For years, we've thought we understood osteoporosis: it's a disease in which the bones become more and more fragile as they lose density, usually due to aging, menopause, and other factors like lack of calcium and vitamin D in the diet.
But today, advances in research are shedding new light on osteoporosis, which is predicted to affect as many as half of all Americans over age 50 by the year 2020. From diagnosis to prevention to osteoporosis treatment, new research is turning our old understanding of osteoporosis upside down.
The "gold standard" test for diagnosing osteoporosis is the DEXA scan (dual energy X-ray absorptiometry), which measures bone density in the spine, hip, or wrist. These are the most common locations for bone fractures. But this test, as advanced as it is, has limitations.
"Many patients with normal bone density measurements on a DEXA scan still have fractures, and a substantial number of patients whose DEXA scan shows osteoporosis don't get fractures," says Sundeep Khosla, MD, a professor of medicine and osteoporosis researcher at the Mayo Clinic in Rochester, Minn. "The DEXA tells you how much bone is present, but not much about the internal structure of that bone." Obviously, doctors would like to be able to predict fracture risk much more accurately, to fine-tune who is at greatest risk of fracture and most in need of medication.
Khosla compares the human skeleton to a bridge made of metal. "You could have two bridges with the same amount of metal in them, but one could be more sturdy, just because of the way it's constructed," he says. "Similarly, because the microarchitecture of one person's bones is different from another's, their actual strength may be quite different."
Khosla and other osteoporosis researchers are studying new imaging and computer techniques that will allow them to look inside the bone, and see specific structural characteristics. This will help them to build models of bone strength that can help predict which patients are most likely to have fractures.
One such imaging technique is computed tomography (CT) scanning of the spine and hip. Researchers take the three-dimensional image of the bone that the CT scan creates, and use a computer modeling technique that breaks the image down into tiny pieces. "The density of each piece allows you to estimate the strength of each piece, and get the overall strength of the structure," says Khosla. "Depending on where a bone is weakest, it may be more or less prone to fracture."