A prosthetic hand is a critical tool that allows amputees to find normalcy in their lives, but some elements, such as complete freedom of movement and sensations of touch, are not the same as a real hand.
“They’ve come a long way and they have a long way to go,” said amputee Charity McFarland, who lost her left hand in a car accident almost four years ago.
McFarland said of the accident, “All I saw were lights and I basically was trying to avoid getting hit, but then the accident happened, so it was like a rollover. They told me that I rolled over three times."
An estimated 1.7 million people in the U.S are missing a limb, according to research at Rice University in Houston.
While existing prosthetic limbs allow amputees to regain some of their abilities, there are very few devices that provide sensory feedback for the users.
Researchers from Rice University, the University of Pisa and the Italian Institute of Technology are working to allow amputees to better perceive what their prosthesis is doing.
McFarland heard about the research and volunteered to help. The focus of the research is to create what are called haptic devices to better replicate a biological hand for amputees.
“Haptics is anything that has to do with the sense of touch. Any textures that you discern or even the ability to realize that you’re making contact with something. How much pressure you’re putting on it, if it’s slipping, all of those are haptic sensations,” said Rice University graduate student Janelle Clark, who was one of the researchers who measured how well test subjects could distinguish the sizes of objects grasped by a prosthesis with and without haptic feedback.
The tests include a rocker placed onto the subject's remaining limb that moves back and forth and stretches the skin so the person can sense what the prosthesis is doing. The amount of stretch correlates to how opened or closed the prosthetic hand is on the user.
“The idea behind the research that we’re doing here is to create haptic devices that are simple, they’re intuitive, they’re not going to break and so that people can start to have an understanding of what’s going on with their prosthetic without looking at it all the time," Clark said.
Researchers found blindfolded test subjects were able to more than double their ability to distinguish the size of objects grasped with a prosthetic hand when they received haptic feedback from a skin-stretch device.
McFarland, however, wasn’t one of them. “I still wasn’t able to sense what it was doing completely,” she said.
“This is going to be a long-term project... to create some sort of artificial hand that has the same capabilities, but maybe there are other changes in the short term that would also be appreciated," Rice researcher Clark said.
For now, McFarland says she would appreciate a prosthesis that looks like a hand and allows the fingers to move and the wrist to bend and rotate just like a real hand.