A biomechanical framework for skeletal injury analysis in upright falls: integrating stress propagation, fracture risk modeling, and injury clustering.

Utilizing the Finite Element Method and the Total HUman Model for Safety model, simulations were conducted of adult subjects landing with both feet on a hard surface from various heights. The biomechanical response was deconstructed using stress analysis, binary logistic regression, and hierarchical clustering based on Jaccard distance. The simulations revealed a stress propagation mechanism and a longitudinal axial distribution of stress concentrations. Fracture risk exhibited two distinct modes: a "stepwise response" in primary load-bearers (e.g., feet, spine) and a "graded response" in secondary structures (e.g., fibular ends). Logistic regression quantified the height-dependent fracture risk for the fibular ends (OR = 1.682), skull (OR = 1.576), and pelvis (OR = 1.236). The hierarchical cluster analysis of injury patterns corresponds to distinct biomechanical phases: the localized injury phase involving local dissipation, the stress propagation phase characterized by axial transmission, and the systemic injury phase marked by comprehensive damage. This study establishes a comprehensive "mechanism-risk-pattern" biomechanical framework that effectively explains the progression of skeletal trauma during falls. This framework provides a powerful tool for hypothesis generation in forensic case analysis. Extensive experimental findings indicate that threshold settings influence model outcomes, making direct quantitative application to case evidence inadvisable before model optimization. The core contribution of this study lies in proposing this interpretive paradigm, which reveals the systemic nature of skeletal injury and provides a structured pathway for deciphering complex trauma.