We've seen some interesting prostheses over the years, from 3D-printed legs to devices for kids with superhero aesthetics. A project from researchers at the Johns Hopkins University is a little different, providing a prosthesis to help women with lower limb amputations to walk in high heels. It's an effort that could have a huge positive impact on peoples' lives, from female veterans to the fashion conscious.

According to the researchers, the new solution represents the first prosthesis designed to play nice with fashionable footwear for women, allowing the user to pop on a pair of heels up to a height of four inches (10 cm).

Creating a device that's capable of that wasn't the easiest task, with the need to adjust to different positions and heights without slipping and causing instability. It also needed to be light, and be capable of supporting a fair bit of weight. On a more basic level, it needed to be slender and aesthetically pleasing so as to comfortably fit women's shoes.

Balancing these requirements involved a combination of mathematical calculations and trial and error tests, all working toward finding a comfortable compromise between strength, flexibility and weight.

The researchers investigated numerous builds, and even toyed with the idea of putting a balloon in the heel to provide springy feedback to the user – a concept that was eventually scrapped. They also experimented with titanium plates and carbon fiber as a base material for the prosthesis, but found them ultimately to be too heavy or not strong enough.

After a great deal of trial an error, the team landed on the current design. Inside the aesthetically-pleasing plastic foot, there are two interlocking aluminum disks that open and close to provide adjustment by means of a lever on the ankle. The ankle itself is an off-the-shelf component – a hydraulic unit that provides smooth movement and flexibility. According to the researchers, the prosthesis performs admirably, weighing in at less than 3 lb (1.4 kg) and supporting weights up to 250 lb (113 kg).

The team successfully tested the device using four different pairs of shoes, including five-and-a-half inch stiletto heels, worn by seven different study participants. Three of the testers were amputees, while the other four trialed the device fitted to the bottom of their feet.

"I had a good time walking" said study participant Alexandra Capellini. "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."

The team plans to continue development of the prosthesis, and is working to assess whether the design might qualify for a patent.

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