A Smart Prosthetic Ankle that Adjusts to the Terrain

Written by Bryan Potok, CPO on August 25, 2018
Last updated on October 23, 2018

Every day, we see prosthetic limbs made better and even more personalized to its user. Without disregarding the fact that these are extremely helpful, we have to admit that we have a long way to go to get them functioning like its real counterparts. Now, we have a new one that just might be a step closer to that reality compared to others: a prosthetic ankle that moves on its own.

Prosthetic foot is capable of adjusting to terrain through microprocessors.

That's right. This ankle can adjust according to the user's movement as well as the terrain that it is on. When your natural ankle works during walking, we give it way less credit than it deserves. It prevents your toe from scratching itself against the ground; it minimizes shock by carefully maneuvering how tilted your foot is; it even helps in shifting weight from one side of the body to the other. The amazing part is that it does all these tedious processes while adapting to uneven terrain. Only a few prostheses can recreate these motions.

Michael Goldfarb, a mechanical engineering professor at Vanderbilt, introduces this ankle prototype that takes it a step further from simple passive shock absorption. The joint has an internal motor and actuator that is managed by a chip. Its chip senses and analyzes motion to create a plan for how each step should be executed.

Goldfarb simply describes the function as adaptive. In a news release from the university, he says, "You can walk up slopes, down slopes, upstairs and downstairs, and the device figures out what you're doing and functions the way it should."

This prosthetic mimics the actions of a natural ankle. It can sense when the foot is lifted up, and it makes sure that the toe area is lifted so that it won't scuff itself on the ground. It then exposes the heel so when the limb feels the pressure of coming down, it can easily roll into the next step. The machine gathers and analyzes the data of the how the user walks as well as the slope and irregularities of the surface. It translates this data in a way that will make every step feel natural.

Mike Sasser, an old-timer whose had a fair share of prostheses, was able to test the device and nothing but good came out of his mouth. "I've tried hydraulic ankles that had no sort of microprocessors, and they've been clunky, heavy, and unforgiving for an active person. This isn't that."

The device is still under development within the confines of the lab. As of this writing, it runs on the power of wires, which isn't all too ideal when you want to go out for that morning work. However, the joint works how it's designed to be. Powering may be an issue now, but maybe not anytime soon. It’s expected to be commercialized as soon as everything is sorted out.