Soft Robotic Exosuit Can Help Stroke Patients

Image: Science Translational Medicine
Image: Science Translational Medicine

Soft wearable robotic exosuits can help patients walk after strokes, a new study finds.

Stroke is the leading cause of disability in the United States. More than 6.5 million Americans are stroke survivors, and the vast majority of them never fully recover the ability to walk. “The fact that many stroke survivors can't, say, walk to the store can in turn lead to a downward spiral when it comes to their health and quality of life,” Conor Walsh, a soft roboticist at Harvard University.

Recent breakthroughs in exoskeleton technology have shown promise as advances over canes, walkers, orthotics, and other traditional aides for stroke patients. However, while the rigid nature of most exoskeletons can help them provide large amounts of assistance for patients who could not otherwise walk, they may not be suitable for people who have some capacity to walk on their own, as they can restrict natural movement, Walsh says.

Instead, Walsh and his colleagues sought to develop a flexible lightweight wearable robot to support a weakened leg's residual ability to move. “By providing a small amount of assistance, our soft exosuit could provide significant benefits for people who retain some ability to walk, such as most stroke survivors, and allow them to move more naturally than they could with a more rigid system,” Walsh says. Walsh and his collaborators detailed their findings in the 26 July online edition of the journal Science Translational Medicine

The 900-gram exosuit they produced consists of a waist belt and leg straps connected to a calf sleeve. Cables attached to a 2.63-kilogram actuator on the waist belt pull on a shoe insole, helping to propel the leg forward and correct a problem with toe and ankle flexing commonly known as drop foot, which affects roughly 20 percent of stroke survivors. A 560-gram battery powers the actuator.

Over two days of testing, nine stroke survivors ranging from 30 to 67 years old wore the exosuit both while walking tethered on a treadmill and walking untethered over open ground. The volunteers all showed roughly 10 percent more efficient and 20 percent more symmetrical strides while wearing this ankle-support device.

“Every person who has suffered a stroke has a slight variation in their impairment; by bringing in a number of stroke survivors, we tried to make sure our technology had broad applicability to a range of people with different impairment,” Walsh says.

The researchers note that exosuit-linked improvements were seen within minutes of powering up the device and were comparable to, if not greater than, therapeutic gains seen after conventional clinical rehabilitation programs. The most gains with the device were seen among the participants who had the slowest unassisted walking speeds, the scientists add.

The researchers suggest that optimized versions of this exosuit will weigh less than 4 kilograms, and can be worn discreetly to minimize their impact on everyday activities. ReWalk Robotics in Marlborough, Massachusetts, has licensed and is commercializing this technology.

The scientists are now planning to see whether continued use of this soft exosuit can help stroke patients learn how to walk better without the device, Walsh says. They are also exploring soft wearable robots for the knee and hip, he adds.

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