Although there are recent advancements in prosthetic technology, not everyone can afford the high price tag that comes with it. To solve this problem, engineers at the Massachusetts Institute of Technology (MIT) created a design for a passive prosthetic foot made from nylon that is affordable and customized to fit the user.
The engineers can adjust the prosthetic foot's stiffness and shape based on the user's body size and weight, which allows the user to walk more naturally.
Although most prosthetic limb manufacturers seek to replicate biological foot movements, the team based their design on the understanding that below-knee amputees can't feel what their prosthetic foot is doing. So, instead of replicating biological feet, the MIT engineers designed a prosthetic foot that would easily recreate natural lower-leg motions as they walk.
The process behind the design
The team consulted a data set of step measurements of "able-bodied" people of a particular size and weight. The data included:
Ground reaction forces.
The changing center of pressure in the foot while walking.
The trajectory and position of the lower leg.
With this data, the team developed a mathematical design for a passive prosthetic foot. They were able to adjust the foot's geometry and stiffness to produce a lower-leg trajectory closer to a normal swing pattern.
Next, the team identified an ideal shape that would be affordable and simple to manufacture, which would keep the costs low. To determine the best designs, the group ran a "genetic algorithm." This resulted in a series of prosthetic feet loaded into a simulation to see which ones had the lowest lower leg trajectory failure. The resulting foot shape looks similar to the side of a sled.
Image courtesy of MIT News
After identifying the best design, the team partnered with Italian company Vibram, known for manufacturing rubber outsoles. The company will design a prosthetic cover that will give a more realistic look to the foot and traction over slippery surfaces.
Compared to a standard passive prosthetic foot made from carbon fiber, which can cost between $1,000 and $10,000, this prosthetic foot design will cost a few hundred bucks. Amputees can go to a prosthetist to have their measurements taken, and then a prosthetic manufacturer will send back a customized nylon passive prosthetic foot.
What do you think of this prosthetic development?