Secondary, osteons

In the early stages of bone formation, the osteons dominate the bone structure to make an overall structure of fiber-matrix composite. While the primary bone has a dense structure, the secondary bone structure is this composite. As a result, the cortical bone structure becomes very complex. It is microscopically porous, has a lamellar structure, and is also a fiber-matrix composite. Size and packing of osteons and canals, and their orientation, determine the mechanical properties of these bones. 

Certain combinations of fibril array organizations result in specific stmctures, like the formation of lamellar bone into secondary osteons, as described in Section 9.03.3.5.2. 

Compact bone is found in the cylindrical shells of most long bones in vertebrates. It often contains osteons which consist of lamellae that are cylindrically wrapped around a central blood vessel (Haversian system or secondary osteon). These secondary osteons form during bone remodeling. Studies have shown that the orientation of the collagen fibrils within individual lamellas is a function of external stresses on the bone and adapted to the specific function." " ... 

The cement line round Haversian systems (secondary osteons) contains less calcium and phosphorus, and more sulphur than nearby parts of bone. This may indicate the presence of more sulphated mucosubstances, making the cement line viscous [9]. 

Ascenzi and co-workers [26-29] distinguish two types of secondary osteon longitudinal osteons, whose collagen fibres have a basically longitudinal orientation, and alternate osteons, whose fibres have markedly different courses in neighboring lamellae. (This difference is a contentious issue.)... 

Vincentelli and Grigorov [35] examined the effect of Haversian remodelling on the tibia. The specimens they reported were almost entirely primary or Haversian, with few specimens having a scattering of secondary osteons. [Unfortunately they probably (it is not clear) allowed their... 

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