srujan ponnapalli
The human hand is a marvel of evolution, capable of performing delicate tasks like playing a musical instrument, as well as powerful actions like lifting weights and throwing a bowling ball. The hand is also a vital part of our social and emotional communication, allowing us to express ourselves through gestures, touch, and sign language. Losing a hand or an arm due to injury, disease, or congenital defect can have devastating consequences for a person’s quality of life, affecting their ability to work, play, and interact with others. But what if technology could offer a solution to this problem? What if we could create artificial limbs that could not only replace the lost functions and sensations of the natural hand, but also enhance them? What if we could utilize the power of science and medicine to transform our limitations into possibilities, and our diversity into strength?
For decades, scientists and engineers have been trying to answer these questions by developing artificial limbs that can restore some of the functions and sensations of the natural hand. However, most prosthetic hands are limited in their capabilities, requiring complex and unreliable control systems that often fail to match the user’s intentions. Moreover, most prosthetic hands lack the ability to provide feedback to the user, making them feel disconnected from their artificial appendage. Progress in the field of prosthetics has significantly picked up pace in recent years, however. A solution to the problem of prosthetic disconnect was found in 2016 when a study demonstrated that ownership of an artificial hand can be induced via electrical stimulation of the corresponding part of the somatosensory cortex in synchrony with touches applied to a prosthetic hand in full view. Later, a 2020 study found that the brain tracks the movements and posture of the hand differently from the arm, suggesting that different strategies are needed to restore proprioception for the hand.
But now, a groundbreaking study published in Science Translational Medicine has shown that it is possible to create a bionic hand that can be controlled intuitively and reliably by the user, using signals from their own nerves and muscles. The study also demonstrates that the bionic hand can provide sensory feedback to the user, creating a sense of embodiment and ownership of the prosthesis.
The study is the result of a collaboration between researchers from the Center for Bionics and Pain Research (CBPR) in Sweden, the Bionics Institute in Australia, Chalmers University of Technology in Sweden, Sahlgrenska University Hospital in Sweden, and Integrum AB in Sweden. The lead author of the study is Professor Max Ortiz Catalan, who is an expert in neural prosthetics and bionics.
The study presents the first documented case of an individual whose body was surgically modified to incorporate implanted sensors and a skeletal implant that connect with a prosthesis electrically and mechanically. The patient is a 40-year-old man who lost his right arm above the elbow due to cancer 12 years ago. He had previously tried several types of conventional prosthetic hands, but none of them satisfied his needs.
The study performed a series of surgical procedures on the patient’s residual limb, involving nerve transfer, muscle transplantation, and osseointegration. Nerve transfer is a technique that involves cutting and rerouting some of the nerves that were severed by the amputation, and attaching them to new muscle targets. This creates new sources of electrical signals that can be used to control the prosthesis. Muscle transplantation is a technique that involves taking muscles from another part of the body (in this case, the thigh) and grafting them onto the residual limb. This provides additional muscle mass and strength for the nerve signals to act on. Osseointegration is a technique that involves inserting a titanium implant into the bone of the residual limb, which becomes firmly anchored over time. This allows for a direct and stable connection between the prosthesis and the skeleton.
The researchers also implanted electrodes into the patient’s muscles and nerves, which were connected to an external computerized control system via wires that passed through the skin. The control system then used artificial intelligence algorithms to decode nerve signals and translate them into movements of the prosthesis. These algorithms were trained to map the patterns of electrical activity in the muscles to different movements of the fingers of the bionic hand. The control system also sent vibrations to a small robot worn on the arm, which stimulated surrounding muscles to better recreate the subliminal physical sensations a user would face without a prosthesis. This provided sensory feedback to the patient, making him feel as if he was moving his own hand.
The patient underwent several months of training and rehabilitation with his new bionic hand, which consisted of five individually controllable fingers and a rotatable wrist. He learned how to perform various tasks with his prosthesis, such as grasping objects of different shapes and sizes, typing on a keyboard, playing video games, and using tools. He also reported feeling sensations such as touch, pressure, and temperature in his artificial fingers through nerve stimulation. The researchers evaluated the patient’s performance and satisfaction with his bionic hand using various tests and questionnaires. They found that he was able to control his prosthesis with high accuracy and reliability, achieving levels comparable to those of healthy individuals using their natural hands. He also expressed high levels of satisfaction and well-being with his prosthesis, stating that it felt like an extension of his body.
The researchers concluded that their approach represents a significant advancement in the field of bionics, offering new hope and possibilities for people with arm amputations worldwide. They also stated that their approach could be applied to other types of prosthetic limbs, such as legs or feet. They plan to conduct further studies with more patients and longer follow-up periods to confirm the safety and efficacy of their method.
The study has received widespread attention and praise from experts and media outlets around the world. But beyond the immediate benefits for the patient and his bionic hand, the study also showcases how science and medicine can use the human body as inspiration to create innovative solutions for challenging problems. By combining surgical and engineering techniques with AI, the researchers have created a bionic hand that mimics the natural hand in both form and function, bridging the gap between humans and machines. This opens up new possibilities for the future of bionics, such as developing more advanced and personalized prosthetic limbs that can adapt to the user’s preferences, needs, and goals. Ultimately, it can improve the quality of life and well-being of people with limb loss or dysfunction, as well as their social and emotional integration, create new opportunities and challenges for the ethical, legal, and social aspects of human-machine interaction and augmentation, and exploring new frontiers in neuroscience, robotics, and artificial intelligence, as well as their potential applications in other domains. The study is a testament to the power of human ingenuity and resilience, as well as the beauty of human-machine harmony. It is a glimpse into a future where technology can enhance our abilities, rather than replace them; where we can overcome our limitations, rather than succumb to them; and where we can celebrate our diversity, rather than fear it.
References:
Collins, K. L., Guterstam, A., Cronin, J., Olson, J. D., Ehrsson, H. H., & Ojemann, J. G. (2017) 'Ownership of an artificial limb induced by electrical brain stimulation.' Proceedings of the National Academy of Sciences, 114(1), 166-171. https://doi.org/10.1073/pnas.1616305114 [accessed July 25, 2023].
Goodman, J. M., Tabot, G. A., Lee, A. S., Suresh, A. K., Rajan, A. T., Hatsopoulos, N. G., & Bensmaia, S. (2019) 'Postural Representations of the Hand in the Primate Sensorimotor Cortex.' Neuron, 104(5), 1000–1009.e7. https://doi.org/10.1016/j.neuron.2019.09.004 [accessed July 25, 2023].
Jan Zbinden et al. (2023) 'Improved control of a prosthetic limb by surgically creating electro-neuromuscular constructs with implanted electrodes.' Science Translational Medicine, 15, eabq3665. https://doi.org/10.1126/scitranslmed.abq3665 [accessed July 25, 2023].