A Comparison of Visco-Hypoelastic and Visco-Hyperelastic Model to Predict the Elastic Strain Energy for Articular Cartilage of Knee Joint

The aim of this work is to propose a viscoelastic material model for human cartilage tissue that allows simulating its structural stiffness and elastic strain energy that absorbs per unit volume. For this, experimental data reported from flat cylindrical indentation test on human samples of seven patients with unicompartmental osteoarthritis (N = 7) were used. These data allowed the use of one linear model and the adjustment of two non-linear material models, a visco-hypoelastic (VE) and a visco-hyperelastic (VHE) model. The finite element models for the indentation test considered the indenter as a rigid body, the cartilage and subchondral bone as deformable bodies. The indentation force (F, material model structural reaction) and resilience modulus (Er, elastic strain energy per unit volume) were considered as validation parameters. The results suggest that largest differences respect to experimental data were found with the linear model (up to 44.33% for Er and 21.75% for F). The best model to reproduce the indentation force was the VHE (mean difference of 3.37±1.03%), while for the elastic strain energy per unit volume, the best model was the VE (mean difference of 16.65±12.74%).