To help stroke patients regain their walking abilities, various robotics groups from industry and academia are developing powered wearable devices — so-called exoskeletons — that can restore gait functions or assist with rehabilitation. Historically, these systems restricted patients to a treadmill in a clinical setting, but in recent years portable systems have been developed that enable walking overground. Working towards the long-term goal of developing soft wearable robots that can be worn as clothing, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), the Wyss Institute for Biologically Inspired Engineering, and Boston University’s (BU) College of Health & Rehabilitation Sciences: Sargent College have developed a lightweight, soft, wearable ankle-assisting exosuit that could help reinforce normal gait in people with hemiparesis after stroke.
In previous studies performed in healthy people, the team demonstrated that their exosuit technology can deliver assistive forces during walking and jogging and that they produce marked reductions in energy costs. Now, in a new study published in Science Translational Medicine, a research team led by Conor Walsh collaborating with BU faculty members Terry Ellis, Lou Awad, and Ken Holt have demonstrated that exosuits also can be used to improve walking after stroke — a critical step in de-risking exosuit technology towards real-world clinical use.
Patients recovering from a stroke develop compensatory walking strategies to deal with their inability to clear the ground with their affected limb and to push off at the ankle during forward movement. Typically, they have to lift their hips (hip hiking) or move their foot in an outward circle forward (circumduction) rather than in a straight line during walking. Usually, rigid plastic braces worn around the ankle are prescribed to help with walking, but they do not help overcome these abnormal gait patterns and about 85 percent of people who suffered a stroke retain elements of their gait abnormalities.
“Current approaches to rehabilitation fall short and do not restore the mobility that is required for normal life,” said Ellis, Director of the Center for Neurorehabilitation at BU’s College of Health & Rehabilitation Sciences: Sargent College and Assistant Professor at BU.
In the new study, the team asked whether the exosuit’s beneficial impact on gait mechanics and energy expenditure during walking they observed in healthy people would also be observed in patients post-stroke who were recruited and enrolled in the study with the help of the Wyss Institute’s Clinical Research Team.
“In treadmill experiments we found that a powered exosuit improved the walking performance of seven post-stroke patients, helping them to clear the ground and push off at the ankle, thus generating more forward propulsion,” said Jaehyun Bae, a co-first author on the study and graduate student at SEAS.
The team also observed a reduced functional asymmetry between the paretic and non-paretic limbs of participants and found that the exosuit’s assistance enabled them to walk more efficiently.
Because walking mechanics and dynamics differ between controlled walking on a treadmill and walking overground in the home or communal environment, the team went on to assess exosuit-provided benefits in an overground walking experiment.
“In an ideal future, patients post-stroke would be wearing flexible adjusting exosuits from the get-go to prevent them from developing inefficient gait behaviors in the first place,” said Ellis.
The study was also authored by Kenneth Holt, Associate Professor at BU’s College of Health & Rehabilitation Sciences: Sargent College, former and current members on Walsh’s team Stefano De Rossi, Lizeth Sloot, Pawel Kudzia, and Stephen Allen, as well as Katy Hendron, N.C.S., who worked in Ellis’ group at BU.
The study was supported by a Defense Advanced Research Projects Agency (DARPA) Warrior Web Program, grants from the National Science Foundation, the American Heart Association and the National Institutes of Health, a Rolex Award for Enterprise, a Harvard University Star Family Challenge, as well as Wyss Institute and SEAS funding.