Women with idiopathic osteoporosis appear to have a low mineralization in trabecular bone, which suggests that alterations in the mineralization processes could be responsible for bone fragility, Jochen G. Hofstätter, M.D., reported at the annual meeting of the American Society for Bone and Mineral Research.
Dr. Hofstätter and his associates assessed bone mineral density distribution using quantitative backscattered electron imaging, and bone biopsies were collected from nine premenopausal women with idiopathic osteoporosis. Bone mineral density distribution was also evaluated for 15 healthy, age-matched women.
Quantitative backscattered electron imaging is a relatively new technique for studying mineralization patterns, said Dr. Hofstätter of the Ludwig Boltzmann Institute of Osteology in Vienna. The sample is scanned using an electron microscope. The quantity of electrons backscattered from a given surface is proportional to the mean atomic number of the measured material, allowing researchers to identify and quantify minerals present in bone.
To determine the bone mineral density distribution, the researchers measured the mean calcium content, the typical calcium content, the variation of calcium content, and the percentage of low-mineralized matrix.
There were significantly lower levels of mean calcium content (−3.1%) and typical calcium content (−2.7%) among the women with idiopathic osteoporosis, compared with those in the control group.
This is “an interesting finding with respect to the [low] bone turnover situation reported in these patients. One would expect exactly the opposite,” Dr. Hofstätter noted. Low bone turnover typically permits prolonged secondary mineralization in a larger number of bone pockets, resulting in higher mineral content.
There were no significant differences between the two groups in terms of the variation of calcium content and the percentage of low mineralized matrix.
The lower degree of mineralization in women with idiopathic osteoporosis, combined with low bone turnover, suggests that there are differences in their mineralization processes, Dr. Hofstätter said. These changes may be the result of alterations in the extracellular matrix and may in turn contribute to increased fragility.