Spinal-cord injuries often shut down the use of one's limbs including the hands, but with a new technology approved Monday by the US Food and Drug Administration, the simple ability to hold on to a cup may be within the grasp of some sufferers.
NeuroControl Corp.'s Freehand System uses implanted electrodes and a pacemakerlike stimulator along with an external joysticklike controller to mimic the brain's nerve impulses that govern the movements of the hand.
"This day has been a long time coming - for 25 years," said Geoff Thrope, a biomedical engineer who joined NeuroControl at its formation in 1993, when it was clear that the device was going to be come a commercial reality.
The first device to help those who suffer from quadriplegia to regain the use of their hands, Freehand is part of a growing body of neuroprosthetics devices currently under development. Neuroprosthetic instruments attempt to mimic or reconnect nerve impulses that are weakened or fail to function due to an accident or disease. These devices - which include retina chips and cochlear implants - return to some very basic functionality to their recipients' limbs and senses.
Freehand allows its users to regain their ability to grip onto objects - a toothbrush, a cup, a paintbrush - with one hand. But there are limits, explained Thrope.
"You shouldn't expect to play the piano or work on carpentry where you have to lift heavy objects. It's not for robust, powerful activities," he said.
Surgeons implant a stimulator right below the collar of the desired hand and then tunnel eight wires along the shoulder and down the arm, terminating the wires on the muscles in the forearm and hand. These muscles govern the hand's ability to flex and relax as well as the four movements of the thumb, Thrope said. An external position sensor, mounted on the opposite shoulder and chest, interprets small motions of this shoulder into hand movements.
A locking mode will allow patients to work their hands into a desired position and then keep it in place during an activity. For example, typing on a keyboard is possible when users lock their grip around a pencil. But only a "hunt-and-peck" motion is possible.
The FDA estimates that 20,000 to 50,000 people in the United States suffer from the type of spinal-cord injury that could be helped by Freehand - but there are a few hoops to jump through. The surgery and rehabilitation period can last as long as six months before patients have functionality, though Thrope said people can recover as quickly as six weeks.
In approving the device, the FDA was looking for Freehand to fulfill one simple criteria. "We asked the 61 patients if, after the surgery and rehabilitation, they could manipulate their hand more than they could before the implant," explained Dan Spyker, FDA deputy director for the cardiovascular, respiratory and neurological devices.
The device is not approved for use in children, nor is it recommended for those who have pacemakers. Spyker added that people with a history of infection or who suffer spasms and have no control over their muscles are not to be outfitted with the device.
Spyker said half of those involved in the test had to have some form of follow-up surgery to reconnect wires to stimulate muscles properly. But all involved continued using the device. "That's a good sign of whether a device is useful or not," he said.
