Doctor Develops a New Prosthetic for Amputees

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A Denver doctor is trying to help amputees live with less pain. Dr. Ronald Hugate and a partner have developed a new prosthetic device that attaches direcly to the bone. He was inspired while working as an orthopaedic surgeon in Iraq during the war. He joins us to talk about it as part of our ongoing series Iraq War Stories, where we talk with Coloradoans who've spent time in Iraq.

Colorado Matters

Iraqi War Stories Interview with Ronald Hugate

November 17, 2010


From Colorado Public Radio, I’m Ryan Warner and this is Colorado Matters.

Despite advances in prosthetic arms and legs, many amputees still deal with pain on a daily basis. Take it from Paul Martin of Lafayette. Years ago he had to have his left leg amputated below the knee after a car accident. Martin is a competitive runner and cyclist.

PAUL MARTIN, Active Amputee:

I experience pain most of my day, so that’s either a little or a lot. Walking around the house, that kind of thing, not that big a deal. But as an active amputee, I like to get out and train four, five days a week and pretty much every time I go running, I’m in some sort of pain.

Warner: He wishes it were different.

Martin: I would love to walk without pain. I would love for my leg not to slip. I would love to run without my leg falling off, you know, on a hot summer 5K.

Warner: Well, Denver doctor Ronald Hugate wants to make that a reality. He’s developing a new type of prosthetic. Dr. Hugate was inspired while working as an orthopedic surgeon in Iraq during the war. He joins us as our series, Iraq War Stories, continues.

Dr. Hugate, thanks for being with us.

DR. RONALD HUGATE, Orthopedic Surgeon:

Sure, my pleasure.

Warner: Describe what this device looks like.

Hugate: This device is made to, essentially, connect someone’s skeleton directly to their prosthesis and there’s a number of reasons why that would be beneficial or important to an amputee.

The actual device is actually a metallic implant. It fits inside the bone of the recipient. A bone is generally pipe shaped, so this is a cylinder that would fit inside of a pipe, if you can think of it that.

The implant is attached to the individuals bone and there is a stem on the end of the implant that actually comes through the skin and we’re attempting to get the skin to seal to this implant to create a barrier against infection. And then that would be the actual implant.

Now the entire apparatus would be that implant, mated with an external prosthesis, which we’re all familiar with. So a knee or a foot made of carbon fiber or made of mechanical elements for the individual to walk with.

Warner: But this differs from how things work now because of that direct connection to the body, that permanent linking up?

Hugate: That’s right. Currently if you were to have an amputation for whatever reason, you would be fit with a molded socket and that socket would form fit to your extremity. And that works well in the lower leg, in other words, below the knee, because the extremity is usually very skinny, the bone is prominent, is right under the skin. And so energy is transferred very easily from your body to that prosthesis.

If you get into amputations that are higher, for example above the knee, there’s a lot of muscle and skin and soft tissue there and so it becomes a lot less efficient. In fact, if you have a below-the-knee amputation, your energy consumption rate when you walk only goes up by about 10%. If you have an above-the-knee amputation, that rate goes up on the order of 50% to 75%.

Warner: Oh, wow.

Hugate: So people have to work a lot harder, because it’s a lot less energy efficient to transfer what you want to have done to the actual prosthesis.

Warner: So that explains some of the benefit here. Practically, what does that mean in a person’s life if, further down the road — this is still in the experimental stages — this were possible for them?

Hugate: Well, it opens up possibilities. If you have an inefficient transfer of energy from your leg to the prosthesis, it makes people work a lot harder to get things done, essentially. Very mundane tasks can be exhausting, especially if you are elderly or have other injuries.

And so by directly connecting to the skeleton, we bypass issues. It takes less energy to do the same things. People, for example, may fluctuate in weight. People often will fluctuate by 10% or 15% over their lifetime and if you’re fit for your prosthesis socket when you are overweight and your weight fluctuates, you may not fit well into that socket later.

Warner: And that’s an expensive change.

Hugate: It is. And so you have to go back and, essentially, restart the process over again.

Also, from a practical standpoint, people perspire and so it’s very difficult for a socket to remain firmly affixed to your residual limb if you perspire.

Warner: And all of this would make a difference in someone’s pain level?

Hugate: It would. For example, the shape of the residual limb changes frequently. It changes, of course, when you have the initial surgery and there’s a fair amount of swelling. It tends to reduce over time and then sort of stabilize.

In the longer term, you can have a change in shape of your residual limb because of disuse or atrophy of the muscles and that can create pressure points. If you have a socket molded when your residual limb is a certain shape and it changes shape slightly, you will eventually have pressurized areas. And what we see is that people who are active tend to get skin breakdown and that’s another good reason to attempt to perfect this technology.

Warner: In this procedure, you are connecting something directly into the body. Does that make a difference in the sensation the person has with a prosthetic limb?

Hugate: It absolutely does. There’s a couple of subtle effects that you lose when you become an amputee. The first is that you lose what we call proprioceptive feedback. You lose the ability to know where your foot is in space.

And we certainly take that for granted, but when you and I walk, we are able to know where our foot is. We don’t have to look for our foot as we’re walking, for example. And the reason is, because it’s directly connected to our skeleton.

If you have a socket prosthesis, for example, in a patient with an above-knee amputation, there is so much wobble in that interface that you may or may not know where your foot is. And so you have to be very vigilant about actually watching your foot and knowing where it is as you walk. And that may seem like a small point, but it’s liberating for people who have these skeletal transcutaneous prostheses that we’re talking about.

The other issue is that folks with amputations who use socket prostheses are not able to distinguish what surface they’re walking on. So, for example, you and I change our gait when we walk on sand versus if we’re walking on a hard concrete surface. But if you happen to have an amputation at the level above the knee, for example, you would have a hard time distinguishing those surfaces without actually looking at what you’re walking on.

And so having that feedback, knowing where your foot is in space, those are two very subtle things that we take for granted, but they’re very important in terms of having a normal gait.

Warner: Yeah. You know, I’m hearing this and I’m just-- I have a new level of gratitude for my limbs when I hear you say this.

Hugate: Absolutely. It’s only when they’re gone do you realize how important they are and do you realize what all these subtleties mean to your every day life.

Warner: You’re listening to Colorado Matters. I’m Ryan Warner and as part of our series, Iraq War Stories, we’re talking with Dr. Ronald Hugate and he has spent time in Iraq as a surgeon there and it’s that work that inspired him, in part, to develop a better approach to prosthetic limbs.

Now the big challenge here, it seems, and you’ve alluded to this, is infection. You are putting a foreign body into the body that is half in and half out, in a way.

Hugate: That’s exactly right. This implant is unique. It’s not like a hip or a knee replacements that’s entirely covered and implanted below the skin. And so naturally there, there’s a protective barrier against infection and, fortunately, infection is very rare.

When you have a foreign body that starts inside the body and passes through the skin to the outer body, the infection rate goes up a fair amount. And, in fact, if you leave a device like this, either a pin or some other foreign body protruding through the skin, eventually you will have a 100% infection risk.

And so the real advancement in the less decade of 15 years has been advancement of materials that will allow for a seal of the implant against the skin, in other words, not allow bacteria to migrate up the implant into the body.

Warner: Is this a seal that’s essentially mimicking a mucous membrane?

Hugate: It has been compared to antlers, for example. So it’s a seal of an external device that travels through the skin and the skin actually permeates and grows into the device to create a barrier against infection.

Warner: I see — antlers. In other words, this would be a harder surface, not a liquid or soft surface?

Hugate: Exactly.

Warner: Okay. This idea arose from a need you saw in Iraq. Would you tell us more about that?

Hugate: That’s right. My background is an unusual background. I have a degree in engineering, mechanical engineering, and I also have a-- obviously, a medical degree in surgical oncology. So I see a lot of patients with limbs that are at risk, for whatever reason, for tumor, most often, but also for infection or trauma.

And then in August of 2003 I was deployed to Iraq to take care of the troops there and worked at a combat surgical hospital in Baghdad and really gained my motivation for advancing this science through that experience. Because here is a group of young, previously athletic, seemingly immortal men and women, who have a devastating injury and then are limited by the technology that we can offer them today in terms of their lifestyles.

Although our government and our system does a wonderful job of presenting them with the best of the best and getting them to the maximum function that they can get to with current technology, I was frustrated by, especially, the patients that had amputations above the knee. Their level of function was not as good as we would like and so that background and experience really motivated me to pursue this technology.

Warner: Is there someone in particular you remember meeting that influenced this?

Hugate: Well, there are several patients that I met in Iraq. I can picture one imagine in my head of a young soldier in his 20s, male, who was near an improvised explosive when it went off. He was with a buddy of his and the explosion completely blew off his right leg above the knee and broke his left leg below the knee.

And so his buddy literally took his leg and used it as a splint. The one that was blown off was used as a splint for the leg that was remaining. And so that is a picture that I see when I think back to my experience there of a young, otherwise healthy person who became traumatic amputee in a second, less than a second, and the type of person who would be benefited most by this technology.

Warner: That’s a horrific scene. And this person came into the hospital in Baghdad?

Hugate: That’s right.

Warner: The experimentation so far with this idea has been, in this country-- there’s been some of this in Europe, right?

Hugate: There has been in Europe. They have a different philosophy there. Currently the implants that they are using don’t make any attempt to seal the skin against the implant. And so they subsequently have a high infection risk.

And so the philosophy that we’ve engaged here in developing our implant is more of an attempt to seal off and reduce the risk for infection, because that will eventually be the main limiting factor with this type of technology.

Warner: And in this country you’ve tried this on some dogs?

Hugate: That’s right. Here in Denver, about five years ago now, Dr. Bob Taylor and I performed implants on seven dogs.

Warner: Dr. Taylor is a veterinarian.

Hugate: Dr. Taylor is a veterinarian. He was the medical director at Alameda East Hospital here in Denver. He’s currently retired. But we were presented with a dog by the name of Triumph, who was found in Europe without her hind legs. They were traumatically amputated below the knee, both of them, and she was rescued by an operation here in the States in Tennessee and was eventually transferred to our care and we were able to perform bilateral hind limb or back leg implants to reestablish her ability to walk and run.

Warner: And how did she do?

Hugate: She did quite well in the short term. We have a number of photographs and videos documented how well she did. She essentially played like a normal dog for the first couple of years.

She, unfortunately, developed loosening of one of her implants and it had to be revised and since Dr. Taylor has retired over the last year or so, he has not, obviously, been following her up.

Warner: But we know that this dog lived for several years in good shape with these implants.

Hugate: Oh, yes. She did quite well in the short term.

Warner: And how does that extrapolate to humans?

Hugate: Well, we can use that information in the design to move forward. There are, obviously, differences between humans and dogs, but if you can have short-term success in a dog, which is, frankly, the worst of many worlds for an implant like this — dogs are not very hygienic. They tend to lick and scratch their implants. And so it was really a nice trial for how effective this barrier can be.

And we will, obviously, take that information that we gained from that experience and also the implant design information and sort of continue to extrapolate that up into, eventually, the human population.

Warner: And is there another animal you’d try before you got to humans?

Hugate: The next step for us is to look at pig skin. Pigs tend to have skin that’s very analogous to humans in terms of its thickness and its anatomy. And so the next natural evolution is to try and bring this technology more and more into an analogous or a similar skin type and the next step for us would be to look at how these implants do in pigs.

Warner: Where does one find amputated pigs?

Hugate: Well, the first stage of these studies would not be amputated pigs. They would actually be implants that went through the skin of a pig, but not in a bone-anchoring sense. It would be purely a skin in-growth study looking at the way the skin reacts adjacent to this new material.

Warner: But eventually you would do the actual procedure?

Hugate: Eventually we would, yes.

Warner: And would you have to amputate the legs of the pigs to do so?

Hugate: Or a leg.

Warner: Some people might hear that and think, oh, that’s grisly. It’s a grisly thing to have to do.

Hugate: That would be the first reaction and I’m an animal lover myself, but the truth is that any medical or surgical procedure, for example, vaccinations, medications, any surgical procedure, even perfumes and dyes and things of that nature, in order to be approved for use on humans, understandably, have to have some reliable experimental data to provide for the safety of the initial folks that are going to get implants.

And so this is a process, unfortunately, that is not optional. It is something that is sort of our homework before we make the jump into human patients, recipients.

Warner: And how soon do you think you could make that jump?

Hugate: Well, we are in the middle of our pig studies at this point. If things go very smoothly, then there may be an opportunity within about two years to start offering these to the right population of human amputees.

Warner: Well, Dr. Hugate, you mentioned that this work was inspired, in part, by your time in Iraq. Have you had contact with the VA about this avenue of research? Is this something that the Veterans Administration is interested in?

Hugate: I have. In fact, about a week ago I met with Dr. Richard Weir, who is with Northwestern University and he actually lives locally here. He’s taking over the local VA rehabilitation office.

And he and I have been discussing over the last two years some advances that he has made and also some advancements that we’re making with the eventual hope to sort of marry those advancements together. But we’re very excited about offering this to a VA population here in Denver, once we’ve proven the efficacy and safety. But we’re certainly in direct talks with the VA Medical Center regarding these technologies.

Warner: Well, thanks for this. It’s been fascinating.

Hugate: Thank you.

Warner: Dr. Ronald Hugate is an orthopedic surgeon in Denver. He’s developing a new prosthetic limb that would be surgically implanted into bone.

Dr. Hugate was inspired by his work in Iraq and later this month he’ll deploy to Afghanistan. His story is part of our ongoing series, Iraq War Stories. We’re marking the end of U.S. combat operations there by talking with Coloradans who have a personal connection to the country. You can hear all the conversations in the series at our website,