Stiff and strong compressive properties are associated with brittle post-yield behavior in equine compact bone material

Our hypothesis was that post-yield mechanical behavior of compact bone material in compression. defined as the stress, strain, or energy absorbed between 0.2% strain-offset and the point Of maximum stress, is correlated with material density, modulus, strength. histomorphometric evidence of remodeling. and post-failure gross specimen morphology. Post-yield behavior of compact bone material from the third metacarpal bone of 10 horses. ages 5 months to 20 years, was investigated using single-load compression-to-failure. The post-yield stress. strain. and absorbed energy were compared with the compressive elastic modulus, yield stress, ash density. post-failure macroscopic appearance of the specimen, and histologic evidence of remodeling. High values of elastic modulus. yield stress, and ash density were associated, with low values of post-yield mechanical properties (stress. strain. and absorbed energy). Macroscopic post-failure morphology was associated with post-yield mechanical behavior, in that specimens displaying fractures were associated with lower post-yield mechanical properties. and that those Without evidence of frank fracture were associated with higher post-yield mechanical properties. Microscopic evidence of remodeling activity was associated with high post-yield mechanical properties, but not with gross post-failure morphology. There was an abrupt change from relatively high values to extremely low values of post-yield mechanical properties at intermediate levels of ash density. This feature may serve as a functional upper limit to the maximization of bone material stiffness and strength. (C) 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.