枢椎环骨折损伤机制的三维有限元分析

Three-dimensional finite element analysis of the injury mechanism of axis ring fractures

中文关键词:  枢椎环骨折  上颈椎  生物力学  有限元分析

英文关键词:Axis ring fracture  Upper cervical spine  Biomechanics  Finite element

中文摘要:

  【摘要】 目的：观察在不同暴力作用下枢椎的应力分布并推测枢椎环骨折的损伤形态，揭示该类骨折的形态学与损伤机制之间的关系。方法：选择1名健康成年男性志愿者，进行头颅和颈椎薄层CT扫描，将CT数据导入软件，通过有限元软件建立颅底至第3颈椎（C0-C3）三维有限元模型，并验证模型的有效性。在头颅几何模型上选择5个受力点：前额中部正中（A点）、头顶部前方正中（B点）、前额上部左侧（C点）、头顶部前方左侧（D点）及枕后部（E点），其中A和B点受力模拟颈椎受到不同程度过伸+轴向压缩暴力，C和D点受力模拟过伸+轴向压缩伴不同程度旋转暴力，E点模拟过屈+轴向压缩暴力。有限元技术模拟上述不同暴力（1400N）作用于上颈椎模型，分析枢椎环的应力分布，推测骨折线的发生部位。结果：本实验成功建立了C0-C3上颈椎三维有限元模型，模型总共包括1315238个单元，305789个节点。有限元模型验证有效后，进行暴力加载提示，A点受力状态下，枢椎环应力主要分布在双侧上关节突后1/4至峡部-椎弓根复合体（pediculoisthmic components，PIC）之间的区域；B点受力状态下，枢椎环应力主要分布在双侧上关节突后1/3至PIC区域；C和D点受力状态下，枢椎环应力主要分布在左侧上关节突后1/3至齿状突侧后方椎体之间和右侧PIC、下关节突及椎板等结构；E点受力状态下，枢椎环应力主要集中分布在椎体及上关节突边缘。结论：过伸+轴向压缩暴力导致双侧或一侧PIC骨折为核心特征的枢椎环骨折模式可能性大，亦可导致骨折线基本平行或对称的双侧上关节突伴椎体后壁骨折；过伸+轴向压缩伴旋转暴力导致一侧关节突和/或椎体后壁骨折伴对侧不同结构损伤为核心特征的枢椎环骨折模式可能性大，亦可导致一侧骨折线为纵行、另一侧为横行的双侧上关节突伴椎体后壁骨折；过屈+轴向压缩暴力导致枢椎椎体骨折或复杂枢椎环骨折可能性大。

英文摘要:

  【Abstract】 Objectives: To observe the stress distribution of the second cervical vertebra(axis) under different forces and predict the injury morphology of axis ring fractures(ARF), and to reveal the relationship between fracture pattern and injury mechanism. Methods: A healthy adult male volunteer was selected for skull and cervical thin slice CT scan. The CT data were imported into the software, and a three-dimensional finite element model of the normal skull base to the third cervical vertebra(C0-C3) was established by using the finite element software. The validity of the finite element model was verified. Five force bearing points on the skull geometric model were selected: the middle of forehead(point A), the front middle of the top of head (point B), the left side of the upper forehead(point C), the front left of the top of the head(point D), and the back of the occipital(point E). The forces at points A and B simulated cervical vertebra subjected to different degrees of hyperextension and axial compression violence; the forces at points C and D simulated hyperextension and axial compression with different degrees of rotational violence; and the force at point E simulated hyperflexion and axial compression violence. Finite element method was used to simulate different kind of forces(1400N) applied to the upper cervical vertebra. Then, the stress of anatomical structure of the axis ring was analyzed, based on the results of finite element analysis. Results: A three-dimensional model of C0-C3 was successfully established in this experiment, which had 1,315,238 units and 305,789 nodes. The finite element model was also validated. The stress of axis ring was mainly distributed in the area between posterior 1/4 of bilateral superior articular process and pediculoisthmic components(PIC) while point A bearing 1400N force. The stress of axis ring was mainly distributed in the area between posterior 1/3 of bilateral superior articular process and PIC while point B bearing the force. The stress of axis ring was mainly distributed in the posterior 1/3 of the superior articular process to the posterior vertebral body of the odontoid process on the left side, and the PIC, inferior articular process and lamina on the right side while point C and D bearing the forces. The stress of axis ring was mainly distributed in the vertebral body and the edge of bilateral superior articular processes while point E bearing the force. Conclusions: When the cervical vertebra was subjected to hyperextension and axial compression force, the stress of axis ring was mainly distributed in the area between the posterior quarter of bilateral superior articular process and PIC, causing ARF pattern with bilateral or unilateral PIC fracture of C2 as the core feature. And this kind of force might also cause bilateral fractures of superior facet and/or posterior vertebral wall fracture of C2, with basically parallel or symmetrical fracture lines. When the cervical vertebra was subjected to hyperextension and axial compression accompanied by rotational force, the stress of the axis ring was concentrated between superior articular process on one side and the posterior vertebral body of the odontoid process and the contralateral PIC, inferior articular process and lamina, causing ARF with one fracture of superior facet and/or posterior wall of the vertebral body of C2 and another contralateral fracture of different structures as the core feature. And such force in some cases might result in bilateral fractures of superior facet and/or posterior vertebral wall fracture of C2, with longitudinal fracture line on one side and transverse fracture line on the other. In the case of hyperflexion and axial compression force, the stress of axis ring was mainly distributed in the vertebral body and the edge of bilateral superior articular processes, revealing a high incidence of body fractures of the axis or complex axis ring fractures.