Compact bone

Most bones of the human skeleton are composed of two structurally distinct types of tissue compact (dense) and trabecular (cancellous, spongy) bone. Both types contain the same elements cells ( osteocytes) embedded in a mineralised matrix and connected by small canals ( canaliculi ). In compact bone, which makes up 85% of the skeleton, these components form elongated cylinders of concentric lamellae surrounding a central blood vessel (called osteon or Haversian system). Cancellous bone, in contrast, forms thin,... 

Figure 9.1. Thin section of compact bone from Schleswig (cf. Table 9.1), after application of a cell stain (methylene blue). Besides the bone cells, exogenous cellular material in the hollow spaces (shown by arrows) indicates previous microbial invasions.

It is estimated that approximately 4% of compact bone is renewed annually in the typical healthy adult, whereas approximately 20% of trabecular bone is replaced. 

Currey, J.D. (1998) The effect of porosity and mineral-content on the Youngs modulus of elasticity of compact-bone. Journal of Biomechanics, 21, 131-139. 

Akkus O, Polyakova-Akkus A, Adar F, Schaffler MB (2003) Aging of microstructural compartments in human compact bone. J Bone Miner Res 18 1012-1019... 

Schaffler MB, Choi K, Milgrom C (1995) Aging and microdamage accumulation in human compact bone. Bone 17 521-525... 

Figure 10.1 Gross structural features of human compact bone. (Adapted from Gartner and Hiatt, 1994 Graphic 4.1.)...

Bone. The structure of bone was described in Section 1.5.2. Recall that bone is a composite material, composed primarily of a calcium phosphate form called hydroxyapatite (HA). The major support bones consist of an outer load-bearing shell of cortical (or compact) bone with a medullary cavity containing cancellous (or spongy) bone toward the ends. 

Figure 5.133 Comparison of tensile properties of fiber-reinforced bone cement (PMMA) and human compact bone. Reprinted, by permission, from Concise Encyclopedia of Composite Materials, A. Kelly, ed., p. 270, revised edition. Copyright 1994 by Elsevier Science Publishers, Ltd.

Shapiro, I. M. The phospholipids of mineralized tissues. I. Mammalian compact bone. Calc. Tiss. Res. 5, 21 (1970)... 

Vitamin A deficiency is associated with faulty modeling of bone, with production of thick, cancellous bone instead of thinner, more compact bone. 

Radium, similarly to calcium, deposits in bone within those areas where new bone mineral is being formed and also on all bone surfaces. Radium remains in those areas of new bone formation, but the radium deposits on bone surfaces eventually move into the depths of compact bone as new bone matrix is deposited on top of them. In this deposition process, short-lived radium-224 rapidly decays, leaving no radioactivity within bone whereas, long-lived radium-226 remains in the skeleton indefinitely (Rowland 1966). Mays et al. (1975) have demonstrated that the radon to radium ratio in bone increased with time after injection in beagles. 

Hert, J., Pribylova, E. and Liskova, M. (1972) Reaction of bone to mechanical stimuli. Part 3. Microstructure of compact bone of rabbit tibia after intermittent loading. Acta anatomica 82 218-230... 

FLUID FLOW IN THE SELF-OPTIMISED STRUCTURE OF COMPACT BONE... 

Abstract Compact bone is a well-organised, multi-level porous structure. Strain-derived fluid flow likely steers the activity of cells within the bone matrix, which in turn orchestrate the concerted activity of bone resorbing and bone forming cells at the surface. We present a model of the strain-driven bone remodelling proces, which could explain the mechanically optimised structure of compact bone. 

Fluid Llow in the Self-Optimised Structure of Compact Bone 299... 

The skeletal age, which is not necessarily identical with the calendar age of the individual, has an important impact on the fluorine uptake, because osteoporosis is a process that fundamentally influences the bone structure. The disease pattern becomes visible in material loss within both the trabecular and the compact bone structure. Furthermore, the mineral density even in a healthy individual is not uniform in compact bone, but is a function of bone stress at this skeletal position and is increased at the point where muscles and tendons are fixed. 

Compact bone like long bones, most abundant among archaeological bone remains, shows basically two different parts a central one called diaphysis, mainly composed of compact bone, and two extremities called epiphysis which are more porous. It contains a fundamental substance - a mixture of the organic and mineral phase - and cells that remodel continuously the bone material as well as the so-called Haversian systems containing channels that provide the nutrition to the bone cells as they accommodate blood vessels and nerves. The Haversian channels exhibit diameters between 10 and 70 pm [26], The periosteum closes the bone at its outside and the medullar cavity at the inside accommodating the bone marrow [40],... 

Martin, B. R., and Burr, D. B., Structure Function and Adaptation of Compact Bone. Raven Press, New York, 1989. 

Compact bone Circumferential, concentric lamellar Prevents bending of long... 

Compact bone Blood cells Periosteum Marrow cavities Source of cells... 

Figure 3.18. Structure of cancellous bone. Cancellous bone is composed of periosteum, an outer layer apposed to the peripheral compact bone. The layer beneath peripheral compact bone contains bone trabeculae, marrow cavities, adipose tissue, hemopoietic cells, and the endosteum.

Figure 3.19. Structure of compact bone. Compact bone consists of an outer layer of mineralized lamellae that are wrapped around the shaft of the bone. Beneath the outer layer are concentric rings of mineralized collagenous lamellae. Each concentric unit is termed an osteon and has a vessel running through its center (haversian canal).

There are two types of bony tissue cancellous or spongy bone and cortical or compact bone. Cortical bone is denser and more highly ordered than the randomly woven cancellous bone tissue. Cancellous bone is open-celled and porous, with from 30% to over 90% porosity. 

Haversian canal The central opening of compact bone contains nerves and blood vessels. 

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