Determine the mechanical properties of articular cartilage using indentation testing

Abstract

Indentation testing is widely used to determine the in situ biomechanical properties of articular cartilage, however, most curve-fitting solutions for indentation analysis require the deformation data of cartilage at the equilibrium state, which often takes the tissue hours to reach. The lengthy testing time reduces the efficiency of indentation, increases the chance of tissue deterioration, and prevents in vivo applications. Moreover, the constitutive models often involve multiple parameters. Determination of all mechanical properties by curve-fitting the indentation creep data is often complicated by over-fitting, local minima and multiple solutions. This thesis aimed to address these two particular problems. First, in order to shorten the indentation testing time, a novel technique based on principal component analysis (PCA) was developed, which can predict the full indentation creep curve based on the deformation data in a short time period. Second, by identifying the role of each mechanical property in the indentation response of cartilage, a highly efficient curve-fitting algorithm was designed, which can uniquely determine the nonlinear mechanical properties of cartilage (compressive modulus, tensile modulus, and permeability) from a single indentation creep curve. Both of these two newly developed techniques have shown high accuracy and efficiency.