Osteoporosis: On the Cutting Edge of Bone Health
Advances in research are changing the way osteoporosis experts think about this widespread disease.
Fine-tuning Osteoporosis Risk continued...
That's taken to a higher level in a new instrument being used to study
osteoporosis, called high-resolution peripheral quantitative tomography.
Because it uses a higher level of radiation, it can't be used at the spine or
near vital organs, but it can be used to image areas like wrist bones. "The
resolution with peripheral scanners is good enough that you can see individual
structural components, which give you much more information about the strength
of the bone," Khosla says.
He predicts that the peripheral scanners, which may not be much more
expensive than today's DEXA, may soon be approved for clinical use. Since CT
scans are significantly more expensive, they may not be used as a stand-alone
screening tool. However, when a patient has a CT scan for another reason, it's
relatively easy to get bone information at the same time.
"We still need to accumulate more data about how these tools predict
fracture risk, but initial results are promising," says Khosla.
Understanding Bone Remodeling
Bisphosphonate drugs were originally thought of as osteoporosis treatments
that helped to build bone mass. But it soon became clear that something more
was going on here. Many patients taking bisphosphonates may see only a modest
increase in bone density -- as little as 1% -- and yet they have a much greater
reduction in their risk of fractures, as much as 50%.
"Research has shown that there is no relationship between how much these
drugs build bone mass and the reduction in fracture risk," says Robert Heaney,
M.D., a professor of medicine at the Osteoporosis Research Center at Creighton
University School of Medicine in Omaha, Neb.
Scientists realized that the drugs were also slowing down the rate of bone
remodeling -- the process in which existing areas of bone is pared away,
later to be replaced with new bone. In menopausal women, that rate of bone
remodeling doubles -- and then it triples by a woman's early 60s.
"Imagine if you started remodeling your house: first you put an extension on
one side, but before you finished that, you decided to tear out the garage, and
before finishing that, you decided to put a deck on," says Heaney. "You'd have
a pretty fragile house. That's what's happening with accelerated bone