腰椎滑脱不同融合术式的三维有限元研究

A study of dieffrent lumbar spondylolisthesis fusion surgeries based on three-dimensional Finite Element analysis

目的通过建立腰椎后路椎间(PLIF)和后外侧(PLF)两种融合术的三维有限元模型,比较并判断融合后融合节段的稳定性以椎弓根螺钉和融合器上的应力及椎体位移有无显著性差异。方法利用健康志愿者L1～L5CT扫描的DICOM数据,通过计算机软件重建腰椎模型,进行有限单元网格划分,在腰4/腰5间置入椎弓根钉内固定系统,然后分别在椎间置入融合器生成腰椎后路椎间融合术式三维有限元模型,在横突间植入自体骨生成腰椎后外侧融合术式三维有限元模型。通过对模型进行轴向加压、前屈,后伸、侧弯及轴向扭转五种加载方法进行实验。结果建立L4/L5腰椎滑脱模型及后路腰椎椎间融合及腰椎后外侧融合的有限元模型,①观察对模型分别施加轴向压缩、侧弯、前屈、后伸、旋转载荷,PLF应力多集中在椎弓根钉与钛棒连接处、PLIF内固定系统应力为Cage所分散,未见明显应力集中;②对比在五种载荷下两种不同内固定位移PLIF组均小于PLF,P<0.05。结论①建立了L4/L5滑脱不同后路融合术式的三维有限元模型。②在前屈、后伸、压缩、侧弯及扭转载荷下,相比PLF,PLIF位移更小,证实椎体间融合的稳定性优于和椎弓根螺钉内固定加后外侧植骨融合;③PLF应力多集中在椎弓根钉与钛棒连接处、PLIF内固定系统应力为Cage所分散,未见明显应力集中。

Objective To establish posterior lumbar interbody fusion （PLIF） and postero- lateral fusion （PLF） of two operation methods of three-dimensional finite element models, and to compare and determine whether or not there is significant difference between the two models on the basis of stability, stress and displacement. Methods we collect DICOM data which were obtained by CT scanning a healthy volunteer＇s L1- L5 and USing these data through computer software to reconstruct the spine model, and three dimensional finite element models of the L4, 5 spondylolysis, vertebral pedicle screw and cage were then established. At last, the posterior fusion models of different approaches were prepared according to the clinical operation types. The models of posterior fusion surgery of the lumbar spondylolysis, including posterolaterial bone graft and cage combined with pedicle screw system, were reconstructed. After setting the boundary and loading the burden, the lumbar spine＇s range of motion and stress distribution in different institutions such as axial compression, anterior flexion, posterior extension, bending and axial rotating were recorded. Results Computer technology was employed to deal with the image from CT scan with CAD software and accurately set up L4/L5 spondylolisthesis model, and posterior lumbar interbody fusion and posterior lateral fusion finite element model, and more refined results were obtained according to materials properties designation of finite element making internal structure of spine （include 94725 tetrahedron, 2 1 1 3 9 nodes ） , observing the loading such as axial compression, anterior flexion, posterior extension, bending and axial rotating： （1） posterior lateral fusion stress concentration lies in the connection between vertebral pedicle screw and titanium stick, while posterior lumbar interbody fusion stress were distributed by cage, and no apparent stress concentration in internal fixation; （2） in comparison between two different internal fixed displacement in five loadings, PLIF is smaller than PLF, P 〈 0.05.