Woman is fitted with 'bionic' arm
The arm in action
A former US Marine has become the first woman in the world to be fitted with a "bionic" arm that she can control by her thoughts alone.
Claudia Mitchell lost her left arm at the shoulder in a motorbike accident.
Her new arm works by detecting movements of a chest muscle that has been connected to the remains of nerves that once went to her real arm.
The first prototype was fitted to double amputee Jesse Sullivan four years ago.
Before the surgery, I doubted that I would ever be able to get my life back
Claudia Mitchell
However, the latest version has been significantly improved.
Using it Ms Mitchell, 26, can now fold clothes, eat a banana and do the washing up.
At a press conference in Chicago to reveal her new arm to the world, Ms Mitchell said: "I can move my elbow up and down and I can open and close my hand simply by thinking that that's what I want to do."
Big advance
With her older prosthetic arm, she could only do one thing at a time - either bend her elbow or open her hand.
The technology, developed by the Rehabilitation Institute of Chicago (RIC), took about five hours to install.
Jesse Sullivan received a prototype version
The ends of the nerves that once controlled the arm were removed from her shoulder and connected to nerves in the chest muscle, some of which conveyed sensation from the skin above.
Over several months the transplanted nerves grew into the muscle tissue.
Once this happened electrodes fixed to a harness worn on the shoulder were able to detect impulses emitted from the nerves into the muscle and forward them to the arm.
These impulses are processed by a computer, which is able to direct the arm to make very precise movements.
Ms Mitchell said: "Before the surgery, I doubted that I would ever be able to get my life back.
"But this arm and the RIC have allowed me to return to a life that is more rewarding and active than I ever could have imagined.
"I am happy, confident and independent."
She said the arm was heavy, but that was due to extra motors which gave it a greater range of function.
Many could benefit
At present, if Ms Mitchell is touched on the patch of skin on her chest where the nerves to the hand have been re-routed, she feels that her hand is being touched.
The next step will be to develop a way to have the signals come back from the fingers on the prosthetic to the nerves in the chest and then the brain, so that Ms Mitchell can feel pressure, heat or cold, and even a sharp edge.
The Chicago team estimates that the technology could potentially help more than 400 US military personnel who have had amputations after serving in the Afghanistan and Iraq wars.
Todd Kuiken, the director of RIC's Neural Engineering Centre for Bionic Medicine, said: "It is so rewarding for me as a physician and a scientist to lead research with the potential to positively impact the lives of amputees."
Ms Mitchell said she was concerned that her new arm looked as attractive as possible.
"When we got the glove that goes over it I asked them if I could put nails on it and they said yes, so I headed straight for the nail salon.
"She (the manicurist) was pretty terrified, she was afraid she was going to mess something up, but I assured her it was OK."
