Nano-Science Revelations in Bone Research

When diagnosing human bone as Osteoporotic, the quantity of bone, assessed by measurement of the bone mineral density (BMD), is often used in the estimate of fracture resistance. However, bone quantity is only one of the factors that determine the ability of bone to resist fracture. Bone quality describes the remaining characteristics and traits that determine the fracture resistance of bone. Bone is a composite material, consisting of minerals embedded in an organic matrix. The mechanical properties of a composite material are determined by the structural interactions of the individual constituents, which is different from the sum of mechanical properties of the individual constituents. The size of the building blocks of bone is in the nanometer range, the diameter of collagen is 100 nanometers and mineral plates range from the typical diameter of 10-20 nanometers to 200 nanometers. To understand the ability of bone to resist fracture, and its quality as a tissue, it is important to appreciate the intricate interplay between these building blocks. This review focuses on the parameters that contribute to bone quality, including recent evidence for the roles of factors such as collagen cross-linking, microcracking and bone remodelling.