Ankle exosuit takes stroke rehab about of lab and into everyday settings

Over 80 per cent of stroke survivors experience gait challenges, often relating to a loss of control over ankle movement. As survivors progress into the chronic stage of stroke, most continue to walk more slowly and less efficiently.

Rehabilitation devices exist to counter this aspect of stroke survival, but their use is limited to lab or clinical settings.

Now, a proof-of-concept study suggests the community-use ankle exosuit could help stroke survivors improve their walking propulsion and boost their overall walking confidence and ability while ambulating around their own homes, workplaces, and neighbourhoods. The work, led by Professor Conor Walsh’s team at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), is published in Annals of the New York Academy of Sciences.

“We saw an opportunity to leverage wearable technology to rethink how we approach physical therapy and rehabilitation,” said Walsh, senior author on the paper. “If we can shift some of these clinical services from the clinic to the home and community, we can improve access, reduce costs and deliver better care. It is exciting to see the fields of engineering and physical therapy come together to make this happen.”

Walsh’s Biodesign Lab at Harvard had previously developed assistive and rehabilitative exosuit technologies for various applications. Some of that technology has already been licensed and commercialised by ReWalk Robotics and been given breakthrough status by the US Food and Drug Administration. To design an ankle exosuit for use in the community, Walsh’s team need to simplify the exosuit’s mechanical components and make it easy for wearers to control.

“In the past, our ankle exosuits had two active actuators – one that helped with dorsiflexion to keep the wearer’s toes up, and another to help with plantarflexion, propelling the foot and body away from the ground,” said Richard Nuckols, a former postdoctoral fellow in Walsh’s lab at SEAS, and co-first author of the paper.

Instead of an active dorsiflexion actuator, the new exosuit contains a passive material that flexes and performs like a spring, helping the toes stay up during the foot’s swing phase and preventing the wearer from catching their toes on the ground.

MORE FROM MEDICAL & HEALTHCARE

“By replacing an active actuator with a passive actuator, the exosuit is inherently safer; in the case of an unexpected power loss or controller failure, the default state will keep the users' toes up and reduce risk of a trip and fall,” Nuckols said in a statement.

“We also developed a mobile app to enable wearers to easily interact with the device and remotely check in with our team,” said Chih-Kang Chang, a PhD candidate in Walsh’s lab and a co-first author on the paper. “The app allows wearers to turn the device on themselves and tell the exosuit when they want to start walking.”

In addition, the team incorporated sensors located on the foot, shank, and pelvis to allow for remote monitoring of the wearer’s progress over time.

“We are collecting data while people are walking in the exosuit, and measuring how they improve their gait over time,” said Chang. “Going forward, this information could be a really powerful aspect of using this exosuit for long-term rehabilitation in partnership with a physical therapist.”

To test the community ankle exosuit, Walsh’s team partnered with the labs of Lou Awad and Terry Ellis from Boston University’s Sargent College of Health & Rehabilitation Sciences. They recruited four participants to use the device in their own community settings for four weeks, walking independently three to five times each week. All participants safely completed the study and reported no safety issues.

Due to individual variability in response (participants with lower baseline walking propulsion saw more benefit from wearing the exosuit), therapeutic benefit was not observed across the whole group. However, two of the participants improved their propulsion by an average of 27 per cent. They also walked an average of 4,000 steps further in the week after the study than they had walked in the week before the start of the study.