The effects of prior damage on the rate-dependent torsional strength of human cortical bone

The effects of damage accumulation on bone mechanical properties are not well understood. Previously, we identified a significant interaction between damage and the viscoelastic properties of human cortical bone loaded in torsion. In the current study, we further investigate this interaction by testing the hypothesis that damage accumulation significantly alters the rate-dependent nature of bone strength. The results indicated that increasing the twist rate of residual strength tests by only one order of magnitude was associated with a significant, 3-fold increase in strength and modulus degradation. The results suggest that damage accumulation may make cortical bone more susceptible to fracture at high loading rates, which has important implications for understanding the increased fracture frequency associated with falls in the elderly.