The effect of a degraded core on the mechanical behaviour of tissue- engineered cartilage constructs: a poroelastic finite element analysis

The structure and functionality of tissue-engineered cartilage is determined by the tissue culture conditions and mechanical conditioning during growth. The quality of tissue-engineered cartilage may be evaluated using tests such as the confined compression test. Tissue-engineered cartilage constructs usually consist of an outer layer of cartilage and an inner core of either undeveloped cartilage or degrading scaffold material. In this paper, a biphasic poroelastic finite element model is used to demonstrate how such a core influences the reaction force vs. time curve obtained from a confined compression test. The finite element model predicts that higher volumes of degraded scaffold in the inner reduces the aggregate modulus calculated from the confined compression test and raises the estimate of tissue’s permeability. The predicted aggregate modulus reduces from 0.135 MPa for a homogenous construct, to 0.068 MPa for a construct that is only 70% cartilaginous. We find that biphasic poroelastic finite modelling should be used in preference to a onedimensional model which assumes homogeniety in estimating the properties of tissueengineered cartilage.