On Science Robotics the Sensibilia project ofUniversità Campus Bio-Medico di Roma and the INAIL Prosthetic Center in Vigorso di Budrio

21 February 2019 – Take a bottle of water from a table, feeling its shape, size and consistency; hold it and let it slide gently to pour the right contents into a glass; then put it back on the table and delicately release your grip, without damaging it or risking dropping the bottle and liquid: apparently simple and natural gestures, which however each of us learned during childhood, during years of traininging', and which are practically impossible to perform for those who have lost a hand and tactile sensitivity.

Actions that, thanks to an experiment conducted by bioingegneri, ingengineers, doctors and techniciansUniversità Campus Bio-Medico di Roma and Inail Prosthesis Center in Vigorso di Budrio (BO), have come back to being reality for Clara, a young amputee who was thus able enjoy sensations again forget for some time, including tactile sensitivity along the fingers and palm. Thanks to this team, formed among others by Vincenzo Denaro, Vincenzo Di Lazzaro, Giovanni Di Pino, Silvia Sterzi, Loredana Zollo for the University Campus Bio-Medico e Simona Castellano, Angelo Davalli, Emanuele Gruppioni, Rinaldo Sacchetti for INAIL, Clara was able to demonstrate that it is possible to regain the dexterity in performing complex movements with the hand that she had lost – due to a domestic accident – ​​over 30 years earlier. A trauma, this, which brought Clara, forty years old from the province of Palermo, to refuse to wear any type of artificial hand that was not purely aesthetic.

Until she agreed to be placed in the experimental project 'Sensibilia', promoted by Inail and UCBM and whose results have just been published in the scientific journal Science Robotics (10.1126/scirobotics.aau9924). The project is the last step of approx fifteen years of study and then experimentation in this area, which was initiated by the historian LifeHand (2008), in which for the first time a patient was able to move a bionic limb through brain impulses, continued in 2013 with LifeHand2, which initiated research into the transmission of tactile sensitivity. All with one strong integration and interdisciplinarity between doctors and bioingegneri, which has always been a characteristic of Università Campus Bio-Medico di Roma, which in the partnership with INAIL adds a particular interest in the transfer of experimental results from laboratories to amputee patients.

To allow her to be 'connected to bionic limbs used in the tests – an experimental hand and a commercial one, both polyarticulated and with high capacity for independent movement of the fingers and for returning tactile feedback, thanks to 6 neural electrodes – Clara was subjected to a delicate surgery inside the Campus Bio-Medico University Hospital. Here, a team of neurosurgeons and orthopedists, with the constant help of neurologists and bioingegneri, inserted them two intraneural electrodes and a 'cuff' (perineural electrodes, i.e. installed around the nerves) for each of the median and ulnar nerves present in the left arm: the interfaces, very thin, have allowed the return – in real time, through special algorithms – of the sensations of touch and movement of the bionic limb to the brain via the peripheral nervous system. This is exactly what happens to all of us when we grab, move, touch an object with our hand. In Clara's case, the credit goes to science.

With the goal of being able to approach this level of accuracy in manipulative control, Clara in 11 long weeks has before 'relearned to produce in your own brain the movement of the lost limb, stimulating cortical areas that have been inactive for some time; therefore, he honed his own ability to receive tactile sensations, managing to perceive them in good 13 different zones of the artificial hand, both anteriorly and posteriorly. Finally, she practiced alongside researchers for restore their ability to fine-tune objects, this time through the artificial hand, managing to move it with increasing dexterity (up 25,7% from the first day of testing) and until now unknown to all previous trials in the world. To the point of being able – blindfolded and with music at full volume in my ears – to recognize and master textures and positions of objects in the hand, until being able to 'try' the sliding sensation of them along the artificial fingers and palm (with a delay below 100 milliseconds, as occurs in biological sensory-motor control), so as to be able to correct any awkward grips while running.

And it is thanks to the rediscovered tactile feedback that the improvement in manipulation skills has gone hand in hand with a newfound brain ability to learn and use sensory feedback to control movement. A novelty that bodes well, in view of the use of increasingly advanced prostheses.

An important step forward along the way towards a use as 'natural' and 'tolerable' as possible of a biomechatronic hand, the so-called bionic hand, by an amputee, impossible without adequate sensory feedback support for the subject, as demonstrated by 'Sensibilia'. A result which, by adding sight and hearing aids, as is typical in the context of everyday life, leads the researchers to hypothesize the possibility of obtaining potentially even better performance and reaction times, more and more comparable with the natural limb.

 "The goal we set ourselves for this experimentation - highlights Loredana Zollo, associate professor of Bioingengineering and responsible ingproject engineering – was to develop and make usable in 36 months a prosthetic system that had a sensory-motor control capacity based on two-way communication with the nervous system and tactile sensitivity, such as to allow the relearning of fine manual skills and the manipulation of objects, as well as the possibility of restore the sense of touch to the patient through the neural interfaces implanted in his nerves. The final result seems positive to us and opens up new scenarios in the prospects of implantation of bionic limbs, probably also through new non-invasive technologies, for many patients of the INAIL Prosthesis Center like Clara".

To achieve the objectives of the Sensibilia project – he specifies Rinaldo Sacchetti, technical and research director of the INAIL Prosthesis Center – the scientific, technological and clinical advances on prosthetic systems for the upper limb were explored, focusing on the development of advanced interfacing and control solutions to make these systems more accessible and improve performance in activities of daily living. The most important novelty of the new study lies in its success to develop three parallel prosthetic hand control subsystems, di tactile sensing need interface with the peripheral nervous system, thus allowing to obtain greater dexterity in the use of the prosthesis. From the technological point of view, an intense activity of miniaturization of prosthetic components and algorithm development able to decode the electromyographic signal expressed by the young woman and to translate it into feedback and movement”.

And, in fact, Clara has achieved her partial objective: a few weeks after the conclusion of the project, in view of the future follow-up, has received a bionic hand prosthesis intelligent similar to those of experimentation, which he uses daily through surface myographic electrodes, capable of perceiving the muscular movements of the amputated limb and decoding the desired movement in order to be able to move dexterously.

While waiting for tactile sensitivity to be made available by scientists through available technologies, Clara's choice testifies that thanks to 'Sensitivity' new and unprecedented perspectives have opened up for many amputees in Italy and around the world: the ability to accept an artificial hand similar to Clara's, with the ability to learn to use it and experience it as if it were the limb you no longer have, from today it is a reality.