The future of prosthetics lies in connecting prostheses directly with the patient's nerves -- a concept that's still very new, and only applied in a handful of cases around the world. Nerve-contacting prosthetics allow the patient, with time and training, to control the limb with their mind.
Three men in Austria have become the first in the world to have been given these mind-controlled prosthetic limbs through a new technique called "bionic reconstruction."
The technique combines selective nerve and muscle transfers, elective amputation and replacement with an advanced robotic prosthesis.
The bionic reconstruction technique was developed by Professor Oskar Aszmann, Director of the Christian Doppler Laboratory for Restoration of Extremity Function at the Medical University of Vienna, together with engineers from the Department of Neurorehabilitation Engineering of the University Medical Center Goettingen.
The three men who received the procedure had each suffered for many years with brachial plexus injuries -- affecting the nerve that runs down through the armpit and into the arm, controlling movement -- from climbing and motor accidents. These injuries resulted in poor hand function.
"In effect, brachial plexus avulsion injuries represent an inner amputation, irreversibly separating the hand from neural control. Existing surgical techniques for such injuries are crude and ineffective and result in poor hand function," explains Professor Aszmann.
"The scientific advance here was that we were able to create and extract new neural signals via nerve transfers amplified by muscle transplantation. These signals were then decoded and translated into solid mechatronic hand function."
Before the procedure took place, all three of the men had to undergo intensive cognitive training, for an average period of around nine months. This involved activating the muscles, then learning to use the electrical signals to control a virtual hand. Once the patient could control the virtual hand, they were moved on to a "hybrid" hand -- a prosthetic hand attached to a device fixed to their non-functioning hand.
In order to be fitted with a myoelectric -- that is, controlled by a patient's remaining muscles -- robotic hand, the patient then had to have their injured hand amputated. Once healed, the patient could begin using the robotic limb attached to their nerves.
Three months after amputation, all three men could use their hands to complete everyday tasks such as picking up objects, using a key, pouring water from a jug, cutting food and unfastening buttons, reporting a much higher level of functionality in the prosthetic hand.
"So far, bionic reconstruction has only been done in our centre in Vienna. However, there are no technical or surgical limitations that would prevent this procedure from being done in centres with similar expertise and resources," Professor Aszmann said.
"In the future, hand and foot reconstruction will see many new approaches to replace lost limbs and recover function. Both biological and technical advances can provide treatments that were unthinkable only a few years ago."