Fatigue data analysis of canine femurs under four-point bending.

When bone is subjected to fatigue loading, micro-cracks initiate and grow. This reduces the mechanical properties and quantitative relationships between stiffness loss and loading cycles may be derived. We developed the relationships between stiffness loss and loading cycles for whole canine femurs subjected to cyclic fatigue in four-point bending. The fatigue data from experiments followed Weibull statistics. When the stiffness loss is less than 15%, a linear relationship is best-fitted (R2 = 0.96, p < 0.0001) between the stiffness loss and loading cycles. However, when the stiffness loss is greater than 30%, a power law relationship is best-fitted (R2 = 0.97, p < 0.0001) between the stiffness loss and loading cycles. Thus, we conclude that the derived relationships between stiffness loss and loading cycles might be useful for the prediction of bone failure under cyclic bending subjected to an initial strain of 2700 microstrain.