October 2020

AFO Puts Spring-cam Back into Stroke Patients’ Steps

A light weight and motor-less spring-cam attached to an AFO provides stroke patients with greater push-off power, stabilizing their walking, and reducing falls. Image courtesy of Tohoku University.

A research group from Tohoku University in Japan has developed a new, lightweight and motor-less device to aid stroke patients in their rehabilitation, improving their gait, and preventing falls. The new device can be easily attached to an ankle-foot orthosis (AFO).

Stroke patients often suffer from motor paralysis as a result of damage to the brain, significantly affecting their walking. Gait disorder results in restrictive disabilities and increased healthcare costs. Rehabilitation is key to stroke recovery. Yet around 40% of stroke patients struggle to function properly due to problems with their walking abilities. One part of the problem is due to insufficient knee flexion during walking. This leads to lower toe clearance and causes patients to fall. To overcome this, patients frequently hip hike on the affected side to move their foot, thus creating an awkward movement.

To help this population, the research group—comprised of Professor Shin-Ichi Izumi, MD, PhD, and Associate Professor Dai Owaki, PhD, from Tohoku University’s Graduate School of Medicine and Graduate School of Engineering, along with Takeo Nozaki and Dr. Ken-ichiro Fukushi from NEC Corporation, Tokyo, Japan—created a device that gives the ankle greater push-off power using a spring-cam mechanism. The elliptical shaped cam rotates in conjunction with the AFO, pushing against the spring. The resultant reactive force from the spring generates significant ankle push-off power.

The research group conducted clinical experiments on 11 stroke patients with paralysis on one side of the body, demonstrating that the device generated greater ankle power. This in turn aided knee flexion while the affected foot was in the swing phase of walking.

“Our device will pave the way for positive impacts on the rehabilitation of stroke patients,” said Owaki. “It will prevent falls and make patients feel more confident in their walking abilities.”

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