The diagnosis of osteoporosis

Quantity vs. Quality
The U.S. National Institutes of Health (NIH) define osteoporosis as a disease characterized by weakening of bones and consequent increase of fracture risk. At present, in clinical practice, no direct method is available for measuring bone strength in cases of primary or secondary osteoporosis or in degenerative bone diseases. Dual Energy X-ray Absorptiometry (DEXA) is currently the golden standard for measuring Bone Mineral Density (BMD). The DEXA test results are stated in the form of T-score, which expresses the number of standard deviations below the average BMD of the young Caucasian adults of the same gender.

However, even though a low value of bone mineral density is considered to increase the fracture risk, the majority of fractures take place in postmenopausal women and elderly men at moderate risk. In fact, without prejudice to the importance of the contribution to bone resistance provided by mineralization, it is well known that the ability of bone to resist the applied loads also depends on the structural architecture of the trabeculae, an aspect which the techniques currently available are not able to take into account. Estimating the bone density alone is not, therefore, a parameter sufficient for a complete evaluation of the load bearing capability of the bone, and, for a better quantitative understanding of bone quality, also the spatial arrangement of the trabecular tissue and its capacity to withstand loads should be taken into consideration.