New implantable nerve guide tricks severed nerves into growing together again

Injuries to the arms and legs can often lead to permanent disability when nerves are severed, crushed or damaged.  Scientists in the U.S. have developed a implantable, biodegradable nerve guide to help severed nerves grow back together again.

Traumatic nerve injury to peripheral nerves outside the spinal cord and brain can have a devastating impact on a patient's quality of life — leading to a loss of sensation, motor function and chronic pain. 

When sections of nerve more than a centimetre or two are damaged, the ends of the remaining nerve can't find each other to heal.  Surgeons currently fix peripheral motor nerve damage in these types of injuries by transplanting sections of nerve from elsewhere in the body and grafting them in to patch the damaged section.  

When you remove a nerve somewhere, you're going to result in numbness and potentially even pain.- Kacey Marra, University of Pittsburgh

That method is "not ideal at all," according to Kacey Marra — a professor of plastic surgery and bioengineering at the University of Pittsburgh, in conversation with Quirks & Quarks host Bob McDonald. 

"When you remove a nerve somewhere, you're going to result in numbness and potentially even pain. But the real challenge is the return of function: that recovery is about 50 to 60 per cent that you'll get a return of sensation and motor function," said Marra.

She felt compelled to come up with a better solution. 

• Research paper in the journal Science Translational Medicine

Slow release of a special protein

Marra and her colleagues created a biodegradable tube made from the same material used in dissolveable medical sutures. A surgeon sews the ends of the tube to the severed ends of a damaged nerve.

After a year we saw close to 80 per cent return to function with our nerve guide.- Kacey Marra, University of Pittsburgh

Embedded in the inner walls of the tube is a special protein that promotes nerve regeneration.

"Our technology is based around small beads containing the protein in the walls of the guide that constantly releases the protein for up to three months, which is plenty of time for the nerve to regenerate across that bridge," said Marra.

The nerve then has a path to growth so the two severed segments can find each other.

From animal models to human clinical trials

They tested this on nerve cells, then on rodents, and eventually on monkeys. She was excited to see the results.

"After a year we saw close to 80 per cent return to function with our nerve guide," said Marra. She's now planning their first human clinical trial on humans with forearm nerve injuries, which she expects to get under way within a year.

But beyond peripheral motor nerves, she's hoping she'll be able to adapt this technology to work on nerve damage "from head to toe."

Written and produced by Sonya Buyting