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Artificial limbs in the high tech age

Jonathan Skillings CNET News

Published: 04 Aug 2005 15:35 BST

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?
Titanium has been around awhile. I think the one that we have adapted most recently that's really been successful is carbon fibre 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 fibre composite.

What about the skin?
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?
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?
First of all you're never going to be normal. That's number one, 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?
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 Six Million Dollar 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?
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.