Prostheses have been used for centuries, dating back to Ancient Egypt, to help people who have lost limbs due to trauma, illness or birth defects. Early designs were made primarily from basic materials, such as wood, leather and fabric.
Today, modern prosthetic limbs are lighter, stronger, and more life-like than ever before – thanks in part to plastics. Many designers are creating innovative prostheses specifically for amputees who wish to continue to lead active lives. Plastics often are used for many of these “active prostheses” because polymers can mimic characteristics of human parts, such as energy return, flex and strength, as well as help to increase grip and friction.
From the ancient times to today’s Paralympics, prostheses have evolved from uncomfortable and less functional first-generation materials to the highly individualized fitting and casting of today’s plastic-based devices. Here’s a look at how far prostheses have come throughout the centuries:
History of Prostheses
• 1069 to 664 B.C.: The Egyptians were the early pioneers of prosthetic technology. Their rudimentary prosthetic limbs were made of wood, leather and organic fibers and were worn for a sense of “wholeness” rather than to enable amputees to function. Archaeologists in 2000 unearthed the world’s earliest functioning prosthetic body part – an artificial big toe. The wood and leather prosthesis was found on an Egyptian mummy in a tomb outside the ancient city of Thebes.
• 300 B.C.: The majority of early prostheses in Europe, the first of which was discovered in Italy, were made to hide injuries sustained in battle. Prostheses fitted for knights were designed only to hold a shield or to make a leg appear in a stirrup, with little attention to functionality. Outside of battle, only the wealthy could afford to be fitted with prostheses designed for daily function.
• 1508: The Renaissance (1400s-1800s) ushered in a new perspective on science and medicine and saw a rebirth in the development of prostheses, which at the time were unwieldy devices made of iron, steel, copper and wood. In Germany, mercenary Gotz von Berlichingen (who lost his right arm in battle) created a technologically advanced iron hand that could be moved using a rudimentary system of springs and releases.
• 1536: French Army surgeon Ambroise Paré is considered by many to be the father of modern amputation surgery and prosthetic design. He introduced functional prostheses for upper- and lower-extremity amputees and invented an above-knee device consisting of a kneeling peg leg and foot prosthesis with a fixed position, adjustable harness, knee lock control and other engineering features still used in today’s devices. His work showed the first true understanding of how a prosthesis should function, and it was the first time that leather, paper and glue were used in place of heavy iron.
• 1696-1800: Dutch surgeon Pieter Verduyn developed the first non-locking, below-knee prosthesis that later would become the blueprint for current joint devices. More than 100 years later in London, James Potts designed an articulated foot controlled by catgut tendons from the knee to ankle. It became known as the “Anglesey Leg” after the Marquess of Anglesey who lost his leg in the Battle of Waterloo.
• 1861-1945: During the U.S. Civil War, the number of amputations rose astronomically, forcing Americans to enter the field of prosthetics. It wasn’t until after World War II, however, that the U.S. government brokered a deal with military contracting companies to improve the functionality of prostheses for returning veterans. This agreement paved the way to development and production of modern prostheses. It was during this time that more advance materials like plastics became incorporated into prosthetic design and began to resemble the prostheses we see today.
Prostheses Today:
With a record number of amputees surviving trauma and returning from combat or recovering from traumatic injuries such as car accidents, active and sports-grade prosthetics are more important that ever. Not only are Paralympic athletes demanding these high-tech prostheses, but many non-competing amputees are seeking to continue an active lifestyle.
“Carbon fiber” composites (plastic-based compounds) are playing a starring role in these developments. The use of carbon fiber springs in prostheses allows improved mobility and shock absorption without increased weight, enabling active amputees to wear limbs that can absorb two to four times their total body weight.
Carbon fibers also play a part in custom fitted sockets which are typically lined with a plastic gelled sock covered in nylon or spandex, allowing an amputee greater comfort throughout the day. Before the development of these socks, layers of light wool socks were often used to achieve this level of comfort.
The design and construction of a modern above-the-knee prosthetic device requires the expertise and support of kinesiologists, doctors, bio-mechanical engineers, structural engineers, materials and fabrication experts, coaches and the athletes themselves. An adjustable plastic-based socket connects the leg to the prosthesis. An artificial knee below the socket, constructed of aluminum, titanium and other metals, is encased in a protective lightweight plastic structure. The knee connects to the lower portion of the prosthesis through a device that both reduces shock and suppresses torque (the force generated by the turning of the knee during running motion) that otherwise would be absorbed by the person.
The prosthesis is then supported by an artificial foot constructed from polyurethane and carefully oriented so that the athlete stays aligned while running. Soft plastic exteriors allow for increased friction and flexibility of grasp, and the resulting biofeedback enables amputees to determine how much pressure they exert – a benefit that metal-only devices cannot offer. Because polyurethane does not easily fatigue, prosthetic designers now can create devices that store and return energy when users exert external force to augment and improve the capabilities of the prosthesis.
While war historically has spurred technological development in prosthetics, the Paralympics Games in the twentieth century proved to be another powerful catalyst. The esteemed international event has helped drive the development of lighter, more functional devices such as the gait-adaptive knee, an artificial limb that can be modified to fit its user. For example, in the 100-meter sprint event during the 2004 Athens Games, the slowest time in the men’s categories was 12.1 seconds, comparing favorably to just under 10 seconds for traditional Olympians.
Modern prostheses have been revolutionized by the development of plastic materials that help make them lighter, stronger, more flexible and more able to mimic the function of a natural limb. Today’s devices also are more functional, durable and comfortable because they are made of plastic, aluminum and composite materials that allow for patient-molded and individually fitted prostheses. And with the advent of microprocessors, computer chips and robotics, prostheses have crossed over from simply providing basic functionality to helping return amputees to their accustomed lifestyles.
