Trabecular bone failure strains

Interestingly, the failure (yield and ultimate) strains of human trabecular bone have only a weak dependence, if any, on apparent density and modulus." - - - A recent study designed to test for intersite differences found that yield strains were approximately uniform within anatomic sites, with standard deviations on the order of one-tenth the mean value, but mean values could vary across sites" (Fig. 8.13). Thus, for analysis purposes, yield strains can be considered constant wiAin sites but heterogeneous across sites. Regardless of anatomic site, however, yield stains are higher in compression than in tension." Ultimate strains are typically in the range of 1.0 to 2.5 percent. Evidence from experiment on bovine bone indicates that yield strains are also isotropic - despite substantial anisotropy of modulus and strength. 

There are two basic structural types of bone cancellous (trabecular, spongy) and cortical (dense) bones. Cancellous bone matter is less dense than that of cortical bone and is found across the ends of the long bones. Owing to its lower density, cancellous bone has also a much lower modulus of elasticity but higher strain-to-failure rate compared to cortical bone (Table 3.1). Bone has higher moduli of elasticity than soft connective tissues, such as tendons and ligaments. The difference in stiffness (elastic modulus) between the various types of connective tissues ensures a smooth gradient in mechanical stress across a bone, between bones and between muscles and bones (Hench, 2014). 

---