刚性固定和动态固定治疗腰椎峡部裂三维有限元分析

Three-dimensional finite element analysis of rigid fixation and dynamic fixation for treatment of lumbar spondylolysis

目的采用三维有限元分析方法探讨刚性固定和动态固定在腰椎峡部裂治疗中的稳定性、邻近节段退变以及内固定断裂风险问题。方法选取3例L_(4)椎体双侧峡部裂患者,利用Mimics、Solidworks、HyperMesh等软件构建L4椎体双侧峡部裂骨骼及内固定有限元模型,分别设定刚性固定、动态固定、未固定3种模型,并对模型施加500 N应力和10 N·m扭力弯矩,模拟腰椎在垂直、前屈、后伸、旋转、侧弯5种运动状态,收集腰椎位移、L_(3~4)椎间盘应力、内固定应力数据。结果相同运动状态下,腰椎位移在垂直、侧屈、旋转状态时动态固定大于刚性固定,但差异均无统计学意义(P>0.05),前屈、后伸状态动态下固定大于刚性固定(P<0.05)。邻近节段L_(3~4)椎间盘应力比较:垂直状态下刚性固定与动态固定比较差异无统计学意义(P>0.05);前屈、后伸、侧屈、旋转状态下刚性固定大于动态固定(P<0.05)。内固定应力比较:垂直、侧屈、旋转状态下刚性固定均大于动态固定(P<0.05),前屈状态下动态固定与刚性固定比较差异无统计学意义(P>0.05),后伸状态动态下固定大于刚性固定(P<0.05)。结论动态固定节段应力能够达到与刚性固定相似的稳定性;动态固定对邻近节段影响明显减小,可以减少邻椎病的发生;除后伸状态外,断裂风险动态固定均低于刚性固定。

Objective To investigate the stablity,adjacent segment degeneration and the fracture risk of internal fixation of rigid fixation and dynamic fixation for treatment of lumbar spondylolysis by using three-dimensional finite element method.Methods Three patients with L4 bilateral lumbar spondylolysis were selected.Mimics,Solidworks,HyperMesh and other softwares were used to construct L_(4) bilateral lumbar spondylolysis skeleton and internal fixation finite element model,three kinds of models with rigid fixation,dynamic fixation,and non-fixation were set,respectively,and 500 N stress and 10 N·m torque were applied to the model to simulate the five motion states of the vertical,anterior flexion,posterior extension,rotation,lateral bending of the lumbar spine,the data of lumbar spine displacement,L_(3~4) intervertebral disc stress and internal fixation stress were collected.Results Under the same lumbar motion states,the lumbar spine displacement with the vertical,lateral flexion,rotation in the dynamic fixation were longer than those of rigid fixation,while there were no statistical differences(P>0.05);under the states of anterior flexion,posterior extension,dynamic fixation were longer than those of rigid fixation(P<0.05).The stress comparison of adjacent segment L_(3~4) intervertebral disc:there was no difference under the vertical state between the rigid fixation and dynamic fixation(P>0.05),and the rigid fixation was bigger than the dynamic fixation under the states of anterior flexion,posterior extension,lateral flexion and rotation(P<0.05).The stress comparison of internal fixation:under the states of the vertical,lateral flexion and rotation,the rigid fixation were all bigger than those of dynamic fixation(P<0.05),and there was no difference under anterior flexion state between dynamic fixation and rigid fixation(P>0.05),the dynamic fixation was bigger than rigid fixation under the state of posterior extension(P<0.05).Conclusions Dynamic fixation segment stress can reach similar stability to rigid fixation,the influence of dynamic fixation on adjacent segments is significantly reduced,which can reduce the occurrence of adjacent vertebral disease;except for the state of posterior extension,the fracture risk of dynamic fixation is lower than that of rigid fixation.