Is the amount of trabecular bone-loss dependent on bone mineral Density? A study performed by three centres of...

For the risk getting osteoporosis as well as for diagnosis of osteoporosis 3 facts are highly important: bone-mass, the amount of bone-loss and bone-structures (microarchitecture of bone). All three parameters can be validated today with high precision but the amount of bone-loss seems to be the most important one, even for the decision of either antiresorptive or bone-stimulating therapy. But to calculate the amount of bone-loss until now at least two measurements of bone mineral density (BMD) are necessary which have to be performed within a certain period of time, depending on the reproducibility of the method to be used. If on the other hand the amount of bone-loss would be dependent on actual base-line bone-mass the right therapy could be started already after only one measurement of BMD. The aim of this study was therefore to investigate if there is any relation between the amount of bone-loss and base-line volumetric BMD. For this we separately measured trabecular and cortical bone densities of 135 women in three independent centres of osteoporosis in Zurich and Munich using the method of high resolution quantitative computed tomography - pQCT - with the Densiscan 1000, Scanco Medical, Zurich. We did this at least twice and then compared absolute volumetric BMD in the first step before we calculated trabecular and cortical bone loss per year for each woman. We could not only confirm again that bone loss in trabecular bone was significantly higher than in cortical bone and that the non-weight-bearing trabecular bone as could be found in the distal radius seems to be the skeletal site of maximum bone-loss, but moreover - and this is the more important finding - we could show that the amount of relative bone-loss was the higher the lower trabecular base-line volumetric BMD was. According to this the rate of fast-loser (more than 3.5% per year) increased the lower trabecular base-line volumetric BMD was. These results may lead to a new screening-test for the assessment of the individual risk of osteoporosis and for the individual risk of fast bone-loss which now can be evaluated with only one single measurement of BMD, to treat the so classified patients not only earlier but even more rational, dependent if either antiresorptive therapy or stimulation of bone-formation seems to be more important.