Finite element modeling of inter-individual variation in soft tissue mechanical response to localized pressure

Pressure ulcers remain a persistent and serious complication in clinical care, often originating in deep soft tissues before becoming visible on the skin surface and leading to suffering, prolonged hospital stays, and increased healthcare costs. Individual variability in soft tissue composition and mechanical properties plays a critical role in modulating internal stress and strain distributions during prolonged loading. In this study, we used anatomically representative finite element models to investigate inter-individual differences in tissue vulnerability under localized pressure. Two multilayered models, incorporating variations in epidermal, dermal, adipose, and muscular thickness, density, and stiffness, were subjected to clinically relevant pressure magnitudes (2-10 kPa), simulating conditions associated with immobility and device-related compression. Mechanobiological metrics, including effective stress, effective strain, and percentile-based exposure thresholds, were computed to quantify internal tissue load transmission and damage risk. Model outputs revealed that high stress localized in superficial layers, while strain peaked in deeper tissues, especially adipose and muscle. Simulated reductions in tissue stiffness, reflecting age- or disease-related softening, further exacerbated internal loading, increasing stress-exposed tissue volume by up to 1.5 times and strain-exposed volume by up to 1.2 times. These results highlight the biomechanical consequences of anatomical and material variability and support the development of personalized risk assessment tools. The proposed modeling approach contributes to mechanobiology-informed strategies for pressure ulcer prevention in high-risk populations.