Bone

The primary tissue of bone is osseous tissues which is a hard and lightweight composite of ‘calsium phosphate’ in the chemical arrangement termed calcium hydrocylapatite. Bone has a relatively high compressive strength and poor tensile strength. It is essentially brittle with anisotropic mechanical properties. All bones consist of living cells embedded in the mineralised organic matrix that makes up the osseous tissue.


Cortical bone:

It is one of two main types of osseous tissues. It has a dense structure and forms the surface of bones, contributing 80% of the weight of a human skeleton.

Cortical bone has anisotropic mechanical properties which are due to different mechanical properties of the constituents (ostenic and interstitial lamellae) and the hierarchical structural organization of material.

microscopic image of ostenic and interstitial lamellae

Trabecular (cancellous ) bone:

It has a spongy structure and makes up the bulk of the interior of most bones, including the vertebra, tibia and femur.

Young's moduli and the strength of cancellous bone are proportional to the square of apparent density of the tissue and are therefore proportional to one another (Rice et al 1988).

	Strength Mpa	Modulus MPa
Cancellous bone in tension and compression	5-10	50-100
Cortical bone in compression	130-220	17000-20000
Cortical bone in tension	80-150	17000-20000

Bone Eng. By Davies