Two Degrees of Separation
Seated: Steven Toddes demonstrates the prototype of a powered arm-orthosis that he helped develop with, from left, Daniel Abramovich, Professor Allen Hoffman, and Michael Scarsella.
For those with muscular dystrophy, a device—developed as a student project—gives users the two degrees of freedom they need to perform everyday tasks.
Since 1989, Allen Hoffman, professor of mechanical engineering, has worked with the Massachusetts Hospital School, in Canton, Mass., on rehabilitation projects that encourage his students to see how their skills can actually help people.
From that relationship came a recommendation by Gary Rabideau, director of reha- bilitation engineering at the hospital, to create a device that helps people suffering from muscular dystrophy perform simple, everyday tasks with their hands.
The result: a prototype of a wearable powered arm-orthosis that restores arm function. Now, after working with several student teams on this project, Hoffman says the device could be ready for patenting and licensing in two years.
“We’re starting to look at how it could be used by people and to see how we can refine it,” Hoffman says. “It could have quite an impact. We’re still in the development stage, but we feel it’s a usable device. Right now, these people need assistance in all these activities. This device would allow them to do a number of activities independently.”
Typically, Hoffman’s students do such work as part of their Major Qualifying Projects in their senior year. Mechanical engineering students Steven P. Toddes ’05, Michael J. Scarsella ’05, and Daniel N. Abramovich ’05 worked with Hoffman last year. Toddes and Scarsella, now ME graduate students, have continued their work with Hoffman this year. Scarsella says the project took on a sense of importance after he met a boy with muscular dystrophy at the hospital school.
“We were there mainly to ask his opinion on the project,” he says, “but when he started telling us how all he wanted was his independence back, and to be able to perform the tasks of daily living he was used to, it really made us all emotional, and more motivated than ever to succeed.”
Scarsella also enjoys the complexity of the project. “The intermeshing of biomechanics, electromechanical components, arm kinematics, manufacturing, and the human aspect, needs to be kept in mind throughout the duration of the project.”
Rabideau says that of the 90 residents at the hospital, including 35 patients in the day program, a dozen have muscular dystrophy. He says it’s frustrating for them to retain dexterity in their hands while being hindered by muscle wasting in the shoulders, upper arms, and trunk.
“They can’t place a hand where it needs to be to do an activity,” he says. “These are bright guys, very creative, but they’re trapped in their bodies. They can’t run a computer or feed themselves, but they can grasp, pinch, and touch. That’s a real frustration to them—there are so many things they want to do, but they just can’t.”
Rabideau, who has a master’s degree in rehabilitation engineering, explains that the powered arm is designed to allow the hands to move through space, not just across the lap tray. He says this approach goes beyond traditional engineering education.
“I think at times there’s a real disconnect between the theory taught in the classroom and its application in terms of seeing the result—especially on people,” he says. “This (device) makes a dramatic difference in people’s lives, beyond entertainment, beyond luxury.”
The most common of the nine types of muscular dystrophy is DMD (Duchenne muscular dystrophy), a degenerative disease that primarily affects males and is passed down through their mothers, according to the national Muscular Dystrophy Association. Victims lack dystrophin, a protein that helps keep muscle cells intact. The onset of the disease is between 2 to 6 years of age, when children generally experience weakness and muscle wasting in the hips, pelvic areas, thighs, and shoulders, and have trouble walking.
By the time they’re 10 to 12, they’re bound to a manual wheelchair, and by their teens, they’re forced to live in an electric wheelchair. Survival is rare past the 20s—DMD affects all the voluntary muscles, including breathing muscles.
Initially, the disease affects the proximal muscles (the muscles closest to the body), but spares the distal muscles (those farthest away from the body), so teenage sufferers can still move their hands. The problem at this stage is they can’t position their hands in a useful manner and instead rest them on their laps or on their lap trays. To compensate, they walk their fingers across the tray to the objects they want to grasp.
The solution for Hoffman and his students was to develop a motor-powered brace that fits over the user’s arm and allows him to flex his elbow and rotate the forearm by operating a joystick with his free hand. The lap tray is used as a horizontal pivot point, giving the user two degrees of freedom. Powered by an electric mechanism, the brace is designed to move an additional three-pound load at the location of the hand, allowing the individual to grip objects, such as a toothbrush or utensils for eating.
The powered arm-orthosis has gone through several changes. At first it was mounted to a wheelchair, but its use was awkward. It also started out with four degrees of freedom—it allowed for an additional two shoulder motions—but that proved to be too complicated.
The remaining challenges for Hoffman and his students are to reduce the weight, simplify the controls, improve the aesthetics, and, finally, test it on someone who actually needs it. “Inevitably, there will be suggestions for improvements,” Hoffman said.
Rabideau says that in his last 15 years at the hospital, he has seen improvements to electronics in wheelchair use, but nothing like what this device would do.
“What I really like about it is that it actually helps these kids use their own hand instead of a robotic-controlled arm,” Rabideau says. “I think it keeps them connected. It’s more therapeutic, more gratifying.”firstname.lastname@example.org
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Last modified: Dec 20, 2005, 16:59 EST