TOPICS > Science

Can modern prosthetics actually help reclaim the sense of touch?

February 13, 2015 at 7:45 PM EDT
Prosthetic limbs have long been clunky, acting more as appendages than extensions. But modern technology is now helping amputees rediscover their sense of touch. Miles O’Brien, who lost his own arm in an accident last year, takes a look at new advances in the field.

JUDY WOODRUFF: Now advancements in technology to help people feel.

Science correspondent Miles O’Brien had much of his left arm amputated last year after an accident while on a reporting trip for the “NewsHour.” He has since been exploring leaps forward for modern prosthetics.

Last night, he tested a prototype robotic arm, and, tonight, one of the hardest things to replicate that might finally be within reach.

His story is part of our Breakthroughs series.

WOMAN: Blindfold first, and feel free to adjust it as needed, OK?

MILES O’BRIEN: A hand without a sense of touch isn’t really a hand at all. It’s more like a pair of pliers. Watch blindfolded hand amputee Igor Spetic try to pick up some blocks using a prosthetic without a sense of touch. It’s not very productive.

That was no sensation?

IGOR SPETIC, Test Subject: No sensation.

MILES O’BRIEN: And so you were just…

IGOR SPETIC: Going blind, literally going blind.

MILES O’BRIEN: Now watch what happens when the sensory perception is turned on. It’s like night and day.

IGOR SPETIC: But then when I grab it, if I grab it just right, I feel all three fingers, if I grab it right, or two fingers. Then I know I have it. Then I move it over and drop it.

MILES O’BRIEN: Is it your phantom hand that you’re feeling it in? Or is…

IGOR SPETIC: Oh, it don’t feel phantom to me when I grab a block. To me, it feels like my hand. Feels like something between my two fingers that’s vibrating.

MILES O’BRIEN: For Igor, who lost his hand in an industrial accident four years ago, something powered by a battery and made of plastic, metal and silicon can become his hand.

This is what every upper limb amputee like me dreams of, not just wearing a functional tool, becoming whole. But I probably shouldn’t get my hopes up too high.

DUSTIN TYLER, Case Western Reserve University: Will you have your hand? No. Will you have something that will make you forget you don’t have a hand? yes.

Well, this speaks to the next phase we want to get to, of course, which is the implanted EMG electrodes directly into the muscle.

That is biomedical engineer Dustin Tyler. He is a researcher at Case Western Reserve University and the Cleveland VA Medical Center.

DUSTIN TYLER: When you feel, when you see this prosthesis touch something, you feel it, not up here, but actually in your fingertip that’s visually colocated with the prosthesis. That’s a pretty big jump to being back to who you are.

MILES O’BRIEN: He is hoping to find way for amputees to access the untapped potential of a new generation of prosthetic arms.

That’s incredible.

MILES O’BRIEN: As I discovered at the Johns Hopkins University Applied Physics Laboratory, researchers have made a lot of progress engineering an arm with near human capability. It was able to decipher the electrical patterns of muscle contractions in my stump. I was able to turn that into fine motor control with relative ease.


DUSTIN TYLER: Sensory is a completely different game, very much more complex, because you stimulate, but then it goes up into the brain and it goes through a bunch of things to the complex ideas of perception, like, what do you feel and how do you feel it. That’s a much more complicated process.

MILES O’BRIEN: The problem is twofold. Touch sensors for prosthetics need improvement. But the bigger challenge is making sensory information understandable and useful to an amputee.

DUSTIN TYLER: So, what we’re looking at is the X-ray of his arm. Probably, this was a couple of weeks after surgery.

MILES O’BRIEN: In 2011, surgeons implanted electrodes that encircle the three main sensory nerve bundles in Igor’s injured arm.

DUSTIN TYLER: And what you’re looking at here is the three different electrodes, and so you can see kind of the points here in the device itself. This is on the ulnar nerve. This is another one that is up on the median nerve. And this is the one that is on the radial nerve.

IGOR SPETIC: That’s the index finger being activated?

MILES O’BRIEN: Sensors in the prosthetic hand that Igor wears transmit impulses through a computer and these wires into the electrodes inside his arm. The electrodes stimulate the sensory nerves they’re attached to, and Igor’s brain does the rest.

IGOR SPETIC: So, in my mind, I actually feel like I’m doing this when I have it between both fingers.

MILES O’BRIEN: Really? And is it second nature to you now?


MILES O’BRIEN: You don’t have to think about it so much?

IGOR SPETIC: No, I don’t have to think about it so much.

MILES O’BRIEN: Igor is able to feel this way with 20 channels of sensory data delivered by the implanted electrodes. It’s staticky AM radio compared to the high-definition sensory capability we’re born with.

DUSTIN TYLER: To control the hand, for example, normally, there’s thousands of axons, thousand of little tiny wires that go and control individual parts of the fingers.

We right now can talk to 10. Right? So you can imagine that that connection, it’s that interface that still needs to be worked on. And that’s where we’re making progress. But, yes, we’re still behind what the biology can do from the engineering perspective.

MILES O’BRIEN: Across the country in a lab at UCLA, mechanical engineer Veronica Santos is trying to close that gap.

VERONICA SANTOS, UCLA Biomechatronics Lab: For a long time, people have been trying to build robots that emulate humans, but there’s now a way that we can actually directly impact someone’s quality of life by building a robot that becomes part of someone’s body.

MILES O’BRIEN: Here, in Dr. Santos’ Biomechatronics Lab, they’re constructing a language of touch that a computer and a human can both understand.

They’re quantifying this with mechanical touch sensors that meet objects of varied shapes, sizes and textures. Using an array of instrumentation, they are able to transact that interaction into data a computer can understand.

VERONICA SANTOS: So, for example, Miles, as you put your hand in there to stop it, we would be able to record the posture of the finger when it came in contact with you, as well as the general areas of the fingertips that were making contact and how much pressure there was or how much the skin was deforming as you made contact.

But those are the types of raw percepts that you would give to someone and then with training they would put it all together and say, hey, I think I’m touching something deformable or soft.

MILES O’BRIEN: The training includes machine learning. The data is used to create a formula or algorithm that gives the computer the ability to each common patterns between the items it has in its library of experience and something it has never felt before.

VERONICA SANTOS: So, we’re interested in developing this idea of artificial haptic intelligence.

MILES O’BRIEN: Making haptic sensation useful for an amputee is the big challenge.

Prosthetic and robotic technology has far surpassed the ability of an amputee to command a limb or understand what the device is sensing. The bottleneck is melding the technology with the biology.

VERONICA SANTOS: I think one of the challenges is understanding how much information can you flood someone with before, you know, they just — they can’t make use of it?

I think, in a perfect world, if we did our job right, you wouldn’t even know we’d done our job. Your prosthetic hand would feel like your native limb, where all of the robotics, algorithms and intelligence that we have built in at the very low level acts just like your spinal cord. You don’t even know they’re there. All you know is, it’s more fun to use this arm, it’s easier to use the arm, and our job would be done.

MILES O’BRIEN: Step by step, researchers are finding ways to let amputees know what they’re feeling and how hard they’re squeezing. Dustin Tyler is working to make his technology implantable, like a pacemaker. For now, the work is confined to a lab.

Igor Spetic looks forward to the day he can take his touchy hand home.

IGOR SPETIC: I have always said I want to feel what it’s like holding my wife’s hand again after four years.

MILES O’BRIEN: This will mean a lot for amputees, won’t it?

IGOR SPETIC: I hope so. One little step forward, it’s big to me.

MILES O’BRIEN: It’s a huge step forward.

IGOR SPETIC: If I get it, I get it. If the next person gets it, that’s even better.

MILES O’BRIEN: Thanks to you, Igor, I might be one of those people.

But, for now, I must make do with the tried-and-true body-powered hook. It’s reliable, rugged and easily repaired, well-suited for my far-flung adventures in the field. But, for me, it’s too hot, too uncomfortable, and not useful enough to wear all the time.

So, mostly, I do without. It turns out navigating with one arm in a bimanual world is not only possible. With some creative thinking, a few gadgets and practice, it becomes trivial. Sometimes low-tech or no-tech is really all I need, for now.

Miles O’Brien, the “PBS NewsHour,” Washington.

JUDY WOODRUFF: Pretty remarkable. Miles is a courageous guy.