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Nanotube Knees and Elbows

Goodbye, metal: Doctors grow new bones.

By Lindsay CarswellMarch 31, 2006 6:00 AM


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If you've had your knee replaced with a piece of metal, you're in good company. Every year, almost 500,000 people go into America's hospitals to receive a total knee replacement, according to the National Center for Health Statistics. But one scientist hopes to do away with bone replacement procedures by actually rebuilding bone inside the body.

Dr. Robert Haddon from the University of California, Riverside thinks there may be another solution. He's been working with carbon nanotubes, which are so small, they're 100,000 times finer than human hair. He hopes that one day doctors might be able to inject these nanotubes into a knee, or another injury, where they would encourage damaged or broken bones to regrow.

The idea would be useful to someone like William Doherty, from Riverhead, New York, who has had a series of operations on his knee over the past few years. "I took a fall on a job, and I went down and tore the knee up," Doherty says. "And then I had the knee replaced after 3 or 4 different unsuccessful types of surgery."

Even though his pain has significantly decreased after receiving the stainless steel implant, Doherty says that he has trouble moving around: "I can't kneel down. If I get down on the floor, it's hard for me to get up."

While they may be tiny, Haddon explains that these nanotubes are the "highest strength material known, yet extremely light in weight." He says that these characteristics make it similar to a key component in the human skeleton, collagen.

Collagen is what gives bones their structure, and Haddon proposed that nanotubes could serve as a good substitute for collagen. As published in the journal Nano Letters fellow researchers at UCR confirmed that bone cells could start to grow on the carbon nanotubes, which serve as the scaffold material for new bone growth.

The results are promising, but Haddon says that growing bone cells in a petri dish is very different than growing new bone. "Now whether it would work ... whether it's toxic, we don't know any of these things," he says.

For now, Dr. Haddon and his researchers at will continue to see if carbon nanotubes could one day help the body repair or even replace broken bones.

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