Microstructure and chemical composition of bone have been credited with influencing fracture characteristics. Results of previous studies have shwon that energy required to fracture cortical bone is influenced by the mineral content. The cement line is believed to prevent crack growth by forming a weak fiber-matrix interface. Pores such as Haversian canals are thought to influence fracture resistance by acting as stress concentrators or crack arrestors as well as reducing the strength. We hypothesized that both tensile (mode I) and shear (mode II) fracture toughness of human bone would be influenced by the microstructure and chemical composition of bone. Therefore, the objective of this study was to investigate the influence of the morphological (porosity, osteon area, corrected osteon area, osteon density, osteon size and size of Haversian canals) and biochemical (density, apparent and true percentage of mineral, organic and water contents) parameters on the tension and shear fracture toughness (G_(Ic) and G_(IIc)) of the human tibia and femur.
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