New prosthetic foot to help tackle tough terrain

Stanford scientists have developed a more stable prosthetic foot which they say could make challenging terrain more manageable for people who have lost a lower leg.

The new design has a kind of tripod foot that responds to rough terrain by actively shifting pressure between three different contact points.

"Prosthetic emulators allow us to try lots of different designs without the overhead of new hardware," said Steven Collins, an associate professor at Stanford University in the US.

"Basically, we can try any kind of crazy design ideas we might have and see how people respond to them," he said, without having to build each idea separately, an effort that can take months or years for each different design.

People with a leg amputation are five times more likely to fall in the course of a year, which may contribute to why they are also less socially engaged.

A better prosthetic limb could improve not just mobility but overall quality of life as well, according to the study published in the journal IEEE Transactions on Biomedical Engineering.

One area of particular interest is making prosthetic limbs that can better handle rough ground.

The solution, researchers thought, might be a tripod with a rear-facing heel and two forward-facing toes.

Outfitted with position sensors and motors, the foot could adjust its orientation to respond to varying terrain, much as someone with an intact foot could move their toes and flex their ankles to compensate while walking over rough ground.

Rather than building a prosthetic limb someone could test in the real world, the team, including graduate student Vincent Chiu and postdoctoral researcher Alexandra Voloshina, instead built a basic tripod foot.

They then hooked it up to powerful off-board motors and computer systems that control how the foot responds as a user moves over all kinds of terrain.

The team can put their design focus on how the prosthesis should function without having to worry about how to make the device lightweight and inexpensive at the same time.

The team reported results from work with a 60-year-old man who lost his leg below the knee due to diabetes.

The early results are promising -- making the team hopeful they can take those results and turn them into more capable prosthetics.

"One of the things we are excited to do is translate what we find in the lab into lightweight and low power and therefore inexpensive devices that can be tested outside the lab," Collins said.

"And if that goes well, we'd like to help make this a product that people can use in everyday life," he said.