Robotic Prosthetics
Prosthetics are devices used in the medical field that may be used to replace lost or deformed limbs. These devices help to give patients the functionality they may have had previously and sometimes can disguise the limb’s absence. Current advances in science have begun to allow for more advanced robotic prosthetic limbs in order to allow amputees various normal limb functions.
Prosthetic limbs started off very simple and have been found from dates as early as 300 B.C. Some of the earliest were as simple as a peg used to replace a leg. Between 476 and 1000, Prosthetics began to include metal hooks, to replace lost hands, or fake legs that were strictly cosmetic. These prosthetics were still very simple, but around 600 years later, Ambroise Paré invented a replacement hand with movable fingers and a prosthetic leg equipped with a bendable ankle joint and knee joint that could be locked. These artificial limbs were soon capable of being controlled by other limbs and more recently prosthetics have grown to include more advanced materials and technologies, including hydrolics and robotics.
Modern prosthetics are making a great leap in not only functionality, but appearance and construction as well. Compared to their predecessors of heavy rubber and plastic, today’s prosthetics are cutting edge, made with advanced plastics and even carbon fiber, making them lightweight, stronger, and more realistic.
Although they are changing and improving, the foundation still remains the same. Most of today’s prosthetics are made of the pylon, socket, and suspension system. The pylon is an internal frame or skeleton that gives a foundation and structure to the prosthetic limb. The socket is the area of the prosthetic that attaches to the socket, stump at the residual limb or area of amputation. Also, the functions of prosthetics differ due to the functionality of the limb lost. Complicated prosthetics require hinged joints such as a transfemoral amputation, meaning that a patient needs a prosthetic knee, as well as the lower leg and beyond. Much simpler is the transtibial amputation, or amputation below the knee, where they are capable of using their current knee. However, with this type of amputation, the foot and lower leg must be created. Overall, the type of amputation affects the difficulty of limb replacement, which is based on the amount of joints that are going to be artificial supplemented.
Prosthetics are made on an individual basis. The phrase “one size fits all” certainly does not apply here. Prosthesist, people who make prosthetics, must cast, mold, and create the prosthetic based upon the individual’s unique needs. Modern prosthetics are using much more than just rubber, plastic and screws into the bone. They are becoming advanced enough to actually interact with the nervous system and an individual can control a prosthetic limb with their brain. Later we will go more in-depth, but basically they use surgically relocated nerves from the amputated limb to tell sensors on the prosthetic to do the appropriate tasks.
So how do they actually work? There are a variety of prosthetics with varying degrees of functionality. From simply cosmetic and realistic looking, to as fully functional as the original limb. These are much more than a pincer split hook that can open and close. Basic controllable prosthetic limbs are usually controlled through motors and relays from working limbs or muscles nearby. These are often done together with firing the opposite leg (right leg) to step forward as the other (left leg) is in the extended, backward phase of walking. Advanced prosthetics use impulses sent from the brain that are read by sensors on the body actually allowing the person to use the prosthetic limb just as it was meant to be. For the example of full arm amputation, there is a surgery required where the neurons that used to go to the arm, hand, and fingers have been rerouted to the chest where they help with muscle movement that in turn operates the prosthetic arm, hand, and digits. Also, they are work with return sensors, controlling pressure and temperature changes that are relayed back to the nerve endings in the muscle, allowing the patients to get a true feeling of what it would be like if they still had their own limb.
This video does a good job explaining this concept.
The current technology does not allow patients to control their prostheses the way they normally would, using their brain, but this technology is currently being developed. A scientist by the name of Dr. John Donoghue, has began creating a system called BrainGate, that is intended to allow for this type of limb control. This system operates by changing brain waves into a form that can be converted into computer commands then utilized by robotic prosthetics. While the system is currently wired directly to the brain, Donoghue and his team hope to someday make this system wireless. Dr. Hugh Herr is working on a microprocessor that, when implanted into the left over limb muscle, can pick up brain signals and cause the limb to move. Once these technologies have advanced, people may be able to control their artificial limbs as they would have their own natural limbs!
By Peter Povolo and Rachael Raspatello
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