Surgical and engineering innovations enable unprecedented control over every finger of a bionic hand

Newswise — Prosthetic limbs serve as the predominant fix for replacing a missing limb. Nonetheless, their manageability is challenging and their reliability often lacks due to limited available movements. Residual limb's remaining muscles are the favored control source for artificial hands. This preference stems from patients' ability to voluntarily contract muscles, enabling the prosthetic hand to interpret the generated electrical activity. Consequently, it can be instructed to perform various actions, such as opening or closing. A significant predicament arises at higher levels of amputation, like above the elbow, where only a limited number of muscles remain to command the multitude of robotic joints required for complete restoration of arm and hand function.

To overcome this hurdle, a diverse group of surgeons and engineers collaborated to devise a solution. They accomplished this by modifying the residual limb's structure and incorporating sensors and a skeletal implant, establishing both electrical and mechanical connections with the prosthesis. Through a meticulous process involving the dissection of peripheral nerves and their redistribution to fresh muscle targets utilized as biological amplifiers, the bionic prosthesis can now access a significantly larger amount of information. As a result, the user gains the ability to command numerous robotic joints at their discretion. For a visual demonstration of this innovation, you can watch the following video: youtu.be/h1N-vKku0hg.

Professor Max Ortiz Catalan spearheaded this groundbreaking research initiative. He serves as the Founding Director of the Center for Bionics and Pain Research (CBPR) in Sweden and holds the position of Head of Neural Prosthetics Research at the Bionics Institute in Australia. Additionally, he is a distinguished Professor of Bionics at Chalmers University of Technology in Sweden. Under his leadership, the multidisciplinary team made significant strides in the field of bionics and prosthesis development.

This article highlights the demonstration of the feasibility and benefits of rerouting nerves to alternative muscle targets in a distributed and simultaneous manner, leading to enhanced control of prosthetics. A notable aspect of our research is the ability to implement more precise surgical techniques and integrate sensors into the neuromuscular constructs during the initial surgery. These sensors are subsequently connected to the prosthesis's electronic system through an osseointegrated interface. Subsequently, artificial intelligence algorithms play a pivotal role in managing the remaining aspects of the process. This approach represents a significant advancement in the field of prosthetics.

The conventional method of attaching prosthetic limbs involves a socket that compresses the residual limb, resulting in discomfort and mechanical instability. However, an alternative approach called osseointegration offers a solution. Osseointegration entails the placement of a titanium implant within the residual bone, creating a strong and secure anchor. This skeletal attachment enables a more comfortable and efficient mechanical connection between the prosthesis and the body. By bypassing the need for a socket, osseointegration revolutionizes the way prosthetic limbs are attached, enhancing overall functionality and user experience.

Dr. Rickard Brånemark, a research affiliate at MIT, associate professor at Gothenburg University, and CEO of Integrum, expresses his satisfaction with the remarkable functionality achieved through their state-of-the-art surgical and engineering innovation for individuals with arm amputations. Having dedicated over three decades to the gradual development of this concept, Dr. Brånemark takes pride in his contribution to the field. As a leading authority on osseointegration for limb prostheses, he conducted the implantation of the interface, solidifying his expertise in this groundbreaking technology.

The surgery was conducted at Sahlgrenska University Hospital in Sweden, which is home to the Center for Bionics and Pain Research (CBPR). Dr. Paolo Sassu, a renowned surgeon, performed the neuromuscular reconstruction procedure. Dr. Sassu is also credited with leading the first-ever hand transplantation in Scandinavia. His expertise and experience in the field played a vital role in the successful execution of the surgical intervention.

Dr. Paolo Sassu expresses his enthusiasm for the remarkable collaborative journey undertaken with the bionic engineers at CBPR, which has resulted in the successful integration of advanced microsurgical techniques and implanted electrodes. This innovative combination enables precise control of individual fingers in a prosthetic arm and even provides sensory feedback. Dr. Sassu believes that this breakthrough offers new hope for patients who have experienced arm amputations, potentially paving the way for a brighter future. Currently, he is working at the Istituto Ortopedico Rizzoli in Italy, continuing his contributions to the field of prosthetics and orthopedics.

The Science Translational Medicine article illustrates how the transferred nerves progressively connected to their new hosting muscles. Once the innervation process had advanced enough, the researchers connected them to the prosthesis so the patient could control every finger of a prosthetic hand as if it would be his own (video: https://youtu.be/FdDdZQg58kc). The researchers also demonstrated how the system respond in activities of the daily life (video: https://youtu.be/yC24WRoGIe8) and are currently in the process of further improving the controllability of the bionic hand.