Fatigue of Cancellous Bone Respect to Normal Walking

Osteoporosis disease makes bone fragile and weak to withstand against load and bodyweight. Crack initiation and damage might occur depends on different morphological indices and types of load impose on trabecular bone. Fatigue analysis with strain-based method is applied for bovine trabecular bone with three different morphological indices to investigate correlation between fatigue life results and bone morphology. Two different analyses were performed, the first was static and the second was dynamic analysis. Axial load imposed on vertical, 45-degree and horizontal samples. Plastic strain in vertical sample initiated at 30% of total and reach to 5.97e-4 at 40% however, at 45-degree and horizontal initiated at 20% and 10% with values of 0.00479 and 0.211 respectively. Then fatigue analysis was performed on samples and S-N curve extracted. Results show that fatigue life of vertical sample at high load amplitude (40% of total load) is 12262 cycles, however this value in 45-degree and horizontal samples decrease drastically to 357 and 5 cycles respectively. In the various morphological indices, BV/TV and BS/TS are counted as crucial factor in correlation between fatigue life and bone morphology. Vertical sample include of less porosity than 45-degree and horizontal, and because of this reason stress localized and plastic strain value in vertical sample value is far below than other two. Fatigue life decrease when porosity of structure increases. Plastic strain and high stresses had been appeared in arch and rod-like of trabeculae.Non study consider contribution of rotated angle of load on fracture of trabeculae so far, in this study results show that the most fracture in inner sites of bone occur when load angle is perpendicular to trabeculae.