Edmund Rath, a 53-year-old from Austria, wants to do simple things such as brush his teeth and slice bread. Most people take such activities for granted but not Rath, who lost his arm just below the shoulder in a truck accident last year that ended his career as a builder. That bad luck was followed by a stroke of fortune.
He was chosen by Austrian surgeons as the first person to have a single operation in May to install a click-on prosthesis that the brain controls with signals to the missing hand. The procedure, known as 'osseointegration' (OI), involved implanting a metal rod into the bone of his residual limb. The rod has an external attachment that anchors his prosthesis to his upper arm bone.
During the operation - which was screened live to an industry congress in Vienna - doctors also took nerves once used to control his hand and connected them to muscles in his upper arm, a procedure called 'Targeted Muscle Reinnervation'. Now when he imagines moving his hand, the muscles in his shoulder contract and are read by electrodes in his prosthesis that does the intended movement.
Rath's challenge is to build up strength and learn the skills to make the so-called 'simple' activities possible. "I don't want to change the world, but everyday things are my goal and I want to be able to do these things as quickly as possible," Rath said.
His experience could have global implications. Millions of people live with limb loss, including around 2 million in the United States alone. And the numbers are expected to grow due to rising prevalence of diseases like diabetes. Demand is particularly strong among US soldiers who lost limbs in wars in the Middle East, according to Horst Aschoff, an expert in OI at the Hannover Medical School in Germany.
SENSE OF TOUCH
The technology to fuse prostheses to the body has changed little for centuries. They are connected to the amputee's stump via a customized socket but they can become sweaty, cause skin irritations and restrict movement so users often end up not wearing them. OI was first discovered in the 1950s by Swedish researcher Per-Ingvar Branemark and is used for dental implants.
The first amputee to receive an OI implant was in Sweden in 1990. The surgery is conducted in the West, mainly on lower limb amputees. Experts in Europe, Australia and the United States are leading a drive to find solutions. Rath said the OI implant allows him to move his arm freely compared to the restricted movement afforded by the socket. But learning to use his robotic arm, which was supplied by artificial limb maker Ottobock, takes daily practice.
"You need to fully concentrate when you want to properly control it (the arm) and that sap's one energy," he said at Ottobock's research center in Vienna. It took six weeks for the implanted nerves to grow into his muscles and he can now control six different functions of his robotic arm, such as opening and closing his hand. One feature of OI is that users can feel some sensation from mechanical vibration in their skeleton, otherwise known as osseoperception, but there is currently no commercially-available product to restore a sense of touch.
That may happen one day.
British start-up Cambridge Bio-Augmentation Systems (CBAS) is working on a 'Prosthetic Interface Device' (PID), a neural interface that is integrated into the bone, the skin and the nervous system. Out from the end of the limb is a standard connector that can plug onto a range of devices.
The PID could give users control of any limb, alongside sensory feedback by applying a small electric current to the nerve that can be sent back to the brain and perceived as touch and temperature, said Oliver Armitage, co-founder and chief scientific officer. "We think of it like a USB connector from the body."
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