Image copyright EPFL

An elastic implant that moves with the spinal cord can restore the ability to walk in paralysed rats, say scientists.

Implants are an exciting field of research in spinal cord injury, but rigid designs damage surrounding tissue and ultimately fail.

A team at Ecole Polytechnique Federale de Lausanne (EPFL) has developed flexible implants that work for months.

It was described by experts as a "groundbreaking achievement of technology".

The spinal cord is like a motorway with electrical signals rushing up and down it instead of cars.

Injury to the spinal cord leads to paralysis when the electrical signals are stuck in a jam and can no longer get from the brain to the legs.

Progress

The same group of researchers showed that chemically and electrically stimulating the spinal cord after injury meant rats could "sprint over ground, climb stairs and even pass obstacles".

Image copyright EPFL Image caption Previous work by the same researchers

But that required wired electrodes going directly to the spinal cord and was not a long-term option.

Implants are the next step, but if they are inflexible they will rub, causing inflammation, and will not work properly.

The latest innovation, described in the journal Science, is an implant that moves with the body and provides both chemical and electrical stimulation.

When it was tested on paralysed rats, they moved again.

One of the scientists, Prof Stephanie Lacour, told the BBC: "The implant is soft but also fully elastic to accommodate the movement of the nervous system.

"The brain pulsates with blood so it moves a lot, the spinal cord expands and retracts many times a day, think about bending over to tie your shoelaces.

"In terms of using the implant in people, it's not going to be tomorrow, we've developed dedicated materials which need approval, which will take time.

"But we really believe this will be a solid and robust technology for humans."

Cracked gold

The implant is built from elastic silicone and the wiring is made from "microcracked" gold.

Normal wiring would not stretch, but tiny cuts in the surface make it flexible.

The implant has worked for two months in the animals, which the researchers say makes it one of the longest-lasting implants for spinal cord injury.

Dr Dusko Ilic, from King's College London, said: "This is quite remarkable, until now, the most advanced prostheses in intimate contact with the spinal cord caused quite substantial damage to tissue in just one week due to their stiffness.

"The work described here is a groundbreaking achievement of technology, which could open a door to a new era in treatment of neuronal damage.

"However, there is still a long way to go before we may see any practical use of such neuroprostheses in humans."

Dr Mark Bacon, the scientific director of the charity Spinal Research, told the BBC News website: "Translation of experimental treatments to humans often falters because insufficient attention is given to some of the more pragmatic aspects of translational science.

"The combination of electrical and chemical stimulation has been proven in principle - in animal models at least - so it is encouraging to see the application of multidisciplinary efforts to take this one step closer to safe testing in patients."