Abstract
The mechanical behavior of articular cartilage is strongly dependent on its microstructure characterized by three-dimensional, depth-dependent densities and anisotropic arrangements of cartilage cells and collagen fibres in extracellular matrix. The inclusion of cartilage microstructure to model analysis is essential for the accurate evaluation of the mechanical property. This study proposes a model-based evaluation method, which could predict tissue microstructure (collagen fibres, proteoglycans, and cartilage cells) based on a time history of reaction force obtained from indentation test, thereby estimating the depth-dependent cartilage mechanical property that is difficult to be estimated by experiment in conventional methods. The model was used for evaluating the viscoelasticities of cartilage at medial (load-supporting) and lateral (non load-supporting) regions on bovine femoral head. The present simulation allows fitting the time-history of reaction force measured from indentation test (R2 = 0.993 ± 0.0012 for lateral region and R2 = 0.990 ± 0.0032 for medial region). The differences of the elastic modulus of collagen fibre and the permeability between medial and lateral regions were consistent to those observed from the chemical composition analysis.
