A Swedish patient with hand amputation has become the first recipient of an osseo-neuromuscular implant to control a dexterous hand prosthesis, reports Chalmers University of Technology.
In the surgery, titanium implants were placed in the two forearm bones (radius and ulnar), from which electrodes to nerves and muscle were extended to extract signals to control a robotic hand and to provide tactile sensations.
The new implant technology was developed in Sweden by a team lead by Dr. Max Ortiz Catalan at Integrum AB and Chalmers University of Technology. This surgery, led by Prof. Rickard Brånemark and Dr. Paolo Sassu, took place at Sahlgrenska University Hospital as part of a larger project funded by the European Commission under Horizon 2020 called DeTOP.
The DeTOP project is coordinated by Prof. Christian Cipriani at the Scuola Superiore Sant’Anna, and also includes Prensilia, the University of Gothenburg, Lund University, University of Essex, the Swiss Center for Electronics and Microtechnology, INAIL Prosthetic Center, Università Campus Bio-Medico di Roma, and the Instituto Ortopedico Rizzoli.
Sensory and motoric control
Conventional prosthetic hands rely on electrodes placed over the skin to extract control signals from the underlying stump muscles. These superficial electrodes deliver limited and unreliable signals that only allow control of a couple of gross movements (opening and closing the hand). Richer and more reliable information can be obtained by implanting electrodes in all remaining muscle in the stump instead. Sixteen electrodes were implanted in this first patient in order to achieve more dexterous control of a novel prosthetic hand developed in Italy by the Scuola Superiore Sant’Anna and Prensilia.
Current prosthetic hands have also limited sensory feedback. They do not provide tactile or kinesthetic sensation, so the user can only rely on vision while using the prosthesis. Users cannot tell how strongly an object is grasped, or even when contact has been made. By implanting electrodes in the nerves that used to be connected to the lost biological sensors of the hand, researchers can electrically stimulate these nerves in a similar manner as information conveyed by the biological hand. This results in the patient perceiving sensations originating in the new prosthetic hand, as it is equipped with sensors that drive the stimulation of the nerve to deliver such sensations.
Two more patients
The patient is following a rehabilitation program to regain the strength in her forearm bones to be able to fully load the prosthetic hand. In parallel, she is also relearning how to control her missing hand using virtual reality, and in few weeks, she will be using a prosthetic hand with increasing function and sensations in her daily life. Two more patients will be implanted with this new generation of prosthetic hands in the upcoming months, in Italy and Sweden, reports Chalmers University of Technology.
Image caption: The patient is instructed by Max Ortiz Catalan to perform movements executed by a virtual hand. Electronic activity in the arm muscles are intercepted by the implanted electrodes and shown on the screen. This information is thereafter learnt by the artificial hand so that it can respond with the desired movements. Photo: Max Ortiz Catalan