Patients who have lost an arm, or a portion thereof, are fitted with a temporary device prior to a permanent prosthesis to ensure correct size and fit. Each fitting can take three technicians as long as four hours to craft, and if they make an error, they must start from scratch. This past fall, undergraduates in the Northwestern University Robert R. McCormick School of Engineering and Applied Science, Evanston, Illinois, Design Thinking and Communication course were given the challenge of developing a new temporary fitting solution to connect the patient’s residual limb to a prosthetic terminal device. The students created three prototypes.
Required of all McCormick freshmen, Design Thinking and Communication is a two-quarter, foundational course that teaches “design thinking”: frame a problem, consider solutions, refine, and execute. The process begins with an understanding of the design problem. For this particular class, students talked to patients and clinician-clients at the Rehabilitation Institute of Chicago, Illinois, to understand the stakes for the temporary prosthetic device were high.
“Imagine if one arm is one inch longer than another, or if the wrist angle is slightly off-you wouldn’t be able to feed yourself,” said Evan Rosati, one of the students in the course.
Over the course of the quarter, the students conducted background research, interviewed experts, sketched their ideas, and worked on their calculations and prototypes. The assignment required students to work within a number of constraints to create an adjustable, customizable, and cost-effective model that could fit with other manufacturers’ permanent fittings, said David Gatchell, PhD, clinical associate professor in the McCormick School’s Segal Design Institute and one of the course’s instructors. Some of those constraints were that the device must require less time to customize than current methods, use less expensive materials, allow for adjustments, and allow for reuse from patient to patient.
“This is an incredibly complex problem; just understanding the hard constraints was a challenge,” Gatchell said. “Furthermore, the temporary device had to be robust enough to protect terminal devices or prosthetics since the terminal devices typically cost tens of thousands of dollars.”
The students created three prototypes: CAREFit, a design that featured two threaded telescoping aluminum tubes and two nested hemisphere-shaped wrist attachments; Triumph, a fitting that could be installed in 40 minutes, adjusted in five minutes, and could support 30 pounds of weight; and Pro-ARM, which featured sliding aluminum plates to allow for maximum length adjustability and a combination of ball joints, threaded aluminum blocks, and spring steel connectors to provide the required adjustability at the wrist.
While the students’ projects show promise, they require further testing as the client works toward a usable design.
Editor’s note: This story was adapted from materials provided by the Northwestern University Robert R. McCormick School of Engineering and Applied Science.