The aim of this study is to quantitatively discern the compressive stiffness along the thickness of bovine cortical bone from the inner surface toward the bone’s periosteum (outer) surface. Ring-shaped bone slices from randomly selected 3 cow bovine bones were cut from mid diaphysis femur. Micro hardness measurements (ASTM E384-11e1 Standard- test method for Vickers hardness of materials with load of 500gf and dwelling time of 10s) were conducted along radial lines emanating from the geometric center of the bone transverse cross section. Values of compressive stiffness (longitudinal young’s modulus, E11) using the slope of the unloading curve of micro hardness tests at maximum load were extracted per the method advanced by Oliver and Pharr. Fitting these data points in a linear fit resulted in statistically significant and simple linear equations for compressive modulus as function of radial distance. For the anatomical anterior and posterior regions, compressive modulus values were found to range from 18 to 23.4 GPa (average of 21.2 GPa) and 23 to 26.0 GPa (average of 23.8 GPa), respectively. This is about 12% increase in average stiffness values of outer lamella near the periosteum as compared with inner regions.

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