棘突间融合装置联合椎体间融合对下腰椎稳定性影响的三维有限元研究

目的探讨棘突间融合装置联合椎体间融合时对下腰椎稳定性的影响。方法在健康成年男性L4-5节段CT扫描图像的基础上,利用软件Simpleware4.2、GeomagicStudio10.0及Abaqus10.0建立L4-5有限元模型(INTACT)。验证模型有效性后建立单侧椎弓根螺钉固定联合椎间融合(UPS)、双侧椎弓根螺钉/钛棒固定联合椎间融合(BPS)和棘突间融合装置固定联合椎间融合(ISF)三种手术模型。对各模型实加500N预载荷的同时以2N.m为间隔,自2N.m开始逐级累加至最大10N.m,观测其应力分布、相邻节段的角位移。结果各工况下三种手术组的角位移(ROM)均较INTACT组明显减小,减小的程度BPS最高,而ISF除右侧弯方向上均高于UPS;三种手术组范氏应力云图显示,BPS组与ISF组相似,UPS组存在较高的应力集中,范式应力峰值无论在椎间融合器还是在内固定器械上由大到小依次均为:UPS>ISF>BPS。结论 ISF联合椎间融合能够为下腰椎脊柱重建提供适度且足够的稳定性,因而可以为下腰椎退行性疾病的治疗提供一种新内固定选择。

A Study on the Biomechanical Stability Offered by Interspinous Fastener Combined with Interbody Fusion for Lower Lumbar Spine through Three-dimensional Finite Element Analysis

Objective To investigate the biomechanical stability offered by interspinous fastener for the single-level lower lumbar segment through finite elemental analysis. Method In this study, a validated 3-dimensioned finite element model （L4-5） was established by the software on the basis of computed tomography scanning images. The intact model was modi- fied to the following tested states： （1） interspinous fused device instrumentation combined with interbody fusion （ISF）, （2） unilateral pedicle screw/rod fixation combined with interbody fusion （UPS）, （3） bilateral pedicle screw/rod fixation combined with interbody fusion （BPS）. Through placing the loadings on all the models （including intact model）, the segmental angular motions and the Von Mises stressing distribution graph were acquired. Result All instrumentation variances reduced angular range of motion （ROM） significantly from normal in all directions of loading. ISF was most effective in limiting flexion and extension and less effective in reducing lateral bending and axial rotation. On the whole, ISF offered stability that was statistically superior to unilateral pedicle screw/rod fixation, but was inferior to bilateral ped- icle screw/rod fixation. Conclusion ISF combined with interbody fusion could provide moderate and adequate stability for the fused intersegments. As such, it creates an alternative to more conventional means of fixation such as pedicle screws, with more immobilization and less potential risk.