Osteoporosis and Lateral Spine DXA


Question

In the new institution that I joined 1 month ago, I have already had multiple consults for osteoporosis. I have discovered that the department that does all of the DXAs at this institution routinely measures the lateral spine BMD. This was not done at any of the other institutions where I trained, and was not mentioned during my ISCD certifcation training at Endocrine University. In my brief review of up-to-date, endotext, the ISCD website, and the published medical literature, I do not see adequate information regarding the use of lateral BMD. If my impression is correct, lateral BMD measurements may be useful for interpreting and following changes in BMD in patients who have aortic calcifcations or osteophytic changes, but should not be used for the diagnosis of osteoporosis. I assume the recommendation to not use it for diagnosis is because there is no fracture risk data regarding BMD measurements using the lateral spine (is this true?). However, at this institution, I have already seen multiple patients diagnosed with osteoporosis on the basis of the lateral spine, with normal or much more mild decrements in BMD at the AP spine and hip. My concern is that primary care physicians and others who have not been trained to read DXAs or understand fracture risk assessment may be overtreating patients because of these lateral spine measurements. If you could please give me a quick overview of the current "state of the art" and guidelines regarding the use of lateral spine BMD, I would appreciate it. Furthermore, if there is data to either support or refute the use of lateral DXA in the evaluation and/or diagnosis of osteoporosis that would be greatly appreciated as well.

Response

Sorry for the delay in responding, as I was out of town. You are correct in that one cannot use the lateral spine DXA for making a diagnosis of osteoporosis, which should be based on femoral neck (or total femur) BMD and/or the AP spine BMD. In my practice, I rely on this measure, combined with the AP spine.

Tha lateral spine imaging may be useful for vertebral fracture analysis (VFA) by DXA and perhaps in research studies. Another problem with it is that the precision of lateral spine BMD seems to be worse than that for the femur neck or AP spine, so it is also problematic in terms of using it for follow up. Sundeep Khosla, MD