WEDNESDAY, Oct. 31, 2018 (HealthDay News) -- The science of spinal cord stimulation has been fine-tuned to the point that three previously paralyzed patients can now walk with minimal assistance, Swiss researchers report.

They can do so with only the aid of crutches or a walker, thanks to incredibly precise electrical stimulation of their spinal cord combined with intensive rehabilitation, the scientists said.

In fact, two of the patients can take several steps without electrical stimulation, a sign that there's been growth of new nerve connections, said senior researcher Gregoire Courtine, chair of spinal cord repair at the Swiss Federal Institute of Technology in Lausanne.

"Walking hands-free really felt more or less like walking normally, and that was a very big achievement," said 28-year-old patient David M., who became paralyzed after a sports accident in 2010 left him with no control of his left leg and only residual control of his right.

Previous studies have revealed that "the spinal cord has its own intelligence system that controls walking," said Dr. Thomas Oxley, director of innovation strategy for the Mount Sinai Health System Department of Neurology in New York City.

"If you think about cutting the head off a chicken, it can still walk around. It doesn't need the brain to walk," Oxley said.

Implanted electrodes that provide direct electrical stimulation to the spinal cord have been shown to allow movement of previously paralyzed legs.

For example, last month the Mayo Clinic reported on the case of a 29-year-old paraplegic who now can walk about the length of a football field with assistance.

The new study takes the medicine and technology of spinal stimulation even further in two ways.

First, patients were implanted with an array of electrodes down the spinal cord, which allowed researchers to target individual muscle groups in the legs.

"Specific configurations of electrodes are activated to control the appropriate groups of muscles, mimicking the signals that the brain would deliver to produce walking," explained co-researcher Dr. Jocelyne Bloch, a neurosurgeon with Lausanne University Hospital. Bloch compared the targeted stimulation to the precision of a Swiss watch.