  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.
