腰1椎体应力的有限元分析及分区

Finite element analysis and zoning of stress in lumbar 1 vertebra

中文关键词:  腰椎  应力分区  载荷  有限元

英文关键词:Lumbar spine  Stress zoning  Loading  Finite element

中文摘要:

  【摘要】 目的：利用有限元分析法研究在不同等级载荷及不同运动状态下腰1（L1）椎体皮质骨及松质骨的应力分布情况，并建立应力分区。方法：选取1例志愿者行胸腰段CT平扫，获取CT原始数据以DICOM导入Mimics、Geomagic、SoliderWorks、HyperMesh、Abaqus等有限元软件，构建正常胸腰段椎体（T11～L2）模型，在T11椎体上缘均匀施加力学载荷，将在载荷500N、弯矩7.5N·m下产生的所有运动状态称为α组，载荷600N、弯矩7.5N·m下产生的所有运动状态称为β组，载荷700N、弯矩7.5N·m下产生的所有运动状态称为γ组。选取L1椎体，从矢状面观正中分割分为上下两部分，上半部分标记为A区，下半部分标记为B区；从椎体正中央至椎体边缘呈同心圆均匀划分6段，上下各构成三维圆弧柱形6部分，从外缘到中央依次标记为1、2、3、4、5、6区，构成A1、A2、A3、A4、A5、A6、B1、B2、B3、B4、B5、B6区域共12部分；分别在α、β、γ三组中均匀采集上述12区域内皮质骨及松质骨应力数据，对皮质骨及松质骨相邻区域内应力值进行两两配对t检验，将差异具有统计学意义的两相邻区域独立成区，将差异无统计学意义的两相邻区域进行合并成区，得到最终应力分区。结果：在α组中，A1区域皮质骨和松质骨的平均应力与A2区域比较差异均具有统计学意义；A2区域与A3区域比较差异无统计学意义；A3区域与A4区域比较差异具有统计学意义；A4区域、A5区域、A6区域三者之间两两比较差异均无统计学意义；B区域规律同A区域。在β组中，皮质骨中A区域及B区域应力均满足α组中统计学意义规律，松质骨中A4区域与A5区域、B4区域与B5区域两两比较差异具有统计学意义，其规律与α组一致。在γ组中，皮质骨及松质骨A4区域与A5区域、B4区域与B5区域应力两两比较差异具有统计学意义，其余与α组规律相同。根据统计学规律，将L1椎体分为A1（AⅠ）、A23（AⅡ）、A456（AⅢ）、B1（BⅠ）、B23（BⅡ）、B456（BⅢ）六个区域，其中AⅡ区域应力分布最为集中，称之为核心应力区，AⅠ、BⅠ、BⅡ应力分布次之，称之为主要应力区，AⅢ、BⅢ应力分布最少，称之为次要应力区。结论：L1椎体应力分布较为固定且呈现一定规律性，其中核心应力区、主要应力区和次要应力区承受应力依次减弱，有助于临床骨折类型预判和评估。

英文摘要:

  【Abstract】 Objectives: To explore the stress distribution of the cortical bone and cancellous bone in the L1 vertebral body under different levels of load and different motion states by finite element analysis, and to establish the stress zone. Methods: One volunteer underwent plain CT scan of thoracolumbar vertebrae. The original data of CT were obtained by DICOM and imported into finite element software such as Mimics, Geomagic, SoliderWorks, HyperMesh, Abaqus and so on. The normal thoracolumbar vertebra model(T11-L2) was constructed, and the mechanical load was applied evenly on the upper edge of the vertebral body. All motion states produced under load 500N and bending moment 7.5N·m were in the group, those produced under 600N and 7.5N·m were in the β group, and those produced under 700N and 7.5N·m were in the γ group. The L1 vertebral body was divided equally into upper and lower parts in the sagittal view, with the upper part marked as area A, and the lower part as area B. Six segments were divided equally in concentric circle from the center to the edge of the vertebral body, and the upper and lower parts formed a three-dimensional circular cylinder. From the outer edge to the center, they were marked as A1, A2, A3, A4, A5, A6, B1, B2, B3, B4, B5, B6, totally 12 parts. The load data of cortical bone and cancellous bone in the above 12 regions were uniformly collected in α, β and γ groups, and the stress values in the adjacent areas of cortical bone and cancellous bone were tested by pairwise t test. The two adjacent regions with statistically significant difference were separated into different regions, and the two adjacent regions with no statistically significant difference were merged into one region, and the final stress zones were obtained. Results: In group α, the average stress of cortical bone and cancellous bone in A1 region was significantly different from that in A2 region, there was no significant difference between that in A2 region and A3 region, and there was significant difference between that in A3 region and A4 region. There was no significant difference among those in A4, A5 and A6. The law of region B was the same as that of region A. In β group, the A region and B region of cortical bone met the statistically significant rule of α group. There were significant differences between A4 and A5, B4 and B5 in cancellous bone, and the others were the same as those in α group. In γ group, the differences between cortical bone and cancellous bone in A4 region and A5 region, in B4 region and B5 region were statistically significant, and the others were the same as those of α group. According to the statistical law, the L1 vertebra was divided into six regions: A1(AⅠ), A23(AⅡ), A456(AⅢ), B1(BⅠ), B23(BⅡ) and B456(BⅢ). Among them, the stress distribution in AⅡ region was the most concentrated and called the core stress zone; the stress distribution in AⅠ, BⅠ and BⅡ was the second, and called the main stress zone; the stress distribution of AⅢ and BⅢ was the least, and called the secondary stress zone. Conclusions: The stress distribution of the L1 vertebral body is relatively fixed and presents a certain regularity. The core stress area, the main stress area and the secondary stress area are gradually weakened, which is helpful for the prediction and evaluation of clinical fracture types.