Trabecular bone tissue density

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). 

Two other common measures of bone density in biomechanical studies are termed tissue and apparent densities. Tissue density p i is defined as the ratio of mass to volume of the actual bone tissue. It is similar for cortical and trabecular bone, varies little in adult humans, and is about 2.0 g/cm. Apparent density p pp is defined as the ratio of the mass of bone tissue to the bulk volume of... 

The percent volume of water, inorganic, and organic components for hydrated trabeculae have been reported at 27%, 38%, and 35%, respectively [11], although the precise values depend on anatomic site, age, and health. Based on reported wet, dry, and ash apparent densities for specimens of defatted human lumbar spine trabecular bone [4], the percentage weights of the inorganic, organic, and water components for this tissue can be calculated at approximately 54%, 26%, and 20%, respectively. 

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