The word “prosthetics” causes most of us to think, perhaps optimistically, about robotic arms and legs. However, recent years have seen significant development, making us ask: How far have they progressed? What has technology offered us in the field of prosthetics? How far have we conquered the integration of mind, body and the prosthetic device? With today’s technology the short answer to these questions is artificial intelligence. The remarkable combination of sensors and prosthetics offers us something which was thought to be impossible.
When the concept of prosthetics was popularised upon it being made into a reality in 1945, by the Artificial Limb Programme, the available options for amputees were quite limited. When Oscar Pistorius won silver in the 2011 World Championships in Athletics using his carbon-fibre bladed legs, the world started acknowledging the developments in prosthetics to the point that they questioned if he had an unfair advantage using them.
There have been several notable advances in bridging the mind-prosthetic gap since the turn of the century. Jesse Sullivan became the first man with a bionic arm connected to nerves in his brain. In 2011, Les Baugh, a double amputee, was subjected to extensive work allowing him to control two bionic arms with his mind simultaneously, courtesy of the Johns Hopkins Applied Physics Laboratory. And in 2013, mentally controlled bionic legs were designed by the Rehabilitation Institute of Chicago.
So how does the mind meet the machine? Motion responsible neurons are identified with the help of brain stimulators. An electrical interface is then built where the unique neurological signals being provided by these neurons can be used to design a complimentary program. The command for a particular movement desired by the user causes the program to send a signal initiating the sensory neurons, thus bringing about the motion. Researchers started their work in neuro prosthesis with the mental control of wheelchair motion; they have now reached technological marvels such as mind controlled games.
Different methods proposed include using Bluetooth to sense commands and outputs from the brain to direct the computer activity. Recently, researchers at the Cleveland Veterans Affairs Medical Center and Case Western Reserve University developed a prosthetic hand that can convey a sense of touch from 19 spots. This is achieved by direct simulation of nerve bundles, although an issue with regards to degradation of tissues due to the electrical interface was present.
Microprocessors, which are like mini computers, have been the best bet for use in prostheses up to now. The microprocessor provides the coordination function normally provided by the central nervous system. They are found in myoelectric prostheses which send signals to the neurons from the muscles which would operate motors in the joints and hands. They are also able to detect lower output from the muscles and amplify them before sending it to the brain in case of muscle fatigue.
Seattle Systems developed a lower limb prosthesis that has multiple sensors that feed data on pressure, position, and speed to a central processor that controls the knee as well as the ankle, foot and socket. They were able to help train the amputees to feel their limbs when touched on the new prosthetic surface. Victhom Human Bionics Inc. came up with energy efficient and dexterous limbs which are capable of flexion and extension, giving the user a much better sense of comfort. The main issue which was faced when it came to amputees was that the way their limbs were amputated had a great impact on the possibility of attaching a prosthetic substitute.
The technological advances in robotic prostheses that have made them viable include greater energy storing lithium-ion batteries, powerful electric motors with rare-earth magnets instead of bio-motors present and miniaturized sensors built into low-power semiconductor computer chips offering coordination with the brain. This package has been able to replicate all basic functions of the original limb. The synchronisation of the user command and the independent motion was a problem faced by passive limbs, but these active limbs do not have that issue. The coordination and syncing provides comfort and mental satisfaction to the user, and is considered to be a major success in the field.
In other words, like what they say in the Six million dollar man TV series, “We can rebuild him, better than he was before. Better, stronger, faster”.