The investigation of mechanical properties of bone, specifically fracture properties, is an important aspect of studying bone quality, and can potentially be used to predict the risk of bone fracture. In this study, a novel microindentation technique, the reference point indentation (RPI) technique, is used to assess the mechanical properties of swine femoral cortical bone. This technique uses successive indentation cycles to introduce a unique parameter, the indentation distance increase (IDI). The IDI is shown to be correlated with fracture toughness. Scanning electron microscopy (SEM) imaging is also used to gain insight into the microstructural properties of femoral cortical bone. Variations in properties are studied as a function of age (i.e. 1, 6, 14.5, and 24 month age groups), gender, anatomical position within the femoral cross-section, and loading orientation (i.e. transverse versus longitudinal). IDI and mean energy dissipated (MED) values decreased significantly with age on both transverse and longitudinal surfaces, while stiffness values increased. The transverse surface generally exhibits lower IDI, lower MED, and higher stiffness values compared to the longitudinal surface. Significant differences in gender are only seen in the 1 month age group, and measurements at different anatomical position also differ significantly in 1 month and 24 month age groups, but not in 6 month and 14.5 month age groups. SEM images show no signs of osteon formation in 1 month bone samples, while comparable amounts of osteons are observed in 6, 14.5, and 24 month age groups. We conclude that by inducing microcracks onto the bone surface, the RPI technique can provide useful information about fracture properties of cortical bone.
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