# Prosthesis

In medicine, a prosthesis (plural: prostheses; from Ancient Greek prosthesis, "addition, application, attachment") or prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through trauma, disease, or a condition present at birth (congenital disorder). Prostheses are intended to restore the normal functions of the missing body part.

## Quotes

* “There’s a dream that in the future, we’ll be sitting in our home and hit a button to print our prosthetics from scratch,” Sadler says. “That might be a further out vision.” But some people think we’re already there. Sadler agrees with Kuniholn about the difficulty of attaching printed prosthetics, saying, “The fitting is a whole other black art. 3-D printing only gets you part of the way.” Of course, that’s for high-end prosthetics, the kind you hope to have. In some parts of the world, the choice is between having a mediocrely-fitting prosthetic and not having one at all. This is the situation that spurred Summit to action, as well as Patrice Johnson, who, according to Sadler, is, “the only person to have successfully designed and sold [a] functional upper limb prosthesis that used 3-D printing.”
** Travis M. Andrews, “Can We Really 3-D Print Limbs for Amputees?”, The Atlantic, (August 23, 2013)
* “Right on the border of Burma and Thailand, there are landmines like you wouldn’t believe,” he says. These landmines leave many residents as amputees, residents who “would typically never see a prosthesis because of [the] fitting and time it would take.” Armed with Physionetics’ technology and good will, Johnson went to Burma and fitted two amputees with the printed arms. “We donated them,” he says. “All I had to do is go out there, show them how it was fit, and within an hour and a half, we had them on these two guys.” Stories like this are what drive Summit to continue his quest for a “self-use viral app for developing countries” that can create prosthetics. “There will simply never be enough prosthetists to meet their needs.” This isn’t his dream for the future; he thinks it’s a scientific possibility now. And he strongly disagrees that the materials 3-D printing can handle aren’t strong enough to work as limbs. He points out that, “the [human] bones that we have are not as strong as titanium,” a material used in many prosthetic limbs. “When you have great flexibility of geometry, as we do with 3-D printing, you can overcome what strength you don’t have,” Summit says. He says he’s found a way to overcome this strength barrier by creating a hollow prosthetic, then filling it with a lattice structure, similar to the construction of a bird’s bone. “Nature’s been doing this for a long time,” he says.
** Travis M. Andrews, “Can We Really 3-D Print Limbs for Amputees?”, The Atlantic, (August 23, 2013)
* An effective prosthesis delivers renewed functionality and is cosmetically pleasing, but it also serves to complete the wearer’s sense of wholeness. A prosthesis then, is as much medical device as it is an emotional comfort, and so the history of prosthetics is not only a scientific history, but the story of human beings since the dawn of civilization who by birth, wound, or accident were left with something missing.
** Mark Lawson Bell, “The History of Prosthetics”, (September 21, 2015)
* The earliest example of a prosthesis ever discovered is not a leg, arm, or even a fake eye, it’s a toe. A big toe, belonging to a noblewoman, was found in Egypt and dated to between 950-710 B.C.E. We all know that toes are important, but it’s interesting that our earliest physical example of the history of prosthetics is a toe and not something that might seem more important, like a leg or an arm.
** Mark Lawson Bell, “The History of Prosthetics”, (September 21, 2015)
* Stories of lives devastated by conflict or disease are all too common across low-income countries. Lack of an arm or leg can be tough anywhere, but for people in poorer parts of the planet, with so much less support and more rickety infrastructure, it is especially challenging. Some are victims of conflict, others were born with congenitall conditions. Many more are injured on roads, the casualty toll soaring in low-income nations even as it plummets in wealthier ones. Every minute, 20 people are seriously injured worldwide in road crashes. In Kenya, half the patients on surgical wards have road injuries. The World Health Organization (WHO) estimates there are about 30 million people like Nhial and Lam who require prosthetic limbs, braces, or other mobility devices. These can be simple to make and inexpensive. As one veteran prosthetist told me, his specialism is among the most instantly gratifying areas of medicine. “A patient comes in on Monday on crutches that leave them unable to carry anything. By Wednesday they are walking on a new leg and on Friday they leave with their life transformed.” Yet more than eight in 10 of those people needing mobility devices do not have them. They take a lot of work and expertise to produce and fit, and the WHO says there is a shortage of 40,000 trained prosthetists in poorer countries. There is also the time and cost to patients, who may have to travel long distances for treatment that can take five days—to assess need, produce a prosthesis and fit it to the residual limb. The result is that unglamorous items such as braces and artificial limbs are among the most-needed devices to assist lives. Yet, as in so many other areas, technology may be hurtling to the rescue, this time in the shape of 3-D printing.
** Ian Birrell, “The Promise of 3-D Printed Body Parts”, The Atlantic, (February 22, 2017)
* Yet for all the agonies and difficulties associated with arm loss, the bigger problem in low-income countries is when lower limb disability leads to loss of mobility. Wheelchairs are expensive and can be difficult to use when roads are pot-holed, streets are muddy and pavements are non-existent. Without a prosthetic limb, people struggle to fetch water, to prepare food and, above all, to work. This throws them back on their families and communities, intensifying any hardship and poverty.
** Ian Birrell, “The Promise of 3-D Printed Body Parts”, The Atlantic, (February 22, 2017)
* “If you wear a prosthesis you are disabled for about ten minutes in the morning while you have a shower, then you put your leg on and go to work. If you do not have one, then your hands are out of use with crutches so you can’t even take drinks to the table,” said Carson Harte, a 59-year-old prosthetist and chief executive of Exceed. “Without a prosthesis there are no expectations. You just go back and rely on the goodwill of your family.”
** Ian Birrell, “The Promise of 3-D Printed Body Parts”, The Atlantic, (February 22, 2017)
* Traditionally, a prosthetist would wrap a stump with plaster of Paris bandages to make a reverse mold and let it dry, then fill it with more plaster that must harden. From this a socket can be forged that fits, with more modifications for precision, to the bone on the stump. Great care must be taken to avoid nerves and tender areas that are not tolerant of pressure. The key for the technician is to understand the pathology of a stump, which differs for each person. This is a cumbersome process that can take a week, especially with gait training for new patients that lasts three days. It can also be messy work, mixing up and molding the plaster, while a prosthetist visiting a rural area must cart around 20-kilo packs of plaster. But with a 3-D scanner, a digital image can be made in half an hour and sent by email, and there is no mess.
** Ian Birrell, “The Promise of 3-D Printed Body Parts”, The Atlantic, (February 22, 2017)
* For Wright, the prosthetic had to have a purpose. She wasn’t interested in something that made her look “normal” if it wasn’t going to help her actually do anything better. And she isn’t alone. More and more amputees, engineers, and prospective cyborgs are rejecting the idea that the “average” human body is a necessary blueprint for their devices. “We have this strong picture of us as human beings with two legs, two hands, and one head in the middle,” says Stefan Greiner, the founder of Cyborgs eV, a Berlin-based group of body hackers. “But there’s actually no reason that the human body has to look like as it has looked like for thousands of years.” Greiner himself has magnetic implants in his fingers and an RFID chip in his skin. “We actually already live in a cyborg society,” he said.
** Rose Eveleth, “A Blueprint for a Better Human Body”, The Atlantic, (May 17, 2015)
* For a long time the history of prosthetics has been inextricably linked with the history of war, and thus of men. After World War II, when soldiers were returning from the battlefield, there was a collective anxiety about whether they’d be able to re-enter their families and workplaces. Many people wanted soldiers to come back, and for everything to go back to normal. But an amputation was a physical reminder that things were not the same. “Physicians, therapists, psychologists, and ordinary citizens alike often regarded veterans as men whose recent amputation was physical proof of emasculation or general incompetence, or else a kind of monstrous de-familiarization of the 'normal' male body,” writes the professor David Serlin in the book Artificial Parts, Practical Lives. Serlin describes the ways in which the media and the military talked about these soldiers, pushing for them to be seen as “normal” in the eyes of the public. In 1946, the comic Gasoline Alley featured a man named Bix whose prosthetic lets him be a “normal American guy.” The comic shows Bix stocking shelves, and features a very surprised boss who exclaims, “I didn’t expect he’d be perfectly normal”—before hiring the man on the spot. Professional photographs taken at Walter Reed Army hospital depicted men with prosthetic devices doing “normal” male activities like lighting a cigarette and reading the sports page, their prosthetic legs adorned with “tattoos” of pinup girls.
** Rose Eveleth, “A Blueprint for a Better Human Body”, The Atlantic, (May 17, 2015)
* In a 2013 interview with The New York Times, De Oliveira Barata described her work on prosthetics as outside of engineering or medicine—the industries with which artificial limb-making are typically associated. “Making an alternative limb is like entering a child’s imagination and playing with their alter ego,” she said. “You’re trying to find the essence of the person.” She works with clients to figure out how they want to look. “It’s their choice of how to complete their body—whether that means having a realistic match or something from an unexplored imagination,” she told The Times. These sculptures aren’t accessible to everyone. Wright says she would love a custom leg, but it’s out of reach for her. “I’ve inquired about getting one,” she told me, “but it’s very ex-pensive! Crazy expensive.” Depending on what the limbs are made of, they can cost anywhere from $4,600 to $21,000. But even if not every amputee gets or wants a spike leg or a feathery suit of armor or even the curved cheetah leg, the fact that people see these alternative bodies out in the world seems to have helped push a cultural shift in how people think about normalcy. That is, at least, in Western nations. In many countries, the stigma against disability and amputation remains. In the United States, Mullins says that today’s kids don’t question her normalcy the way her peers once did, they don’t see her as disabled at all. “They see a rebuilt body as something powerful. If I’m walking around in carbon fiber or titanium or bionics, standing on a street corner, and some little kid is walking by, they presume power. They want to know if I can fly, how fast I can run.”
** Rose Eveleth, “Blueprint for a Better Human Body”, The Atlantic, (May 17, 2015)
* The earliest known prosthesis, dating possibly as far back as 950 B.C., was discovered in Cairo on the mummified body of an ancient Egyptian noblewoman. The prosthesis is made largely of wood, molded and stained, its components bound together with leather thread. It is, as prostheses go, tiny. Because it is a toe. The prosthetic digit—the oldest little piggy in the world—is extraordinarily lifelike, its curved nail sunken into a similarly curved bed. Which is, in its way, remarkable. A toe! One that is several thousand years old! And it's not just a toe-sized peg—a little device that would have made mobility more manageable for someone who was, by reasons of birth or amputation, missing her big toe. The prosthesis is, as much as it possibly could be, humanoid: maximally lifelike and maximally toe-like. The "Cairo Toe," as it's been dubbed, is prosthetic and cosmetic at once—evidence not just of ancient manufacturing stepping in where biology was limited, but of manufacturing engaging in an ancient form of biomimcry. Compare the Cairo Toe to today's prostheses, many of which—especially those that dominate the public imagination—seem to be inspired less by "man," and more by the Bionic Man. The blades. The hooks. The exoskeletons. This week alone has brought news of a roboticized prosthetic hand that, possibly inspired by the workings of the claw crane, foregoes five fingers for three. It has brought news of a woman who created her own prosthetic leg ... out of LEGOs. Those stories come as part of a flood of coverage of the next generation of prostheses, in which technologies from adjacent fields—3D-printing, robotics, chemistry—are helping humans to transcend nature's narrow definition of humanity.
** Megan Garber, “The Perfect, 3,000-Year-Old Toe: A Brief History of Prosthetic Limbs”, The Atlantic, (November 21, 2013)
* One of the earliest written references to prosthetics is found in a book published in France in 1579. That year, French surgeon Ambrose Pare (1510–1590) published his complete works, part of which described some of the artificial limbs he fitted on his amputees. As a military surgeon, Paré had re-moved many a soldier's shattered arm or leg, and he eventually began designing and building artificial limbs to help the men who had been maimed. Ambroise Paré was the official royal surgeon to four successive kings, and earned his position by practicing medicine on the battlefield, attempting to save, or at least treat, wounded soldiers. As a doctor, he was most disturbed by the reaction of some of the people whom he had saved. He found that some soldiers took their own lives rather than live without limbs, or with terrible wounds. To try to combat this problem, Paré began crafting artificial limbs. This was not new. There is evidence for the use of prostheses from the times of the ancient Egyptians. Prostheses were developed for function, cosmetic appearance and a psycho-spiritual sense of wholeness. Amputation was often feared more than death in some cultures. It was believed that it not only affected the amputee on earth, but also in the afterlife. The ablated limbs were buried and then disinterred and reburied at the time of the amputee’s death so the amputee could be whole for eternal life. One of the earliest examples comes from the 18th dynasty of ancient Egypt in the reign of Amenhotep II in the fifteenth century B.C. A mummy in the Cairo Museum has clearly had the great toe of the right foot amputated and replaced with a prosthesis manufactured from leather and wood. The first true rehabilitation aids that could be recognised as prostheses were made during the civilisations of Greece and Rome. During this period, prostheses for battle and hiding deformity were heavy, crude devices made of available materials—wood, metal and leather. Records of ancient prosthesis can be found all over the world.
** Philippe Hernigou, "Ambroise Paré IV: The early history of artificial limbs (from robotic to prostheses)", Int Orthop. 2013 Jun; 37(6): 1195–1197
* In China, King-his Tse, invented in the 500 b. C. a flying magpie of wood and bam-boo, and a wooden horse able to jump. Around year 200 B.C., Philo of Byzantium, inventor of the repetitive catapult, constructed an aquatic robot. In 206 B.C., the first Han Emperor found the Chin Shih Hueng Ti's treasure. It included a mechanical toy orchestra that moved independently. In old Greece, Archytas of Tarento (referenced in [English]] as Archytas of Tarentum, and in some references in Spanish as Architas de Tarento), philosopher, mathematician and contemporary politician of Plato, considered the father of mechanical engineering and precursory of the robotics, in-vented the [w:Screw|screw]] and the pulley, among other many devices. The materials used for the construction of robots were wood (parts with form), iron (fixed structure, supports, hinges), copper (which is mouldable and allowed the construction of thinner parts), leather (cables, footwear) and fabrics. The first models used the application of direct force to make movements, facilitated with sets of pulleys, gears and handles. In this phase the robots were replicas of the human being that made a series of simple movements. The machines began assuming tasks of aid to the man and ended up repelling their conception of the world and animated beings. The mechanics affected the study of nature, spreading to the anatomy science; of which agreed models with that conception were elaborated, such as “De Humani Corporis Fabrica” (On the workings of the human body) from Andreas Vesalius (1514–1564) who conceived the man as a complex mechanical structure.
** Philippe Hernigou, "Ambroise Paré IV: The early history of artificial limbs (from robotic to prostheses)", Int Orthop. 2013 Jun; 37(6): 1195–1197
* People have used all sorts of artificial devices probably from the beginnings of human history to help them compensate for the loss of a limb. Thus in very ancient times, the first and simplest prosthesis may have been a forked tree that was used as a crutch to help someone walk whose leg may have been badly damaged or lost in an accident or to a disease. What began as a modified crutch with a wooden or leather cup and progressed through many metamorphoses has now developed into a highly sophisticated prosthetic limb made of space-age materials.
** Philippe Hernigou, "Ambroise Paré IV: The early history of artificial limbs (from robotic to prostheses)", Int Orthop. 2013 Jun; 37(6): 1195–1197
* A 3000-year-old mummy was recently discovered sporting a prosthetic big toe. The wooden toe had been meticulously fit to the woman’s foot, with attachment straps designed for comfort. The craftsmanship was extraordinary; the toe could even flex. The toe is one of the oldest examples, but from pirates’ peg legs to Tycho Brahe’s metal nose, replacement body parts have a long and inventive history. Even before the toe’s discovery, prosthetics were known to be ancient technology. Replacement body parts are mentioned prominently in the classical literature of multiple cultures. The mythical Greek hero Pelops, accidentally ingested by the Gods, sported an ivory shoulder after his reconstruction. Herodotus mentions warriors with wooden feet, and there are examples from Asia and Rome as well.
** James MacDonald, “A Brief History of Prosthetic Limbs, Daily.Jstor, (July 21, 2017)
* In France and Switzerland, from the late fifteenth through the nineteenth centuries, a variety of custom-designed limbs were built. Made of combinations of wood, metal, Leather|leather, and other materials, some of these designs were truly fantastic. Controlled by cables, gears, cranks, and springs, these limbs could be rotated and bent. There were prosthetic fingers made to grip objects. The limbs were not completely practical, as they had to be operated by a different hand, but they had their uses. For example, a hand could be cranked shut around a pen or fork. Flexing, spring-loaded legs were also available. These fantastic objects were ahead of their time: cable control was a precursor to the standard post-World War II design. Following those early designs, prosthetic limbs improved by leaps and bounds. World Wars I and II, as well as other large-scale conflicts, such as Vietnam, unfortunately increased demand for prosthetics, leading to improvements.
** James MacDonald, “A Brief History of Prosthetic Limbs, Daily.Jstor, (July 21, 2017)
* There is a moment when each ultra-realistic prosthetic limb crafted by Sophie de Oliveira Barata transitions from a hunk of silicon into something more. “It happens around this point,” the artist explained, gesturing to a half-finished leg jutting mid-kick from her work bench. “I’ll know it’s happened when I handle a limb a bit roughly, and I find myself apologizing to it: ‘Oh, sorry!’” It’s an easy mistake to make. With precision molding, hand-painted veins, and real human hairs, the limbs scattered around Sophie’s studio look uncannily real: legs on the verge of dancing and hands ready to burst into applause. With these prostheses, Sophie enables her customers to conceal their absences and blend in. But the artist also caters to another kind of clientele: amputees wanting to stand out. She works with these clients to imagine the missing parts of their bodies as fantastical works of art: an arm housing a motorized coiling snake, a jewel-studded leg with embedded stereo, a bird-wing arm with a metal hook for a talon. “Instead of seeing what’s missing,” she remarked, “you see what’s there.”
** Roc Morin, “The Art of Designer Artificial Limbs”, The Atlantic, (January 15, 2014)
* Q: Do the clients always know what they want?
   * Some of them have definite ideas of what they want. A lot of the men want to look like some kind of superhero—loads of Iron Man requests. Other people don’t know what they want at all and need you to help them pull the information out. That’s really good fun. I usually tell them to go on the Internet and just search for images that speak to them and save them in a folder. When they’ve got, say a hundred images, we’ll be able to see a pattern as to what they’re interested in—whether it’s color or composition or materials or an atmosphere—there’ll be something, and then you’ll talk that through together.
   * Roc Morin, “The Art of Designer Artificial Limbs”, The Atlantic, (January 15, 2014)
* Q: Being so focused on other people’s limbs all the time, I wonder, what’s your relationship with your own limbs like?
   * Well, it’s interesting, I feel differently about them than I did when I was younger. With my feet for example, since I started making limbs, I really like them from an artistic perspective. I’ve got loads of little thread veins. I get really excited if an older person comes in for a realistic limb, because it just means more detail. There’s more personality there. Of course, not everybody feels that way. I had a woman come over the other day to watch me sculpt a leg for her. Originally, all she wanted was a match of her existing leg, but when I gave her the opportunity for feedback, she said “I don’t want the yellow on the toenails, and maybe not so many veins.” And it’s like, “Hold on a minute, it’s not going to look anything like the other one!”
   * Roc Morin, “The Art of Designer Artificial Limbs”, The Atlantic, (January 15, 2014)
* [H]uge number of casualties in the American Civil War caused demand for artificial limbs to skyrocket. Many veterans turned to designing their own prosthetics as a response to the limiting capabilities of the limbs on offer.
** William Park, “The geniuses who invented prosthetic limbs”, BBC, (November 2, 2015)
* For the first time, artificial limbs were being mass-produced in response to the enormous number of casualties in World War One. In the US, the Walter Reed Army Hospital produced a large number of artificial limbs for the returning veterans. This example is of a welding attachment and other tools integrated into the limbs for amputees to return to work after the war. It wasn’t all work, however. Also in the collection of the National Museum of Health and Medicine, USA, is an attachment for playing baseball. The Walter Reed Army Hospital is still a centre for artificial limb production in the US, 100 years later. The technology continued to develop after WW1. DW Dorrance invented the split hook artificial hand shortly before World War I. It became popular with labourers after the war who were able to return to work using the attachment because of its ability to grip and manipulate objects. It’s one of the few designs that have remained relatively unchanged over the past century. Dorrance demonstrated its multi-functionality in the 1930s by driving a car using the arm. In the UK, Queen Mary’s Hospital, Roehampton, became a centre for manufacturing artificial limbs in the World War Two. It opened in 1939. In its first year, 10,987 war pensioners attended the centre, with an additional 16,251 limbs being sent by post. At the outbreak of war, the factory was expanded because of the realisation that 40,000 UK servicemen had lost limbs in WW1. However in WW2 there was around half the number of amputees. As Leon Gillis, QMH Consultant Surgeon from 1943-1967, observed, advances in surgical techniques, treatment of infections and the availability of blood transfusion after WW1 all reduced the need for amputation.
** William Park, “The geniuses who invented prosthetic limbs”, BBC, (November 2, 2015)
* At a lab at Johns Hopkins University, researchers are building a prosthetic hand unlike any other: It can sense pain. It’s easy to understand why you might want a prosthesis that can feel the squishiness of a grape or the warmth of another person’s hand. But pain? Well, pain could be useful, too. “If you think about how we humans use pain, it’s to protect our bodies, to prevent damage,” says Luke Osborn, a graduate student in Nitish Thakor’s lab at Hopkins, who co-authored a new paper on the pain-sensitive hand. People born without the ability to feel pain stumble through life with dangerous freedom. Babies who do not feel pain are known to chew their fingers raw; children without pain will plunge their hands into boiling water. Pain is a signal that says, Hey, watch out. “People do damage their prosthetic limbs a lot. They use them as tools they weren’t designed to be used as,” says Levi Hargrove, a bioengineer at the Shirley Ryan AbilityLab, who was not involved in the study. It’s easy, for example, to bang an unfeeling piece of plastic and metal against a table. Pain could make a prosthesis feel more real, more lifelike—less a tool and more like a natural part of the body.
** Sarah Zhang, “Why Would You Want a Prosthetic Hand That Feels Pain?”, The Atlantic, (June 20, 2018).

## Kevin J Zuo and Jaret L Olson, “The evolution of functional hand replacement: From iron prostheses to hand transplantation”, Plast Surg (Oakv). 2014 Spring; 22(1): 44–51.

* The concept of an ‘automatic’ body-powered upper limb prosthesis was pioneered by German dentist Peter Baliff in 1818. Using transmission of tension through leather straps, Baliff’s device enabled the intact muscles of the trunk and shoulder girdle to elicit motion in a terminal device attached to the amputation stump. For the first time, an amputee was able to operate his prosthesis with fluid body motions, rather than as a distinct foreign object. In the 1860s, the Comte de Beaufort in France adapted the design for use by wounded soldiers. A shoulder harness with a strap buttoned to the trousers was passed through a loop to the contralateral axilla and missing limb, allowing an amputee to manipulate the strap tension to open and close a double spring hook, or flex and extend the thumb on a simple hand with fused fingers. In 1916, German surgeon Dr Ferdinand Sauerbruch described his prosthetic design with digits controlled by transmission of upper arm muscle movements. Video captures from the era show amputees effectively using the prosthesis to drink from a teacup and even to remove a match from a box to light a cigarette. Unfortunately, due to the high cost of production, few individuals were able to afford the device.
* World War I (1914 to 1918) resulted in casualties in numbers previously unimagined. In the United States (US), amputee rehabilitation programs were created to help the >4400 amputees, of which the majority (54%) were upper limb, to regain some ability to work on farms or in factories. The distribution of prosthetics with sockets and a universal terminal device allowed the attachment of various work tools. In 1917, the Surgeon General of the US Army is-sued a landmark invitation for limb makers to meet in Washington, DC. The result was the creation of the Association of Limb Manufacturers of America, today the American Orthotic & Prosthetic Association. In Canada, a national charter in 1920 recognized the need to provide support to amputees, leading to the creation of the Amputations Association of The Great War, today known as the War Amps.
* During World War II (1939 to 1945), improved shock management and antibiotics saved lives but resulted in 3475 upper limb amputees in the US (9). The huge demand for artificial limbs led to the creation of a US Committee on Prosthetics Research and Development in 1945 and the Canadian Association of Prosthetics and Orthotics in 1955. The thalidomide tragedy (1958 to 1962) resulted in the birth of many children with shortened limbs, further driving demand and investment for improved prosthetics. In 1948, the Bowden cable body-powered prosthesis was introduced, replacing bulky straps with a sleek, sturdy cable. Despite new materials and improved craftsmanship, today’s body-powered prostheses are essentially adaptations of the Bowden design. Durable, portable and relatively affordable, body-powered prostheses allow the user an impressive range of motion, speed and force in operating a terminal device – most commonly a two-pronged hook – by changing the tension in a cable via preserved shoulder and body movements. The ability to use both hands simultaneously, rather than requiring a healthy hand to control the prosthesis, permits the user to complete tasks more efficiently. Furthermore, by sensing cable tension, the amputee is able to predict and adjust the position of the prosthesis without visual feedback. Although prolonged wearing can be uncomfortable, complicated motor tasks are limited and appearance is not human-like, body-powered prostheses are widely used
* In 1919, a German book titled Ersatzglieder und Arbeitshilfen (Limb Substitutes and Work Aids) contained conceptual designs for the first externally powered prostheses, using pneumatic and electric power sources. Unfortunately, these revolutionary designs were too complex to be feasible with contemporary technology.
* In 1948, Reinhold Reiter, a physics student at Munich University (Munich, Germany), created the first myoelectric prosthesis, a device that amplifies surface electromyography (EMG) potentials to power motorized parts. Although Reiter published his work, it was not widely appreciated, and this potentially ground-breaking invention did not gain commercial or clinical acceptance.

## See also

* Sculpture
* Cybernetics