Effects of Joint Congruency on the Response of a Tension-Compression Nonlinear Constitutive Model for Cartilage

Abstract

Articular cartilage exhibits inhomogeneous, rate-dependent and tension-compression (TC) nonlinear material properties. It is a biphasic material (solid and fluid phases) and its solid phase is stiffer in tension than compression [1]. Despite this complex material behavior, elastic, incompressible material models can be used to predict the short-time loading response of cartilage [2]. To our knowledge, the use of an anisotropic incompressible material to represent cartilage in a finite element (FE) joint model has not been investigated and thus the importance of the TC nonlinearity in the analysis of 3D articular contact models is limited [3]. We have been investigating a TC nonlinear incompressible constitutive model to represent hip cartilage. The objective of this study was to assess the influence of TC nonlinearity on FE predictions of stress and strain as a function of congruency between two spherical cartilage layers. It was hypothesized that the TC nonlinear and neo-Hookean constitutive models would yield a similar response when the cartilage layers were nearly congruent, but as the congruency of the cartilage layers decreased the predicted response from the two materials would be different.