Comparative analysis of axial and radial mechanical properties of cortical bone using nanoindentation

We investigate differences in mechanical properties between anatomical regions and bearing surfaces of cortical bone at the microscale.

Eight samples were prepared from fresh femoral bones, and then loaded onto the four sides of the anatomical region, including the front, back, inside, and outside, as well as the axial and radial directions. Nanoindentation testing was performed on each sample using six indentations to acquire load-depth curves. The curves were then analyzed to determine the elastic modulus and hardness of the materials. Statistical analysis was subsequently conducted to assess the data distribution and variability. Finite element simulation may have been utilized to establish a more comprehensive mechanical behavior model.

The mechanical properties of cortical bone varied significantly across various anatomical regions and bearing surfaces, the elastic modulus and hardness of the anterior and medial sides were significantly greater compared with those of the posterior and lateral sides. The elastic modulus in the axial direction was significantly higher relative to that in the radial direction by 21.94% $(p<!--FUNCTION\; APPLICATION--><0.001)$. The hardness increased by 13.3% $(p<!--FUNCTION\; APPLICATION-->=0.03)$. The elastic modulus and hardness of cortical bone increased in the same direction, showing a strong positive correlation (${R<!--FUNCTION\; APPLICATION-->}^2=0.817$, $p<!--FUNCTION\; APPLICATION--><0.001$). Under the same conditions, the stresses in the axial direction of the cortical bone exceeds those in the radial direction.