Austrian doctors pioneering so-called bionic reconstruction have replaced the disabled hands of three men with robotic nerve connected prosthetics in a first of its kind experiment, now reporting excellent results.
The technique, developed by scientists at the Medical University of Vienna, uses residual nerves that are no longer sufficient to control the real injured hand, but with a little help may provide just enough neural stimuli for an artificial one.
All of the three patients of Professor Oskar Aszmann, who leads the Vienna Medical University’s Christian Doppler Laboratory for Restoration of Extremity Functions, lost control of their limbs following motorcycle or climbing accidents that damaged a group of nerves known as the brachial plexus.
“Brachial plexus avulsion injuries represent an inner amputation, irreversibly separating the hand from neural control,” Professor Aszmann explained. “Existing surgical techniques for such injuries are crude and ineffective and result in poor hand function.”
Even though the patients still had their hands, they were not able to use them. Although not an easy choice, they opted for voluntary amputation to become part of the experiment, which saw the doctors transferring muscles from other parts of their bodies to help control the robotic hands equipped with highly sensitive sensors capable of responding to the electrical impulses from the muscles.
“The scientific advance here was that we were able to create and extract new neural signals via nerve transfers amplified by muscle transplantation,” said Professor Aszmann. “These signals were then decoded and translated into solid mechatronic hand function.”
Following extensive rehabilitation, all three patients reported great results. Only three months after the surgery, the men were able to carry out simple everyday tasks, such as picking up a ball, pouring water from a jug or using both hands to undo buttons – something they could not do with their damaged hands.
Ahead of the surgery, the men spent nine months in preparations. First they were training in a virtual environment, learning how to control a virtual hand by the sheer power of their will.
Once they had mastered the virtual environment, they practised using a hybrid hand - a prosthetic hand attached to a splint-like device fixed to their non-functioning hand.
Professor Aszmann, who developed the procedure together with his colleagues from the Department of Neurorehabilitation Engineering of the University Medical Center Goettingen, said the Vienna centre is currently the only place in the world that has mastered the technique.
The UK’s Professor Simon Kay, who performed the first hand transplant in Britain, said the results were certainly encouraging.
“This approach provides additional neural inputs into prosthetic systems that otherwise would not exist,” he wrote in a comment. “However, the final verdict will depend on long-term outcomes, which should include assessment of in what circumstances and for what proportion of their day patients wear and use their prostheses,” he added, pointing out that amputees frequently avoid using their artificial limbs because they are uncomfortable, heavy and noisy.