According to a report in New Scientist magazine, researchers have tested implants which amplify weak signals from the spinal cord in animals and are keen to carry out clinical trials in humans within two years.

Around four in five people with spinal injuries still retain some ability to move muscles in their legs.

In cases where the spinal cord in not totally severed, some neural pathways to the brain can allow weak signals to pass through.

Implants in the vertebra

Scientists believe that the implants could be used in these patients to stimulate movement and restore at least partial mobility.

The scientists, Arthus Prochazka and Vivian Mushahwar of the University of Alberta in Edmonton in Canada, have developed implants which can be attached directly to a vertebra.

Microwires attached to the implant are extended into the spinal cord and are used to boost any signals coming from the nerves.

The scientists carried out an experiment on four anaesthetised and four unanaesthetised cats, using a small electric current delivered between 25 and 40 times a second.

As a result of the electric current being sent to different parts of the spinal cord, they were able to get both groups of cats to flex their rear legs, and the unanaesthetised cats to raise the rear of their bodies.

The cats did not seem to feel any pain and, in the case of the unanaesthetised cats, they carried on eating. The scientists say that the fact that it was painless is extremely encouraging, as it would likely to be the same in humans.

Movement for paraplegics

Although the cats in the experiments had no spinal injuries, the scientists believe that if the implants can amplify the weaker signals which are sent along a damaged spinal cord, they may eventually be able to restore movement to some parapelgics.

However, they stress that their trials are at an ealry stage and say they do not want to raise false hopes.

Dr Prochazka hopes to carry out human trials in conjunction with the Alberta Paraplegic Foundation and the Alberta Heritage Foundation for Medical research.

The first aim would be to help paralysed people stand up and move their legs, and walking may later be posible with the aid of a frame.

Dr Richard Apps, a neurophysiologist in the department of physiology at Bristol University, said that although he had not seen the details of the study, it could be an innovative technique.

"It sounds like a very promising and exciting area of investigation," he said.

"The neural circuits are highly complex and it's surprising that something as simple as this sounds could have this effect."