Experimental investigation of Poisson's ratio as a damage parameter for bone fatigue.

The fatigue loading of bone results in the degradation of mechanical properties such as strength and stiffness. Even though several authors have investigated the relationship between the longitudinal modulus and loading cycles, the reduction in Poisson's ratio and its relationship to fatigue loading cycles have not previously been investigated. In this study, the reduction in the major Poisson's ratio and longitudinal modulus for cortical bone specimens as a result of tensile fatigue was experimentally investigated. We compared the results of the major Poisson's ratio reduction to the reduction in longitudinal modulus to determine if there was a relationship between the two. The results showed that the reduction in Poisson's ratio was about 8-22% higher than the reduction in longitudinal modulus, indicating that more microdamage accumulated transversely than longitudinally. Both the longitudinal modulus and major Poisson's ratio decreased in a logarithmic fashion with increasing loading cycles for the bone specimens tested.