Students Reinvent Crutches

Anyone who’s fractured a foot or sprained an ankle knows that having to rely on crutches to walk around can be an agony worse than the injury.

Sameer Saiya, while studying at Purdue’s School of Mechanical Engineering, had never had to endure the pain and discomfort of hobbling around campus on a pair of crutches. So when one of his fellow students, Brett Adams, pitched an idea for an alternative to crutches during a brainstorming session for a senior design course, Saiya was unmoved.

“Brett was recounting to us how he was on crutches for several months from a snowboarding injury,” Saiya said. “Basic things were hard to do, going upstairs, opening doors. At the time I didn’t understand that problem at all. As it happened, the next week I sprained my ankle. In the next 24 hours I understood everything he had said.”

In addition to the problems of stairs, doors, and terrain, Saiya learned that crutches keep the hands from holding phones, and that hopping on one leg is exhausting. He was also occupied by thoughts about long-term use problems, such as nerve ending damage and atrophied leg muscles. “When you actually heal, you discover you have injured your body in ways you hadn’t thought of,” he said.

Needless to say, after his own accident, Saiya quickly hopped on board with Brett’s idea for a crutch replacement.

Both Adam and Saiya’s injuries had been below the knee, and they wanted to create something that would take advantage of the user’s ability to bend a leg. They researched other solutions on the market and found those put too much force on the knee. They wanted to put that pressure on the quadriceps, a relatively strong muscle and the obvious one to turn to for approximating a normal gait. They consulted a professor of biomechanical engineering to make sure they wouldn’t be constricting any major blood vessels. He approved the project but warned that any solution they came up with would have to include shock absorption.

The team was puzzling over the problem when the answer came to them. “We were sitting in the CAD lab and realized, “When you get bored you start adjusting the chair spring to go up and down. That was the ‘aha’ moment—from fidgeting.”

With a computer model and their office chair gas spring, the group started thinking about producing it. Advanced polymers, CNC, and 3-D printing, all seemed like good possibilities. “We threw together a prototype with scrap wood and aluminum tubing we cut to size,” said Saiya.

They quickly found that imitating the human gait required more finesse than they had imagined. But, since the prototype was a medical device, they had no approval for testing it. “To tweak it we’d have to sneak into the hallways after the professors left.”

The sneaking and the tweaking paid off. The Clutch Crutch, as the students have named their invention, allows the injured to walk with a nearly normal stride with the pressure of each step applied neither to the knee nor the foot, but to the quadriceps. Force-resistive sensors revealed that the force at the injured site was never more than a newton. “Literally like touching something with a finger,” said Saiya.

At the moment, the device is a bit heavier than it needs to be—15 pounds. But a future Clutch Crutch could easily be made lighter by replacing the wood and aluminum with a honeycombed pattern. The students have secured a patent with the help of the university’s Office of Technology Commercialization. Now graduated, the team awaits funding to make the Clutch Crutch a reality.
Michael Abrams is a technology writer based in New Jersey.
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