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Will a robotic arm ever have the full functionality of a human limb?

February 12, 2015 at 6:30 PM EDT
Improvements in body armor have kept more soldiers alive, but many veterans returning from Iraq or Afghanistan have come back with debilitating injuries. Science correspondent Miles O’Brien, whose left arm was amputated last year, tests out some of the future limbs now in development.

GWEN IFILL: Next: a report on the possibilities and limits of robotic arms and prosthetic technology.

It’s also a story with a real and personal connection for us through the experiences of our science correspondent, Miles O’Brien. One year ago, he was involved in an unlikely accident that led to the amputation of much of his left arm. Since then, he’s been reporting and exploring what might be available to help him and others.

Here’s the first of two reports.

Lots of people wonder why I don’t wear a high-tech bionic arm. It’s a fair question for an arm amputee who happens to be a reporter with more than 20 years on the science and technology beat. People expect a professional nerd like me would have an arm that approaches what Luke Skywalker or Colonel Steve Austin wore.

ACTOR: We can rebuild him. We have the technology. We can make him better than he was.

MILES O’BRIEN: Not yet, but maybe soon, as I discovered not far from my home in Washington at the Johns Hopkins University Applied Physics Laboratory.

Here, they’re using knowledge gained, building compact, complex systems like spacecraft and missile warheads to push the envelope in upper limb prosthetics.

MICHAEL MCLOUGHLIN, Johns Hopkins Applied Physics Laboratory: This is the modular prosthetic limb. This has been designed to have most of the functionality of the human limb.

MILES O’BRIEN: Chief engineer Mike McLoughlin introduced me to the Modular Prosthetic Limb, the MPL. It’s the mostly sophisticated artificial limb in the world.

MICHAEL MCLOUGHLIN: So, the arm has 26 joints controlled by 17 different motors. So it can do just about everything that you can do with a natural limb. One of the few things it can’t do, if you’re a “Star Trek” fan, you won’t be able to do this. But, other than that, we can pretty much do everything.

MILES O’BRIEN: “Star Trek” isn’t my thing anyway, even though many people think I stole my name from Chief Miles O’Brien on “Deep Space Nine.”

Like nearly other advancement in prosthetic technology, the impetus for innovation was war. Better body armor meant soldiers who would have died on the battlefield a generation ago were coming home from Iraq and Afghanistan alive, but often more seriously maimed.

Meanwhile, upper limb prosthetic technology was several wars behind. Wounded soldiers were and still are routinely fitted with a body-powered prosthetic, the design first developed during the Civil War. The split hook is, relatively speaking, a modern marvel, patented in 1912.

Here’s how a body-powered upper limb prosthetic works. There’s a strap tied across my chest. It is attached to a cable, just like a bike brake cable. When I move forward, it bends the elbow or, if I spread my shoulders out, same thing. If I stop and lock the elbow, those same motions will open the hook, which closes on the force of some rubber bands.

It’s confining and clunky, really not much more than a hook on a stick. It’s better than nothing sometimes, but not always. The technology had stagnated because it’s such a tall order to replace a human arm and hand with its complex, varied mission, and there just aren’t many of us, only about 100,000 upper limb amputees in the U.S., compared to a million who have lost legs, big challenge, tiny demand.

So, in 2006, the Pentagon’s research and development enterprise, DARPA, launched its $48 million Revolutionizing Prosthetics program. The Modular Prosthetic Limb is one of the outcomes of that effort. The arm has 22 degrees of freedom and is designed to be almost as intuitive and functional as the one I lost.

Right now, it is still in the testing phase. It won’t be available for widespread use for years. But the research team was kind enough to offer me a test drive, if you will.

COURTNEY MORAN, Johns Hopkins Applied Physics Laboratory: I’m going to kind of generate an array around your arm, which is to say that I’m going to position these kind of staggered like this all the way around your arm.

MILES O’BRIEN: Courtney Moran is a prosthetist here. She stuck an array of electrodes to my stump and connected them to the arm bolted on a stand. She then helped me teach it to do my bidding using pattern recognition. The electrodes detect the faint electrical impulses generated when I contract my muscles.

COURTNEY MORAN: Now I want you to take a moment to kind of envision what you’re going to do, and I’m going to say, and go.

MILES O’BRIEN: Every distinct movement that I try to make fires a different array of muscles, creating a unique pattern. It’s not unlike training voice recognition software.


A word of explanation. Like most amputees, I feel my missing limb as if it was still there. It’s an omnipresent phantom. In my case, it feels as if my arm is bound up in a sling, partially asleep and often painful. Paresthesia is the medical term. If I focus carefully, I can move my missing hand and fingers partially and slowly.

COURTNEY MORAN: And go. And rest.

MILES O’BRIEN: After only a few minutes of training the arm to understand the language of my muscles came a magical moment for me.

COURTNEY MORAN: All right, so now we’re going to do elbow extend. So, ready, and go. And rest. So you did that.

MILES O’BRIEN: I expected there to be some kind of lag, you know, but that’s amazing.

COURTNEY MORAN: You are in control right…

MILES O’BRIEN: Yes. That is incredible.

It was nothing short of thrilling. For the first time since I lost my arm, it occurred to me that technology might one day restore nearly all the function I lost.

COURTNEY MORAN: And ready, and go. And rest. And open again. Ready, and go. And rest. And open again. Ready, and go. There it is. OK. And now we’re going to close. Ready, and go.

Let’s just see if we have enough here. See if you can open up.

MILES O’BRIEN: And close.

COURTNEY MORAN: All right. You are ready to throw out the first pitch.


COURTNEY MORAN: Try again. See if you can open up.

MILES O’BRIEN: Pretty cool.


MILES O’BRIEN: But I was erratic, and soon found the limits of my ability to move my missing hand, and thus the artificial one.

COURTNEY MORAN: Go ahead and open the hand, if possible. It’s going to be — you have a lot…

COURTNEY MORAN: Yes. All right, now I want you to close your eyes. I want you to fully rest, yoga breaths here. And then there we go.

That happens all the time.


COURTNEY MORAN: Again, all of this down at the wrist and hand is controls that you theoretically should not have intuitively that you do. So, awesome.

MILES O’BRIEN: To control it better, I would need to undergo targeted muscle reinnovation surgery.

JOHNNY MATHENY, Modular prosthetic limb test subject: I will tell you what I’m doing with my phantom limb.

MILES O’BRIEN: Johnny Matheny had the surgery in 2011.

JOHNNY MATHENY: It’s like, right now, I’m opening my hand up.

MILES O’BRIEN: The nerves that transmitted commands…

JOHNNY MATHENY: Closing my hand.

MILES O’BRIEN: … to his missing arm are now implanted…

JOHNNY MATHENY: Flexing my wrist back.

MILES O’BRIEN: … in muscles that remain.

JOHNNY MATHENY: Bringing it forward.

MILES O’BRIEN: Johnny’s surgeon is Dr. Albert Chi of Johns Hopkins.

DR. ALBERT CHI, Johns Hopkins University: It’s essentially rewiring electrical information that wasn’t previously accessible to a way that we can now record it from, not only record from, but have a natural amplifier to those muscles and then record from it in a noninvasive means.

JOHNNY MATHENY: Putting on the prosthetic arm, in the beginning, it was basically the same as with any prosthetic arm.

COURTNEY MORAN: So, these are our battery packs right here. And they’re rechargeable.

JOHNNY MATHENY: If after that — the sensors starts, you know, picking up this, and then you start seeing, you know, how the hand moves in fluid motion and all this kind of stuff, that’s when the world really starts separating itself. You go into operating a prosthetic just by thinking. I’m doing the moves.

COURTNEY MORAN: Stretch again. Ready, and go.

JOHNNY MATHENY: That was just truly amazing. It’s just an all-natural control, just like your normal hand and stuff.

It’s A-OK, Joe.

DR. ALBERT CHI: We have had actually patients, after targeted muscle reinnovation, have individual finger control. We have interfaced with gaming programs such as “Guitar Hero.”  And patients have been able to not only play the guitar and play the guitar accurately through the gaming console.

MILES O’BRIEN: But it’s hard to play the guitar without a sense of touch. The arm has sensors in its fingertips that are able to offer sensory feedback. Making that information available and useful to an amputee is the next big challenge in the world of advanced prosthetics.

More on that next time.

Miles O’Brien, the PBS NewsHour, Laurel, Maryland.

GWEN IFILL: That is just amazing.

Tune in tomorrow night for that next report, when Miles explores the science of touch.

Online, Miles shows us how he has adapted to doing daily activities with one arm. His blog is on our home page.