The Evolution of Prosthetics
A prosthetic is an artificial device used to replace certain parts of the body that may have been lost as a result of a disease, trauma or at birth. Prosthetic devices have been around for years and have significantly improved the quality of life of amputees and people with congenital defects. Over the years, they have evolved to become more efficient and restore as much function as possible to enable maximum range of motion.
Here are some of the limb prosthetics that have been made over the years:
Wood and metal prosthetics
The first recorded use of a prosthetic was from 950 to 710 BC. Pathologists discovered in 2000, a mummy from this time buried near ancient Thebes in the Egyptian necropolis that had an artificial big toe. This toe, which consists of wood and leather, showed proof of use. When recreated by researchers in 2011, it was observed that this prosthetic enabled its user to walk in Egyptian style sandals as well as barefoot.
Another historical prosthetic was that that of Götz von Berlichingen, created at the beginning of the 16th century was popular and very refined.
Advancements before the 20th century
Prosthetics underwent many advancements before the 20th century. One of the pioneers who contributed to this was Ambroise Paré. An above-knee system that was a kneeling peg leg and foot prosthesis with a fixed location, adjustable brace, and control of the knee lock was among his inventions. His advances’ functionality showed how potential prosthetics could evolve.
Other advancements include:
- Pieter Verduyn -Prosthesis of the first non-locking under-knee (BK).
- James Potts- Prosthesis consisting of a wooden shank and socket, a steel knee joint and an articulated foot operated from the knee to the ankle by catgut tendons. This later came to be known as “Leg Anglesey” or “Leg Selpho”.
- Dubois Parmlee - Used a suction socket, polycentric knee, and multi-articulated foot.
- Marcel Desoutter & Charles Desoutter- First aluminium prosthesis.
- After the Crimea War, Henry Heather Bigg and Henry Robert Heather Bigg, earned the Queen’s order to supply “surgical appliances” to wounded soldiers. They developed arms that felt more natural, made of ivory, felt and leather.
Advancements in the 20th century
- Most limbs were made of a mixture of wood and leather following World War II. Although these materials offered many advantages for the wearer, the prosthetics were heavy and leather was difficult to keep clean, especially because it absorbed sweat.
- As thin, easy-to-clean alternatives to the wood and leather versions — plastics, polycarbonates, resins and laminates were introduced. Prosthetics were manufactured from lightweight materials including carbon fiber. Synthetic sockets were custom-fitted to ensure individual, comfortable, and hygienic fit for each patient.
2000–present
Prosthetics have progressed to highly sophisticated design including high-performance, lightweight running blades, sensitive legs and feet for varying terrain navigation, and sensor and microprocessor powered motorized hand prosthetics.
The Advent of Bionics
Bionic limbs are artificially devised limbs that are made to create seamless movement by using signals from a person’s muscles or brain. So how are these limbs better than traditional prosthetics?
Prosthetics that are currently used have sockets that are fitted precisely onto the amputee’s stump by a prosthetician. It is important that the fit is accurate, since most prosthetics have to be changed frequently, which is time-consuming, expensive, and sometimes inconvenient. Even though they are custom made, they are not ideal and the stump may slip against the surface of the prosthetic, become sweaty and extended use may be painful. This is particularly a problem for lower limb prostheses. As the body’s weight bears down onto the socket , the risk of sores and infections resulting from them is high.
A step up from cosmetic or passive prosthetics, functional prosthetics also need body strength to move. Functional prosthetics are usually available in both body-driven and electrically powered types, with the electrically operated alternative relying on batteries and motors to control movements.
With the use of sensors and computers that respond to both thoughts and muscle activity, a bionic limb gives the user much more power and movement. This feature takes much of the workload off the body and acts more like a real limb. Control is achieved due to a phenomenon called myoelectricity. The remaining muscles of the stump still respond when the user “ moves ”the missing leg, resulting in electrical signals on the skin that can be identified by sensors inserted into the socket.
Myoelectric control depends on the fit between the stump and the prosthesis, so it is important to precisely position the sensors that detect the muscle signal in the correct area of the skin. Moreover, this technology is best suited to arms and hands. Legs present a different set of issues, as the movement of knees, feet and ankles in normal walking are more independent and less conscious than those of hands , arms and fingers; they often have to deal with different forms of stress and perform a more mechanical and supporting function.
Advanced lower limb prosthetics contain more passive systems, based on mechanical joints whose rigidity can be adjusted automatically during walking in the most advanced cases. Known as active joints, they use pneumatics that are controlled by electronic actuator which helps to create realistic knee and ankle movements. The most advanced lower limb available is widely agreed to be the Linx device, developed by Blatchford, a UK based company, whose joints automatically adapt to changes in posture and which also can be used on soft and rough surfaces.
Kianoush Nazarpour, a Newcastle University bioengineer, is one among many who are developing ways to improve existing technology. Nazarpour ‘s project, through which he collaborates with Imperial College London and the universities of Leeds, Keele, Essex and Southampton, focuses on providing sensory input to prosthesis users. For this, he uses relatively simple sensors in the fingers of the prosthetic to detect temperature , pressure and shear. Their output is converted into small electrical currents that are applied to the stump’s skin.
The integration of machine vision into prosthetic hands is one intriguing direction the research has taken. An off-the-shelf camera is attached near the wrist facing the fingers, and a processing algorithm assesses how best to position the fingers to grip the object when the user moves the hand towards an object. A similar system could be used on a prosthetic leg; a camera monitoring ahead of the foot could move the prosthetic foot into the best position to help the user climb steps.
We are living in an era where technology is advancing day by day. With each new advancement, things that were previously thought impossible to achieve are now within the realm of reality. Maybe, some day , we will be able to create and design prosthetics that are capable of completely reproducing all the functions of a natural limb.
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