Loss of a limb is irreversible in our times. Amputations are done as a last resort in order to save a life. An unstoppable cancer or an infection or maybe to prevent excessive loss of blood amputations are performed. The progress in the field of prosthetics is fueled by the needs of amputees. Though a prosthesis of our time is far from effectively replacing an original limb. But it is designed to give back some of the lost sensations and partially satisfy the needs of day to day life. It is however perfect for saving a society from accumulating loads of amputations. In this era of neuroscience, prosthetics witnessed the biggest revolution seen in the field in centuries in the form of bionics. After the emergence of bionics, prosthetics were able to offer more for less hassle.
A modern prosthetic arm equipped with bionic technology is controlled by an onboard microcomputer. This computer is able to translate electromyographic signals into signals and gestures. The electromyographic signals are generated by the muscles and picked up by non-invasive EMG sensors placed on the skin. Thus a bionic prosthesis can serve the will of its wielder. This system is however not perfect and presents major shortcomings expected to be addressed in near future by emerging new technologies. This article will discuss the shortcomings and try to understand the promise held by our future.
It is not for everyone
Bionic prostheses in order to function require the EMG signals generated by the residual muscles of an amputee. Due to the candid nature of the amputations, not every amputee is blessed with these muscle residues. Hence, bionics is far out of reach to these individuals. Amputees with neuropathologies of progressive nature are also very unlikely candidates for the application of a bionic prosthesis. Additionally, an injury affecting the relevant dermatomes also renders an amputee ineligible to wield a prosthesis.
Absence of sensory inputs
Bionic prostheses due to their non-invasive sensor placements are incapable of reaching the deep embedded sensory nerves. Additionally, it lacks the receptors needed for sensing heat, pressure, friction etc. A different point of view however can conclude this loss as a small price to pay for a non-invasive application paradigm. Indeed a physiologically practical choice but at a steep cost.
Limitations of activity
The human hand is a complicated organ design to execute tasks of a wide variety and complexity. Imitating a human arm functionally is indeed a challenging adventure to undertake. Even the most adept bionic prostheses offer only a few actions and very little room for innovation. And the limitations will understandably persist till the emergence of lab-grown organs as a mainstream means post-amputation of rehabilitation.
The maintenance question
An amputee willing to wield a bionic prosthesis must go through a rigorous training and incubation program in order to learn and understand the capabilities and limitations of the prosthesis. In addition to that certain habits must be developed for ensuring a long term experience with the prosthesis. Additionally, the presence of cutting edge technology makes the prosthesis a sensitive device to wield and active assistance from the manufacturer is often essential. Without the promise of a good service and assistance network, it is not wise to own a piece of technology such as bionic prostheses.
Sensations can however emerge as a more humanitarian choice in the near future and the sensor placement paradigm might shift. A more invasive neuromusculoskeletal sensory paradigm can replace the non-invasive EMG sensors. Those future prostheses are expected to be able to deliver sensory information from their surface to the sensory nerves.
During the first phase of existence, prostheses were made of heavy materials like wood and metal. With the progress in allied disciplines prosthesis have become lighter, and easier to wield. The future might introduce materials with high strength to weight ratio. As a result, prostheses are expected to become a lot less heavy. Electronics are bound to become more advanced by the introduction of more efficient computers and more sensitive sensors.
The emergence of 3D printed organs will not happen any time soon, and till then bionics will remain the best option for prosthesis mediated rehabilitation. And the progress in this field will most definitely yield friendly results.