For the first time, a small group of individuals with below-the-knee amputations successfully controlled the movements of their prosthetic legs using neural signals – rather than relying solely on pre-programmed cycles for all or part of a movement – and walked naturally once more. The achievement demanded a highly specialized amputation surgical procedure, combined with the precise attachment of a non-invasive floor electrode to a state-of-the-art robotic prosthetic for the lower extremities. The latest findings from a study on applied sciences were published in today’s edition of the journal.
“What ensues is nothing short of miraculous.” Individuals equipped with this cutting-edge neural interface can now walk at normal velocities, navigate stairs and inclines with ease, and successfully overcome obstacles without giving it a second thought. It’s pure. According to Dr. Rachel Kim, a pioneer in developing bionic prosthetics, “It’s involuntary, despite being constructed from titanium and silicone, the prosthetic limb behaves as if it were an organic extension of their body, functioning seamlessly without deliberate contemplation.”
The methodology hinges on the specific surgical procedure at the amputation site to establish an anatomically meaningful interface (AMI). The procedure involves pairing specific muscle groups (typically two pairs for below-knee amputations) and incorporates proprietary prosthetic components.
The interface establishes a seamless dialogue between human physiology and electronic machinery. Electrodes embedded within the prosthetic limb’s muscles transmit real-time signals to a miniaturized computer, which then deciphers these inputs into precise measurements of joint angle and force data, specifically for the ankle and ball-of-the-foot regions. The device also transmits information about the hypothetical limb’s location, updating a map that illustrates where the prosthetic is situated.
Video 1
According to Dr. Ferris, a University of Florida neuromechanical engineer, “The actual mode of management is far more advanced than anything else that’s been given.” This innovative concept has been meticulously developed over eight years, yielding promising results for advanced bionic lower-limb prosthetics. Notably, the latest publication boasts an expanded participant pool, featuring seven treatment subjects and seven control subjects with amputations and conventional prosthetic legs.
To verify the performance of the bionic legs, participants were asked to walk at varying speeds on flat surfaces, ascend and descend ramps and stairs, and navigate around obstacles. AMI customers exhibited an exceptionally natural gait, eerily mimicking the fluid motion of someone using their unaffected limbs. Researchers have found that incorporating extra naturalistic movement into daily activities can significantly boost one’s sense of freedom and fluidity, particularly when navigating challenging terrain. Moreover, studies have consistently demonstrated reduced energy expenditure, lower physical stress, and even social benefits for individuals who are amputated.
A team member and postdoctoral researcher at MIT notes that they were taken aback by the impressive efficacy of their bionic configuration. Although the prosthetic interface transmitted only 18% of the normal information typically sent from a limb to the spine, this limited amount of data proved sufficient to enable patients to walk with a considered normal gait.
The next stages of development for a bionic leg will focus on refining its functionality and portability. This includes enhancing the prosthetic’s ability to detect and respond to various terrain types, as well as improving its energy efficiency and reducing its overall size.
Amputations resulting from AMI have become a common occurrence at Brigham and Women’s Hospital in Massachusetts, where the study’s co-author is based. As a direct result of individual benefits conferred by reduced pain and enhanced usability through the use of even non-robotic prosthetics, this approach or something similar may prove highly transferable beyond the confines of the current research setting. To date, approximately 60 people globally have undergone the anterior medial approach (AMI) surgery on either their elbow or knee joint.
Initially, Dr. Herr stated that an individual who had previously undergone amputation of a limb may benefit from acute myocardial infarction rehabilitation, and he is strongly considering this process. According to the Amputee Coalition, over 200,000 individuals are living with a missing limb each year in the United States, resulting from amputation procedures.
Regarding this aspect, existing industrial-grade leg prosthetics could potentially be adapted to integrate a neural interface seamlessly. The realm most in need of improvement appears to be the integration between an amputee’s website and their prosthetic care. According to Herr, the commercialization of this interface is likely to take around 5 years to become a reality.
Professor Herr’s ultimate goal is to achieve seamless neural integration and embodiment, where a prosthetic becomes an intuitive extension of one’s physical body rather than a mere tool. This groundbreaking study marks a significant milestone in our understanding.
