齿突下软骨基质融合部对枢椎骨折类型影响的有限元分析

目的 建立并验证精细枢椎三维有限元模型,应用该模型探讨在前、后不同载荷条件下枢椎齿突下软骨基质融合部骨质不同发育程度对枢椎骨折类型的影响.方法 基于正常成人颈椎CT图像建立枢椎精细三维有限元模型.模拟体外生物力学实验验证模型.模型经验证后对齿突施加不同角度载荷,通过降低枢椎软骨基质融合部位松质骨的弹性模量以模拟该部位松质骨发育不同程度,分析枢椎在2种不同约束条件下的应力、应变分布情况,并探讨可能发生的相应骨折类型.结果 模型验证结果与体外生物力学实验结果基本一致.边界约束模式1下齿突前部垂直和水平方向不同角度加载模型预测结果与屈曲位水平角度载荷下预测应力分布图显示,应力集中区域随加载角度变化而发生转变,骨折类型可由Ⅲ型转变为Ⅱ型齿突骨折.边界约束模式2下受不同水平载荷角度加载后,模型预测骨折类型可由对称性Hangman骨折向不对称性Hangman骨折的转变.垂直方向上不同角度载荷下,预测骨折类型可由对称性Hangman骨折向Ⅱ型齿突骨折转变.齿突下软骨基质融合部位松质骨的发育程度不改变枢椎在垂直、水平、屈曲位不同角度受力下的应力集中带分布情况,皮质骨承受主要应力.结论 枢椎骨折的发生类型除了与所遭受暴力的方向、大小有关外,同时还与受伤瞬间寰枢椎相对应的位置情况和枢椎齿突的解剖差异有关.体外对枢椎骨折的生物力学研究实验中,除了加载暴力的方向外,尸体标本的固定与加载方式直接影响枢椎骨折类型的复制.齿突下软骨基质融合部对枢椎骨折类型无明显影响.

Finite element analysis of subdental synchondrosis to axis fracture type

Objective To establish and validate the detailed three-dimensional axis finite element （FE） model and to explore the influence of the ossification degree of the subdental slchondrosis to the fracture type of the axis. Methods Based on a nonna] adult ema, ical spine continuous lamellar spirM CT images, a detailed thlve-dimensionM axis finite element model wts reconstructed. For vidalion, the FE model was constrained and loaded as the plvious biomeehanics studies. By altering the trabecular bone＇s Young＇s mMulus of the cartilage matrix ossification region, the validated FE model was loaded in different orientation under 2 boundary conditions and theoretic-,d stress distributions of the axis was calculated to explore the stress distributions and predict the possible types of the axis. Results The resuhs of the present FE model closely corrdate with the biomechanieal results obtained in the previous biomechanics studies. Under boundary condition I , the yon Mises stress patterns in vertical and horizontal h,ading pauems shmved cmlceotrated stress distribution shill with the changes in of the loading angles, which predicted a transition from type Ill Ilodonloid fracture. Under condition 2, in horizontal loading patterns, the wm Mises slress distibu- lions predicted a mmsition from symmetry to, asymmetU in vertical loading pallerns, the wm Mises slrcss distri- bulions prediclcd a transition from symmetry Hangman fracture to type llodontoid fracture. The ossification degree of the subdental snchondmsis did no obviously influence lhe stress dislributions inand horizontal extension loading, and in flexion loading. The corlical bone heated the main stress when the axis suffer a violem rce. Conclusion Besides lhe direction and size, the inslanl correslding atlanloaxial positions in injured and the anatomical difference of the dens can influence lhe axis fracha＇e types. In addition to the direction of Ihe violence, diflerent reslriclions of the cadaverie sample might directly impact the reprluclion of the axis fiacture lytrs.s in the axis fraeture biomeehmieer studies. The degree ossification of the subdental swlehon＆＇osis did not obviously impacl the tcxis fracture type.