Estimating tissue-level properties of porcine talar subchondral bone

Tissue-level properties of bone play an important role when characterising apparent-level bone biomechanical behaviour and yet little is known about its effect at this hierarchical level. In combination with trabecular morphological data these properties can be used to predict bone strength, which becomes an invaluable tool for clinicians in patient treatment planning. This study developed specimen-specific micro-finite element (mu FE) models using validated continuum-level models, containing grayscale-derived material properties, to indirectly establish tissue-level properties of porcine talar subchondral bone. Specimen-specific continuum finite element (hFE) models of subchondral trabecular bone were setup using mu CT data of ten cylindrical specimens extracted from juvenile porcine tali. The models were validated using quasi-static uniaxial compression testing. Validated hFE models were used to calibrate the tissue modulus of corresponding mu FE models by minimising the difference between the mu FE and hFE stiffness values. Key trabecular morphological indices (BV/TV, DA, Conn.D, Tb.Th, EF) were evaluated. Good agreement was observed between hFE models and experiment (CCC = 0.66). Calibrated Etiss was 504 +/- 37.65 MPa. Average BV/TV and DA for mu FE specimens were 0.37 +/- 0.05 and 0.68 +/- 0.11, respectively. BV/TV (r(2) = 0.667) correlated highly with mu FE stiffness. The small intra-specimen variation to tissue-level properties suggests that variations to apparent-level stiffness originate from variations to microarchitecture rather than tissue mechanical properties.