间盘von Mises应力情况。结果 除前屈工况外，模型1、2较正常模型各方向下ROM及椎间盘von Mises应力改变不明显，模型3较正常模型各方向下ROM及椎间盘von Mises应力出现较为明显增加，前屈、后伸、左侧弯、右侧弯、左旋转及右旋转时 ROM 分别增加 27％、4％、3％、13％、5％、16％，von Mises 应力分别增加 32％、4％、2％、5％、9％、5％。模型4、5较正常模型各方向下ROM及椎间盘von Mises应力增加显著，模型4的ROM分别增加27％、14％、6％、24％、7％、167％，von Mises 应力分别增加 33％、13％、3％、32％、10％、130％;模型 5 的 ROM 分别增加 27％、17％、6％、25％、7％、167％，von Mises应力分别增加33％、29％、8％、33％、12％、138％。结论 随着单侧小关节切除范围的增加，颈椎节段ROM和椎间盘von Mises应力极值逐渐增加。当单侧小关节切除超过1/2时，颈椎出现较大的ROM增加及应力改变。临床手术中应尽量保留1/2以上颈椎小关节，避免医源性失稳。
Effects of Unilateral Graded Facetectomy of Facet Joints under Endoscope on Stability of Cervical Spine
Objective To investigate the effect of facet joint resection at different ranges under endoscopy on the stability of the cervical spine and provide a biomechanical theoretical basis for clinical surgery.Methods A normal finite element model of the cervical spine C5-6 was established based on CT data,and unilateral facetectomy models with different ranges(0,25％,50％,75％,and 100％)of laminectomy were obtained(Models 1-5)by simulating cervical endoscopic surgery.The ranges of motion(ROMs)of C5-6 and the von Mises stresses of the discs for the models in each group were compared and analyzed.Results Except for flexion,Models 1 and 2 showed insignificant changes in ROMs and disc von Mises stresses in each direction compared with those of the normal model.Model 3 showed a noticeable increase in ROMs and disc von Mises stresses in each direction compared with those of the normal model:ROMs under flexion,extension,left lateral bending,right lateral bending,left rotation,and right rotation increased by 27％,4％,3％,13％,5％,and 16％,respectively,and von Mises stresses increased by 32％,4％,2％,5％,9％,and 5％,respectively.Models 4 and 5 exhibited a significant increase in the ROMs and disc von Mises stresses in each direction compared to the normal model.For Model 4,ROMs were increased by 27％,14％,6％,24％,7％,167％,and von Mises stresses were increased by 33％,13％,3％,32％,10％,130％.For Model 5,ROMs were increased by 27％,17％,6％,25％,7％,167％,and von Mises stresses were increased by 33％,29％,8％,33％,12％,138％.Conclusions As the range of unilateral facetectomy increased,cervical ROM and disc von Mises stress extremum gradually increased.The cervical spine shows a significant ROM increase and stress changes when facet joint resection on one side exceeds 1/2.More than 1/2 of the facet joint should be preserved during surgery to avoid medical instability.
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