A man who had been paralyzed from the waist down and had lost all function in both his hands can move his fingers after doctors rewired his nerves to bypass the damaged ones in a pioneering surgical procedure, according to a case study published on Tuesday.

The 71-year-old man, who had become paralyzed after he was injured in a car accident in 2008, still had limited arm, elbow and shoulder movement, but because the C7 vertebrae in his spinal cord had been crushed, the nerve circuits responsible for sending signals from the brain to the muscles in his hands were severed and all control was lost.

However, the nearby nerves had not been injured in the accident and surgeons were able to cut an undamaged nerve in the man’s elbow and connect it to the damaged nerve responsible for activating muscles in the hand responsible for grasping objects. 

"The circuit [in the hand] is intact, but no longer connected to the brain,” Surgeon Ida Fox, an assistant professor of plastic and reconstructive surgery at Washington University, explained to the BBC. "What we do is take that circuit and restore the connection to the brain."

Surgeons explain that nerve transfer surgery is essentially borrowing a healthy and working nerve and transferring it into another nerve that has lost function.

Fox and colleagues had severed the nerve that controlled the man’s brachialis, an arm muscle that helps bend the elbow, and stitched it to the damaged nerve that controlled his hands.

"We had to sacrifice something that's 'sacrificable,'" Fox told ABC News, and explained that the biceps and other elbow-bending muscles would be able to work for the brachialis.

The surgery was meant to resurrect the connection between the brain and the hand so that the man could slowly regain hand function as the inserted nerve establishes new connections to the brain which will reprogram itself to move the fingers by activating the elbow nerve. 

"The brain has to be trained to think, "OK, I used to bend my elbow with this nerve, and now I use it to pinch,'" said Fox, according to ABC News.  "We're not changing any of the biomechanics; we're just changing the wiring. So it's more of a mental game that patients have to play with themselves."

After months of intensive physical therapy, surgeons reported that the man was able to feed himself and even write with some assistance, according to doctors writing in the Journal of Neurosurgery.

Video: Surgeons have restored some hand function in a quadriplegic patient

The doctors explain that patients with C7 and C6 vertebra injuries, like the man in the case study, while considered quadriplegic, can move their shoulders, elbows and wrists because those nerves are attached to the spinal cord just above the location of the injury, making the nerve transfer operation possible.

However, experts say that the same nerve transfer surgery would probably be unsuccessful in restoring hand and arm function for people who are injured higher up along the spinal cord from the C5 to C1 vertebra.

"This procedure is unusual for treating quadriplegia because we do not attempt to go back into the spinal cord where the injury is," Fox said in a statement. "Instead, we go out to where we know things work -- in this case the elbow -- so that we can borrow nerves there and reroute them to give hand function."

Surgeons said that the patient’s progress was encouraging because it showed that the people paralyzed because of nerve damage can still regain movement even after some time.  The man had undergone the surgical procedure in 2010, two years after the car accident that paralyzed him.

Doctors say that as long as the muscle remains healthy and the damaged nerve- even though it can no longer send signals to the brain- remains connected to the support and nourishment of the spinal cord, function can be restored even years after the injury.

"This is not a particularly expensive or overly complex surgery," senior author Susan Mackinnon, who developed and performed the surgery, said in a statement. "It's not a hand or a face transplant, for example. It's something we would like other surgeons around the country to do."