3-D print of a portion of the knee has color on it to show
pressure points on the joint.
Your knee hurts, you get a MRI. But what
does it really show? While your doctor knows what they mean, those
black-and-white MRI images can seem as lifeless as the Kansas
landscape in "The Wizard of Oz."
Technology that turns MRI data into a
three-dimensional color map of the knee is on its way, helping both
patient and doctor see the problem.
The map can even be turned into a
life-size model, created by a 3-D printer, that can help forecast
when knee replacement will be necessary. "Showing the patient
something in color can help convince the patient what medical
procedures and interventions they need," says Robert D. Peters,
a project manager at GE Healthcare in Waukesha. "It helps them
to be more informed."
Peters jokes that some of his runner
friends might want to keep their knee models as a sort of trophy.
During an operation, of course, the 3-D-printed model serves a more
practical purpose, giving the surgeon a point of reference for the
While 3-D printers have come onto the
consumer market in just the last few years, MRI machines have been
around since the ’80s. Magnetic resonance imaging uses the body’s
natural magnetic properties to produce detailed images from any part
of the body — about 90 images for knee MRIs. A GE team headed by
Peters is partnering with a New York-based company to develop
software that creates a single, comprehensive picture.
This so-called digital segmentation view
of the knee aims to improve the diagnosis of osteoarthritis, a
degeneration of the cartilage that affects about 27 million
Americans. People over the age of 65, the obese and those who are
sedentary are most at risk for osteoarthritis, according to the
Centers for Disease Control and Prevention.
There is no effective drug therapy for
osteoarthritis. Cortizone shots only numb the pain and can lead to
even more damage, says Peters. "It’s important you catch it
as early as possible, so you can either modify your exercise or
perhaps take steps to repair the cartilage," says Peters.
Even in a healthy knee, that important
layer of cartilage is not uniformly thick. At best, it measures
about 3/16ths of an inch — that shows up as purple on the new type
of picture. But in a knee wracked by osteoarthritis, the cartilage
can be completely gone and displays as black.
Taking advantage of the new imaging, some
patients could have MRIs at regular intervals so that damage can be
monitored, says Peters. That would include people who have sustained
an ACL tear; half of such patients develop osteoarthritis, usually
just 10 or 12 years later.
By 2016, it is estimated that as many as 2
million Americans a year will need cartilage repair surgery, and
another 1 million will have total joint replacement. Knee
replacements usually last from 15 to 20 years, according to the
American Association of Hip and Knee Surgeons. "For younger
folks, you want to delay, whenever you can, the first full-joint
replacement you have," Peters explains.