Osteon

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,... 

The geometry and structure of a bone consist of a mineralised tissue populated with cells. This bone tissue has two distinct structural forms dense cortical and lattice-like cancellous bone, see Figure 7.2(a). Cortical bone is a nearly transversely isotropic material, made up of osteons, longitudinal cylinders of bone centred around blood vessels. Cancellous bone is an orthotropic material, with a porous architecture formed by individual struts or trabeculae. This high surface area structure represents only 20 per cent of the skeletal mass but has 50 per cent of the metabolic activity. The density of cancellous bone varies significantly, and its mechanical behaviour is influenced by density and architecture. The elastic modulus and strength of both tissue structures are functions of the apparent density. 

Parfitt AM (1994) Osteonal and hemi-osteonal remodeling the spatial and temporal framework for signal traffic in adult human bone. J Cell Biochem 55 273-286... 

A section through a human toe bone (fifth metatarsal, amputated by Roger Gundle who took the pictures in 1.3) is shown in Fig. 9.18. The circular patterns relate to the Haversian system responsible for blood flow in the bone. The regions around the holes are osteons. The osteons appear with different contrast in this picture. As always this relates to different mechanical properties. In this case it enables you to distinguish the different ages of osteons, because the variation in contrast is related to different degrees of mineralization. 

Crossfire Crosslinked Poly(ethylene) (12) I Iowmedica Osteonics Corp. 

Duration Stabilized UHMWPE (12) Howmedica Osteonics Corp. 

D.-C. Sun and C.F. Stark, Non-oxidizing polymeric medical implant, US Patent 6818020, assigned to Howmedica Osteonics Corp. (Mah-... 

Ascenzi, A., Bonucci, E. The osteon calcification as revealed by the electron microscope. 

Fig. 14.1. Raman spectrum of osteonal bone tissue. Major band assignments are marked. Reprinted with permission from [1]...

Fig. 14.3. (a) Bone section under polarized light, black line outlines where Raman images were acquired. Polarized Raman images of (b) phosphate V2/amide III, (c) phosphate Vi/amide I, and (d) carbonate/phosphate V2 band ratios at the interface between osteon and interstitial bone, (e and f) Three-dimensional view of phosphate Vi/amide I ratio for different polarization directions. Reprinted with permission from [1]... 

Figure 3. A pie-shaped section of an osteon. The osteonal canal is on the upper right, the cement line to the left. The osteonal canal is part of the vascular porosity (PV), the lacunae and the canaliculi are part of the lacunar-canalicular porosity (PLC) and the material in the space that is neither PV or PLC contains the collagen-apatite porosity (PCA).The three interfaces, the cement line, the cellular interface (IC) and the lacunar-canalicular interface are each indicated. The radius of an osteon is usually about 100 mm, and the long axis of a lacuna is about 15 mm. Using this information it should be possible to establish the approximate scale of the printed version of this illustration. Previously published in Cowin (1999).

Figure 7. Strain amplification A plot of the strain amplification ratio er as a function of the load frequency for different load magnitudes. Strain amplification ratio is defined as the ratio of the hoop strain in the cell process membrane to the bone surface strain at the osteonal lumen, e is the strain on the whole bone s is the load on the whole bone. Previously published in You et al. (2001).

Martin, R.B. and Burr, D.B. (1982) A hypothetical mechanism for the stimulation of osteonal remodeling by fatigue damage. Journal of Biomechanics 15 137-139... 

Wang, L., Fritton, S.P., et al. (1999) Fluid pressure relaxation depends upon osteonal microstructure modeling of an oscillatory bending experiment. Journal of Biomechanics 32 663-672... 

Zeng, Y., Cowin, S.C., Weinbaum, S. (1994) A fiber matrix model for fluid flow and streaming potentials in the canaliculi of an osteon. Annals of Biomedical Engineering 22 280-292... 

The structure of this material is generally similar to that of reinforced concrete, which contains steel rods embedded in concrete. Researchers are currently attempting to calculate the predicted strength of the osteon-mucopolysaccharide composite and to compare it with observed values. 

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