Quantitative Assessment of the Structural Effects in Foot Soft Tissues Depending on the Mechanical Contact Between Joints.

Developing realistic numerical foot models is essential to accurately predict the structural behavior of its bones and soft tissues. The representation of the foot joints is a crucial point that must be considered to recreate these models' natural behavior. Numerically, different types of contact represent these interactions, two being the most common: one that allows movement between bones and one that restricts it. However, the structural behavior of the model is affected depending on which type of contact is chosen to simulate the interaction. Therefore, this paper aims to develop a numerical foot model to analyze and quantify both types of mechanical contact and determine their effect on soft tissues by evaluating and comparing different structural parameters. The results show that the TA, CPF, LPF, EDB, and FDBT soft tissues reach the maximum stress and strain levels like the highest displacement values. The differences between models in these tissues reach percentage values of up to 74.69% for the principal stresses and up to 68.42% for the principal strains. Significant differences were also found in the displacements obtained in the anteroposterior axes (X) and the vertical or the load axis (Y) of up to 42.03% and 37.47%, respectively. These results allow us to quantify the impact that the choice of the contact type of the foot joints has over its soft tissues and suggest that the way of simulating the movement between bones contributes significantly to the quantitative variation of the structural parameters, affecting thus, the predictions made in the several studies performed with foot numerical models; a contact type that reproduces the natural joint movement is the better option based on this work results.