Our skeleton needs to carry the body weight and to resist mechanical impacts. This capability or, conversely, bone fragility are controlled by the amount of bone mass, the shape and internal architecture of the bones, as well as by the material of which they are built. Bone material consists of a complex multi-scale arrangement of mineralized collagen fibrils containing also water, proteoglycans as well as some non-collagenous proteins. This organization is by no means constant during our life time. It changes with growth and bone maturation but even adult bone is constantly remodeled and, thus, able to repair damaged tissue and to adapt to the loading situation. In preventing fractures, the most important mechanical property is toughness, which is the ability to absorb impact energy without reaching complete failure. There is no simple explanation for the origin of the toughness of bone material and this property depends in a complex way on the internal structure of the material on all scales from nanometers to millimeters. Hence, fragility may have different structural origins, depending on which toughening mechanism is not working properly. The lecture reviews current knowledge about the multi-scale structure and quality of bone material appearing in humans and in animal disease models during bone growth, remodeling and healing, and discusses its putative relation to bone fragility.
Disclosure: Receipt of grants/research support: Lion Corporation, Japan.
27 - 30 Jun 2015