Definition and evaluation of a finite element model of the human heel for diabetic foot ulcer prevention under shearing loads

TL;DR

This study develops and evaluates a finite element model of the human heel to predict strains related to diabetic foot ulcers, using experimental data and digital volume correlation for validation, highlighting variability in tissue properties.

Contribution

The paper introduces a new FE model of the heel with tissue properties fitted to experimental data and evaluates its accuracy using DVC, addressing a gap in model validation techniques.

Findings

FE model shows similar strain patterns to DVC validation.

Different tissue constitutive laws produce diverse strain results.

Model highlights the need for further research on soft tissue properties.

Abstract

Diabetic foot ulcers are triggered by mechanical loadings applied to the surface of the plantar skin. Strain is considered to play a crucial role in relation to ulcer etiology and can be assessed by Finite Element (FE) modelling. A difficulty in the generation of these models is the choice of the soft tissue material properties. In the literature, many studies attempt to model the behavior of the heel soft tissues by implementing constitutive laws that can differ significantly in terms of mechanical response. Moreover, current FE models lack of proper evaluation techniques that could estimate their ability to simulate realistic strains. In this article, we propose and evaluate a FE model of the human heel for diabetic foot ulcer prevention. Soft tissue constitutive laws are defined through the fitting of experimental stretch-stress curves published in the literature. The model is then evaluated through Digital Volume Correlation (DVC) based on non-rigid 3D Magnetic Resonance Image Registration. The results from FE analysis and DVC show similar strain locations in the fat pad and strain intensities according to the type of applied loads. For additional comparisons, different sets of constitutive models published in the literature are applied into the proposed FE mesh and simulated with the same boundary conditions. In this case, the results in terms of strains show great diversity in locations and intensities, suggesting that more research should be developed to gain insight into the mechanical properties of these tissues.