Age- and Sex-Specific Thorax Finite Element Model Development and Simulation

Objective: The shape, size, bone density, and cortical thickness of the thoracic skeleton vary significantly with age and sex, which can affect the injury tolerance, especially in at-risk populations such as the elderly. Computational modeling has emerged as a powerful and versatile tool to assess injury risk. However, current computational models only represent certain ages and sexes in the population. The purpose of this study was to morph an existing finite element (FE) model of the thorax to depict thorax morphology for males and females of ages 30 and 70 years old (YO) and to investigate the effect on injury risk.Methods: Age- and sex-specific FE models were developed using thin-plate spline interpolation. In order to execute the thin-plate spline interpolation, homologous landmarks on the reference, target, and FE model are required. An image segmentation and registration algorithm was used to collect homologous rib and sternum landmark data from males and females aged 0–100 years. The Generalized Procrustes Analysis was applied to the homologous landmark data to quantify age- and sex-specific isolated shape changes in the thorax. The Global Human Body Models Consortium (GHBMC) 50th percentile male occupant model was morphed to create age- and sex-specific thoracic shape change models (scaled to a 50th percentile male size). To evaluate the thoracic response, 2 loading cases (frontal hub impact and lateral impact) were simulated to assess the importance of geometric and material property changes with age and sex.Results: Due to the geometric and material property changes with age and sex, there were observed differences in the response of the thorax in both the frontal and lateral impacts. Material property changes alone had little to no effect on the maximum thoracic force or the maximum percent compression. With age, the thorax becomes stiffer due to superior rotation of the ribs, which can result in increased bone strain that can increase the risk of fracture. For the 70-YO models, the simulations predicted a higher number of rib fractures in comparison to the 30-YO models. The male models experienced more superior rotation of the ribs in comparison to the female models, which resulted in a higher number of rib fractures for the males.Conclusion: In this study, age- and sex-specific thoracic models were developed and the biomechanical response was studied using frontal and lateral impact simulations. The development of these age- and sex-specific FE models of the thorax will lead to an improved understanding of the complex relationship between thoracic geometry, age, sex, and injury risk.研究目的：胸廓的形态、尺寸、骨密度及骨皮质厚度随年龄与性别存在显著差异，这会对损伤耐受性造成影响，尤其在老年等高风险人群中。计算建模已成为评估损伤风险的强大且通用的研究工具。然而当前的计算模型仅能表征人群中特定年龄与性别的个体。本研究旨在对现有胸廓有限元（finite element, FE）模型进行形态变形，以描绘30岁与70岁男女的胸廓形态，并探究其对损伤风险的影响。 研究方法：本研究采用薄板样条插值（thin-plate spline interpolation）法构建年龄与性别特异性的有限元模型。开展薄板样条插值需在参考模型、目标模型与有限元模型上采集同源标志点数据。本研究使用图像分割与配准算法，从0至100岁的男女个体中采集肋骨与胸骨的同源标志点数据。对同源标志点数据进行广义Procrustes分析（Generalized Procrustes Analysis），以量化胸廓中年龄与性别特异性的独立形态变化。以全球人体模型联盟（Global Human Body Models Consortium, GHBMC）50百分位男性乘员模型为基础进行形态变形，构建年龄与性别特异性的胸廓形态变化模型（缩放至50百分位男性体型）。为评估胸廓的生物力学响应，设置2种载荷工况（正面轮毂冲击与侧向冲击）进行仿真，以分析年龄与性别相关的几何及材料属性变化的影响。 研究结果：由于年龄与性别相关的几何及材料属性变化，正面与侧向冲击下的胸廓响应均存在显著差异。仅材料属性变化对最大胸廓力或最大压缩百分比几乎无影响。随着年龄增长，胸廓因肋骨上旋而变硬，这会导致骨应变增加，进而提升骨折风险。相较于30岁模型，70岁模型的仿真结果预测出现更多肋骨骨折。相较于女性模型，男性模型的肋骨上旋程度更高，这使得男性的肋骨骨折数量更多。 研究结论：本研究构建了年龄与性别特异性的胸廓模型，并通过正面与侧向冲击仿真研究了其生物力学响应。此类年龄与性别特异性胸廓有限元模型的开发，将有助于进一步理解胸廓几何形态、年龄、性别与损伤风险之间的复杂关联。