腰椎弓根延长术对关节突关节力学影响的有限元分析

Biomechanical Influence of Pedicle⁃Lengthening Osteotomy on Lumbar Facet Joints and Finite Element Analysis.

目的探讨腰椎椎弓根延长术对关节突关节生物力学的影响,分析关节突关节发生异常应力变化前椎弓根的最大延长长度。方法取1名腰椎健康志愿者的CT图像,建立L3~L5正常腰椎的有限元模型,在其基础上构建L4椎弓根延长术后模型,L3椎体上表面均施加垂直于水平面400 N的压力,模拟正常人腰椎所承载重力,固定支撑L5椎体下表面。通过建立不同椎弓根延长长度的术后模型,分析在力矩为5 Nm时L3/4的应力分布云图及相应的应力-应变曲线,得出相同力矩下L3/4关节突关节应力极值随椎弓根延长长度变化的曲线图。结果施加5 Nm力矩下,L3/4小关节左旋工况下应力先随延长长度的增加而增加,在椎弓根延长3.8 mm时达到最大,为9.133 MPa;随后,L3/4小关节的应力骤然减小,曲线发生不可逆变化。结论力矩加载为5 Nm时腰椎弓根延长术的最大延长距离为3.8 mm,临床应结合腰椎管狭窄的严重程度,选择减压所需的延长长度,取得更好的手术疗效。

Objective To investigate the biomechanical influence of lumbar pedicle⁃lengthening osteotomy on lumbar facet joints,and to analyze the maximum extension length of the pedicle before the abnormal stress changes in the facet joint.Methods CT images of a healthy lumbar spine volunteer were taken to establish the finite element model of normal L3⁃L5 lumbar spine.Based on the normal lumbar spine model,the L4 pedicle extension postoperative model was established,and pressure was applied to the upper surface of L3 vertebra at 400 N perpendicular to the horizontal plane,simulating the gravity of normal lumbar vertebrae.The lower surface of L5 vertebrae was fixed.By establishing postoperative models with different lengthening lengths,the stress distribution nephogram of L3/4 and corresponding stress⁃strain curves were analyzed respectively when the torque was 5 Nm,and the curves of stress extremum of the articular process at L3/4 changing with the length of pedicle lengthening were obtained.Results In pedicle lengthening,when the operative segment was L4 and 5 Nm torque was applied,the stress of the L3/4 joint increased with the increase of the lengthening length,and the maximum stress was 9.133 MPa when the pedicle was lengthened 3.8 mm.Subsequently,the stress of the L3/4 facet joint decreases,and the corresponding stress⁃strain curve and the curve of the stress extreme value of the facet joint change abnormally with the extension length.Conclusion The maximum extension distance of lumbar pedicle lengthening was 3.8 mm when the torque loading was 5 Nm.The length of extension required for decompression should still be selected clinically based on the severity of lumbar spinal stenosis to achieve better surgical outcomes.