Robotic Exosuit Improves Walking After Stroke

Dr. Yun Freudenberg-HuaMedscape – August 3, 2017

A soft wearable robotic exosuit can help improve walking ability in stroke patients with chronic gait impairment, preliminary research suggests.

In a small study, exosuit-induced improvements in poststroke gait were observed “within minutes of powering the device and were comparable to, if not greater than, therapeutic gains observed after single-session and multisession clinical gait training programs,” report the researchers, led by Conor J. Walsh from the Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, Massachusetts.

“Although long-term therapeutic studies are necessary, the immediate improvement in walking performance observed using the powered exosuit makes this a promising approach for neurorehabilitation,” they write.

The study was published online July 26 in Science Translational Medicine.

The exosuit consists of a waist belt and leg strap connected to a calf sleeve. Bowden cables attached to a battery-powered actuator on the waist belt apply gait-restoring forces to the ankle joint to aid forward propulsion and correct weakness of ankle and toe dorsiflexion (drop foot).

The research team evaluated the immediate effects of the exosuit actively assisting the paretic limb of nine individuals in the chronic phase of stroke recovery during treadmill and overground walking.

They demonstrated that the exosuit functions in synchrony with a wearer’s paretic limb to immediately increase the paretic ankle’s swing phase dorsiflexion and generate forward propulsion (P < .05).

These improvements in paretic limb function contributed to a 20% reduction in forward propulsion interlimb asymmetry and a 10% reduction in the energy cost of walking, which is equal to a 32% reduction in the metabolic burden associated with poststroke walking, the researchers say.

The findings also suggest that lower-functioning individuals may benefit more from exosuit intervention than higher-functioning individuals.  Although this requires validation, it supports the potential use of the exosuit in more disabled cohorts after stroke, the researchers say.

Important First Step

“Although this investigation’s primary finding is an improvement in poststroke gait mechanics and energetics during exosuit-assisted walking versus walking with an exosuit unpowered, our secondary finding that wearing a passive exosuit did not significantly influence participants’ walking is equally important for a complete appreciation of the exosuit technology,” they write in their paper.

“Together, these findings demonstrate that exosuits are capable of providing targeted gait assistance through a human-machine interface that imposes minimal biomechanical and metabolic penalties when worn unpowered…. Future work will focus on understanding how exosuit-induced improvements in walking performance may be leveraged to improve mobility after stroke,” the researchers conclude.

Bruce T. Volpe, MD, from the Center for Biomedical Science, The Feinstein Institute for Medical Research, Northwell Health, Manhasset, New York, thinks the device has promise.

“It works with the subject to abet movement. It is not just a passive motion machine that just supports the toe to clear the ground in swing phase or just stabilizes heel strike. The device interacts and thus can be individualized with each subject’s gait difficulties, and the subject must interact and attempt to move as much as possible,” Dr. Volpe told Medscape Medical News.

“Form follows function,” he added, “and that the device improved gait mechanics and energetics is an important first step. The initial design of the untethered wearable device appears relatively sleek, as ‘smart prosthetics’ develop in the 21st century. Real-world outcome is not yet measured, but there is optimism that future controlled clinical studies will demonstrate device effectiveness and establish a new horizon for some with post-stroke gait impairment,” Dr. Volpe said.

The study was supported by the 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, the Harvard University Star Family Challenge, and Wyss Institute and SEAS funding. The authors have disclosed no relevant financial relationships.