U-M student draws on personal experience for prosthetics research


ANN ARBOR—The Rehabilitation Biomechanics Laboratory at the University of Michigan looks part playground, part film studio, part bionic woman.

A mechanical foot sliced off cleanly at the ankle sits on a shelf—a prosthesis for testing. Twenty cameras on tripods of various heights are aimed toward the center of the room at a cluster of random objects: A door that opens into nothing. A desk phone on a table. A pitcher of water and a glass. A chair. A long, shallow sandbox.

Actually, these objects aren't random at all, explains U-M doctoral student Susannah Engdahl. They've been carefully selected to measure and compare the range of motion of people who use prosthetics against those who don't.

This is Engdahl's area of research, and her own disability has proven helpful in setting up these experiments. Engdahl is missing both hands and most of both feet.

She shrugs and sips her coffee:

"I was born this way. The doctors never nailed down a cause."

Engdahl, 25, earned her bachelor's degree at Wittenberg University in Ohio, and says she decided on the U-M program in biomedical engineering because it "hit all the checkmarks"—health, math, science and the human body.

"Biomedical engineering is a broad field and prosthetics stood out because I already knew how important prosthetics can be in improving quality of life," Engdahl says.

She has been in U-M faculty member Deanna Gates' Rehabilitation Biomechanics Laboratory for three years. Part of the School of Kinesiology, the lab is tucked in the basement of the Central Campus Recreation Building in a converted racquetball court that still feels faintly humid.

Susannah Engdahl, biomedical engineering doctoral student, opens a prop door in the Biomechanics Laboratory, where experiments are conducted to record muscle movement. Image credit: Austin Thomason, Michigan Photography
Susannah Engdahl, biomedical engineering doctoral student, opens a prop door in the Biomechanics Laboratory, where experiments are conducted to record muscle movement. Image credit: Austin Thomason, Michigan Photography

Engdahl has been lucky with her own prosthetic hands, she says, because she's had very little pain or awkwardness, which is a huge problem among prosthetic users. Hers is among the family of prosthetics called myoelectric, which work by capturing electrical signals from the body—in this case, her arms—to control her hands.

Other prosthetics are body powered—they're held to the body by harnesses and move when cables are activated by body movement. Each has advantages and disadvantages, but one big upside of Engdahl's is that at first glance you don't even know she's wearing them. She received her first pair of prosthetics when she was about 2.

"The cosmetic factor probably helped my parents make that decision," Engdahl says, contemplating the flesh-colored stretchy sleeve that encases the hard plastic shell protecting the tiny electronics and motors that move the fingers of her hands.

But despite their natural look, the prosthetics can move only in one direction. The hands open with the thumb moving in opposition to the fingers, and close with the thumb moving towards the fingers. The thumb, index finger, and middle finger come together to create a "tripod" grip.

"Developing prosthetics that can move more similarly to a natural hand is an active area of research," Engdahl says, gripping her cardboard cup.

Quantifying how people use different types of prosthetics is one of Engdahl's dissertation research projects, and a career interest.

"It's important because most of the current research on prosthetic function is from patient feedback," says Gates, lab director and assistant professor with appointments in kinesiology and biomedical engineering.

"There's no clear direction to focus on improvements in quality of movement or range of motion, and no clear way to convince insurance companies to pay for advanced prosthetic devices."

It's natural to wonder how people with prosthetics perform everyday tasks: How do you type? Open doors? Tie your shoes? Engdahl doesn't even think about her own work-arounds, but compensations are a part of life for any prosthetic user.

Engdahl demonstrates one of these adaptations when she opens the prop door in the lab.

"It's hard for me to stand in front of the door, so I take a step over," she says. She doesn't have any wrist motion, so she moves slightly to one side of the knob for leverage, then turns the handle.

From real life to research to teaching

Engdahl not only uses her experiences with limb loss to inform her research, she also parlays them into teaching opportunities to spark future scientists. Every year, she helps Gates with the annual FEMMES event, which stands for Females Excelling More in Math, Engineering and the Sciences.

"We show the girls how the brain sends signals to muscles and how these can be measured and then used to control prosthetics," Gates says. "Susannah is generous enough to bring in one of her old sets of hands for the girls to try and she shows them how she uses them to do different things."

The girls spend the day measuring their muscle activity and making moveable hands of paper, string and straws.

"It's a great event that wouldn't be possible if Susannah weren't so open to talking with the girls about her experiences," Gates says.

When asked whether she's naturally optimistic, Engdahl says it's not easy to compare people in terms of "getting past" issues. She's always had access to the best health care and a supportive family, so it could be much simpler for her to overcome something that's difficult for someone without those advantages, she says.

"Although it did take me awhile to figure out all the tricks of the trade, I've found that most of the things I need to do in daily life can be accomplished with patience and creativity," Engdahl says. "I don't have a reason to feel intimidated by physical barriers because I'm usually able to find solutions. Admittedly, sometimes my solutions aren't ideal. But self-sufficiency is important to me, and I'd rather get a task done slowly than just not do it at all."

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More information:

‘Touchy-feely’ bionic hands come closer to reality

From Business Standard

“Touchy-feely” bionic hands have come closer to reality as researchers are exploring new approaches to designing prosthetic hands capable of providing “sensory feedback.”

University of Michigan’s Paul S. Cederna and colleagues wrote that emerging sensory feedback techniques will provide some sensation and enable more natural, intuitive use of hand prostheses, adding that these breakthroughs pave the way to the development of a prosthetic limb with the ability to feel.

As per the researchers, upper limb loss is a “particularly devastating” form of amputation, since a person’s hands are their tools for everyday function, expressive communication and other uniquely human attributes. The functional, psychological, economic, and social impact is even greater since most upper limb amputations occur in young, otherwise healthy individuals.

Current robotic prostheses approach the fine dexterity provided by the human hand, but these advances have outpaced developments in providing sensory feedback from artificial limb. The lack of sensation is the key limitation to reestablishing the full functionality of the natural limb, they noted.

Providing some sense of touch to the artificial hand would lessen the cognitive burden of relying solely on vision to initiate and monitor movements, while also providing tremendous psychological benefits for patients.

The review focuses on recent and emerging technologies to create sensory interfaces with the peripheral nerves to provide feeling to prostheses. Already in use is a technique called sensory substitution.

A promising newer technique is targeted muscle reinnervation (TMR), in which nerves are transferred to provide sensation to intact muscles and overlying skin. Another “next generation” approach is the use of optogenetic technology to control nerve signaling using specific light wavelengths.

Researchers wrote that the ultimate goal is to develop a prosthesis that closely mimics the natural limb, both in its ability to perform complex motor commands and to elicit conscious sensation.

The study is published in Plastic and Reconstructive Surgery.

Artificial foot recycles energy for easier walking

By Nicole Casal Moore
From Michigan News

ANN ARBOR, Mich.—An artificial foot that recycles energy otherwise wasted in between steps could make it easier for amputees to walk, its developers say.

“For amputees, what they experience when they’re trying to walk normally is what I would experience if I were carrying an extra 30 pounds,” said Art Kuo, professor in the University of Michigan departments of Biomedical Engineering and Mechanical Engineering.

Compared with conventional prosthetic feet, the new prototype device significantly cuts the energy spent per step.

A paper about the device is published in the Feb. 17 edition of in the journal PLoS ONE. The foot was created by Kuo and Steve Collins, who was then a U-M graduate student. Now Collins is an associate research fellow at Delft University of Technology in the Netherlands.

The human walking gait naturally wastes energy as each foot collides with the ground in between steps.

A typical prosthesis doesn’t reproduce the force a living ankle exerts to push off of the ground. As a result, test subjects spent 23 percent more energy walking with a conventional prosthetic foot, compared with walking naturally. To test how stepping with their device compared with normal walking, the engineers conducted their experiments with non-amputees wearing a rigid boot and prosthetic simulator.

In their energy-recycling foot, the engineers put the wasted walking energy to work enhancing the power of ankle push-off. The foot naturally captures the dissipated energy. A microcontroller tells the foot to return the energy to the system at precisely the right time. Watch a video demonstration.

Based on metabolic rate measurements, the test subjects spent 14 percent more energy walking in energy-recycling artificial foot than they did walking naturally. That’s a significant decrease from the 23 percent more energy they used in the conventional prosthetic foot, Kuo says.

“We know there’s an energy penalty in using an artificial foot…We’re almost cutting that penalty in half.” Art Kuo

“We know there’s an energy penalty in using an artificial foot,” Kuo said. “We’re almost cutting that penalty in half.”

He explained how this invention differs from current technologies.

“All prosthetic feet store and return energy, but they don’t give you a choice about when and how. They just return it whenever they want,” Kuo said. “This is the first device to release the energy in the right way to supplement push-off, and to do so without an external power source.”

Other devices that boost push-off power use motors and require large batteries.

Because the energy-recycling foot takes advantage of power that would otherwise be lost, it uses less than 1 Watt of electricity through a small, portable battery.

“Individuals with lower limb amputations, such as veterans of the conflicts in Iraq and Afghanistan or patients suffering from diabetes, often find walking a difficult task. Our new design may restore function and reduce effort for these users,” Collins said. “With further progress, robotic limbs may yet beat their biological forerunners.”

This paper demonstrates that the engineers’ idea works. They are now testing the foot on amputees at the Seattle Veterans Affairs Medical Center. Commercial devices based on the technology are under development by an Ann Arbor company.

The paper is called “Recycling Energy to Restore Impaired Ankle Function during Human Walking.”

This research was funded by the National Institutes of Health and the Department of Veterans Affairs.