Age-Dependent Factors Affecting Thoracic Response: A Finite Element Study Focused on Japanese Elderly Occupants

Abstract

Objectives:The ultimate goal of this research is to reduce thoracic injuries due to traffic crashes, especially in the elderly. The specific objective is to develop and validate a full-body finite element model under 2 distinct settings that account for factors relevant for thoracic fragility of elderly: one setting representative of an average size male and one representative of an average size Japanese elderly male.Methods: A new thorax finite element model was developed from medical images of a 71-year-old average Japanese male elderly size (161cm, 60 kg) postmortem human subject (PMHS). The model was validated at component and assembled levels against original series of published test data obtained from the same elderly specimen. The model was completed with extremities and head of a model previously developed. The rib cage and the thoracic flesh materials were assigned age-dependent properties and the model geometry was scaled up to simulate a 50th percentile male. Thereafter, the model was validated against existing biomechanical data for younger and elderly subjects, including hub-to-thorax impacts and frontal impact sled PMHS test data. Finally, a parametric study was conducted with the new models to understand the effect of size and aging factors on thoracic response and risk of rib fractures.Results: The model behaved in agreement with tabletop test experiments in intact, denuded, and eviscerated tissue conditions. In frontal impact sled conditions, the model showed good 3-dimensional head and spine kinematics, as well as rib cage multipoint deflections. When properties representative of an aging person were simulated, both the rib cage deformation and the predicted number of rib fractures increased. The effects of age factors such as rib cortical thickness, mechanical properties, and failure thresholds on the model responses were consistent with the literature. Aged and thereby softened flesh reduced load transfer between ribs; the coupling of the rib cage was reduced. Aged costal cartilage increased the severity of the diagonal belt loading sustained by the lower loaded rib cage.Conclusions: When age-specific parameters were implemented in a finite element (FE) model of the thorax, the rib cage kinematics and thorax injury risk increased. When the effect of size was isolated, 2 factors, in addition to rib material properties, were found to be important: flesh and costal cartilage properties. These 2 were identified to affect rib cage deformation mechanisms and may potentially increase the risk of rib fractures.

Multiscale Computational and Artificial Intelligence Models of Linear and Nonlinear Composites: A Review

“…Diosa et al [ 208 ] formulated an FE model of a dynamic indentation test on the skin to predict the effect of changes in microscale topography due to aging. Antona–Makoshi et al [ 209 ] developed an FE model to study the relevant factors for the thoracic fragility of the elderly in frontal impact scenarios. Acun et al [ 210 ] performed in vitro experiments and developed human‐induced pluripotent stem cell (hiPSC)‐derived cardiomyocyte‐based aged myocardial tissue as an alternative research platform to study cardiovascular disease progression.…”

Evaluation and Validation of Thorax Model Responses: A Hierarchical Approach to Achieve High Biofidelity for Thoracic Musculoskeletal System

“…Yang et al (2006) reviewed thorax FE models published before 2005 and after 2005 (Yang, 2018). These models were either isolated thorax models (Deng et al, 1999;Shen et al, 2008) or integrated into full body model (FBM) (Robin, 2001;Haug et al, 2004;Kimpara et al, 2005;Song et al, 2009;El-Jawahri et al, 2010;Pipkorn and Kent, 2011;Antona-Makoshi et al, 2015;Iwamoto et al, 2015;Poulard et al, 2015;Schoell et al, 2015;Zhu et al, 2016). Despite the significant difference of modeling details, the primary goal of these models was to evaluate human thoracic response, understand thoracic injury tolerances, and assess injury risks under various impact loads.…”

Age-related changes in thoracic skeletal geometry of elderly females

“…Computational modeling offers unique opportunities to specifically address the safety concerns of at-risk or vulnerable populations by providing tools that better represent those populations and the risks they face. For example, increased thorax injury risk is seen in simulations that incorporate agespecific parameters into finite element models of the thorax (Antona-Makoshi et al 2015;Schoell et al 2015). In order to adequately model age as a human factor, quantitative descriptions of the morphometric changes that occur with age must be made available.…”