椎间孔镜术中行关节突成形有限元模型的建立及生物力学分析

Establishment of finite element model and biomechanical analysis of facet joint arthroplasty in transforaminal endoscopic spinal surgery

目的建立L_(1)-S_(1)节段有限元模型,分析椎间孔镜术中行关节突成形对腰椎生物力学的影响。方法取1位无既往腰椎病史志愿者的腰椎三维CT数据,获得正常L_(1)-S_(1)节段有限元模型并验证模型的有效性。在该模型的基础上,依据椎间孔镜术中关节突成形情况,建立L_(4-5)椎间盘突出模型(M1)、5 mm关节突成形模型(M2)和7.5 mm关节突成形模型(M3)。在左旋、右旋、左侧曲、右侧曲、前屈及后伸工况下,分析三组模型的L 4椎体位移程度,L_(3-4)、L_(4-5)及L 5-S_(1)椎间盘内压力变化和L_(4-5)关节突关节的应力变化。结果本研究建立的有限元模型有效。L_(4-5)左侧关节突关节在前屈工况下,M2和M3模型较M1模型应力下降;左侧屈工况下,M2和M3模型应力大于M1模型。L_(4-5)右侧关节突关节在前屈工况下,M2和M3模型较M1模型应力上升;左旋工况下,M3模型应力大于M2,M2模型应力大于M1;后伸工况下,M3模型L_(4-5)间盘应力大于M1和M2模型;右旋工况下,M3模型该椎间盘应力大于M2,M2模型该椎间盘应力大于M1。结论与5 mm的关节突成形相比,7.5 mm的关节突成形在左侧屈或左旋时会增大关节突关节和节段椎间盘的应力,可导致手术节段椎间盘的退变,但不会引起邻近节段的退变。

Objective To establish a finite element(FE)model of L_(1)-S_(1)segment to analyze the effect of facetoplasty on lumbar biomechanics during transforaminal endoscopic surgery.Methods CT data of the lumbar spine were obtained from a volunteer without lumbar history.A FE model of the normal L_(1)-S_(1)segment was created and the validity was verified.L_(4-5)disc herniation model(M1),5 mm facetoplasty model(M2)and 7.5 mm facetoplasty model(M3)were established.The degree of L 4 vertebral displacement,pressure changes in the L_(3-4),L_(4-5),and L 5-S_(1)intervertebral discs,and stress changes in the L_(4-5)facet joints of the three groups of models were analyzed under six conditions.Results The finite element model developed in this study was effective.The M2 and M3 models of the left synchondral joint of L_(4-5)showed a decrease in stress compared to the M1 model in forward flexion;the M2 and M3 models displayed a greater stress than the M1 model in left lateral flexion;the M2 and M3 models of the right synchondral joint of L_(4-5)showed an increase in their stress compared to the M1 model in forward flexion;the M3 model presented a higher stress than the M2 model,and the M2 model showed a higher stress than the M1 model in left rotation;in posterior extension,the M3 model of the disc of L_(4-5)demonstrated a greater stress than the M2 model;in right rotation,the M3 model of that disc showed a greater stress than the M2 model and the M2 model of that disc displayed a greater stress than the M1 model.The L_(4-5)intervertebral disc stress was greater in the M3 model than in the M1 and M2 models in the posterior extension condition;in the right rotation condition,the disc stress was greater in the M3 model than in the M2 model,and in the M2 model than in the M1 model.Conclusion In this study,the 7.5 mm facet arthroplasty is found to increase the stress of facet joints and segmental intervertebral discs in left flexion or left rotation,which may lead to disc degeneration at the operated level but does not cause degeneration at the adjacent level.