Contribution, development and morphology of microcracking in cortical boneduring crack propagation

A fracture mechanics study of cortical bone is presented to investigate the contribution, development morphology of microcracking in cortical bone dur ing crack propagation. Post-hoc analyses of microcrack orientation, crack p ropagation velocity and fracture surface roughness were conducted on previo usly tested human and bovine bone compact tension specimens. It was found t hat, consistent with its higher toughness, bovine bone formed significantly more longitudinal, transverse and inclined microcracks than human bone. Ho wever, in human bone more of the microcracks that formed were longitudinal than transverse or inclined, a feature that would optimise bone's toughness . Crack propagation velocity in human and bovine bone displayed the same ch aracteristic pattern with crack extension, where an increase in velocity is followed by a consequent decrease and vice versa. On the basis of this pat tern, a model or crack propagation has been proposed. It provides a detaile d account of mocrocrack formation and contribution towards the propagation of a fracture crack. Analyses of fracture surfaces indicated that, consiste nt with its higher toughness, bovine bone displays a rougher surface than h uman bone but they both have the same basic fractured element, i.e. a miner alised collagen fibril. (C) 2000 Published by Elsevier Science Ltd. All rig hts reserved.