【作者】 陈凌强；

【导师】 张宏其；

【作者基本信息】 中南大学 ， 外科学， 2010， 博士

【摘要】 本研究应用计算机辅助工程(computer aided engineering, CAE)软件,建立了基于CT图像的完整Lenke6型特发性脊柱侧凸三维非线性有限元模型；采用正交试验对初步模型进行优化,然后对优化模型进行有效性验证；在此基础上,仿真模拟Lenke6型特发性脊柱侧凸后路CD矫形技术各个步骤；进而利用CD矫形模拟不同的矫形策略工况,探讨关键椎置钉技术和选择性融合的矫形效果。目的应用CAE软件,建立基于CT图像的Lenke6型特发性脊柱侧凸三维非线性有限元模型。方法选择1例14岁女性Lenke6型特发性脊柱侧凸志愿者作为研究对象。取仰卧位,应用螺旋CT从T1上缘至尾骨以1mm间距进行连续扫描,获得Dicom格式CT图像511张。导入逆向工程软件Mimics10.01,建立包括胸-腰-骶椎和胸廓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,然后导入有限元前处理软件HyperMesh8.0划分有限元实体网格,并参照文献添加椎间盘及韧带结构单元,生成完整的特发性脊柱侧凸三维有限元模型。参照文献赋予模型材料参数和实常数。结果建立了完整的Lenke6CN型特发性脊柱侧凸三维非线性有限元模型,包括12节胸椎、5节腰椎、椎间盘、骶尾骨、胸廓及脊柱所有韧带、关节结构。模型共采用4种单元类型,13种材料性质；划分节点208739个,全部单元849787个,四面体单元758197个,壳单元90776个,线缆单元680个和杆单元134个。网格划分后的整体图形和仰卧位的X线片对比,外观基本上吻合。结论成功构建了基于CT图像的Lenke6CN型特发性脊柱侧凸三维有限元模型,模型完整、逼真地还原了被模拟对象的脊柱特点。目的对初步建立的有限元模型进行进一步参数优化,使模型的形态和材料属性均实现个体化；验证优化的Lenke6型特发性脊柱侧凸三维有限元模型的有效性。方法将上胸段、主胸段、胸腰段和下腰段等4个区域的椎间盘材料属性分为柔软型、中间型和僵硬型三个水平,系数分别为0.2、1、8。按照正交试验设计进行四因素三水平分析,找出使模拟结果和实际情况差异最小的系数搭配,进而生成优化后的个体化模型。将仰卧位的优化模型进行加载,模拟出左右侧屈位,和站立位,并分别与实际对应的X线片比较外形、侧凸Cobb角度和各椎体质心与CSVL的偏移距离。在优化的模型中提取T1-T4、L4-S1两个节段,分别参照同类体外(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。结果正交试验结果显示使模型和实际差异最小化的较好组合是：椎间盘属性在上胸段为0.2,主胸凸段为1,胸腰段为1,下腰段为8。验证结果：优化后各个体位的有限元模型Cobb角度与临床X线片相比较,角度最大相差2.5°,最小为0；椎体质心偏离骶骨中线的距离：仰卧位、站立位、仰卧左右侧屈位X线片与有限元模型相比较,P>0.10,两者没有差别；T1-T4、L4-S1两个节段与相关的生物力学实验研究相比较,活动度均在相关生物力学实验研究的范围内。结论有限元模型建立后采用正交试验对于模型材料属性进行个体化的方法是可行的,也是必要的,优化后的模型与实际更为相符。从几何外形、仰卧位左右侧屈试验、站立-仰卧试验及分段加载实验,验证了优化后的Lenke6型特发型脊柱侧凸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。目的利用优化后的Lenke6型特发性脊柱侧凸有限元模型,按步骤模拟后路CD矫形技术。方法建立椎弓根钉及矫形棒的有限元模型,并在侧凸模型上去除矫形融合段的棘间韧带、棘上韧带和上下关节囊,模拟脊柱松解。于融合段各椎体双侧按解剖结构置入椎弓根钉,在左侧(矫形侧)生成矫形棒,并予X、Y方向位移使矫形棒成为目的形状。在棒上生成手柄模拟手术钳功能,将棒旋转90°,把冠状面的侧凸畸形转化为矢状面的正常生理后凸和前凸。安置右侧稳定棒并依次将螺钉逐步靠拢稳定棒的位置。锁定钉棒间关节活动度,释放应力,完成手术。结果顺利完成了CD矫形手术各步骤的模拟,模拟完成后胸腰弯Cobb角度为29.2°,主胸弯Cobb角度为24.4°,胸腰弯矫形率47.8%,主胸弯矫形率43.9%,冠状面序列基本恢复正常,矢状面胸椎后凸及腰椎前凸均较术前有改善。结论首次在完整的Lenke6型脊柱侧凸有限元模型上按CD矫形技术各步骤完成侧凸后路钉棒矫形手术的模拟,为预测病人治疗效果、旋转矫形策略、探讨脊柱侧凸治疗中的争议等提供参考意见,也为本研究下一步矫形策略的选择的有限元研究奠定基础。目的通过有限元模型矫形手术模拟的方法探讨关键椎置钉技术的可行性及矫形效果,分析Lenke6型脊柱侧凸是否适合采用选择性融合策略。方法利用后路CD矫形手术模拟技术,分别模拟全节段椎弓根钉技术矫形工况、关键椎置钉技术矫形工况、胸腰弯选择性融合工况等。测量各种工况完成后双弯Cobb角度、计算矫形率,分析各种工况的矫形效果。结果全节段椎弓根钉技术(非选择性融合)：胸腰弯矫形率47.8%,主胸弯矫形率43.9%；关键椎置钉技术：胸腰弯矫形率44.2%,主胸弯矫形率19.1%；胸腰弯选择性融合：胸腰弯矫形率43.5%,主胸弯矫形率14.3%。结论全节段椎弓根钉技术因矫形力施加点更多,矫形效果较关键椎置钉技术更佳；Lenke6型脊柱侧凸采用选择性融合策略应慎重,非选择性融合策略能明显矫正双弯,纠正脊柱序列,更适合该类型病例。更多还原

【Abstract】 In this study, computer aided engineering (CAE) software was used to establish a complete three-dimensional finite element model of Lenke 6 idiopathic scoliosis based on CT images, including all thoraco-lumbar-sacral vertebrae and thoracic cage. Then optimized the model parameters and validated the final model. On the basis, we simulated all the main steps of posterior Cotrel-Dubousset (CD) technique correction surgery using this IS finite element model. Then simulated different correction strategy to explore the effect of key-segment instrumentation technique and selective fusion strategy.Objective The CAE softwares was used to build three-dimensional finite element model of Lenke 6 idiopathic scoliosis based on CT images.Methods A 14-year-old female Lenke 6 idiopathic scoliosis patient was included as volunteer for current study. CT transverse scanning in supine position was done from T1 to caudal end in lmm layer interval, to obtain 511 CT dicom images. All CT images were imported into Mimics 10.01 to form qualified IS three-dimensional geometric model after geometry clean, including all thoraco-lumbar-sacral vertebrae and thoracic cage, which was further delivered to HypherMesh 7.0 to build 3d finite element IS model by mesh partition and quality control. A variety of material parameters were given to different mesh according to references.Results A three-dimensional finite element model of Lenke 6 idiopathic scoliosis was built successfully, including all thoraco-lumbar-sacral spine and thoracic cage, using 4 mesh types and 13 kinds of material parameters, in consist of 208739 nodes,758197 tetrahedron elements,90776 shell elements,680 cable elements and 138 rod elements.Conclusions A three-dimensional finite element model of Lenke 6 IS in details, was built successfully based on CT transverse scanning images.Objective To personalized the mechanical properties of finite element model of Lenke 6 IS 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 four factors and three levels of disc material property to optimize the parameters, and then achieve the biomechanical property of the individual.Compared the model with upstanding posterior-anterior X-Ray, supine posterior-anterior X-Ray and lateral flexion X-Ray of supine posterior-anterior position. Chose T1-T4 and L4-S1 to compare with related results of biomechanics empirical study.Results Orthogonal experiment results showed that the best combinations, which mimimized the difference of model and the actual, were dise property in the proximal thoracic segments is 0.2, the main thoracic segments is 1, the thoracolumbar segments is 1, and the lower lumbar segments is 8.Compared the Cobb angles of optimized model and actual X-ray film, the largest difference was 2.5°, and the mibimum is 0. Compared the center of mass deviated from sacral middle line between X-Ray and optimized model, P>0.10, which considered no differences between them. Chose T1-T4 and L4-S1 to compare with related results of biomechanics empirical study, the rotation of the model was in the boundary of related results.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. The optimized three-dimensional finite element model of Lenke 6 idiopathic scoliosis was well validated by geometry appearance, left and right supine bending test, standing-spuine test and segment validation, which was qualified for further biomechanical simulation study.Objective To simulate posterior CD correction surgery using the optimized finite element model step by step.Methods Established the pedicle screws and rods finite element model. Simulated posterior release by removing the interspinous ligaments, supraspinous ligaments and joint capsule of instrumented segments. Anatomically implanted the pedicle screws into the sconliosis model. Generated the correctted rod in the left side. Given the rod displacement of X, Y direction to shape the prupose correctted rod. Generated handles and rotated the rod 90°, which translated the coronal scoliosis into sagittal kyphosis and lordosis. Then placed the stable rod. Turned the screws to move closer to the rod. Locked the joint activity of screw-rod, released the stress.Results Successfully completed each step simulation of CD correction technique. After correction the Cobb angle of thoracolumbar curve was 29.2°with the 47.8% correction rate, and the Cobb angle of the main thoracic curve was 24.4°with the 43.9% correction rate. The alignment of the spine was improved.Conclusion It was the first time to completely simulate all main steps of Cotrel-Dubousset (CD) surgery in the finite element model of Lenke 6 scoliosis. This could help to evaluation, prediction and even optimize the surgical plan and provide a theoretical support.Objective To explore the feasibility and effect of key-segment instrumentation and the suitability of selective fusion strategy for Lenke 6 scoliosis by finite element analysis.Methods Simulated the following conditions:all-segment pedicle screw instrumentation surgery, key-segment pedicle screw instrumentation surgery, selective thoracolumbar curve fusion surgery. Measured the curve Cobb angles and calculated the correction rate in all above conditions. Analyzed the correctted effect of these conditions.Results The correction rates of thoracolumbar curve and main thoracic curve were:47.8% and 43.9% in all-segment pedicle screw instrumentation surgery (non-selective fusion),44.2% and 19.1% in key-segment pedicle screw instrumentation surgery,43.5% and 14.3% in selective thoracolumbar curve fusion surgery. Conclusions The effect of all-segment pedicle screw instrumentation surgery was better than key-segment pedicle screw instrumentation surgery for the more force placements. Non-selective fusion, which could correct the two curve and improve the alignment significantly, was more suitable for Lenke 6 scoliosis.更多还原