A team of Johns Hopkins University (JHU) students, working with a JHU physician and outside prosthetics experts, has developed an early version of a prosthetic foot that can be used when wearing high heels. Called the Prominence, it would be the first prosthetic foot on the market that is not custom made that adapts to popular fashion for heels up to 4 inches high.
“High heels have become an integral part of the female lifestyle in modern society, permeating through all aspects of life-professional and social,” the five students who graduated this May from the university’s Whiting School of Engineering wrote in their final project report. “For female veterans of the U.S. Armed Services with lower-limb amputations, that seemingly innocuous, but so pervasive, and decidedly feminine part of their lives is gone.”
While there are prosthetic feet on the market that can be worn with high heels, they cannot accommodate a heel height over 2 inches. Further, with about 2,100 American women who lost a leg or foot in military service, and more women entering combat assignments, the demand for a prosthesis that accommodates women’s fashion footwear may grow. The students, who created the Prominence as their final senior project in mechanical engineering, hope their work can help.
Their challenge was to create a foot that can be adjusted to a range of heel heights without a separate tool, holds the position without slipping, supports up to 250 pounds, weighs less than 3 pounds, and is slender enough to accommodate a woman’s shoe. The students’ two semesters of work on the problem unfolded as a mix of mathematical calculations on paper and trial and error involving tests by machines and people.
The students had to find a balance between the foot’s strength and flexibility, reliability and convenience, and sturdiness and lightness. A 28-layer carbon fiber footplate formed the base of the foot. They built a heel-adjustment mechanism with two interlocking aluminum disks; it opens and closes with an attached lever at the ankle. For the ankle, they used an off-the-shelf hydraulic unit that enables a smooth gait and flexing at the sole.
Using four types of women’s shoes-including a gold 5½ inch stiletto-the team had the foot tested by seven people. Three were individuals with lower-limb amputations; four were able-bodied subjects who attached the foot to the bottom of a bulky boot, a bit like walking on stilts. One tester recommended a stiffer, longer toe. Another suggested moving the adjustment lever.
Alexandra Capellini, a Johns Hopkins University junior who lost her right leg to bone cancer as a child, tried the foot with a flat shoe and liked it. She said it felt stable. “An adjustable ankle is useful in contexts even beyond high heels. Ballet flats, sneakers, boots, and high heels especially, all vary in height, so an adjustable ankle opens up opportunities to wear a variety of shoes,” she said.
The design is still a work in progress. “I think the final prototype produced showed the way forward,” said Nathan Scott, PhD, a senior lecturer in the Whiting School’s Department of Mechanical Engineering, who advised the student group. “As usual we just need to go around the design and prototyping loop one more time.”
Editor’s note: This story was adapted from materials provided by Johns Hopkins University.