The oldest known prosthesis was a non-functioning toe, discovered in a tomb from Ancient Egypt. Since then, prosthetic technology has made incredible breakthroughs.
But, even with the progress of technology, which includes computers, bionic ankles and comfort liners, the issue of joint pain in leg amputees is a problem that Craig McGowan is trying to remedy.
McGowan, an assistant professor in the Department of Biological Science at the University of Idaho, said while he is still far from his desired result, he has made significant progress in the last five years. His research focuses on prosthetic pain and developing a computer simulation model on how prosthetics interact with the body.
McGowan said his working hypothesis is that pain or discomfort occurs for amputees because the devices are not matched to the body, or what he called the “residual limb.” He said the device is like a big spring that is being loaded. When the individual launches back off of the spring, the muscles have to work to harness the energy of the athlete’s movement if the joints aren’t appropriately aligned with the prosthetic.
“I think that what that’s doing is loading the joints in ways they were never meant to be loaded, so that’s causing damage to the residual neuromuscular system,” McGowan said.
Prior to making headlines for the shooting death of his girlfriend, Oscar Pistorius, the “blade runner,” made the news when he was banned from the Olympics. Officials from the International Association of Athletics Federation (IAAF) felt he had an unfair advantage with his J-shaped prosthetics that enabled him to run.
McGowan worked with a team of scientists to prove the ruling against Pistorius was false. He said it gave him an opportunity to look into someone who was performing at an elite level, but who had a different shape.
Because Pistorius is a bilateral amputee, with prosthetics on both legs, McGowan said they had nothing to compare with. Soon after working with Pistorius, he was given the opportunity to work with the U.S. Paralympic team, which gave him insight into unilateral amputees. With this, he was able to compare what the biologic leg was doing relative to the leg with the prosthesis.
Two important revelations came from working with the athletes, McGowan said. One was that researchers still have no idea how the individuals are using the devices. The engineers create them, and the athletes perform at extreme levels, but they have no idea how they control them or how they adapt to the device.
The other revelation McGowan discovered is that all the individuals were experiencing some degree of secondary pain in their knees, hips and backs, which he said is true of most below-knee amputees.
For his doctorate work, McGowan worked with kangaroos and wallabies. The animals helped him understand how organisms use elastic mechanisms in locomotion. He said they store large amounts of elastic energy in their tendons when they hop, so their hopping is more efficient. His research on the athletic amputees has included kangaroo rats to help him understand the relationships between muscle, tendon, bone and the design of the limb.
“I’ve been working with the kangaroo rats as a smaller version of the same biomechanical system,” McGowan said. “But they have very different properties in their tendons, so they’re not quite as springy as wallabies.”
McGowan said he and fellow researchers are working to understand how these different tendon properties allow kangaroo rats to perform basic muscle functions, like hopping.
“We’re trying to understand why and how that influences how they move,” McGowan said. “But, really if we look at running versus hopping, it’s the same basic behavior “” it’s just alternating the legs rather than having the legs move together.”
While his research is focused on lower-leg amputees and athletes, McGowan said the long-term goal is to improve the technology for everyone using leg prosthetics.
“Working with the athletes I think is an exceptional opportunity, because it gives us a kind of an upper limit to what people can do,” McGowan said. “It’s a very small subset of the population, but it’s the highest performing subset of the population, so figuring out how they do it gives us an upper limit of what the body is capable of.”
Jace Malek, a UI student and student coach for the Vandal football team, was recently fitted with a full-leg prosthetic after doctors removed his right leg at the hip due to cancer. While he is still getting used to the leg, he said most of his discomfort comes from skin irritation at the hip where the surgery was performed to remove the biological leg. He said he is unsure how they could make the prosthetics more comfortable, but said that even in the last few months there has been progress made in prosthetic technology.
“This one does a lot,” Malek said. “This one is a higher class one. It has a computerized knee in it and it reads your weight and everything “” makes it easier to sit down and makes it more comfortable, and I’ll be able to sit and stand and move around and go up and down stairs a little bit easier.”
His prosthesis is called a C-leg, which he said stands for “computer leg.” Marshall Black, owner of OrthoPro of Lewiston, specializes in custom prosthetics and orthotics and said he worked with the German company, Ottobock, about 15 years ago, training the first people in the U.S. with the C-leg.
“It takes a reading 50 times per second and it will tell whether you are going uphill, downhill, un-level surface “” if you’re starting to trip it recognizes that,” Black said.
He said there are many different types of prosthetic devices, from earlier, simpler technology, to the more recent C-legs, which are also known as RHEO legs. These legs are often used for full-leg amputees because the technology is in the knee.
Black said that money usually plays into what type of device an amputee will receive. He works with a lot of diabetic patients and Medicare often decides which device, if any, the patient will receive.
Black said there are five categories Medicare classifies for amputee ability called K-levels. The lowest level, K0, is people who have no ability to walk and a prosthetic would not be provided. A person who is a K1 could walk slowly, one speed on level ground. K2 could maneuver a little better, but would still have trouble on uneven ground and walks at one gait speed.
He said the biggest jump is from a K2 to a K3. The K3 is much more mobile. These individuals would be able to walk at different cadences, run a little bit and navigate uneven terrain. They are able to receive upper-end prosthetics, such as the C-leg or the RHEO leg. And then the highest level, K4, would be the athletes McGowan works with. These are the highest functioning individuals, usually in their teens or 20s.
Black said he has not had an issue with patients having pain as McGowan describes with the athletes “” the biggest problem has been with blisters and sore spots. When it comes to recent advancements, Black said silicon liners have probably been one of the greatest inventions to go along with prosthetics. The developers, after a problem with pigment leaching out over time when they dyed the liners skin-color, found they could add aloe into the silicon. The aloe leaches out every day over a period of about six months and gives the amputee a skin treatment.
Despite these advancements, Black said there is bound to be some pain associated with wearing a prosthetic device.
“The same problems and issues that a normal person has, someone with a prosthesis has the exact same problems,” Black said. “And it can be compounded. I mean energy level, wearing a prosthesis “” just normal walking takes more energy.”
He said he couldn’t give an exact number, but people have theorized the energy level to be compounded by around 25 to 33 percent.
Chris Symons, a 10-year amputee, said he has joint pain all over.
Symons, 33, an Iraq war veteran and business owner in Texas, lost his left arm and leg when his motorcycle met a Ford F-250 head-on, with a combined impact of 160 mph.
“It ripped my left arm off immediately, above the elbow, my leg was split open from hip to ankle on my left leg,” Symons said. “They later took my leg off at the hospital, and that was taken above the knee.”
Symons said the accident was so severe, his heart stopped.
“When I wrecked I didn’t have a helmet on,” Symons said. “I died instantly “” actually that’s what saved my life, was dying. I was dead for a couple minutes from just the blunt force trauma.”
Symons said he has terrible pain in his back that causes him to take pain medication. He said that while he is not an athlete, he does work very hard, and his biological leg and his joints are in constant pain. Like Malek, Symons has a C-leg and also has a running leg. In addition to devices for his leg, he also has an arm prosthesis, which Symons said he never wears because it is more a hindrance than a help.
A lot of his discomfort, he said, also comes from phantom pain. He said it is like being “tased,” getting shocked when he is not expecting it.
“Otherwise it’s pretty amazing how these things work and how I adapted to it,” Symons said. “When my heel hits the ground, I can feel my heel hitting the ground and when my toe gets off the floor “¦ Of course it doesn’t feel like my real toe, but I can sense that my toe is leaving the ground.”
Symons described a new technique in the United Kingdom where they surgically attach a titanium rod directly to the bone, which then affixes directly to the C-leg, instead of wearing a bulky socket to hold the prosthesis onto the residual limb, so it feels more like a real leg, he said.
“It’s not approved here, but they are doing it over in Europe,” Symons said. “I am interested in what the future holds.”
McGowan said there is a strong emphasis on trying to recreate a limb similar to the one that was lost because amputees do not want to stand out or draw attention to themselves, but he said that for performance or recreation it may simply be that they can’t reproduce a foot-ankle complex that resembles and functions like the original limb.
“But maybe we could design something else based on what we see in biology that interacts with the residual system and provides the function that was lost,” McGowan said.