David Moinina Sengeh: The sore problem of prosthetic limbs
MANOUSH ZOMORODI, HOST:
It's the TED Radio Hour from NPR. I'm Manoush Zomorodi. On the show today - friction. And right now, I would like you to imagine you are running down a rocky hill in a pair of shoes that are way too tight.
DAVID SENGEH: If it's too tight, then you're going to hurt your body from inside. Your toes and all your legs are going to be really painful. Like, it's going to hurt. It's going to lead to blisters. You're going to have blisters, first of all. You're going to have all of these pains internally.
ZOMORODI: OK. So now imagine you're going down this hill wearing shoes that are way too big.
SENGEH: If you're wearing a big pair of shoes, then you're going to break your skin from outside. Your foot is just going to slide in and out. You're going to get some cuts at the back of your foot. You're going to get cuts in other parts, you know, because it's not fitting well.
ZOMORODI: This is what everyday life can be like if you wear a prosthetic leg.
SENGEH: Lots of pressure sores, lots of back pain and hip pain.
ZOMORODI: And it can be hard to get a good fit. So just walking - never mind running down a hill - can lead to that pain.
SENGEH: Now prostheses have several compliments. The biggest problem that was affecting the pain was on the socket, which is the part that connects to the body. The prosthetic socket has to be perfectly fit for you to be comfortable and for you to avoid injuring yourself even more.
ZOMORODI: This is David Moinina Sengeh.
SENGEH: I am sitting in my office in New England Ville in Freetown, Sierra Leone.
ZOMORODI: From that office, he serves as the nation's education minister as well as its chief innovation officer. But before joining the government, David spent years in the U.S. researching and testing ways to make better-fitting prostheses. And what he discovered was that it all came down to having just the right amount of friction.
SENGEH: So there's a fine balance between how friction plays here. You want the friction. You want to attach your prosthetic leg to your biological leg, to prevent your leg going in and out so loosely in the socket. But you also don't want it to be too tight because then what's going to happen is you're just going to have these internal soft tissue stresses and strains.
ZOMORODI: Solving this problem became a personal mission for him. Here's David Sengeh on the TED stage.
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SENGEH: I was born and raised in Sierra Leone, a small and very beautiful country in West Africa, a country rich both in physical resources and creative talent. However, Sierra Leone is infamous for a decade-long rebel war in the '90s when entire villages were burnt down. An estimated 8,000 men, women and children had their arms and legs amputated during this time.
As my family and I ran for safety when I was about 12 from one of those attacks, I resolved that I would do everything I could to ensure that my own children will not go through the same experiences we had. They would in fact be part of a Sierra Leone where war and amputation were no longer a strategy for gaining power.
As I watched people who I knew - loved ones - recover from this devastation, one thing that deeply troubled me was that many of the amputees in the country would not use their prosthesis. The reason, I would come to find out, was that their prosthetic sockets were painful because they did not fit well.
ZOMORODI: So, David, was this specifically a problem in Sierra Leone, or is this just every person who wears a prosthetic leg has to deal with this, this pain that can come from where the cup of the prosthesis connects to the body?
SENGEH: So when I started this, I thought that this is a Sierra Leone problem 'cause that's what I knew. And then I went to the U.S., and I met Professor Hugh Herr. He's a professor at MIT. He's a double amputee himself. And here was a tenured MIT professor with all kinds of patents and really brilliant and runs his own lab - he's a double amputee, and he has the same problems as the people in Sierra Leone. And he had a robotic ankle.
ZOMORODI: So even the state-of-the-art prosthesis, he had the same issue.
SENGEH: Yeah, exactly. He had powerful robotic ankles, but he had the same pressure sores, and his prosthetic sockets sucked the same way that other people's prosthetic sockets sucked. And we connected on this. We connected on the fact that this was unacceptable and how was it that it didn't matter whether you were in Freetown and a kid who was begging on the street or you were a professor at MIT or an ex-military person in the U.S., you all had the same problem.
ZOMORODI: So you ended up going to MIT. And what did you say to your professor? Did you say, like, I want to try and solve this problem with you? How did you even begin to tackle it?
SENGEH: So when we were developing the technology in 2014, our thesis was this - if you touch the human body, it's made out of different materials. The tissue, the fat, the skin and the bone react to these external pressures when you walk or when you stand. So we said, OK, if the body is made up of multi-material, then a prosthetic interface, a socket, that is also multi-material will minimize the internal stresses and strains. You essentially just want to have soft where you need soft, but you also want it to be structural.
ZOMORODI: OK. So how do you get a prosthetic leg to be more human?
: So just below your kneecap, if you press below your kneecap...
ZOMORODI: I'm doing it now.
: ...That can take a lot of load, on that tendon. So we essentially drove a lot of the pressures through that, to the patellar tendon, and then also to the back of your leg because your back of your leg has lots of muscle. And we removed the pressures from what we call the fibular head. So on the outside of your leg just below the knee, if you rub your hand down, you feel...
: ...Some bones there. You see a really sharp bone.
ZOMORODI: Yup, yup. I found it. It's kind of knobby.
: Yes. And that's the fibular head. Almost every amputee will tell you that they have a pressure sore there or pain or blister. It's the worst place for them.
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: And so you essentially want that to be super, super soft. And then if you rub your hand on your shin, your tibia, that has little skin, right?
: So if you have friction there, you're going to be in pain all the time. So just imagine, then, that the amputees have most of their pain on the fibular head and then on the tibia and then on under their legs. And so we were building these models that will reduce pressures at those locations and put it in other places where you can take those pressures.
(SOUNDBITE OF TED TALK)
: I use magnetic resonance imaging to capture the actual shape of the patient's anatomy, then use finite element modelling to better predict the internal stresses and strains on the normal forces and then create a prosthetic socket for manufacture. We use a 3D printer to create a multi-material prosthetic socket which relieves pressure where needed on the anatomy of the patient.
ZOMORODI: You know, when I watched your talk, you had one of these sockets onstage with you. And I was kind of surprised. It was very beautiful. The one that you had was rainbow colored. It almost looked like sand art. It was pretty.
: It was gorgeous. It was gorgeous.
: The thing with the multi-material 3D printers is that each material has different color, and you can choose. And I must say - years in the past, my thesis, when my professor said, oh, it's sexy.
: And I was like, ah, that. And then he also said it's like walking on pillows.
: And so if - I think if your professor says it felt like walking on pillows compared to what he had and that it was sexy, then I think I was like, OK, fine, I'll get this Ph.D.
ZOMORODI: So you have since returned home to Sierra Leone. You are the country's first chief innovation officer. More recently, you were also appointed the minister of education. It's impressive. I mean, my understanding, though, is that while you're no longer working on the project, it is still up and running.
: Yes. And it's very interesting. I go to church, and on Sunday, this just past Sunday, this gentleman comes - I didn't know where he heard it from, or something, but he'd heard about the bionics work and was like, oh, I'm so happy that this is coming. I can't wait that I can use my prosthetics here 'cause he was in pain, and he was showing me his pain. So it's - even though they know that I'm a minister and I'm in education and CIO, you still have lots of people who still come to me to say, so these prosthetics work. When am I going to use it?
ZOMORODI: Oh, they're excited about it. OK.
: Yes, absolutely.
ZOMORODI: So what do you say to him? Like, if he's like, when am I going to get it, Minister? - what do you say?
: I say, soon. I say, look, we're working on it, and it really is wonderful.
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ZOMORODI: That's David Moinina Sengeh. He is Sierra Leone's chief innovation officer and minister of education. His book, "Radical Inclusion," will be out in 2023. And you can see his full talk at ted.com.
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