Cutting-Edge Composites May Be The Future Of Orthopedics

Thu, August 04, 2011

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KMUW / Fletcher Powell

With some 75 million baby boomers wanting to stay active even as they enter old age, the orthopedics market in the US appears to be growing dramatically. But like any other technology, orthopedic joint replacements must be updated to cope with the new and changing demands of an aging population.  As part of our Sound Mind and Body series, KMUW’s Fletcher Powell takes a look at the cutting edge of orthopedic research.

This is a typical day in the mechanical testing lab at the National Institute for Aviation Research.

The institute—often called by its acronym, NIAR, sits on the east end of the Wichita State University campus, and the engineers in the lab spend most their time testing the strength and endurance of various metals and other materials.

What you’re hearing is stress. In order to figure out whether something is strong enough, the engineers apply more and more stress to a material with a variety of machines. If nothing happens, they keep going. And going. And going. Until:

(POP)

It breaks.

One of the major trends in aviation research right now is based around the use of what are called “composite materials” in building aircraft, and so that’s a lot of what the mechanical lab engineers spend their time trying to break. The easiest way to think of a composite is just as two or more materials with different properties combined to make a single material, hopefully with new uses. Fiberglass, for instance—or, on an even more basic level, combining straw and mud to make bricks, like the ancient Egyptians did.

Of course, the composites they’re working with at the mechanical testing lab are a bit more complicated. But a lot of why researchers are so interested in these new materials, things like carbon fiber-based composites, is because they’re generally a lot stronger and a lot lighter than the metals that have traditionally been used in building aircraft.

But aerospace engineers aren’t the only people interested. Now, this might sound like a plot from a comic book, but it turns out there are researchers who are wondering how these new, lightweight, strong materials might be used in… people.

Wooley: Paul Wooley, I’m the chief scientific officer for CiBOR

Dr. Wooley is one of those researchers. He heads the Center of Innovation for Biomaterials in Orthopaedic Research, “CiBOR” as he called it an organization sponsored by Wichita State, Via Christi, and the Kansas Bioscience Authority that works to find medical applications for aerospace materials.

Since Dr. Wooley’s background is in orthopedic research, he’s spent a lot of time looking for a better way to make basic orthopedic implants—things like replacement hips and knees. And he says that the stuff out there right now is really showing its age.

Wooley: If you look at a conventional current orthopedic device, the basic design of it, and really the materials, are about 50 years old. We use metals, stainless steels are used extensively in Europe, cobalt chrome alloy, and we use plastics—polyethylene.

And it’s not just that these current implants are based on old technology. Wooley says that they can cause a lot of problems, too.

Wooley: If you watch TV at all these days, you tend to see adds from lawyers who are asking you, “have you ever had a metal implant?” And, of course, metal ions released into the body can do a couple of things—they can cause a sensitivity or allergy, and they can also, in high doses, be directly toxic to tissues.

So it makes sense that researchers would want to find something that’s just a little bit less foreign to the human body than metal and plastic.

Wooley: If we go to carbon-based materials—of course, we, ourselves, are carbon-based organisms—the chances of having improved bio-compatibility are greatly enhanced.

Carbon-based materials… like the carbon-fiber composites they’re working on in the labs at NIAR.

It’s no coincidence that CiBOR, which deals with orthopedic research, and NIAR, which deals with aviation research, are both in Wichita. The idea all along has been to take advantage of the knowledge and resources of a city so heavily invested in the aerospace industry in order to adapt aviation technology to the medical world. And it’s working.

Wooley: We have a number of current investigations going on. For instance, surgical instruments can be made with classic carbon fiber-based materials, with typical epoxies to strengthen them. That means, also, that they’re x-ray transparent, they’re very useful to trauma surgeons… they will not interfere with the appearance of the injury under the x-ray.

But the even bigger breakthroughs seem to be coming from using these carbon-based materials to create better, more durable orthopedic implants.

Wooley: We are very interested in carbon foam, which is used as a coring material in wings of aircraft

This carbon foam, Wooley says, is porous enough that it’s good for creating what’s called a “scaffold” for the bone that will be around the implant. Meaning, the bone surrounding, say, a new knee, can actually grow into the pores of the carbon foam, helping new bone to form.

Wooley: Bone can never actually grow into a solid piece of plastic or a solid piece of metal, but if you can engineer something with the correct porosity—pore sizes that are appropriate to the ingress of bone-forming cells, then that’s true tissue engineering.

Using these materials, Wooley feels that they can not only eliminate the chemical drawbacks of putting metal and plastic inside the body, but because of the carbon composite’s light weight and durability, these implants ought to last much, much longer than the current models. And the longer they last, the less likely it is that people with these implants will have to undergo the painful procedures that are currently necessary to fix artificial joints that are breaking down.

Wooley: So, the original implant has to be taken out, and of course, normally, it’s a—it fails in a manner that’s not good for the surrounding bone. So, a revision procedure is a lot longer, a lot more complicated, than the primary procedure, and, frankly, the outcome never achieves the level of relief of pain and restoration of function that the primary procedure does. So it’s our overall goal to keep patients away from requiring revisions.

Dr. Wooley admits that there are plenty of other groups that have been trying to develop these “scaffolds” for bone to grow into. But he’s pretty sure that CiBOR is unique in directly trying to adapt aerospace technology to medical uses. And having the massive resources and engineering capabilities of NIAR behind them certainly can’t hurt.

Ultimately, Wooley hopes to take what CiBOR develops and actually start to manufacture these surgical instruments and orthopedic implants in Wichita. As he says, if everything works out the way they’ve envisioned, this is the sort of thing that could create new jobs in the area, taking advantage of the experience and knowledge that’s already here. The instruments, he says, ought to be set to go within the next year.

The implants, unfortunately, are at least seven years away, because of the necessity of clinical trials and FDA approval. And while Dr. Wooley certainly won’t be creating a Six Million Dollar Man, he is hoping that after all those trials, these new parts will be better and stronger, even if he can’t get them here any faster.


CiBOR’s website [Link]