Predicting Small-Stature Young Female Rib Response with an Isolated Rib Finite Element Model

Thorax injuries are a significant cause of mortality in automotive crashes, with varying susceptibility across sex and age demographics. Finite element (FE) human body models (HBMs) offer the potential for injury outcome analysis by incorporating anthropometric variations. Recent advancements in material constitutive models, cortical bone fracture and continuum damage mechanics model (CFraC) and an orthotropic trabecular bone model (OrthoT), offer the opportunity to further improve rib models. In this study, the CFraC and OrthoT material modes, coupled with age-specific material properties, were progressively implemented to the Global Human Body Model Consortium small female 6th rib. Four distinct 6th rib models were developed and compared against sex and age-specific experimental data. The updated material models notably refined the predictions of force–displacement responses, aligning them more closely with the experimental averages. The CFraC model significantly improved the prediction of displacement at fracture, suggesting that incorporating stress triaxiality criteria can better account for the complex loading conditions ribs face in crashes, such as combined cortical tension and shear due to rib bending and torque. The study highlights the importance of using biofidelic material models and sex and age-specific data to simulate hard tissue fractures. The improved rib model demonstrates the effectiveness of integrating updated material properties and constitutive models to enhance injury prediction accuracy, which can inform better automotive safety designs and reduce mortality rates. Further research is recommended to extend these models across different demographic groups to fully capture population variability in rib fracture risk.