【作者】 林旻中；

【导师】 张宏其；

【作者基本信息】 中南大学 ， 临床医学， 2013， 博士

【摘要】 本课题应用计算机辅助工程(computer aided engineering, CAE)软件,建立了基于两个志愿病人CT图像的伴有骨盆矢状位失衡的特发性脊柱侧凸三维非线性有限元模型。分析了两个模型的生物力学结构,然后对优化模型进行有效性的验证。在这基础上,我们仿真模拟伴有骨盆矢状位失衡的特发性脊柱侧凸后路矫形手术,讨论选择不同下固定椎(lowest instrumented vertebra, LIV)的矫形效果差异以及脊椎的应力和应变水平变化。第一章伴骨盆矢状位失衡的特发性脊柱侧凸三维有限元模型的建立目的：应用CAE软件((Mimics和HyperMesh),建立基于志愿者CT图像的伴骨盆矢状位失衡的特发性脊柱侧凸三维非线性有限元模型两个。方法：选择1例17岁男性伴骨盆矢状位失衡的特发性脊柱侧凸志愿者和1例15岁男性伴骨盆矢状位失衡的特发性脊柱侧凸志愿者作为研究对象。均采取仰卧位,应用32排螺旋CT从T1上缘至尾骨以lmm间距进行连续扫描,获得Dicom格式CT图像分别为539张和544张。分别导入软件Mimics10.01,建立包括胸-腰-骸尾椎-胸廓和骨盆等结构的完整脊柱侧凸三维几何模型。对模型进行几何清理,然后分别导入有限元前处理软件HyperMesh10.0,划分出有限元实体网格,并添加椎间盘和韧带等结构单元,定义了接触和连接,生成完整的特发性脊柱侧凸三维有限元模型。结果：成功建立了两例包括全部胸腰椎(T1-L5)、骶尾骨、完整胸廓、椎间盘、脊柱所有韧带、小关节关节突及骨盆的伴骨盆水平失衡的特发性脊柱侧弯有限元模型,采用5种单元类型和14种材料性质；第一例模型(A志愿者)共包含节点数197195,六面体单元9633个,四面体单元578031,壳单元228273个,线缆单元5239个和杆单元1441个,总单元数821676个；第二例模型共包含节点数219162,六面体单元10559个,四面体单元601982,壳单元2330646个,线缆单元6528个和杆单元1320个,总单元数852133。建立的模型分别与两位患者的X线的脊柱几何形态相似性非常接近。结论：成功构建了两例基于CT图像数据的伴骨盆矢状位失衡的特发性脊柱侧凸三维有限元模型,模型均完整、逼真地还原了被模拟患者的脊柱形态。第二章伴骨盆矢状位失衡的特发性脊柱侧凸三维有限元模型的生物力学有限元分析和有效性验证目的：对初步建立的两个有限元模型进行参数优化,使模型的形态结构和材料属性均实现个体化,验证优化的三维有限元模型的有效性。探讨伴骨盆矢状位失衡的特发性脊柱侧凸椎间盘、小关节突关节、椎体等的应力的分布,为病变的发生、发展的生物力学机制提供可靠地依据。方法：对两个建立的三维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X线片对照,应用SPSS19.0软件按照正交实验设计进行三因素三水平分析,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,参照文献数据在脊椎各个节段施加载荷模拟站立形态,然后分段加载实验验证：在两个建立的模型中均各自提取T7-11、T11-L1以及L1-S1三个节段,分别参照历史同类体外(尸体)实验对有限元节段模型进行约束加载,并将加载结果与各自参照的体外实验结果进行比较,验证模型的有效性。在前屈、后伸、左侧弯、右侧弯四种工况下对模型进行加载,计算和分析脊柱的活动度、椎间盘、椎体及小关节关节突的应力分布。结果：各椎体中心位置以及矢状面、冠状面上各弯的角度,两个有限元模型与各自对应患者的仰卧位X线片之间均有很好的一致性；T7-11、T11-L1以及L1-S1三个节段各段有限元模型加载结果与各自参照的历史体外(尸体)实验结果基本吻合。两例三维有限元模型比正常腰椎的活动度要小,椎间盘应力分布趋向于椎间盘的四周,后伸运动时各椎间盘应力最大,侧弯顶点椎体容易出现应力集中的情况,在后伸工况下小关节关节突的应力集中最明显,尤其以侧凸顶点节段的小关节关节突影响最大。结论：几何外形及分段加载实验均验证了所建立的两例三维有限元模型的可靠性和有效性,为下一步生物力学模拟研究奠定了基础。伴骨盆矢状位失衡的特发性脊柱侧凸顶点容易出现应力集中,后伸运动可加重侧凸发展。第三章伴骨盆矢状位失衡的特发性脊柱侧凸后路三维矫形有限元分析目的：利用建立的两例伴骨盆矢状位失衡的特发性脊柱侧凸有限元模型,分别模拟后路三维矫形手术过程,并探讨研究选择不同下固定椎对矫形效果的影响。方法：应用建立的两例伴骨盆矢状位失衡的特发性脊柱侧凸有限元模型,均模拟后路全椎弓根螺钉固定三维矫形手术。具体约束加载过程如下：参照文献在T1-S1各椎节分别施加模拟自身重力和肌肉韧带因素的向下载荷,在固定节段凹侧模拟置入“椎弓根螺钉”,并放入“预弯”的矫形钛棒,在棒末端施加向凹侧的旋转力矩,使棒向凹侧旋转90°,模拟旋棒矫形操作；同时在顶椎区(A患者模型为T12-L3,B患者模型为T10-L2)固定螺钉施加10Nm的扭矩,模拟椎体的去旋转矫形。A患者模型的上固定椎选择T10,下固定椎分别选择L4、L5、S1；B患者模型的上固定椎选择T7,下固定椎分别选择L4、L5、S1。比较三种固定方案的矫形效果。结果：两例模型分别模拟的三种不同方案有限元模拟矫形最终的腰椎侧凸Cobb角已测。A患者模型三种方案分别为：25°、23。、20°,B患者模型三种方案分别为：29°、24°、21°。胸腰段和腰椎矢状面生理曲度得到维持。结论：1本研究成功实现了后路手术的90°去旋转操作和压缩撑开矫形过程的三维有限元模拟。有限元模拟为伴骨盆矢状位失衡的特发性脊柱侧凸矫形手术方案优化和治疗效果评估提供了足够的理论依据和精确的操作平台。2本研究中两例三维有限元模型的椎体序列恢复明显,脊柱外观通过矫形方案操作后基本变直,但也存在融合节段至S1后出现应力过大的问题,我们需进一步的模拟出保护S1螺钉的方案,适当的加载约束,这也是本课题需要进一步深入研究、有待解决的问题。3A患者的方案二和B患者的方案C为对应三维有限元模型模拟矫形手术后所取得的最佳方案,矫形效果最佳且对应的椎体应力较平均,能尽量短节段融合,保留一定的节段活动度。更多还原

【Abstract】 In this study, computer aided engineering (CAE) soft ware was used to establish two complete three-dimensional finite element models of idiopathic scoliosis with pelvic imbalance based on CT images, including all thoraco-lumbar-sacral vertebrae and thoracic cage. Then optimized two models parameters and validated the final models. On the basis, we simulated all main steps of posterior Cotrel-Dubousset (CD) technique correction surgery using these two IS finite element models. We simulated different correction strategies to explore the effect of investigating correction effectiveness with different lowest instrumented vertebra.Chapter One. Establishment of Three-dimensional Finite Element Models of Idiopathic Scoliosis with Pelvic ImbalanceObjective The CAE software was used to build three-dimensional finite element models of idiopathic scoliosis with pelvic imbalance based on CT images.Methods A17-year-old male and a15-year-old male idiopathic scoliosis patients were included as volunieer for current study. CT transverse scanning in supine position was done from T1to caudal end in lmm layer interval, to obtain539and549CT dicom images. All CT images were imported into Mimics10.01to form qualified IS three-dimensional geometric model after geometry clean, including all thoraco-lumbar-sacral vertebrae and thoracic cage, which was further delivered to HypherMesh10.0to build3D finite element IS model by mesh partition and quality control. A variety of material parameters were given to different mesh according to references.Results Two three-dimensional finite element models of idiopathic scoliosis with pelvic imbalance were built successfully, including all thoraco-lumbar-sacral spine and thoracic cage, using5mesh types and14kinds of material parameters, in consist of197195nodes,9633hexahedron elements,578031tetrahedron elements,228273shell elements,5239cable elements and1441rod elements in patient A model. Patient B model included219162nodes,10559hexahedron elements,601982tetrahedron elements,2330646shell elements,6528cable elements and1320rod elementsConclusions Two three-dimensional finite element models of IS with pelvic imbalance in details, were built successfully based on CT transverse scanning images. Chapter Two. Personalization of the mechanical property and validation of optimized finite element modelObjective To personalized the mechanical properties of finite element models of IS with pelvic imbalance built in chapter one, verify the validity of the optimized model.Methods The personalization of the mechanical properties is done using the flexible tests routinely done prior to the surgery-based on preoperative stereoradiography and flexibility test radiographs. And using the orthogonal experimental design analysis of three factors and three levels of disc material property to optimize the parameters, and then achieve the biomechanical property of the individual. Compared the models with standing posterior-anterior X-ray, overhang posterior-anterior X-ray and lateral flexion X-ray of supine posterior-anterior position. Chose T7-T11、T11-L1and L1-S1to compare with related results of biomechanics empirical study.Results Orthogonal experiment results showed that the best combinations, which minimized the difference of model and the actual, were dise property in the proximal thoracic segments is0.2, the thoracolumbar segments is1, and the lower lumbar segments is8. The activity of the two three-dimensional finite element models is smaller than the normal lumbar. Intervertebral disc stress distribution tended to intervertebral disc around, extension movement each intervertebral disc stress is maximum, apex vertebral prone to stress concentration, the extension under the condition of facet joint stress concentration of the obviously, especially in the facet joint effect of scoliosis vertex segment of the maximum.Conclusions The way using orthogonal experimental design analysis to optimize the parameters was feasible and necessary. The optimized model was more in line with the actual.Chapter Three. Three-dimensional Finite Element Simulation of Posterior Surgical Correction of idiopathic scoiliosis with pelvic imbalanceObjective To simulate posterior correction surgery using finite element models of IS with pelvic imbalance and investigate correction effectiveness with different lowest instrumented vertebra (LIV).Methods Posterior pedicle screws on concave side and pre-bent rod placed were placed on IS finite element models, constraints and loadings were applied at the same time as follows:sacrum constrained horizontally, corresponding downward forces applied to every segment for gravity and muscle actions according to references,10Nm torsion moment against convex applied to apical zone, and proper torsion moment applied to rod to rotate90degrees backward. The upper instrumented vertebra (UIV), was selected to T10and LIV down to L4, L5, S1in patient A.;The upper instrumented vertebra (UIV), was selected to T7and LIV still down to L4, L5, S1in patient B, with comparison of correction effect nesses among the three LIV choices in each patient.Results Coronary lumbar deformity was corrected to25°、23°、20°or all three surgical protocols used in the simulation in patient A. Coronary lumbar deformity was corrected to29°、24°21°or all three surgical protocols used in the simulation in patient B. Physiological saggital configuration was maintained. Correction rates were significantly different among the three LIV choices.Conclusions3-D finite element simulation on the successful implementation of the posterior operation of90°rotation operation and distraction correction process of compressing. Finite element simulation provides sufficient theoretical basis and accurate operation platform for the evaluation of idiopathic scoliosis with pelvic imbalance correction optimization operation scheme and effect of treatment of scoliosis; in this study, two cases of three-dimensional finite element model of the recovery rate, spinal appearance by orthopedic operation after the straight, but there are also problems too large stress appeared the fusion segment to S1, we need to simulate the protection of S1screw scheme, the appropriate loading constraints, this is the need for further study, the problems to be solved; The best solution scheme of two in patient A and scheme of C in patient B with scheme for three-dimensional finite element model of the corresponding simulation after orthopedic operation, the best orthopedic effect and the corresponding vertebral stress than the average, can try short-segment fusion, the segmental motion.更多还原