January 15, 2008
Bionic Arm Lets Stroke Victims Get a Grip
By PAT HAGAN
A NEW device implanted in the arm is helping stroke victims regain movement in their hands.
It works by sensing when the patient is moving forward to lift or grab something.
The implant then stimulates muscles in the arm so that the fingers automatically open.
Once the arm stops moving, the fingers snap shut again.
Called the STIMuGRIP, the implant has already been tested on three patients who suffered strokes during childhood and have been unable to move their affected hands for decades.
'They now spontaneously use their affected hand in daily life, whereas before they would ignore it,' said Dr Paul Taylor, who is leading trials on the device at the Functional Electrical Stimulation Centre, based at Salisbury Hospital.
'For one volunteer this is the first time in 47 years he has been able to use his damaged hand.' Stroke is the third most common cause of death in England and Wales, after heart disease and cancer.
It kills around 200 people every day and leaves thousands more disabled.
The NHS spends an estimated Pounds 2.8billion a year dealing with the aftermath of strokes.
Strokes occur when the blood supply to the brain is cut off due to a clot in a blood vessel in the head.
Many victims end up with paralysis down one side of the body, often leaving the hand permanently twisted at a 45 degree angle and the fingers curled up like a claw.
The new technology, designed by Herts-based firm FineTech Medical, follows on from an earlier invention by the same company to help stroke sufferers affected by 'drop foot', where they lose the power to lift their feet properly when walking.
To begin with, the patient has a general anaesthetic and a tiny receiver, no bigger than a two pence piece, is placed inside the forearm.
Two electrodes attached to the receiver are then wired up to the muscles that control the wrist and fingers. ONCE the wound from the implant has healed, the patient wears an iPod-sized gadget around the arm, like they would a wristwatch.
Inside this is a device called an accelerometer, a computer chip that measures the body's rate of acceleration.
This is the same technology used in the hugely popular computer games console, the Nintendo Wii, where it senses the speed and force with which a player hits the imaginary tennis ball, or punches a boxing opponent.
In the STIMuGRIP, the accelerometer is programmed to respond only when the arm moves forwards and at certain speeds.
For stroke patients with limited feeling, the device might be triggered by using their upper body to lunge forward with the arm.
The accelerometer detects the movement and sends a signal through the skin to the implant, telling it to contract the muscles that work the wrist and fingers.
The implant does this by firing a small electrical impulse through the nerves connected to the muscle.
When the muscles contract, the wrist straightens and the fingers open.
Once the hand is next to the object being lifted, the patient stops moving. A split second later the fingers shut around it.
They only loosen their grip around the object when the arm is moved back again..