Prosthetics that never have to be removed

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DENVER, Co. (Ivanhoe Newswire) – 1.7 million Americans are living without an arm or leg. This year alone, 65 thousand more will undergo an amputation. Now, a medical breakthrough could change their lives.

The show “Baghdad ER” shows the reality of war at a combat support hospital.

Seeing that wartime reality firsthand, in a combat emergency room, inspired Dr. Ronald Hugate.

“For four months we just saw a lot of traumatic amputations,” Ronald Hugate, MD, Board Certified Orthopaedic Surgeon, Presbyterian/Saint Luke's Medical Center, told Ivanhoe.

Dr. Hugate came home to help people like 16-year-old Woody Roseland, who lost his lower leg to cancer.

“Seeing patients like Woody, who are here and is a normal high school kid playing football that has a cancer that really motivates you to try and make things better,” Dr. Hugate said.

Hugate’s quest is to design a permanent prosthetic. So far, it has been a success on a dog, named Triumph.

“I can’t wait to see it change people’s lives,” Woody told Ivanhoe.

In the University of Denver Human Dynamics Lab, Woody’s movements are caught on video with an infra-red tracking system. Engineering students use the data to design a prosthetic that attaches to a post inside the remaining part of the leg. Skin grows into the trabecular metal lining.

“The implant is no longer fitting around the skin it is just snapping to the end of this prosthetic. So, it would improve the life of amputees exponentially,” Dr. Hugate said.

Making this, the first step into helping patients feel whole again.

The permanent prosthetic design could eliminate the current socket technology that can be painful and tiring. Dr. Hugate said he thinks a permanent prosthetic could restore function to nearly normal, especially for young active people. He expects it will take another three or four years before the permanent prosthetic is ready for people.

Ronald Hugate, MD, Board Certified Orthopaedic Surgeon, Presbyterian/Saint Luke's Medical Center Denver, talks about a new technology to give amputees permanent prosthetics.

Would you give us a little bit of background of permanent prosthetics? It’s been a long, slow process, but are you making progress quickly now? 

Dr. Hugate: Permanent prosthetics have been around in Europe for decades, maybe 20+ years. The problem has always been infection because the implant goes through the skin. The bacteria can move along the implant back into the body. The real issue has been how do we prevent the infection, how do we make the implants more long lasting, and that’s where the current crux of the research is happening. 

Why a permanent prosthetic? What difference will it make?  

Dr. Hugate: With current technology, if you have an amputation, you essentially get a molded socket around your residual limb, then you fit your residual limb into the socket, and then you propel the prosthetic through your soft tissues-it’s really energy inefficient. It takes a lot of energy to move when you have that type of a prosthetic. If you happen to fluctuate in weight, if you have skin problems or if you perspire, the socket may not adhere to your residual limb quite as well.  So for all of those reasons, it’s not practical for most active people to have prosthetic sockets.  It can be very difficult for some people to wear sockets. If we are able to attach the implant or the prosthetic directly to the skeleton, it becomes more energy efficient.  It’s really a part of the patient at that point. There are no issues with skin breakdown, weight fluctuations or perspiration because the prosthetic is directly attached into the bone. You really alleviate a lot of the practical issues that the prosthetic wearer may see.

Has it been done successfully with animals?

Dr. Hugate: It’s been done successfully with animals and with limited success in humans in Europe.  Still, the infection rate in Europe is high with these types of implants.  In the United States, we have recognized the benefits of this type of an implant and we are judiciously following them along, but we are also adding innovation to this in a way that we can improve it, and specifically to reduce the infection rate with these implants to make this a more durable solution for patients. 

How much longer until it can be used on people in the U.S.? 

Dr. Hugate: I would say it’s really had to tell. Our studies have been really successful up until this point.  We want to approach this very slowly, though, because it is important to have the implant as safe as possible to minimize the risk to the patients that receive it. Assuming everything goes well with our studies, I would say in the next 3 to 4 years we are looking at something that we could offer a person.

Will you tell us a little bit about Woody?

Dr. Hugate: Woody is a patient of our clinics and he had a cancer in his leg called osteosarcoma.  It was a cancer of the bone in the lower leg, just below the knee. He underwent surgery a few years ago, and has had a few recurrences, both in his leg and in his lungs as well. I believe about 2 years ago, he had an amputation because of a recurrence. Now, he is currently an above-the-knee amputee and is a really interesting fella.  He is full of life and captures life despite all of the setbacks that he has experienced. He has beat cancer something like 5 times now. He has been helping us in this project to see what the practical issues that people face, young active people especially. Also, he is helping us determine what the forces that an average young person may put their prosthetic leg through because that’s important. That is an important part of the equation when you are designing an implant- can it tolerate the everyday forces that patients may impact on the implant?

So, it’s not just for walking? 

Dr. Hugate: Right.

Is it for running too?

Dr. Hugate: Walking, running, jumping, getting up from a chair, going up and down stairs, tripping, catching your foot on something as you walk. We want to capture all of that data about forces on the leg and then use that data to develop an implant that will last for his lifetime. 

Could you explain the Denver University study?

Dr. Hugate: Woody visited the DU folks and met with Dr. Peter Laz at DU, he is a professor of mechanical engineering and material engineering. He runs their biomechanics lab, and they have been helping us design the mechanical portions of this implant. They invited Woody out to collect data and use him as their test subject. He put on reflective markers and went through a series of common tasks like walking, getting in and out of a chair, jumping, and things of that nature. The DU engineers measured what he was doing both in terms of his position, and they measured the force that he was exerting through his leg. Then we used that data to help develop the mechanics of the prosthesis. 

Did that change things?  

Dr. Hugate: Yes, it gives us a good idea.  This is a relatively new field in orthopedics, so the more data we can get, the better.  A lot of the information about amputees is on older people because older people are typically the ones that get amputations, so it’s nice to have more and more data on young people specifically with the war. A lot of young people coming back from the war with lower extremity injuries and also for patients like Woody who are young and have cancer and survive their cancer, but still want to have a good quality of life. So we are collecting data on those younger people to make sure the implant will last them forever.

How does it work? 

Dr. Hugate: This is a model of the thigh bone and this is the hip above.  The hip is a ball and a socket joint so this is the ball portion of the ball and the socket. You can imagine if you had an amputation this is what your bone would look like. This is an above the knee amputation, so this is about midway through the thigh. The bone is hollow like a pipe, so what we will do is basically clear out the center of the bone.  This is a model of the implant here-it has an orange stem portion and this is the portion that anchors in the bone. The white portion is really what’s revolutionary. The skin adheres once the implant is in place. With the surgery, what we would do is prepare the bone and place the implant in the bone like this and that gives a nice anchor, so now this is permanent. This is connected to the person’s actual skeleton. This portion of the implant comes through the skin.  This area looks like a mushroom is actually made of a material called trabecular metal which is a metal that has porosity. It’s about 70% porous and what that allows for is the skin will actually grow into and seal into the implant; almost like a deer’s antler.  The skin will seal around the base of the implant and not allow infection to get into the bone. Once this is in place, and the skin is healed to this ring, then the patient can snap their prosthetic directly onto this implant.  We do have another piece here as part of the design that allows this to break away in case there is an exertion, an incredibly high force; for example, if you are skiing, and you want your bindings to break away and not your ankle to break. In a similar way, if there is an injury or a fall; we don’t want the implant to break the bone, we want it to break out here, so we have a breakaway mechanism here much like the binding on a ski in case that happens. Then the sky is the limit from there, the patient can put on whatever leg they want to use for that particular activity they are doing.  It’s very easy to get this on and off because you essentially just snap it to here. It doesn’t matter if you gain or lose weight, it doesn’t matter if you perspire, and it doesn’t matter if you have a skin breakdown issue because the implant is no longer fitting around the skin. It’s just snapping to the end of this prosthetic, so it improves; it would improve the quality of life for amputees exponentially.

Were you in Iraq? 

Dr. Hugate: Yes, I was.

Were you in the military? 

Dr. Hugate: Yes, I was an Army Reservist from 1995 through 2011.  In June of 2003; I was at the Mayo Clinic doing my fellowship in bone reconstruction for tumors when I was first deployed to Iraq. Within 2 weeks I was in Baghdad at a Combat Surgical Hospital-I spent 4 months there. Have you seen the Baghdad ER television show? That’s the hospital that our unit established in the green zone in Baghdad. For four months we saw a lot of traumatic amputations. The military protects the center of mass really well. Our soldiers had really good flak vests and Kevlar helmets. The problem is if there is an explosion nearby it protects your center of mass, but it doesn’t protect your arms and your legs so although more soldiers are surviving their injuries (which is good), we see a lot of amputations, way more than we saw percentage-wise in previous conflicts. I have also been deployed to forward surgical teams in Afghanistan as well and I can tell you the same holds true in that theater of war as well.

Is that what sparked your interest?  

Dr. Hugate: Absolutely. Many of these soldiers I have treated are extremely motivated and some even get back into the fight. I also perform limb salvage work here at the Denver Clinic, and seeing young, healthy patients  who were doing well before their injury or illness and want to get back to an active quality of life motivates me to want a better solution for them than what we currently offer.   Seeing patients like Woody who was a normal  high school kid playing football that gets cancer and eventually loses his leg- I want something better for him. That really motivates me to try and improve the technology for that group.


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