A damage assessment model for cadaveric cortical bone subjected to fatigue cycles

A model is developed to evaluate the fatigue damage of cadaveric human cortical bone by incorporating stiffness reduction of bone materials as the number of fatigue cycles progresses. The structure of cortical bone has been characterized as a natural fiber-reinforced composite material consists of Haversian osteons (fibers) embedded in interstitial bone (matrix) and separated by weak cement line interfaces. The proposed damage model included such mechanical and histological parameters as osteon volume fraction, donor age, cyclic stress magnitude, secant modulus of osteons, and cement line interfacial strength. The capability of damage model was evaluated based on experimental fatigue damage data of cortical bone samples for various human age groups as both magnitudes and number of stress cycles varied. Predicted fatigue damage results were found in good agreement with several experimentally obtained damage results of cortical bone samples tested by different laboratories.