Bone mass and architecture determination: state of the art.

Bone fracture occurs when the bone strength (i.e. the ability of the bone to resist a force) is less than the force applied to the bone. In the elderly, falls represent the more severe forces applied to bone. Bone density is a good marker of bone strength, and has been used widely in this respect. Nevertheless, many aspects of bone strength cannot be explained by bone density alone. For this reason there has been increasing interest in studying architectural parameters of bone, beyond bone density, which may affect bone strength. Macro-architectural parameters include e.g. bone size and geometry assessed with techniques such as radiography, dual-energy x-ray absorptiometry (DXA), peripheral quantitative computed tomography (QCT), computed tomography (CT) and magnetic resonance imaging (MRI). Micro-architectural parameters include fine cortical and trabecular structural detail which can be evaluated using high-resolution imaging techniques such as multidetector CT, MRI, and high-resolution peripheral QCT. These techniques are providing a great deal of new information on the physiological architectural responses of bone to aging, weightlessness, and treatment. This will ultimately lead to the prediction of fracture risk being improved through a combined assessment of bone density and architectural parameters.