Research team develops prosthesis of the future, the first in the world with magnetic control

This is the first magnetically controlled prosthetic hand that allows amputees to reproduce all movements simply by thought and to control the force applied when gripping fragile objects. No wires, no electrical connection, just magnets and muscles to control finger movements and enable everyday activities such as opening a jar, using a screwdriver, picking up a coin.

A research team from the BioRobotics Institute of the Scuola Superiore Sant’Anna in Pisa, coordinated by Professor Christian Cipriani, has developed a radically new interface between the amputee’s residual arm and the robotic hand to decode motor intentions.

The system involves implanting small magnets into the muscles of the forearm. The implant, integrated into the Mia-Hand robotic hand developed by the spin-off Prensilia, was successfully tested on the first patient, a 34-year-old Italian named Daniel, who used the prosthesis for six weeks.

The results of the trial were presented in the journal Scientific robotics and represent a significant advance for the future of prosthetics.

“This result rewards a research journey of several decades. We have finally developed a functional prosthesis that meets the needs of a person who has lost a hand,” says Christian Cipriani, professor at the Institute of BioRobotics of the Scuola Superiore Sant’Anna.

Myokinetic control for the development of a natural prosthesis

Myokinetic control involves decoding motor intentions using magnets implanted in the muscles. This is the frontier explored by the research team at the Scuola Superiore Sant’Anna to revolutionize the future of prosthetics.

The idea behind the new interface, developed as part of the MYKI project, is to use small magnets, a few millimeters in size, to be implanted in the residual muscles of the amputated arm and to use the movement resulting from the contraction to open and close the fingers.

“The forearm is made up of 20 muscles, many of which control hand movements. Many people who have lost a hand continue to feel it as if it were still in place, and the remaining muscles move in response to commands from the brain,” Cipriani explains.

The research team mapped the movements and translated them into signals to guide the fingers of the robotic hand. The magnets have a natural magnetic field that can be easily localized in space. When the muscle contracts, the magnet moves, and a special algorithm translates this change into a specific command for the robotic hand.

The first patient to test the new prosthesis

Daniel lost his left hand in September 2022: “I suddenly found myself without a hand: one moment I had it and the next it was gone.” He was selected as a volunteer for the study because he still felt the presence of his hand and the residual muscles in his arm responded to his movement intentions.

In April 2023, Daniel underwent surgery to implant magnets in his arm. The procedure was performed at the Azienda Ospedaliero-Universitaria Pisana (AOUP), thanks to the collaboration of a team coordinated by Dr. Lorenzo Andreani of the Orthopedics and Traumatology Surgical Unit 2, Dr. Manuela Nicastro of the Anesthesia and Resuscitation Unit of the Orthopedics and Burns Center, and Dr. Carmelo Chisari of the Neurorehabilitation Unit.

“This is a significant advance in the field of advanced prosthetic medicine,” says Dr. Lorenzo Andreani.

“The operation was a success thanks to careful patient selection, based on strict criteria. One of the most complex challenges was to identify the residual muscles in the amputation area, which were precisely selected using preoperative MRI and electromyography. However, the actual state of the tissues, due to scarring and fibrosis, required intraoperative adaptation.

“Despite these difficulties, we were able to carry out the implant and establish the connections, a success that would have been impossible without the collaboration of an exceptional team that I would like to thank.

“Starting with Dr. Manuela Nicastro, head of the anesthesia department, to the nurses who worked with dedication and professionalism, contributing decisively to the positive outcome of the operation, which represents an important advance in medical research.”

Six magnets were implanted in Daniel’s arm. For each one, the team of surgeons and doctors located and isolated the muscle, positioned the magnet and checked that the magnetic field was oriented in the same way.

“To facilitate the connection between the residual arm where the magnets were implanted and the robotic hand, we made a carbon fiber prosthetic socket containing the electronic system capable of localizing the movement of the magnets,” explains Cipriani.

The results of the experiment far exceeded the most optimistic expectations. Daniel was able to control the movements of his fingers, grasp and move objects of different shapes, perform everyday actions such as opening a jar, using a screwdriver, cutting with a knife, closing a zipper; he was also able to control the force when he had to grasp fragile objects.

“This system has allowed me to recover lost sensations and emotions: I feel like I’m moving my own hand,” says Daniel.

“Seeing the work of several years of research carried out in this study was a great emotion. Working with Daniel gave us the awareness that we can do a lot to improve his life and that of many other people. This is the greatest motivation that drives us to continue our work and to do always better,” explains Marta Gherardini, assistant professor at the Scuola Superiore Sant’Anna and first author of the study.

“We are ready to extend these results to a wider range of amputations,” Cipriani concludes. “In fact, our work on this new implant is progressing thanks to European and national funding.”

Provided by the Sant’Anna School of Advanced Studies in Pisa