What does bone quality mean?

Bone quality is a new concept included in the current defini-tion of osteoporosis. It arises since bone mineral density (BMD) as measured by densitometry only partially explains the bone resistance to the fractures. The effects of the drugs on bone quality, reflected in the reduction of the risk of fractures, are observed before changes in BMD are detectable. We do not have a single method to measure the quality of bone. Only some tools, that allow partial and complementary aspects of what bone quality means, are currently available. Bone remodeling is not only related with bone mass but also determines the bone geometry, the microarchitecture, the bone ultrastructure and the protein matrix characteristics. For the assessment of bone remodeling the available techniques are histomorphometry in bone biopsies after tetracycline labeling, biochemical markers of remodeling in blood and urine and positron emission tomography (PET). For the valuation of the microarchitecture, besides the histomorfometry, magnetic nuclear resonance imaging (MRI), and micro-computed tomography (μCT) in vitro and vitro, among other methods, are valuable tools. All these techniques permit an evaluation of bone beyond a purely quantitative assessment, applicable in clinical routine in a near future.