Passing the Bone Mass Test

Bone is a living tissue. Like every other part of the body, it needs proper nutrition and exercise at each stage of life. Conditions such as osteoporosis and certain types of cancers can weaken bone, causing fractures. Bones can also crack or splinter at any time for a number of reasons. The standard clinical tests that currently measure bone density, like dual energy X-ray absorptiometry (DXA), measure the quantity but not the quality of the bone. This is key, because approximately half of the patients who “pass” a DXA test — including people over the age of 50; postmenopausal women not taking estrogen; people taking corticosteroids, anti-seizure medication, or high-dose thyroid replacement drugs; and people with diabetes, liver disease, kidney disease, or a family history of osteoporosis — still experience a fracture. In short, “passing” the test provides a false sense of security for many of those still at risk.

The most common causes of fractures — not including osteoporosis — are trauma (accidents) and overuse (people who participate in intense physical activity, such as athletes, manual laborers, and military personnel). In fact, medical costs relating to the treatment of military personnel with stress fractures exceed $10 million annually. Add the treatment costs for osteoporotic related fractures and the country is footing a bill in excess of $13 billion each year. Researchers in the Department of Aerospace and Mechanical Engineering think that’s a bit steep for preventable injuries, and so do the agencies sponsoring them.

Assistant Professor Ryan K. Roeder and Associate Professor Glen L. Niebur, funded by the U.S. Army Medical Research and Materiel Command, the Centers for Disease Control and Prevention, and the National Institute of Arthritis and Musculoskeletal and Skin Diseases program, are developing new contrast agents for micro-computed tomography of microdamage in bone. The goal of their work is to design compounds that, binding to a microfracture, will more accurately identify damaged tissue on a CT scan or X-ray. These new contrast agents could help researchers develop applications for assessing the effects of the damage to bone strength, load capabilities, and fracture susceptibility, improving the diagnosis and prevention of fractures. Working with Roeder and Niebur are Mark Z. Zhang, a postdoctoral researcher in the department; graduate students Matt Landrigan and Ryan Ross; and undergraduates Carl Berasi and Matthew Meagher.

<< As part of the “Contrast Agents for Micro-computed Tomography of Microdamage in Bone” project, University researchers employ 2-D, above, and 3-D micro-CT images of notched, cortical bone specimens. The bright region above each notch is stained with a heavy metal contrast agent to highlight microdamage. Shown from left to right, the “stain” or damage increases as the number of loading cycles is increased. The images shown here were generated by Xiang Wang (Ph.D., AME ’05) and Huijie Leng (Ph.D., AME ’06) in conjunction with Assistant Professor Ryan K. Roeder and Associate Professor Glen L. Niebur.