【作者】 王永福；

【导师】 张宏其；

【作者基本信息】 中南大学 ， 外科学， 2010， 博士

【摘要】 背景特发性脊柱侧凸的前路手术因矫形力直接作用于椎体、能提供强大的去旋转力,且融合节段少,有利于保留运动节段,适用于胸腰段或腰段脊柱侧凸,但存在假关节形成和内固定失败等并发症发生率较高的问题。随着内固定器械的革新及三维矫形理论的发展,椎弓根钉技术被广泛运用于侧凸矫形。相对于椎板钩及椎弓根钩,椎弓根螺钉通过前、中、后三柱,能提供更佳矫形力和显著的远端向中线矫正能力,节省融合节段。近年来全节段椎弓根螺钉矫形术被广泛用于胸腰段和腰段脊柱侧凸,取得了很好的疗效。因此目前胸腰段或腰段特发性脊柱侧凸在手术入路、融合节段的选择等问题上仍存在争议。有限元法作为一种数字模拟技术,已成为脊柱侧凸生物力学研究的热点。目前侧凸矫形的有限元模拟多集中在后路CD手术,前路手术或前后路手术对比的有限元模拟报道甚少。目的利用相关的CAE软件(Mimics和HyperMesh)建立基于CT图像的Lenke5型青少年特发性脊柱侧凸(AIS)的三维有限元模型。对模型的材料性质和皮质骨厚度的参数进行优化和模型的有效性进行验证后,再分别模拟Lenke5型AIS的前、后路手术矫形操作,比较不同手术入路的各种不同矫形方案的矫形效果,以及脊椎的应力、应变水平。方法1三维有限元模型的建立对1例女性Lenke5型青少年特发性脊柱侧弯患者,行仰卧位胸1至尾骨的CT扫描,将获得的CT图像导入医学建模软件Mimics10.0,通过一系列模块的处理后获得医学三维仿真模型,对模型进行几何清理。再将清理后的医学仿真模型导入有限元分析软件HyperMesh 8.0,利用软件的前处理工具进行网格划分,定义接触与连接,参照文献定义材质属性,添加椎间盘、各种韧带等,建立Lenke5型AIS患者的三维非线性有限元模型。2模型的参数优化和有效性验证对建立的有限元模型赋予不同材料属性和皮质骨厚度,模拟左、右侧屈试验,并与临床试验对照,应用SPSS软件按照正交实验设计进行四因素三水平分析,再用直观分析法对正交实验结果进行分析,实现模型材料性质和皮质骨厚度的参数优化。将所建立的有限元模型与原始卧位X线片比较,验证模型的几何外形。通过模拟临床卧位侧屈实验,参照文献在各脊椎节段施加载荷模拟站立,然后提取脊柱的不同节段,将约束加载得到的结果与各自参照的体外实验结果进行比较等,验证模型的有效性。3不同矫形方案的手术操作模拟在建立的脊柱侧凸有限元模型上构建前、后路手术的钉棒系统有限元模型,根据临床前、后路手术融合节段的不同,设置前路短节段融合、端-端融合和后路下固定椎为下端椎或稳定椎的四种不同矫形方案,模拟各种方案90°去旋转和压缩序贯矫形操作,比较不同方案的位移、冠状面及矢状面成角变化、旋转度变化,手术矫形后脊椎的应力水平。结果1成功建立了包括全部胸腰椎(T1～L5)、骶尾骨、完整胸廓、椎间盘、脊柱所有韧带及关节的特发性脊柱侧弯有限元模型,采用4种单元类型,14种材料性质；共包含节点数170784,四面体单元633668个,壳单元126636个,线缆单元680个和杆单元132个,建立的模型与该患者的X线的脊柱几何形态相似性非常好。2利用材料参数和皮质骨厚度优化后的模型模拟临床侧屈实验、站立实验,其生物力学行为和临床基本符合。分段加载实验验证的结果和与各自参照的体外生物力学实验结果基本吻合。3四种不同方案有限元模拟矫形最终的腰椎侧凸Cobb角分别为：22°、23°、26°、26°,胸腰段和腰椎矢状面生理曲度得到维持。前路短节段融合的脊椎应力水平明显较高。而在下端固定椎止于下端椎时,前路单棒固定与后路全节段椎弓根钉固定获得的顶椎旋转的矫正度分别为41.68°和37.79°。结论1基于个体化的CT图像,利用相关计算机软件建立的Lenke5型AIS的三维有限元模型形态逼真,真实反映了脊柱的形态学特征。2进行参数优化的有限元模型顺利通过有效性验证,真实反映了实际个体脊柱的生物力学特性。3首次成功实现了前、后路手术的90°去旋转和压缩矫形的序贯有限元模拟。有限元模拟为Lenke5型AIS矫形手术方案的优化和治疗效果的评价提供了理论依据。4对柔韧性较差的Lenke5型AIS,前后路手术均可获得满意的矫形效果,但前路短节段融合脊椎应力水平明显较高。在远端融合止于下端椎时,后路全椎弓根螺钉固定可取得与前路单棒固定相同的矫正效果。更多还原

【Abstract】 BackgroundsAnterior instrumentation surgery had been a good choice of treatment for the thoracolumbar and lumbar AIS,because anterior procedures may give greater correction through a direct manipulation of the vertebral body and good coronal correction and apical derotation can be obtained. Furthermore, anterior correction has the potential advantage of preserving additional motion segments by instrumentation of fewer vertebrae.However, complications such as high pseudarthrosis rate and implant failure still have not been resolved.. With the rapid development of internal fixators and 3D correction theory, posterior segmental pedicle screw instrumentation have been widely used in the surgical treatment of thoracolumbar and lumbar AIS. Compared to hook or wire approach, the pedicle screws get a grip with 3-column purchase and offers an enhanced 3-dimensional deformity correction and preservation of motion segments by reducing the extent of fusion. Excellent Correction of thoracolumbar and lumbar AIS was achieved with Segmental pedicle screw instrumentation. For the discussions above, issues of surgical approaches, extent of fusion level of thoracolumbar and lumbar AIS still have been the subject of some debate so far.As a new technique of digital simulation, finite element method has been a hot topic of scoliosis biomechanics recently. Finite element simulation of correction procedure had been focused on posterior CD surgery, few simulation of anterior correction or comparison of posterior and anterior correction was reported.Objectives Using a series of Related CAE software, To develop three dimensional finite element models of the Lenke5 Adolescent Idiopathic scoliotic spine based on quantitative computed tomography scans. After parameters optimization and Validation, the three-dimensional finite element model was used to simulate anterior and posterior correction, investigate the corrective effect of different surgical protocols, and analyse biomechanical stress and strain of the scoliotic spine.Methods1. Development of the three dimensional Finite element model Obtain CT digital data from T1 to caudal end of a female Lenke5 AIS Patient in the supine position.ImPort The CT digital information into the computer software Mimics, and rebuild a 3-Dimension simulation model with surface mesh by the following steps:orientation, division, erase, draw, erode, dilate, boolen operation, define Polyline,remesh. ImPort the simulation model into the computer software HyperMesh 8.0.Remesh the model From surface mesh into body mesh. Define the surface on different vertebrae, ribs and intervertebral discs. Refer to the literature, present the spine with relative material parameters and append the parenchyma such as ligaments and disc.2. Parameters optimization and model validation For parameter optimization, the Emodule of the intervertebral disks and the thickness of the cortices wer emodified based on the clinical bending test. Orthogonal experiment designed by the computer software SPSS is performed and nine groups of experiment plans with three levels and four factors, L 9(34) are adopted to optimize experimental factors. Then data from orthogonal test was treated by Intuitive analysis. For model validation, geometric shape was compared between supine X-ray films and finite element simulation. Bending test and Erect test were simulated. Different segments were extracted from the whole finite element model, and were respectively constrained and loaded referring to historical specimen biomechanical in vitro studies.3. Simulation of corrective surgery of different surgical protocols The finite element model of internal fixation devices was developed According to different surgical approach and fusion level, we designed and simulated four surgical strategy with the model of scoliosis. All the main steps including derotation and compression of each strategy were simulated. The stress variation of the spine, different vertebral displacement, as well as rotation and angle changes were compared among the protocols of different surgical approach and fusion level. Results1 A Three-dimensional Finite Element Model of the Lenke5 Adolescent Idiopathic scoliotic spine including T1—T12, L1—L5 and sacrum has been developed based on quantitative computed tomography scans. Using 4 mesh types and 14 kinds of material parameters, the model consists of 170784 nodes,633668 tetrahedron elements,126636 shell elements,680 cable elements and 132 rod elements. The three dimensional Finite Element Model of the scoliotic spine showed good geometric similarity with supine X-ray.2 Biomachanical bahaviour in simulating Bending test and Erect test was consistentwith clinical practice. The segment simulation results of subsection validation were similar to their references respectively.3 Coronary lumbar deformity was corrected to 22°,23°,26°and 26°espectively for all four surgical protocols used in the simulation., physiological saggital configuration was maintained, but higher stress in the anterior short fusion group. A similar apical rotational correction was recorded,41.68°nd 37.79°, between anterior single-rod corrction and posterior segmental pedicle screw fixation when instrumented to the lower end vertabra. Conclusions1 Based on CT images, the three-dimensional finite element model of Lenke5 idiopathic scoliosis were well established and validated2 The validity of the optimized finite element model was verified successfully, so it was proved to be able to represent the biomechanical behaviour of the actual scoliotic spine.3 The model was successfully used to simulate correction procedures including 90°derotation and compression for the first time. Finite element method may provide theoretical basis and guidance for the operation planning and efficacy evaluation.4 Simulation of all four surgical protocols obtained excellent correction, but short segment fusion maybe not a good choice because of higher stress. Similar correction can be achieved with segmental pedicle screw fixation compared to anterior single-rod corrction when instrumented to the lower vertabra.更多还原