Posted on 10/07/2004 10:17:13 PM PDT by neverdem
WHAT'S NEXT
In mint condition, the knee is a biomechanical marvel, an intricately linked interaction of bones, ligaments, tendons and cartilage that produces smooth, stable motion.
But as professional athletes and weekend exercisers know only too well, the knee is also a classic weak spot, vulnerable to damage and slow to heal. Strengthening it after injury or surgery may require hours on the bulky machines of a hospital or gym.
Now a mechanical engineer at Northeastern University has devised a small portable device that people may be able to strap onto their knees to rehabilitate them as they walk around doing daily chores.
The device is an adaptation of a standard off-the-shelf knee brace. Constantinos Mavroidis, an associate professor of mechanical and industrial engineering at the university, and his students added small, tightly sealed containers to either side of the brace at the knee.
They filled the containers with sets of small plates and a special "smart" fluid that changes from liquid to gel when it is zapped by electricity.
When a computer-controlled voltage is sent to the plates, an electric field is created and the fluid within instantly grows viscous. As the knee flexes and the plates rotate relative to one another, resistance is created.
The device imitates the job of the large machines used for training, exercise and rehabilitation in a gym. But instead of increasing the resistance with heavy blocks or bars, scientists can control the brace by changing the voltage.
"It's basically a weight-lifting machine that you can slap on your leg," said Jason Nikitczuk, a graduate student in mechanical engineering who worked with Dr. Mavroidis on the project. "You can adjust how much weight you are applying, just like you change weights on a machine."
The device cannot yet be bought off the shelf; it exists only as a research prototype in Dr. Mavroidis's laboratory.
He hopes, though, that it will eventually be manufactured, and is now in discussion with Spaulding Rehabilitation Hospital in Boston to explore clinical trials of the device.
Joel Stein, chief medical officer at the hospital, said that devices like the one developed by Dr. Mavroidis and his group that use smart or electro-rheological fluids were promising rehabilitative tools. "The appeal of this technology is that it allows them to vary the force that the brace exerts during the gait cycle or other activities," he said.
Conventional braces, called orthotics, typically are not programmable. "They are mechanical, and don't easily vary the forces over a range of activities," he said. But Dr. Mavroidis's prototype can be programmed to produce different levels of resistance for walking, for example, and stair climbing.
"This could be a nice portable way to put an exercise machine on a patient instead of going to a gym," Dr. Stein said.
Dr. Mavroidis said that the next generation of his device would provide not only controllable resistance, but also the power to push the joint itself. This might be useful, for instance, for a patient who is recovering mobility after a stroke. "The device will be able to move the joint, just like a physical therapist does manually now," he said.
Work on developing the actuators for the prototype has been financed by the National Science Foundation.
The apparatus is expected to operate using a relatively lightweight battery. The resistance can be varied in several ways. "We can use a control knob that a person rotates to select resistance," Dr. Mavroidis said, "or there can be a software program that a physical therapist uses to individualize treatment with patients."
Dr. Mavroidis said he had chosen the knee for the first device, but that similar principles could be applied to a brace for the elbow. The machines he hopes to produce one day will probably cost roughly $2,000, he said.
Brian Weinberg, a graduate mechanical engineering student at Northeastern, did much of the design work for the device, integrating the plates and fluids in their sealed containers onto the existing brace. "As soon as it worked well," he said, "we took it apart and started improving the design and control for the next generation of the device."
Paolo Bonato, director of the Motion Analysis Laboratory at Spaulding Rehabilitation Hospital, is a member of the team that is looking into clinical testing of the brace. Dr. Bonato is an assistant professor in the department of physical medicine and rehabilitation at Harvard Medical School.
One of the advantages of the technology is its quick response time, Dr. Bonato said. The liquid can turn to a gel in a millisecond or two. "The electro-rheological fluids provide good feedback," he said, "so that you could potentially adjust the properties of an artificial joint or orthotic according to the task you are performing."
Dr. Bonato expects the technology to be most promising as an exercise aid. "If they design it as wearable," he said, "you can continuously exercise in daily activities," as opposed to doing rehabilitation only at a hospital or gym.
Dr. Bonato said that a number of researchers were pursuing programmable rehabilitative devices. "It's exciting, what's happening in orthotics and prosthetics," he said. But these devices won't be on the market for a while. "It will probably be at least five years before we move from prototypes to actual products," he said.
Dr. Mavroidis hopes that his invention may one day find use far from earthbound exercise rooms. Long trips in space cause significant loss in the bone and muscle mass of astronauts, he said. But a device like his might be worn by the astronauts during their daily activities to strengthen their legs.
"I think it might work to prevent the effects of weightlessness," he said.
E-mail: Eisenberg@nytimes.com
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very cool.
That sounds interesting, but I'll have to wait till I see an article in a reputable publication.
I don't know if that's going to happen, but CBS news is going to have a segment on it...
Not all exercises involving the knees are actually good for your knees. In particular knee extension machines put incredible stress on the knee joints. A lot of my knee problems cleared up after I was advised to stop doing these exercises.
I have tried some other ways of improving the health of my knees and they feel a lot better than when I went to the doctor. Obviously there are many situations when people really do need surgery.
Here's a google. This phenomenon has been around since the late 1980s apparently, at least.
Best of luck to you.
Ouch. Deepest wishes for a quick recovery.
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