Humans have been replacing amputated limbs for thousands of years. A device consisting of a leather and wood toe was found with the mummy of an ancient (3,000 or so years) Egyptian noblewoman. Early prostheses were designed more to cover up the area of deformity (the stump resulting from an amputation) than to restore significant function. It was not until the Renaissance that prosthetics began to be engineered for greater functionality. In the early decades of the 1500s, the barber-surgeon Ambrose Pare (c.1510–1590) developed new post-amputation techniques that significantly enhanced healing and improved long-term outcome. He created functional above- and below-the-knee prostheses. The long-leg prosthesis contained a kneeling peg as well as a knee lock and a movable foot. Pare also designed functional arm prostheses with hands that could be moved by manipulating springs and catches with the remaining hand. Pare is considered an important pioneer in prosthetics and amputation surgery.
With the advent of biotechnology, there have been enormous advances in the development and implementation of prosthetics and implants. Military conflicts beginning during the late twentieth century resulted in a significant increase in the number of young and otherwise healthy multiple amputees. The U.S. Defense Advanced Research Projects Agency (DARPA) has infused considerable research and funding to the development of biomechatronic, neurally controlled, highly functional artificial limbs.
Humans are living longer and have begun to wear out their joints. Diseases associated with old age have resulted in increased need for implants and prosthetics among elders. The advancing sciences of biotechnology have contributed significantly to lightweight, functional, biosimilar implants and prostheses easily accepted by the body.
Historical Background and Scientific Foundations
The earliest recorded example of a leg prosthesis was unearthed in Capri, Italy, in 1858. It was dated to around 300 BC, was made of bronze and iron over a wooden core, and it appeared to be designed for a below-the-knee amputation. The Scholar Pliny the Elder (AD 23–79) wrote about a Roman General who lost his right hand in the Second Punic War between 218 and 210 BC. He had an iron hand made so he could hold a shield and return to battle. Between AD 450 and 1000, few non-traumatic amputations were successful; most leg prostheses were made from wooden pegs and arm prostheses were hand hooks. Between the early Middle Ages (476–800) and the Renaissance (c.1300–c.1700) there was a surge of interest in creating more functional replacement limbs. Prosthetics were designed by all manner of tradespeople, with watchmakers significantly contributing to functionality of design. During the Renaissance there was increasing focus on both functionality and appearance of prostheses, which were typically made of iron, steel, wood, and copper.
Ambrose Pare, a sixteenth-century French barber-surgeon, is considered a pioneer of modern surgical amputation techniques, as well as design of increasingly functional prosthetics. He discovered that applying ointment and bandaging post-amputation sites resulted in better healing than those treated with heated oil or by a hot iron application. He presaged modern above-the-knee prostheses with his design of a fixed position kneeling pegged leg and foot prosthesis attached by means of an adjustable harness. It featured a knee lock control and sophisticated engineering. Along with his technically complex arm prosthesis designs, he created an artificial hand that was operated by means of springs and catches.
Pieter Verduyn invented a non-locking below-the-knee prosthesis in 1696; this design was used as a standard until modern times. James Potts of the United Kingdom designed a prosthesis called the “Anglesey Leg” in 1800, containing a wooden socket and leg with steel knee joint and articulated foot controlled by tendons made of catgut that ran from the outside of the thigh to the ankle. William Selpho brought this prosthesis design to the United States in 1839, where it was known as the “Selpho Leg.” Benjamin Palmer improved the Selpho Leg in 1846 by enclosing the tendons in the body of the prosthesis, adding an anterior spring to the knee joint, and enclosing the entire artificial limb in a more skin-like cover. He strove to improve the appearance as well as to make the leg's movement more closely resemble a natural gait.
Americans became involved in prosthetics development as a result of the large number of traumatic amputations resulting from the Civil War. James Hanger (1843–1919) had the first documented traumatic above-the-knee amputation in the Civil War. He was dissatisfied with the lack of functionality of the prosthesis he was given, and designed another out of barrel staves, rubber, and wood. He placed hinges at the knee and foot. This became the prototype for replacement limbs during the Civil War; it was called the Hanger Limb. Hanger went on to found a prosthetics company where he designed and marketed multiple refinements of his original models.
There were large numbers of amputees during World War II (1939–1945), and they expressed considerable dissatisfaction with the quality and functionality of available prosthetics. The National Academy of Sciences established the Artificial Limb Program in 1945. The American federal government began funding orthotics and prosthetic research in 1946; the American Orthotics and Prosthetics Association was created in 1950.
In the 1960s the Russians created a prosthetic hand capable of movement; the Americans developed a functioning arm at about the same time. Prosthetics became progressively lighter, more comfortable, and more functional in subsequent decades. With the growth of bio- and nanotechnology, replacement limbs have become increasingly more functional and begun to be able to communicate with the central nervous system of the wearer.
Impacts and Issues
Lower limb prosthetics have a similar structural design regardless of composition or advanced technology. The pylon forms the skeleton of the prosthesis; it provides structural support and bears the weight of the limb as well as a portion of body weight. Historically, the pylon has been composed of metal rods; more recent technological advances have led to the use of carbon-fiber composites, which are lighter yet very durable. The pylons may be enclosed in foam or cloth molded and dyed to match the skin tone of the wearer in order to give a more lifelike appearance. The socket attaches the prosthesis to the residual limb. Extremely exact fitting is essential, because the socket area is where forces from the prosthesis are transferred to the stump; poor fitting can result in pain and skin breakdown as well as loss of functionality. A prosthetic liner or sock (or both) is generally placed between the residual limb and the device to improve fit and comfort. The suspension system maintains the attachment of the replacement limb to the wearer. The design of the system depends on the type and location of the amputation. Transtibial prostheses can often be attached by means of suction, whereas transfemoral amputations nearly always require the use of some form of harness system.
Prosthetic limbs can be controlled in several different ways. Traditionally, arm prostheses have contained a hand hook, operated by movement of the opposite shoulder. Externally-powered limbs utilize a motor that is operated by switch or button controls. Myoelectric prostheses utilize electrical signals generated by the muscle in the residual limb. In transfemoral devices, it is necessary to engineer a functional knee joint that will be sensitive enough to respond to changes in movement or gait type. Microchips and nanocomputer devices have facilitated the development of this technology, allowing for progressively smoother and more natural gait transitions.
Until the past few decades, arm prostheses largely consisted of a hook and cable system that relied on the movement of the opposite shoulder in order to open and close the hand hook. Injuries arising from the military conflicts in Iraq and Afghanistan have resulted in a very significant increase in the number of multiple limb traumatic amputations among ground troops, typically involving one or both legs as well as the arm that holds a weapon.
The U.S. Department of Defense has been supporting the advancement of prosthetics development through DARPA. DARPA has been involved in developing an artificial arm that utilizes the principles of biomechatronics to mimic nature closely. The arm is connected to the central and peripheral nervous system by means of a series of electrodes placed under the skin of the chest, attached to muscles. Nerves from the residual portion of the amputated arm are moved into the chest and placed near the muscle surface. Wiring from the prosthesis is connected to the electrodes, and the wearer controls the device neurally, by thinking about the desired arm movement. Current users of the prototype arms are involved in their ongoing refinement through research participation. The performance and functionality of the biomechatronic artificial limbs are being refined continuously as they are prepared for eventual commercial distribution.
It is anticipated that the prosthetic arms will be made to look progressively more like natural limbs. The new arms contain functioning fingers capable of picking up and manipulating small objects as well as moderately heavy ones. Concurrently, research is ongoing to develop synthetic skin containing sensors similar to those found in nerve endings. It is anticipated that the addition of the skin eventually will enable wearers to feel pressure and touch, as well as heat, cold, and pain.
Not all body part replacements involve externally visible prostheses; the field of knee joint implantation has experienced technological advances analogous to those of artificial lower limbs. Developments in biotechnology and microprocessing have advanced the functionality of prosthetic knees resulting in artificial joints that can sense and adapt to changes in gait, speed, and gravitational impacts (whether carrying light or heavy loads) continuously. They are able to sense changes in terrain and make automatic functional adjustments, enabling the wearer to maintain an even gait and experience improved joint stability.
In addition to the increased need for prosthetics resulting from traumatic amputations, there is a growing need for implants and prosthetics for a global population that is living longer and outlasting a variety of body parts. Bio- and nanotechnology have enhanced the mechanics and structural compatibility (acceptance by the body) of prosthetic devices. The use of calcium phosphate and other biocompatible coatings on titanium-alloy implants has improved their acceptance and integration by the body, measured in speed and degree of proliferation of osteoblast cells.
Primary Source Connection
The amazing power of prosthetics outlines the topic for this piece. Neuroelectrical signals from the brain’s nervous system enable the performance of this amazing technology. A description follows of the creation of a bionic hand powered by these neural signals, and one of the first persons to test the new appendage. A year later, after extensive rehabilitation and months of practice, the recipient is realizing the full potential of his prosthetic hand. Continued success in the field of prosthetics is on the horizon, and there is hope that other candidates may soon yield the same results.
Europe’s First Bionic Hand Still Going Strong A Year On
Austrian scientists pioneer a bionic hand powered by neural signals. The first man to get one says he can do things that would have been impossible a year ago, such as ride a bike and eat with a fork and knife.
For decades, humans have speculated about upgrading, or replacing their body parts to include bionic implants. Cochlear implants and pacemakers have become commonplace. But the Austrian company Bionic Reconstructions is pioneering a technique to perform elective amputations to replace severely damaged hands with cyborg-like appendages controlled directly by the brain.
Patrick Mayrhofer has one of these new bionic hands. Doctors were able to save his left arm after he was severely electrocuted three years ago during a work accident, but not even nine operations made it possible for Dr. Oskar Aszmann and his team of surgeons to save Mayrhofer’s left hand.
Otto Bock Healthcare, however, was able to create a bionic replacement for Mayrhofer that Aszmann attached to the 23-year-old a year ago.
The hand ‘Michelangelo’
The company’s hand, called Michelangelo, has a metallic frame, with chrome-colored joints and skinny fingers of white plastic.
“The hand is connected to the body though a socket and electrodes sit in the sockets and contact directly the skin,” said Janos Kalmar, one of Otto Bock Healthcare’s main researchers.
It’s the electrodes that can receive neuroelectrical signals from the brain’s nervous system through the skin that set the bionic hand apart from standard prosthetics. Even if a real hand no longer exists, the brain can still fire neurons to move it, and the brain dutifully sends out that same jolt to the bionic hand’s electrodes.
“Using the electrodes, we can pick up these muscle activations, small voltages on the skin, and with the two of them, we can open and close the hand,” Kalmar added.
Amputating his damaged hand
After seeing how the mechanical hand could work, Mayrhofer agreed to become one of the first people to test the bionic hand, which won’t be released as a commercial product until later this year.
But first he had to convince his family that amputating his existing hand was not a crazy idea.
“They said, ‘Oh my God, what are you doing!’” he remembered. “But with the company, I made videos and showed them to my family, and they said, ‘Wow that is amazing! You go to Vienna and three hours later, you can grab your glass—something you haven’t been able to do with your hand for years.’”
The amputation was the simple part, said Aszmann. More important, he added, was creating a new neurological network that would generate a signal strong enough to power the prosthetic what he calls “bionic reconstruction.”
Bionic biking, climbing and eating
After months of practice, Mayrhofer thinks of moving his hand in certain ways and his bionic hand obeys. He uses the new hand to ride a bicycle, go rock climbing and eat with a fork and knife.
He is the first person to go through such a procedure in Europe, according to Aszmann, but not the last. In April, Aszmann attached a bionic hand for a patient who had not been able to move his human hand for the last 10 years.
The Austrian government has given 3 million euros ($4.3 million) to the hospital to create a new Center of Bionic Reconstruction, which is set to open in September.
Aszmann said he sees about one person a week who could become candidates for the bionic device.
“We can re-route nerves, get new muscle attached, we can alter skeletal environment, so that the patient in the end will have excellent conditions for a prosthetic device,” he said.
Pinnameneni, Sruthi. “Europe's First Bionic Hand Still Going Strong A Year On.” Deutsche Welle (June 7, 2011).