Prosthetics go high tech

Your legs may not seem all that smart, but they're pretty good at letting you walk without having to think about what you're doing.

That hasn't been the case with artificial limbs, which have long required wearers to put a lot of thought and effort into a simple stride. Now, though, a newer generation of prosthetic devices is making use of chip technology to make walking a more natural act for amputees.

One such device is the C-Leg, from Otto Bock HealthCare, a German company that got its start working with war victims in the first years after World War I. The C-Leg is a decidedly 21st-century device, with a microprocessor in the knee that reads data 50 times a second--from real-time sensor data--to help the wearer negotiate changing terrain. The company also provides upper-body devices such as a new "dynamic arm" that for the first time has power-assist technology in elbow.

Bert Harman, president and CEO of Otto Bock's Americas region, recently spoke with CNET News.com about R&D challenges, getting nerves to talk to prosthetics and the current state of bionics.

Q: How big a business is high-tech prosthetics, and what is Otto Bock's part of that business?
Harman: Well, if you start as high-tech prosthetics, it's relatively small. In fact the whole prosthetics industry is a small industry. In United States alone, there are about 1.2 million people that are amputees.

It's a small industry and because of that there is very little fundamental research, so we are generally late to adopt things. Electronics and composite materials and all the things that make up high tech today have been around for a long time, but it's only been in the last five to 10 years it was applied into this portion of the business.

What is the state of the collaboration between the medical and scientific community?
Harman: There is a fair amount of collaboration in centers (such as) the Mayo Clinic, the Cleveland Clinic, Johns Hopkins, Stanford...There are a number of people who are interested, and have established gait labs as an example, to study the gait and how prosthetics impact that. That's adequate. I think what we're missing is the ability to develop good clinical claims...because again there aren't that many people. In a traditional drug study, a drug company might study 5,000 patients or more, and if we do a C-Leg study, we're lucky to get 20 patients.

What percentage of that 1.2 million amputees would go high tech, would have devices like the C-Leg?
Harman: In total, it's probably less than 10 percent of the population that would receive high-tech componentry. To give you an example, the C-Leg in the United States is a product that is generally recommended for mid- to high-active patients, and there are only about 8,000 of those a year that would be an above-the-knee, active amputee.

And we are taking about products that, from what I've read, are in the $40,000 to $60,000 price range?
Harman: That's a bit misleading. The products themselves are only a percentage of that. A $40,000 device would include all the components; the socket, which has the interface between the residual (limb) and the componentry; and the prosthetist's time. They can be that expensive, but it's a part of a total package.

Are we still in the first generation, or we are in a second generation of chip-based technology for the prosthetics?
Harman: As far as lower extremity is concerned, we're moving into the second generation. Now in upper extremity, which doesn't get a lot of press...myoelectric upper-extremity componentry has been around a long time. While (those devices) didn't use chip technology, they did use micro motors and batteries and power supplies and electrodes, so that was kind of a frontrunner. Actually, upper extremity really started the whole high-tech push.

How have the chips altered the design and use of the products?
Harman: Much like just about anything else where chip technology is applied today, it's basically making decisions faster. In this case what chip technology has allowed us to do is...very quickly monitor the terrain and the speed of the wearer and make adjustments, so that in essence the patient is in a much safer mode. Prior to chip technology, just to go down the stairs, typically an amputee takes one step at a time, and it would be good leg first and then they'd drag the prosthetic device behind them. With chip technology, an amputee goes down the steps one foot after another much like you or I would. The decision process is taken out of it (for the amputee), and it's made in the leg itself.

What are the limitations of something like the C-Leg and these higher-end devices? How reliable are they, what is their life span?
Harman: I don't think that the technology has a limitation. I think it's cost-return, cost-benefit that's the limiter at this point, because again we are not producing that many units. It's not like we're making cell phones or calculators where you just continue to drop the price down because of volume.

What's the next big step?
Harman: The next big step is probably going to be motorized or power-assist (additions). Today you're under your own power--there's a battery that drives the electronics, but it's your leg that powers the movement of the device. In the future there's some technology around

that will assist the patient, to actually in this case go upstairs, power its way up. That should be here in the next couple of years. To me the next step is to be able to connect to the neuromuscular areas of the body and actually have the body (use) the brain power of the device. Instead of having to think "I'm going to move my leg" and then move it, you just think and the nerves will fire and you'll move forward.

That's the myoelectric aspect, right?
Harman: Myoelectric is that way. The difference is, myoelectric (technology) uses an external electrode--when you flex a muscle you're powering the electrode, you're sending an electrical signal. In this case, we're talking about implants, where you're actually implanting the electrode, and wrap it around a nerve or wrap it around a particular part of the muscle and then have, either through radio frequency technology or some other technology, have that nerve speak to the device, and the device will move. I think that's 10 years away or less.

And there's osteointegration we've been playing with for a long time. There's a lot of headway being made there. Today a prosthetic device is attached to a socket--your residual limb is put into the socket. You could eventually see where you're actually attaching prosthetic devices directly to the bone, and if we can solve some of the issues associated with that, it will be a much more comfortable and probably more responsive prosthetic device.

What about some of the other materials--the plastics used for the skin, the titanium or whatever the metal is that is part of the frame?
Harman: Titanium has been around awhile. I think the one that we have adapted most recently that's really been successful is

carbon fiber composites, right out of the aerospace industry, both in foot design as well as in some of the materials that make high-tech products like the C-Leg. We've been using composites now for I guess somewhere around 10 years or less.

There will be some other materials coming down the road, especially in the plastics area, but we haven't found anything as strong or light yet as a carbon fiber composite.

What about the skin?
Harman: I don't think there is a lot of fundamental research being done there...The future of having a more sensitive cosmesis, something that is more tactile, maybe has some sense to it or feel to it--there isn't a lot of work being done in that area. It's very, very expensive.

There were three parts to the technology question. I think I only covered the one, the limiting factor.

The reliability and the life span?
Harman: We're finding that with electronic and electronic-assist, with some of these new materials we're getting much longer life out of the limbs. A typical prosthesis, a hydraulic knee joint or standard knee joint and foot, might last about three years. With C-Leg--this is our sixth year in the United States, and we don't get that many back. Part of that has to do with the fact that materials are certainly that much better, but also these now require service intervals, where a traditional hydraulic knee joint and foot didn't require that at best. But with a C-Leg and the electronics that are associated with it, you get it back here once a year or once every two years, and the electronics and everything are just about rebuilt when you go back out again.

At a risk of using the wrong term, how close does the prosthetic get someone to being "normal," to having the equivalent of the arm and leg they were born with?
Harman: First of all you're never going to be normal. That's No. 1, and that's the first thing I think any prosthetist would tell an amputee--define "normal," I guess--but you're never going to be like you were. I think that the more we can give them or the more our products can take (out) the risk associated with been an amputee, take the decisions out of it, the closer we'll get to normal activities. An amputee can ride bicycles, can run, can swim. They can walk up and down stairs, they can walk up and down rough terrain with these devices, a lot easier. So rather than saying how normal would they get, I would say they could get much closer to normal everyday activities using these devices.

There were some reports a couple of weeks ago in the Australian press about a man who has just gotten what was described as the first "dynamic arm," an Otto Bock product. What is a dynamic arm? Is that a new product?
Harman: Yeah, it's a new product. All of our upper-extremity prosthetic devices had power-assist in the hands and wrists, so you could rotate through the wrist and you could open and close the hand, with myoelectric technology. The elbow was always a mechanical move--someone had to literally shift their weight to throw an elbow up or down, and lock it. The new technology is power-assist in that area, so it's basically moving up the arm with the technology.

That reference to power assist ties into the whole notion of bionic limbs--when somebody hears the term "bionic," they think of the TV show "The $6 Million Man," where someone is capable not just of normal activity, but has ability above and beyond what they originally had. Is that something that's coming--you can put on a dynamic arm and be able to lift a small truck or something like that?

Harman: I don't see anything like that, I think again because of the cost. When we talk about power assist or bionics, we are trying to get people back again as close to everyday activity as we can get them. I don't know of any work that's being done to make them superior to what they were. Now the military is working on a number of projects--and we're involved in that--to not make the soldier better, but get the soldier who has lost a limb back into combat, if that's what they choose to do, back into a more active military life. In the past, anyone who lost a limb in the military pretty much was discharged and they were then part of the VA system...But again it's not to make them superior, they're not going to run faster or shoot straighter or anything else. When we speak about bionics it's still all about normal activity.