Biomedical Engineering Reference
In-Depth Information
Osteons
Circumferential
lamellae
Spongy
bone
Marrow
cavity
Interstitial
lamellae
Compact bone
Trabeculae of
spongy bone
Vein
Artery
Lamellae
Endosteum
Canaliculi opening
at surface
4.1
Structure of osseous tissue (adapted from Martini, 1989).
immature woven bone. Lamellar bone is highly organized; stress-oriented
collagen of lamellar bone gives its anisotropic properties.
4.1.3 Bone physical properties
one of the fundamental differences between cortical and trabecular bone
is its apparent porosity. Apparent porosity is the ratio of the mass bone
tissue in a specimen to the bulk volume of the specimen. Typical apparent
densities for cortical bone and trabecular bone are 1.85 g cm
-3
and 0.30 g
cm
-3
, respectively with a much higher variability and standard deviation for
trabecular bone. Physical properties vary from one bone to another depending
on various parameters such as apparent density, ash density (total mineral
content divided by bulk volume), histology (number of osteons, primary
versus secondary bone), collagen composition and content, orientation of
the collagen fibers and mineral, composition of the cement lines, bonding
between the mineral and collagen phases, and accumulation of microcracks in
the bone matrix and around osteons (Burstein
et al
., 1975; Schaffler and Burr,
1988). Apparent density can be correlated to Young's modulus and ultimate
strength using a power law with exponents for modulus ranging from 1.5 to
7.5. Volume fraction (proportional to apparent density) and mineral content
(proportional to ash density) can also be correlated to Young's modulus and
