骨质疏松腰椎三维有限元数字化模型的建立

Construction of three-dimensional finite element digital model of osteoporosis lumbar spine

目的:探讨利用螺旋CT建立骨质疏松腰椎三维有限元模型的高度数字化方法,以为腰椎骨质疏松的生物力学实验提供标准模型。方法:实验于2004-06/10在南方医科大学生物力学实验室完成。选取老年男性正常人体脊柱标本1具,范围从L4～L5,先行X线检查以排除可见的脊椎病变及损害。经螺旋CT沿横断面1mm层厚扫描,以jpg格式输出其断面图像并转入微机保存。利用三维重建软件Mimics建立L4～L5段正常脊柱骨性结构的三维模型,再经过自由造型系统进行表面光滑化处理及对1mm层厚引起的数据丢失予以修补。利用有限元软件Ansys的前处理功能,在脊柱模型骨性结构的基础上,补充建立终板、椎间盘、髓核、前纵韧带、后纵韧带、黄韧带、棘间韧带、棘上韧带等结构。采用合适的材料性质和实体单元类型对模型进行智能有限元网格划分。结果:①正常腰段脊柱三维模型有限元网格划分结果:利用三维重建软件Mimics和有限元软件Ansys成功进行正常腰段脊柱三维模型有限元网格划分。共有82563个单元,131204个节点,建成后的三维有限元模型与实体组织具有良好的几何相似性。②骨质疏松腰椎三维有限元模型的建立:利用有限元软件Ansys的前处理功能,对不同组织的物理特性进行定义,椎体和后部结构的弹性模量均减少30%左右,符合真实的生物力学要求,真实模拟了骨质疏松椎体的材料特性,成功建立骨质疏松腰椎三维有限元模型。结论:建立的骨质疏松腰椎三维有限元模型接近真实的生物力学标本,是理想的研究骨质疏松腰椎生物力学的数字化模型,可应用于骨质疏松腰椎损伤程度的评估。

AIM： To investigate the high digital method of three-dimensional finite element model of lumbar spine with osteoporosis established by spiral CT, so as to provide standard model for biomechanical experiment of osteoporosis lumbar spine. METHODS： This experiment was conducted at the Laboratory of Biomechanics, Southern Medical University from June to October 2004. One spinal sample from L4 to L5 was chosen from a normal aged man. X-ray examination was performed to exclude visible spinal defect and damage. Scanning was conducted at 1 mm interval along cross section, and the image of cross section was output with jpg format then stored in the computer. Three-dimensional model of L4-L5 segment normal spinal osteal structure was established with three-dimensional reconstructed software Mimics, then surface smoothness treatment and repair of 1 ram thickness-caused data loss were performed with free form system. With the pretreatment function of finite element software Ansys, the structure of lamina terminalis, intervertebral discs, nucleus pulposus, anterior longitudinal ligament, posterior longitudinal ligament, ligamenta flava, interspinal ligaments, supraspinal ligament were established supplementarily based on the osseous structure of spinal model. Proper material features and entity unit type were used for intellectual finite element mesh division. RESULTS： ① Finite element mesh division of three-dimensional model of vertebral column at normal lumbar segment ： Three-dimensional reconstructed software Mimics and finite software Ansys were used successfully to perform finite element mesh division of three-dimensional model of vertebral column at normal lumbar segment. There were 82 563 units and 131 204 nodes. Constructed three-dimensional finite element model and entity tissue were well similar in geometry.② Construction of three-dimen- sional finite element model of osteoporosis ： With the pretreatment function of finite element software Ansys, physical features of different tissues were defined. Elastic modulus of vertebral body and back both reduced by 30% or so, which satisfied the real demand of biomechanics and simulated the material features of osteoporosis vertebral body . Three-dimensional finite dement model of osteoporosis occurred at lumbar vertebra were constructed successfully. CONCLUSION： The constructed three-dimensional finite element model of osteoporosis lumbar vertebra approaches to real biomechanical sample, is an ideal digital model for study the biomechanics of osteoporosis lumbar spine, and can be applied in the evaluation of injured degree of osteoporosis lumbar spine.