High-tech boot could speed healing

When wearing a stiff orthopedic boot to recover from a foot or ankle injury, patients are commonly told to put less weight on the limb in question.

Sounds simple enough, but modern medicine has two blind spots when this advice is put into practice:

Are patients good at following the directions? And are the directions even meaningful?

Now comes the SmartBoot, a device that University of Delaware researchers have customized so it measures forces on the patient's foot.

Colored LED lights alert the patient to whether the amount of force falls within a predetermined desired range. And the measurements are stored on a chip for later retrieval by the doctor or physical therapist. The data can also be streamed in real time with a laptop or smartphone.

The Delaware team has a provisional patent on the device and is talking with manufacturers, but in the meantime, the goal is research.

Whether it's an Achilles injury, a broken foot, or a severe ankle sprain, the right amount of weight to put on the leg is something of a mystery, said engineer Brian Knarr, an associate scientist at the Delaware Rehabilitation Institute. Clinicians typically suggest a percentage of body weight - but what that figure should be, and how patients should determine whether they've hit it, aren't at all clear.

"It's a very soft science," Knarr said. "If you ask three different doctors, one might say 20 percent. One may say 40 percent. One may say only 'toe touch.' "

Scientists know some amount of muscle loading helps in the repair of bones, but the device will enable researchers to test how much, and how soon, is best for various ailments, said project coleader Jill Higginson. And they can test whether patients are able to follow their doctors' marching orders.

"We don't know how compliant people are," said Higginson, an associate professor of mechanical engineering at Delaware.

It all began last year, when Knarr was talking to physical therapist David S. Logerstedt, then at Delaware and now at the University of the Sciences in Philadelphia.

Logerstedt said he and some physical therapy colleagues had been lamenting the fact that they could measure forces on patients' limbs in the lab but had little idea what went on at home. Was there some way to mount sensors on a patient?

Knarr and Higginson set a team of senior engineering students to work on building a prototype, starting with an off-the-shelf orthopedic boot.

Melissa Groome, David Schnall, Michael Schenk, Meg O'Brien, and Timothy West took the result to a competition at a June biomechanics conference in Utah, earning third place.

Still, it needed work. The initial device relied on ultrathin force sensors that, though good for saving space, generated measurements with a lag time of nearly a half-second, West said.

"It has to be a pretty much instantaneous response," said West, who graduated in May and now works as a software test engineer.

The team decided to switch to thicker but faster-responding force sensors called strain gauges - similar to what is used in a bathroom scale.

The new prototype was not ready in time for the Utah conference but during the summer, another student, biomedical-engineering major Collin Patterson, helped Knarr finish it.

Patterson, 21, demonstrated the device recently, supporting himself with crutches as he watched the lights flash on top of his foot.

The team had programmed the device so a 160-pound user could learn to keep the amount of force at 30 percent of body weight, give or take 10 percent - just under 50 pounds.

Blue meant Patterson was applying too little weight. Red was too much. Green meant just right.

But would patients focus too much attention on the foot and not on the path ahead? No, said Patterson, a senior from Wilmington.

"It doesn't take very long to teach yourself," he said.

And the alert signal could end up being nonvisual, such as a beep or buzz, Higginson said.

The boot can be programmed to respond to different body weights. It has a control box and a lithium-ion battery mounted on one side, and weighs about 10 percent more than a normal boot, Knarr said.

Future versions will be lighter and more streamlined, with the electronics incorporated inside the device, he said.

Logerstedt, the physical therapist, said he looks forward to seeing it in wide clinical use.

But research comes first, with Achilles tendon injuries among those high on Delaware's agenda.

"It will spin off into a bunch of different projects," Higginson said.

Makes sense, Logerstedt said. Clinicians need to learn what works best before they can teach their patients.

"There's never really been any good hard studies or science to say this is what we should do to improve healing," Logerstedt said. "It's just kind of been expert opinion."

tavril@phillynews.com

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