PROSTHETICS

In a narrow sense, prosthetics is a branch of medicine, specifically of surgery, concerned with the replacement of missing body parts (upper and lower limbs, and parts thereof) after amputation. It is related to orthotics, a branch of medicine that deals with the support of weak or ineffective joints or muscles using supportive braces and splints. In dentistry, prosthetics or prosthodontics is that branch concerned with the replacement of missing teeth and other oral structures. In this narrow sense, a prosthesis is a replacement artificial limb or tooth. In a broader sense, prosthesis is the name for any artifact used to restore bodily functions, and prosthetics is the field concerned with the development and fitting of artificial body parts, which is the sense at issue here.

Approaches to Prosthetics

Prostheses in this broad sense are an important focus of the relatively new field of bioengineering, or biomedical engineering, which is concerned with the application of engineering techniques to medicine and the biomedical sciences. Bioengineering is itself a broad field, with applications ranging from molecular imaging tools to medical radiation devices. The development of prosthetic techniques and devices is only one of its interests.

Several areas in bioengineering have special relevance to prosthetics. Rehabilitation engineering is an area concerned with ameliorating the impairments of individuals with disabilities. It includes prosthetics and orthotics as defined at the beginning of this entry, but also addresses other disabilities, specifically sensory and speech impairments. It does not address functional impairments in internal organs, however. Other relevant areas include tissue engineering, which involves the repair or replacement of organic cells, tissues, or organs with laboratory-grown biological substitutes; biomaterials engineering, which aims to develop synthetic or natural materials that can replace or augment tissues, organs, or bodily functions; biomechanics, which studies the human musculoskeletal system and its mechanical aspects and includes artificial limb and joint design; cardiovascular engineering, which studies the cardiovascular and blood system and develops techniques and systems for diagnosis, intervention, therapy, and replacement; and neural engineering, which studies the nervous system and develops means to repair or replace damaged and non-functioning nerves and sensory systems. Neuroprosthetics is a rapidly growing subfield of neural engineering that aims to develop devices or systems that communicate with nerves to restore functionality of the nervous system.

Although research in prosthetics and bioengineering is primarily aimed at restoring damaged human functions, there has been a growing interest in the augmentation of human functions. Human augmentation or enhancement is a relatively new field in bioengineering directed at developing prosthetic devices that augment normal function or prevent injury to function.

Together with artificial intelligence and robotics, bioengineering is the successor of bionics (a conflation of biological electronics), which emerged in the 1950s with the aim of using biological design principles to create novel technological devices and mechanical substitutes for the extension of biological organs. Bionics is specifically concerned with the development of bionic devices or bionic implants, which are electromechanical devices that do not merely replace a body part but also closely mimic or surpass the behavior of a replaced organ, and that are often able to communicate with the nervous system. To attain its aims, bionics relied on a feedback-control framework that was provided by cybernetics, the science of communication and control in animal and machine. Cybernetics has been partially superseded by systems theory, a field that studies the general principles underlying the organization of systems of any kind. Cybernetics has yielded the term cyborg, a conflation of cybernetic organism, meaning an organism that is part human, part machine. A cyborg is an individual whose biological functions are aided or controlled by technological devices, particularly by bionic implants.

A large number of human biological functions can be restored or improved with the aid of prostheses. The list of implants and related devices is extensive:

• artificial limbs, including robotic ones and ones with sensory feedback to the body
• artificial joints, hips, and vertebrae
• artificial muscles made of polymer
• artificial skin used to promote healing
• artificial bone used to help heal fractures and replace diseased bone
• bracing systems, cervical implants, and spinal cages to support the spine
• silicone or plastic implants to build bony structures of the face
• breast implants
• penile implants
• dental implants and false teeth
• speech synthesizers and artificial larynxes to restore speech
• retinal implants (experimental), intraocular lenses, and artificial corneas to restore vision
• cochlear implants that replace the inner ear and involve a microphone, speech processor, and wiring to the nervous system
• artificial nerves (experimental)
• cardiac pacemakers, defibrillators, artificial heart valves, and heart-assist pumps
• artificial hearts (experimental)
• artificial blood vessels and urological systems
• artificial blood (experimental)
• implanted drug-delivery systems (experimental)
• electrodes implanted in the brain to control seizures or tremor
• implanted chips to locate persons or to regulate devices in "intelligent environments"
• orgasmatrons (implants for women that produce orgasms; experimental)
• spinal neuroimplants with handheld remote control to block pain signals
• motor neural prostheses based on functional electrical stimulation systems, which stimulate motor nerves for movement, respiration, and bladder function
• artificial hippocampi in the brain (experimental)

Research is underway on bioartificial livers, kidneys, pancreases, lungs, and other organs, as well as on more advanced neural prostheses to restore functions of the brain and nervous system.

Anthropological Theories

Most philosophical and anthropological theories that refer to the notion of prosthesis are not so much concerned with understanding prosthetic technologies as normally defined but with an understanding of technology in general by means of the concept of prosthesis. Prosthesis is used as a metaphor to understand technology and its relation to human beings. In prosthetic theories of technology, which have been proposed since at least the late nineteenth century by a variety of different authors, it is claimed that there is no essential distinction between prosthetic and other technologies, because all technologies in some way aim to replace or augment aspects of human functioning. This view has been proposed by, among others, Marshall McLuhan (1911–1980), Henri Bergson (1859–1941), Arnold Gehlen (1904–1976), Ernst Kapp (1808–1896), and Lewis Mumford (1895–1990).

According to the prosthetic view of technology, every technological artifact or system extends the human organism in that it takes human faculties outside the body, thus amplifying already present abilities. The body is itself a toolbox that its owner uses to do things in the world. Technical artifacts serve to replace, extend, or augment tools in this organic toolbox. Weapons and tools such as bows, knives, and saws are extensions of human hands, nails, and teeth; clothing extends the heat control and protection functions of the skin; the wheel extends the mobility functions of the legs; bags extend the ability of the hands and arms to carry things; the radio and telephone extend hearing; television and photography extend the visual function; writing and print media extend human language and memory functions; and the computer extends a large variety of human cognitive functions. Prosthesis, in the narrow sense, is therefore only an instance of the general ability of technology to extend or replace functions of the human organism, and all technologies should be understood in terms of their relation to human functioning.

Even if this view is correct, it is recognized by many authors that all artifacts do not extend the human organism in the same way. Some technological artifacts have a symbiotic relation to the body, whereas others function independently. A relevant distinction seems to exist between artifacts that serve as direct extensions of human functioning by engaging in a symbiotic relationship with human limbs, senses, or other body parts, such as telescopes, glasses, hammers, and canes, and those artifacts that operate separately from the body and are themselves the object of interaction or perception, such as dinner plates, stereo systems, and computer screens. Phenomenologist Don Ihde (1990), drawing on the work of Maurice Merleau-Ponty (1908–1961), argues that humans are able to engage in embodiment relations with some artifacts, which are incorporated into the body schema or body image, meaning that they are integrated with the image that human beings have of their own sensorimotor abilities—an image that defines them as agents and separates them from a world that is to be engaged. (Other artifacts remain separate and subject to interpretative or hermeneutic relations.) Embodiment relations have found support in psychological studies of body schemas.

Cyborg Theories

Cyborg theory or cyborgology—the multidisciplinary study of cyborgs and their representation in popular culture—provides another perspective on prosthetics. Studies in cyborg theory tend to use the notion of the cyborg as a metaphor to understand aspects of contemporary—late modern or postmodern—relationships of technology to society, as well as to the human body and the self. In cyborg theory, the notion of cyborg refers to hybrid organisms in science fiction (e.g., The Six Million Dollar Man, RoboCop, X-Men, Star Trek's The Borg), contemporary human beings with prostheses or implants, as well as (contemporary) human beings in general, who are all conceived as cyborgs in the sense of being inherently dependent on technology.

The advance of cyborg theory as an area of academic interest has been credited to Donna Haraway, in particular to her 1985 "Manifesto for Cyborgs." In this essay, Haraway presents the cyborg as a hybrid organism that disrupts essentialist presuppositions of modern thinking, with its black-and-white dichotomies of nature–culture, human–animal, organism–technology, man–woman, physical–nonphysical, and fact–fiction. Cyborgs have no preexisting nature or stable identity, and cut through oppositions because of their thoroughly hybrid character. Haraway holds that modernity is characterized by essentialism and binary ways of thinking that have the political effect of trapping beings into supposedly fixed identities and oppressing those beings (animals, women, blacks, etc.) who are on the wrong, inferior side of a binary opposition. She argues that the hybridization of humans and human societies, through the notion of the cyborg, can free those who are oppressed by blurring boundaries and constructing hybrid identities that are less vulnerable to the trappings of modernistic thinking.

According to Haraway and other authors such as N. Katherine Hayles (1999) and Chris Hables Gray (1995), this hybridization is already occurring on a large scale. Such hybridization is a consequence of the transition since World War II from an industrial to an information society, as a result of technological advances in biotechnology, information technology, and cybernetics. In the new world order that is ensuing, boundaries are constantly blurring, and linguistic categories and symbols increasingly reflect this fact. Many basic concepts, such as those of human nature, the body, consciousness, and reality, are shifting and taking on hybrid, informationalized meanings. In this postmodern, post-human age, power relations morph, and new forms of freedom and resistance are made possible.

Sharing the positive outlook of cyborg theorists on the technological transformation of human nature, but otherwise quite distinct from it both politically and philosophically, transhumanism is a recent school of thought or movement that advocates the progressive transformation of the human condition through technological means. Its early inspirational source was FM-2030 (formerly, F. M. Esfandiary) (1989), a futurist who wrote on the notion of the transhuman in the 1970s and 1980s, while its current main organizing body is the World Transhumanist Association, cofounded in 1998 by Nick Bostrom and David Pearce. Transhumanists want to move beyond humanism, which they commend for many of its values, such as its orientation toward reason and science, its commitment to and belief in progress, and its rejection of faith and worship, but which they fault for a belief in some fixed human nature. Transhumanists want to use modern technology to alter human nature in order to augment human bodily and cognitive abilities and extend human life. They see converging developments in genetic engineering, biomedical engineering, artificial intelligence, nanotechnology, and cognitive science as transcending human nature, thus leading humanity to a transhuman or posthuman condition. They argue that this development should receive full support, because of its potential to enhance human autonomy and happiness and eliminate suffering and pain, and possibly even death.

Ethical Issues

The research, development, application, and use of prostheses and implants raise a number of ethical issues relating to health and safety, distributive justice, identity, privacy, autonomy, and accountability. Special ethical issues are raised by human augmentation or enhancement research.

HEALTH AND SAFETY. The functioning of a prosthesis for the remainder of someone's life cannot be predicted reliably on the basis of a few clinical trials with human subjects or tests with animals. There is a real risk, therefore, that people will be fitted with prostheses or implants that malfunction, have harmful side effects, or are even rejected by the autoimmune system. Negative experiences with silicone breast implants and artificial hearts have already shown the body's resistance to technological interventions. Ideally, prostheses would be tested over many years, decades even, and involve a large number of human subjects. But such extensive clinical trials and experimental uses are often considered too lengthy and costly and raise ethical issues by making guinea pigs out of human beings. Tests on animals often cannot serve as a substitute, while raising ethical issues of their own.

JUSTICE. The development of increasingly sophisticated prostheses and implants presents issues of distributive justice: Will there be a division between biological haves and have-nots? Will there be a division between those who receive no prosthesis or a low-quality or high-risk one and those who receive the best medical care? Do people have a moral right to a replacement part for a malfunctioning organ, when such parts exist? And will all be able to obtain implants that are attuned to their biological characteristics and lifestyle? In a 2003 incident in the United Kingdom, a black woman with an amputated foot was told that she would have to be fitted with a white prosthetic limb unless she paid an additional £3,000 (U.S.$ 5,500) for a black one. Although this is an obvious instance of discrimination, the situation is not always so clear. Who, for example, should pay the extra costs when a person has mild allergic reactions to a prosthesis and demands a much more expensive version that will not cause such reactions? Do producers have a duty to develop special prostheses for people whose biological features do not fit the norm, and should they be able to charge extra for those?

IDENTITY. Acquiring a prosthesis requires people to come to terms with the fact that a part of their body is artificial, and that they are dependent on a piece of technology for their biological functioning. This may be even more of an issue with bionic and neuroprosthetic implants, which may display or induce behaviors only partially controllable, with which one may thus find it hard to identify. Even more so, cognitive prostheses, which are neuroprostheses that aid cognitive function, may be developed in the future, and these may undermine identity even more directly as they directly interface with the mind. Some critics of prostheses have argued for the integrity of the human body, with all its defects and flaws, and worry that as humans increasingly become cyborgs, the essence of humanity will be lost. Social identity may be at issue as well. A particular controversy has arisen over cochlear implants; deaf advocates have argued that they may place children in between the deaf world and the hearing world, and that they may end up destroying the deaf community with its rich history and culture.

PRIVACY. Privacy issues are at stake when implants process or store information or emit identifying signals that can be registered from a distance. Implantable chips for tracking, already common in pets and livestock, are also being considered for children and adults, and they make it possible to trace individuals over long distances. Sensory and neuroprosthetic devices and prostheses equipped with biosensors process and sometimes store information about people's biological states, behaviors, and perceptions that may be accessed by third parties.

AUTONOMY. Prostheses can clearly enhance individual autonomy by restoring functions, but it has been argued that they can also reduce it. Having a prosthesis means being intrinsically dependent on technology. A prosthesis also creates dependence on others for maintenance, diagnosis, and testing. Bionic and neuroprosthetic implants may not even leave their wearer in complete control of their actions or thoughts.

ACCOUNTABILITY. Bionic and neuroprosthetic implants may raise issues of accountability, because the behavior or cognitive processes of their wearers will be determined in part by the workings of machines. If such individuals cause accidents or make bad decisions, who is to blame: they or their implants?

ETHICAL ASPECTS OF HUMAN AUGMENTATION. The field of human augmentation or enhancement raises a number of special ethical issues in addition to the ones already mentioned. Is it ever morally permissible to destroy or impair healthy human tissue or organs to fit an augmentation, considering that this destruction may be irreversible? Can an employer require an employee to have enhanced functions, or put a premium on the possession of such functions? Human augmentations is still a young field, and questions of this sort have mainly been raised in relation to cosmetic surgery, which can be understood as a special type of human augmentation with the purpose of enhancing aesthetic rather than functional qualities. Specifically, breast implants intended to create bigger breasts—as opposed to restoring breasts after a radical masectomy—have created controversy because they have been argued to be "unnatural" and to involve health and safety risks that cannot be justified by reference to their subjective aesthetic value. If certain augmentations become popular, there is also a risk that they will become accepted as the norm and people without them will be seen as cripples. To an extent, this is already happening with breast implants and other cosmetic surgery in some communities, but it may also happen with prostheses that enhance perceptual, motor or cognitive functions.

A large part of the debate on human augmentation, finally, has focused on military applications, specifically the possibility of creating supersoldiers. But should military research be devoted to the creation of a supersoldier, involving implants, steroids, amphetamines, genetically altered muscles, integrated weaponry, and lightning-fast artificial nerves?

Many parts of the human body can already be replaced by prosthetic devices, and revolutionary developments in bioengineering are rapidly expanding the reach of prosthetics. Biomedical engineers and medical specialists have a special, professional responsibility in dealing with the ethical issues that arise as a result, as they are primarily responsible for the development and fitting of prostheses. Many ethical issues also need to be addressed at the level of legislation and public policy. Special moral concerns are raised in the areas of human augmentation or enhancement and neuroprosthetics.

PHILIP BREY

SEE ALSO Androids;Bioengineering Ethics;Cyborgs;Disability;Posthumanism;Therapy and Enhancement.

BIBLIOGRAPHY

Brey, Philip. (2000). "Technology as Extension of Human Faculties." In Metaphysics, Epistemology, and Technology, ed. Carl Mitcham. London: Elsevier/JAI Press. A study of prosthetic theories of technology from Kapp to McLuhan and beyond.

FM-2030. (1989). Are You a Transhuman? Monitoring and Stimulating Your Personal Rate of Growth in a Rapidly Changing World. New York: Warner Books. Culminative statement of the transhumanist project by this transhumanist pioneer.

Gray, Chris Hables, ed. (1995). The Cyborg Handbook. New York: Routledge. Reader with important papers in cyborg theory as well as some historic papers in cybernetics, with a foreword by Gray.

Hayles, N. Katherine. (1999). How We Became Posthuman: Virtual Bodies in Cybernetics, Literature, and Informatics. Chicago: University of Chicago Press. A broad-ranging study of how cybernetics and computer science have fostered a disembodied, posthuman conception of human beings as information constructs.

Ihde, Don. (1990). Technology and the Lifeworld: From Garden to Earth. Bloomington: Indiana University Press. A phenomenological study of the relation between human beings and technology, including embodiment relations.

Prosthetics

Prosthetics is a branch of surgery that is involved in devising and fabricating a prosthesis for a missing or infirm body part. A prosthesis is an artificial part used to restore some amount of normal body function. The classic example of a prosthesis is a false leg or arm to replace one that has been amputated. A diseased heart valve can be removed and replaced by an artificial one.

Artificial body joints have been designed to replace diseased or impaired ones, especially those that have been damaged by osteoarthritis, the most common form of arthritis causing degeneration of the main body joints.

There are a wide range of prosthetic devices for different parts of the body and for internal and external use. Some prosthetic devices are used to improve a body function such as a hearing aid. Others, such as breast implants used after mastectomies, are mainly designed for cosmetic rather than functional purposes. Another example of a cosmetic prosthesis is a glass eye designed to replace an eye lost in surgery. Hip and knee replacements

are examples of internal joint replacements with artificial parts.

Prosthodontics is a branch of dentistry that provides replacements of teeth and other related supportive dental structures. The two main types of replacements are either partial or complete dentures and crowns and bridges, which are placed over existing teeth.

Orthotics is a branch of medicine, allied to prosthetics, that designs devices, such as braces, to correct or control a bone deformity or other anatomical problem that interferes with the correct performance of a part of the body such as the leg, arm, or wrist.

Arthroplasty is a branch of surgical orthopedics in which artificial joints or parts of joints are used to replace joints in the hip, knee, finger, shoulder, and elbow.

Bionics is a field of science that combines mathematics , electronics , biochemistry , and biophysics with the study of living systems to develop innovations in both general and medical technology. It has been responsible for recent major developments in prosthetics. With the application of bionic principles, new prostheses have allowed amputees and those who are paralyzed to walk with feeling by using electronic neuromuscular stimulation. Microprocessors are able to transmit a voltage charge to muscles triggering a reflex response.

Artificial limbs

Artificial limbs have been used for more than 2,000 years. The earliest known artificial limb was a leg made of metal plates surrounding a wooden core. It was not, however, until the World War II that the major developments in artificial limbs occurred. In this period, much progress was made by surgeons and prosthetic makers to help wounded soldiers adjust to civilian life with the help of newly designed and effective prostheses.

War has been the greatest impetus for advances in prosthetic design. For centuries, amputation was the most common therapy for traumatic injuries to a soldier's extremities. But until the middle of the nineteenth century, most patients died of infection due to the unsanitary surgical techniques of the time, leaving little room for advances in prosthetic technology for the survivors. Amputated hands were often replaced by simple hooks, and amputated legs by wooden pegs topped with open saddle-like sockets. Since the second world war, improvements in low-weight, high-strength materials and techniques for fitting and shaping artificial limbs have made these types of prosthesis much more useful and comfortable for the patients.

Candidates for artificial limbs to replace legs, feet, arms, and hands are those who have either lost the limb as a result of surgical amputation or were born with an impaired or missing limb. The process of preparing a patient for an artificial limb begins with the amputation. The amputating surgeon considers the best design for the stump or remaining part of the limb. After the wound has healed, a prosthetist chooses an artificial limb or prosthesis that will either have to be a weight-bearing replacement, or an arm and hand prosthesis that will have to manage a number of different movements.

There are several criteria of acceptability for limb prostheses. They must be able to approximate the function of the lost limb. They should be light, comfortable to wear, and easy to put on and take off. Substitute limbs should also have a natural appearance.

Pre-constructed artificial limbs are available for ready use. Going to a prosthetist, one who specializes in constructing and fitting artificial limbs, gives better results in adjusting the prosthesis to the individual's requirements. Recent technological developments have enabled prosthetists to add to artificial joints made from plastic, carbon fiber, or other materials that enable the wearer to include a variety of motions to the limb prosthesis. These motions include rotation around the joint and counter pressures that stabilize a weight bearing joint, like the knee, or they may even be able to control the length of the stride of an artificial leg.

The prosthetist first makes a mold from the stump of the missing limb. This mold forms the basis for the artificial limb and holds the top of the prosthesis comfortably on the stump. The socket can be constructed from various materials, such as leather, plastic, or wood and is attached to the stump by a variety of means. The leg prosthesis socket in which the residual limb fits is aligned with the feet, ankles, and knees for each individual. Improvements have been made in foot design to make them more responsive and in designing comfortable and flexible sockets. Materials such as carbon graphite, titanium , and flexible thermoplastics have permitted great advances in leg prostheses. Applications of electronic technology allows for a wider range of sensory feedback and control of artificial knee swing and stance.

Extending from the socket is the strut, which is the artificial replacement of the thigh, lower leg, upper arm, or forearm. Different types of material can go into the making of the strut. The strut is covered by foam rubber pressed into the shape of the limb it is replacing. The outer covering for the finished prosthesis can be made from different types of materials, such as wood, leather, or metal.

The aerospace industry has provided materials and electronic technology for developing prosthetic devices that can approximate movements of the muscles. Hand and arm replacements are usually operated by voluntary muscle control from the opposite shoulder through cables that connect from the shoulder harness to the artificial hand or hook, called the terminal device. Arm prostheses may also be operated by myoelectric control. (Myo means muscle.) The electrochemical activity of key arm muscles is received by electrodes in the prosthesis and is then transmitted to a motor that operates the prosthesis. Although this branch of prosthetics is still in its infancy, there is great hope that electronic controls will result in much more articulate hand movement, and will eventually replace cables that can simply open or close a hook or artificial hand.

Ironically, progress in prosthetic technology has been slowed by advanced surgical techniques, which have made amputation as a result of traumatic injury much more rare. Orthopedic surgeons can now repair limbs that would have once been routinely amputated. Severed limbs can even be re-attached in many cases.

Effectiveness

Artificial legs are usually more effective than artificial arms or hands in duplicating the motions of the natural limb. The broad and straight movements of the legs are easier to duplicate than the more intricate and quicker actions of the arms and hands. To compensate for these difficulties, artificial hands and arms with advanced designs that include electronic circuitry allow for a wider range of motion and use. Nerve impulses reaching the stump are transformed to appropriate movements of the prosthesis. Individuals using specialized hand and arm prostheses may have several different ones for different occasions. One could be a glove for social use while another for work might be shaped like a claw or have several different power attachments.

Arthroplasty

Replacing all or part of diseased or degenerated joints through the use of prosthetic joint parts provides the basis for a form of orthopedic surgery known as arthroplasty. Hip replacements were the first arthroplasty operations. They are still being performed with a high rate of success. Other routine joint replacement operations now also include knee joint replacement, finger joint replacement, and the replacement of the shoulder and elbow.

Hip replacement

Hip replacement surgery goes back to the 1930s. By the 1960s three substantial improvements in hip surgery made this procedure both popular and successful. The materials used for the hip prostheses were made from metals and plastics that were strong enough to support the weight brought on the hip and were also self-lubricating. Cements were developed to adhere well to the bone. Extremely antiseptic operating rooms and clothes worn by the operating personnel reduce the danger of infection that accompanies a hip replacement operation.

The hip is the joint between the pelvis and upper end of the femur (thigh bone). It is an example of a ball-and-socket-joint that is subject to several major disorders. The most common disorder is osteoarthritis. Pain and stiffness accompany the movements of the hip. Other types of arthritic disorders can cause similar malfunction. Fracture of the hip often occurs with the elderly, who may be prone to falls. In the case of extreme trauma there may be a dislocation of the hip, which is rare but may occur in such mishaps as an automobile accident.

Hip replacements are surgical procedures in which either part or all of the hip joint is replaced with artificial parts. In the operation, the hip joint is exposed from around the surrounding fat and muscle tissue . The thigh bone (femur) and pelvis is prepared to accept the two component parts for the replacement to the natural hip joint. The components consist of a metal shaft and ball as one unit replacing the shaft of the thigh bone with its natural ball and a socket that is made either from metal or plastic. The new socket receives the shaft and ball after it is cemented into the pelvis. These parts are bound into place by a special cement into the surrounding bone. After the new ball is attached to the socket, the muscles and tendons are stitched back into place and the incision is closed.

Recently, a robot has been devised that can drill a hole in the femur much more accurately than a surgeon can. The robot's precise hole can hold the prosthesis much better, thus extending the life of the hip replacement. A surgeon can be as much as 30% off in his drilling. When that happens, only twenty percent of the implant comes in contact with the bone, leaving wide gaps around the prosthesis. Use of the surgical robot brings 96% percent of the implant in contact with the bone and gaps were reduced from 0.15-0.02 in (4.0-0.5 mm). This technology is still in an early state of development.

Recovery

It takes about a week for the cement to become fixed. In that time the patient is expected not to engage in movements that would dislocate the new joint. They are given special advice on how to sleep (on their backs) and told not to cross their legs. Care must be exerted during this period in conducting such movements as getting in and out of a bathtub. Recent research indicates that when the candidates for hip replacement surgery perform the rehabilitation exercise before the surgery the rate of recovery time is significantly reduced.

While hip joint replacements have proven to be very successful there is a problem of the cement loosening after an extended period of time. Research is being done for designs that do not rely as much on the use of cements. Hip replacements are usually not advised for those under 50 because of the unknown long-term effects, especially with the use of cement. Younger patients, however, are now considering cementless artificial hips as an alternative to the conventional procedures that do use cement. The newer technique that does not use cement takes longer, but some orthopedists believe the procedure offers better long-term results.

These newer types of hip replacements are of special interest to athletes in need of relief from hip pain. Athlete Bo Jackson returned to play with the Chicago White Sox after an operation that replaced his left hip.

Knee joint replacement

Large hinges were used in early examples of knee joint replacements. Operations for knee joint replacement, today, are implants within the joint using metal and plastic parts used to cover the worn parts of cartilage in the joint. The objective is to save as much of the joint as possible. This procedure is used mostly for elderly patients suffering from osteoarthritis or rheumatoid arthritis. Younger people are usually not advised to have a knee prosthesis because it reduces the range of movement for the knee and usually will not withstand the strains of vigorous use.

In the operation to install the knee prosthesis the flat undersurfaces of the knee joint are exposed. The lower end of the femur (thigh bone) is smoothed down to accept the prosthesis and then holes are drilled to fasten it. Likewise, the upper end of the tibia (leg bone) is prepared and the back part of the patella (knee cap) is prepared to accept the patellar component of the prosthesis. The parts are then cemented and tested to see if the joint movements are proper. The knee prosthesis consists of the femoral component and the tibial component along with the patella component.

The main purpose of the knee joint replacement procedure is to reduce pain and to restore some movement to the joint. The outcome of the operation lacks certainty and the duration of the prosthesis is limited. Research continues to find better cements and materials for the joints as well as designs that come closer to the actual joint.

Wrist and finger implants

The wrist is a complex joint consisting of eight bones and lies between the lower forearm and the hand. In the United States there are about 2,000 wrist implants and 7,000 hand and finger implants each year. There have been studies that indicate these implants may have damaging effects since they use silicone materials to replace damaged bone. The silicone particles may travel to nearby tissues, causing an immune response that ultimately damages surrounding bone. Many patients require additional surgery as a result. Some physicians maintain that the implants can cause more damage to the healthy bone than the harm done by the disease itself. So far the FDA has not decided to investigate these implants.

Breast implants

Due to the prevalence of breast cancer in women, which necessitates the removal of one or more breasts, breast reconstruction surgery is a common procedure. This involves the implantation of a sac filled with silicone gel or saline. Breast augmentation is also practiced as a purely cosmetic procedure by women who wish to enlarge their breasts.

The use of silicone in this procedure has become controversial. Silicone is a polymer , that is, a silicon compound united with organic compounds. While silicone rubbers have been used for many years, in 1992 the FDA asked that the use of silicone for breast implants in cosmetic surgery be suspended in order to have time to study the complaints against silicone. There have been reports of autoimmune reactions caused by implanted silicone. Some cases showed permanent sores and lumps arising after the implant. There was also a fear expressed by researchers of the possibility that silicone might migrate to the lungs, causing death. Although subsequent testing cast doubt on the actual negative side effects of silicone implants, they have been replaced in most cases by implants using saline solution .

Implanted prosthetic materials

Heart valve implants and plastic surgery for the face or in smoothing wrinkles employ the use of silicone materials as well. The FDA continues to study other high-risk medical prostheses. These include inflatable penile implants, testicular implants, heart-bypass pumps, cranial stimulators, and saline-filled breast implants.

Heart transplants

Heart disease is one of the most common killers of middle-aged men and women. Artificial heart valves are now commonly transplanted into living hearts to replace malfunctioning valves. However, this procedure only treats one type of heart malfunction. Many types of artificial heart have been tested, with the hope of replacing the entire organ with an electro-mechanical substitute. This technique attracted a great deal of publicity in the early 1980's, when a few patients received permanent mechanical replacement hearts. Unfortunately, these patients lived only a short time after receiving the transplants. Though research continues into smaller, more reliable devices that do not trigger rejection from the body's auto-immune system, they are still considered temporary expedients that allow a patient to remain alive until a suitable human heart is available for transplantation. Even then, artificial hearts and Vascular Aid Devices (VAD) are used in only the more desperate cases, since infection and rejection can cause further damage, which would reduce the chances of a successful human heart transplant, causing the patient to be removed from the transplant list.

Bionics

The field of prosthetics has received a major impetus from the development of bionics. In bionics, engineering problems are solved by studying the properties of biological systems. For example, studying the swimming movements of fish and the flight of birds give the bionics engineer clues on how to solve problems in jet and rocket propulsion. Problems of conservation of energy in engineering are studied in relation to other biological examples.

Bionics is an outgrowth of the field of study known as cybernetics . The concern of cybernetics is to relate the way machines communicate, are controlled, and acquire information to similar processes in life systems. Bionics, like cybernetics, depends on the understanding of physiology , biochemistry, and both the physical and mechanical properties of living things. The bionic scientist must be prepared to apply mathematics, physics , and electronic engineering for the formulations of the interfaces between living and mechanical systems.

Bionics grew out of a concept known as the general-systems theory. Nicholas Rashevsky, a Russian-American scientist, was the first to develop a correlation between the workings of the central nervous system and mathematical models. After his initial studies, other physicists and engineers entered the field of bionics. They have studied the way in which visual images are established within biological visual systems. From these investigations technologically advanced cameras, television , and optical-recognition systems have emerged. Those who studied biological auditory systems were able to devise major improvements in radio transmitters and receivers.

Along with all of its other applications, bionics has been a major force in the development of prosthetics. The field of artificial organ transplantation owes its development to bionics. Artificial limbs—arms and legs—can now be electronically controlled by an electronic process that recognizes various patterns of electrical movement. Complicated movements of the prosthesis can be brought about by microcircuits that detect the patterns of electrical impulses within the tissue of the surrounding muscle as it is expressed on the outer skin. Electronic motors then carry the prosthesis to its task.

Other prosthetic devices employing bionic principles allow some of the blind to regain a sense of sight by transmitting nerve impulses around the damaged neural pathways to ones that are still capable of transmitting signals. Hearing aids are another example of prosthetic devices that have benefited from bionic research.

Resources

books

Delisa, Joel A., et al. Rehabilitation Medicine. Philadelphia: Lippincott, 1993.

Sanders, Gloria T. Amputation Prosthetics. F.A. Davis Company, Philadelphia, PA., 1986.

Wilson, A. Bennet, Jr. "History of Amputation Surgery and Prosthetics." Atlas of Limb Prosthetics: Surgery and Prosthetic Principles. Americal Academy of Orthopedic Surgeons, C.V. Mosby Company, St. Louis, MO., 1981

periodicals

Jones, Stella. "Making Artificial Organs Work." TechnologyReview 97 (September 1994): 32-41.

Padula, Patricia A., and Lawrence W. Friedmann. "Acquired Amputation and Prostheses Before the Sixteenth Century." The Journal of Vascular Disease (February 1987).

Randall, Teri. "Silicone Implants for Hand and Wrist." TheJournal of the American Medical Association 268. (July 1, 1992): 13-16.

Romm, Sharon. "Arms by Design: From Antiquity to the Renaissance." Plastic and Reconstructive Surgery (July 1988).

Sterling, Bruce. "The Artificial Body." The Magazine of Fantasy and Science Fiction (October-November 1994): 138-147

Jordan P. Richman

KEY TERMS

Autoimmune reactions

—The use of certain substances in prosthetic devices may trigger the production of antibodies from the immune system causing adverse effects.

Ball and socket joint

—A type of joint that allows the widest range of movement found in the hip and shoulder joint.

Bionics

—A new field of science that combines engineering with biology.

FDA

—The Unites States Federal Drug Administration; oversees and regulates the introduction of new drug products into the medical marketplace.

Femur

—The thigh bone which is the site for the implantation of hip and knee prostheses.

Myoelectric control

—The electrical stimulation of prosthetic devices from the surrounding muscle tissue.

Osteoarthritis

—The most common form of arthritis which is responsible for the degeneration of the cartilage in bone joints.

Silicone

—A controversial substance that has been used in breast and other types of implants. It has moved from a low-risk prosthetic material to a high-risk category by the FDA.

Socket

—The part of a limb prosthesis that fits over the stump of the amputated limb.

Tibia

—The leg bone.

Prosthetics

Artificial limbs

Arthroplasty

Hip replacement

Knee joint replacement

Breast implants

Heart transplants

Bionics

Resources

Prosthetics is a branch of surgery that is involved in devising and making artificial replacements for a missing or damaged body part. Each replacement is called a prosthesis. Put another way, a prosthesis is an artificial part used to restore some amount of normal body function.

The classic example of a prosthesis is a false leg or arm to replace one that has been amputated. Recipients of such a prosthesis can lead a virtually normal life. A diseased heart valve can be removed and replaced by an artificial one, although even in 2006 heart transplant surgery is still a high-risk procedure.

Artificial body joints have been designed to replace diseased or impaired ones, especially those that have been damaged by osteoarthritis, the most common form of arthritis causing degeneration of the main body joints. For example, each year in the United States, then of thousands of people receive artificial hips or knees.

There are a wide range of prosthetic devices for different parts of the body and for internal and external use. Some prosthetic devices are used to improve a body function such as a hearing aid. Others, such as breast implants used after mastectomies, are mainly designed for cosmetic rather than functional purposes. Another example of a cosmetic prosthesis is a glass eye designed to replace an eye lost in surgery. Hip and knee replacements are examples of internal joint replacements with artificial parts.

Prosthodontics is a branch of dentistry that provides replacements of teeth and other related supportive dental structures. The two main types of replacements are either partial or complete dentures and crowns and bridges, which are placed over existing teeth.

Orthotics is a branch of medicine, allied to prosthetics, that designs devices, such as braces, to correct or control a bone deformity or other anatomical problem that interferes with the correct performance of a part of the body such as the leg, arm, or wrist. An orthotic that fits in a shoe can adjust a faulty stride and provide relief to the kness and hips, for example.

Arthroplasty is a branch of surgical orthopedics in which artificial joints or parts of joints are used to replace joints in the hip, knee, finger, shoulder, and elbow.

Bionics is a field of science that combines mathematics, electronics, biochemistry, and biophysics with the study of living systems to develop innovations in

both general and medical technology. It has been responsible for recent major developments in prosthetics. With the application of bionic principles, new prostheses have allowed amputees and those who are paralyzed to walk with feeling by using electronic neuromuscular stimulation. Microprocessors are able to transmit a voltage charge to muscles triggering a reflex response.

Artificial limbs

While modern-day technology has made some prosthetics virtual mimicks of the real thing, the use of prosthetics dates back centuries. Artificial limbs have been used for more than 2,000 years. The earliest known artificial limb was a leg made of metal plates surrounding a wooden core. It was not, however, until the World War II that the major developments in artificial limbs occurred. In this period, much progress was made by surgeons and prosthetic makers to help wounded soldiers adjust to civilian life with the help of newly designed and effective prostheses.

Indeed, war has been the greatest impetus for advances in prosthetic design, since one consequence of warfare is the loss of limbs. For centuries, amputation was the most common therapy for traumatic injuries to a soldier’s extremities. But until the middle of the nineteenth century, most patients died of infection due to unsanitary surgical environment of the time, leaving little room for advances in prosthetic technology for the survivors. Amputated hands were often replaced by hooks, and amputated legs by wooden pegs topped with open saddle like sockets that supported the hip. Since World War II, improvements in low-weight, high-strength materials and techniques for fitting and shaping artificial limbs have made these types of prosthesis much more useful and comfortable for the patients.

The process of preparing a patient for an artificial limb begins with the amputation. The surgeon considers the best design for the stump or remaining part of the limb, and adjusts the surgery to produce the optimum result. After the wound has healed, a prosthetist chooses an artificial limb or prosthesis that will either have to be a weight-bearing replacement, or an arm and hand prosthesis that will have to manage a number of different movements.

There are several criteria of acceptability for limb prostheses. They must be able to approximate the function of the lost limb. They should be light, comfortable to wear, and easy to put on and take off. Substitute limbs should also have a natural appearance.

The prosthetist first makes a mold from the stump of the missing limb. This mold forms the basis for the artificial limb and holds the top of the prosthesis comfortably on the stump. The socket can be constructed from various materials, such as leather, plastic, or wood and is attached to the stump by a variety of means. The leg prosthesis socket in which the residual limb fits is aligned with the feet, ankles, and knees for each individual. Improvements have been made in foot design to make them more responsive and in designing comfortable and flexible sockets. Materials such as carbon graphite, titanium, and flexible thermoplastics have permitted great advances in leg prostheses. Applications of electronic technology allows for a wider range of sensory feedback and control of artificial knee swing and stance.

Extending from the socket is the strut, which is the artificial replacement of the thigh, lower leg, upper

arm, or forearm. Different types of material can go into the making of the strut. The strut is covered by foam rubber pressed into the shape of the limb it is replacing. The outer covering for the finished prosthesis can be made from different types of materials, such as wood, leather, or metal.

The aerospace industry has provided materials and electronic technology for developing prosthetic devices that can approximate movements of the muscles. Hand and arm replacements are usually operated by voluntary muscle control from the opposite shoulder through cables that connect from the shoulder harness to the artificial hand or hook, called the terminal device. Arm prostheses may also be operated by myoelectric control. (Myo means muscle.) The electrochemical activity of key arm muscles is received by electrodes in the prosthesis and is then transmitted to a motor that operates the prosthesis. Although this branch of prosthetics is still in its infancy, there is great hope that electronic controls will result in much more articulate hand movement, and will eventually replace cables that can simply open or close a hook or artificial hand.

Ironically, progress in prosthetic technology has been slowed by advanced surgical techniques, which have made amputation as a result of traumatic injury much more rare. Orthopedic surgeons can now repair limbs that would have once been routinely amputated. Severed limbs can even be re-attached in many cases.

Arthroplasty

Replacing all or part of diseased or degenerated joints through the use of prosthetic joint parts provides the basis for a form of orthopedic surgery known as arthroplasty. Hip replacements were the first arthroplasty operations. They are still being performed with a high rate of success. Other routine joint replacement operations now also include knee joint replacement, finger joint replacement, and the replacement of the shoulder and elbow.

Hip replacement

Hip replacement surgery goes back to the 1930s. By the 1960s three substantial improvements in hip surgery made this procedure both popular and successful. The materials used for the hip prostheses were made from metals and plastics that were strong enough to support the weight brought on the hip and were also self-lubricating. Cements were developed to adhere well to the bone. Extremely antiseptic operating rooms and clothes worn by the operating personnel reduce the danger of infection that accompanies a hip replacement operation.

The hip is the joint between the pelvis and upper end of the femur (thigh bone). It is an example of a ball-and-socket-joint that is subject to several major disorders. The most common disorder is osteoarthritis. Pain and stiffness accompany the movements of the hip. Other types of arthritic disorders can cause similar malfunction. Fracture of the hip often occurs with the elderly, who may be prone to falls. In the case of extreme trauma there may be a dislocation of the hip, which is rare but may occur in such mishaps as an automobile accident.

Hip replacements are surgical procedures in which either part or all of the hip joint is replaced with artificial parts. In the operation, the hip joint is exposed from around the surrounding fat and muscle tissue. The femur and pelvis is prepared to accept the two component parts for the replacement to the natural hip joint. The components consist of a metal shaft and ball as one unit replacing the shaft of the thigh bone with its natural ball and a socket that is made either from metal or plastic. The new socket receives the shaft and ball after it is cemented into the pelvis. These parts are bound into place by a special cement into the surrounding bone. After the new ball is attached to the socket, the muscles and tendons are stitched back into place and the incision is closed.

Knee joint replacement

Large hinges were used in early examples of knee joint replacements. Operations for knee joint replacement, today, are implants within the joint using metal and plastic parts used to cover the worn parts of cartilage in the joint. The objective is to save as much of the joint as possible. This procedure is used mostly for elderly patients suffering from osteoarthritis or rheumatoid arthritis. Younger people are usually not advised to have a knee prosthesis because it reduces the range of movement for the knee and usually will not withstand the strains of vigorous use.

In the operation to install the knee prosthesis the flat undersurfaces of the knee joint are exposed. The lower end of the femur is smoothed down to accept the prosthesis and then holes are drilled to fasten it. Likewise, the upper end of the tibia (leg bone) is prepared and the back part of the patella (knee cap) is prepared to accept the patellar component of the prosthesis. The parts are then cemented and tested to see if the joint movements are proper. The knee prosthesis consists of the femoral component and the tibial component along with the patella component.

The main purpose of the knee joint replacement procedure is to reduce pain and to restore some movement to the joint. The outcome of the operation lacks certainty and the duration of the prosthesis is limited. Research continues to find better cements and materials for the joints as well as designs that come closer to the actual joint.

Breast implants

Due to the prevalence of breast cancer in women, which necessitates the removal of one or more breasts, breast reconstruction surgery is a common procedure. This involves the implantation of a sac filled with silicone gel or saline. Breast augmentation is also practiced as a purely cosmetic procedure by women who wish to enlarge their breasts.

The use of silicone in this procedure has become controversial. Silicone is a polymer, that is, a silicon compound united with organic compounds. While silicone rubbers have been used for many years, in 1992 the FDA asked that the use of silicone for breast implants in cosmetic surgery be suspended in order to have time to study the complaints against silicone. There have been reports of autoimmune reactions caused by implanted silicone. Some cases showed permanent sores and lumps arising after the implant. There was also a fear expressed by researchers of the possibility that silicone might migrate to the lungs, causing death. Although subsequent testing cast doubt on the actual negative side effects of silicone implants, they have been replaced in most cases by implants using saline solution. In 2006, Canadian health regulators once again gave approval for the use of silicone breast implants.

Heart transplants

Heart disease is one of the most common killers of middle-aged men and women. Artificial heart valves are now commonly transplanted into living hearts to replace malfunctioning valves. However, this procedure only treats one type of heart malfunction. Many types of artificial heart have been tested, with the hope of replacing the entire organ with an electro-mechanical substitute. This technique attracted a great deal of publicity in the early 1980’s, when a few patients received permanent mechanical replacement hearts. Unfortunately, these patients lived only a short time after receiving the transplants. Though research continues into smaller, more reliable devices that do not trigger rejection from the body’s auto-immune system, they are still as of 2006 considered temporary expedients that allow a patient to remain alive until a suitable human heart is available for transplantation. Even then, artificial hearts and Vascular Aid Devices (VAD) are used in only the more desperate cases, since infection and rejection can cause further damage, which would reduce the chances of a successful human heart transplant, causing the patient to be removed from the transplant list.

Bionics

The field of prosthetics has received a major impetus from the development of bionics. In bionics, engineering problems are solved by studying the properties of biological systems. For example, studying the swimming movements of fish and the flight of birds give the bionics engineer clues on how to solve problems in jet and rocket propulsion. Problems of conservation of energy in engineering are studied in relation to other biological examples.

KEY TERMS

Autoimmune reactions— The use of certain substances in prosthetic devices may trigger the production of antibodies from the immune system causing adverse effects.

Ball and socket joint— A type of joint that allows the widest range of movement found in the hip and shoulder joint.

Bionics— The combination of engineering and biology.

FDA— The Unites States Federal Drug Administration, which oversees and regulates the introduction of new drug products into the medical marketplace.

Femur— The thigh bone which is the site for the implantation of hip and knee prostheses.

Myoelectric control— The electrical stimulation of prosthetic devices from the surrounding muscle tissue.

Osteoarthritis— The most common form of arthritis which is responsible for the degeneration of the cartilage in bone joints.

Socket— The part of a limb prosthesis that fits over the stump of the amputated limb.

Tibia— The leg bone.

Resources

BOOKS

Lusardi, Michelle M. and Caroline C. Nielson. Orthotics and Prosthetics in Rehabilitation. Burlington. MA: Butterworth-Heinemann, 2006.

Misch, Carl E. Dental Implant Prosthetics. New York: Mosby, 2004.

Shurr, Donald G. and John W. Michael. Prosthetics and Orthotics. 2nd ed. New York: Prentice Hall, 2001.

Jordan P. Richman

Prosthetics

Prosthetics (pronounced prahs-THEH-tiks) is the branch of medicine that deals with the artificial replacement of a missing body part. A prosthesis (pronounced prahs-THEE-sis) is the general term for the artificial part itself that replaces the body part usually lost to disease or injury. Prosthetics has a long history, and recent design advances that use battery power and new lightweight composite materials are making prostheses better and easier to use.

History

Although nothing can ever fully replace any part of our bodies, most people who have suffered the loss of a body part or who were born missing something that everyone else has and needs—like a foot or a hand—would agree that something is usually better than nothing. 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 limb 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.

The known history of prosthetics or designing and making prostheses goes back at least to 300 b.c., from which time we have evidence of crude devices being made to replace a missing lower leg. These consisted of metal plates being hammered over a wooden core, which was then strapped to the stump of the remaining leg. These very early prostheses were usually made by blacksmiths, armor makers, and other artisans who were skilled at using metal, wood, and leather.

One of the earliest written references to prosthetics is found in a book published in France in 1579. That year, French surgeon Ambroise Paré (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 removed 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. Once Paré's work became better known, others tried to follow his lead. German history tells of the Knight of the Iron Hand who had lost his arm in battle, but who was fitted with an artificial arm that had gears and levers that moved his metal fingers. It is said that he became an even fiercer warrior with his new arm. By the 1700s, metal hooks attached by a wooden or leather shell and leather straps were being use to replace missing hands. In the next century, articulated joints or those that could bend began to replace the stiff solid limb.

Wartime advances

Wartime always pushes surgery beyond its limits, and it is not surprising that most of the advances in prosthetics have taken place during wars. The American Civil War (1861–65) was especially gruesome when it came to maiming healthy young men, and over 30,000 amputations were performed on the Union side alone. A manufacturer in New York priced its wooden socket limbs anywhere from $75 to $150. Most of these prostheses differed little from those of a century before, and it was not until the two twentieth-century world wars that any real progress was made in the design and manufacture of artificial limbs.

During and after World War II (1939–45), newer and lighter materials like plastics and aluminum were joined to newly updated mechanical joints, and for the first time, prostheses became more comfortable and easier to use. With postwar research supported by the U.S. Veteran's Administration, mechanical arms were developed whose hook end could open or close with a shrug of the shoulder. Advances were also made in above-knee and below-knee devices for amputees. Following the Vietnam War during the 1960s and 1970s, a new wave of needy amputees spurred further refinements in prosthetics, and by then electronic control was being introduced.

Many types of prostheses

It should be noted that the term prosthetics does not refer only to the replacement of lost arms or legs. In fact, the word prosthesis includes any artificial body part, and therefore includes everything from a set of false teeth to an artificial breast for women who have undergone a mastectomy (pronounced mass-TEK-tuh-mee) or breast removal. However, the fact that the amputee population in the United States alone ranges somewhere between 400,000 and 1,000,000 makes those in need of a limb predominate. This is especially so since nine out often of these amputations involve the leg from the foot to the knee. Further, three-fourths of these amputations are necessitated by disease, usually cancer or a circulation disease associated with diabetes. The remainder are caused by accidents, with a very small percentage being due to birth defects.

Modern advances in design

Given these numbers, it is obvious that there is a real need for new and better prostheses. Fortunately, the beginnings of a major change in design is taking place as composite materials—such as those that combine plastics and carbon fiber—are used more and more. These new materials are much stronger, lighter, and more durable than traditional materials. Silicon-based compounds are used to make artificial arms that are not only softer and more comfortable to wear than the old rigid plastic ones, but are also more real-looking. Often a person can have a mold made of a remaining limb, and a new one is cast to look just like its twin. These new limbs are also adjustable so they can be changed if the person gains weight or increases his or her level of activity. Further, amputees may have shock absorbers in their new knees, which can be made more and more flexible as they become more accustomed to their new leg.

Computers not only assist in the design and manufacture of some of these newer devices, but are being used to revolutionize all manner of prostheses as well. Amazingly, artificial eyes are being researched that will replace a damaged retina and allow certain blind people to see at least basic shapes and movements. Cochlear (pronounced COCK-lee-ur) implants stimulate the auditory nerve with electricity and allow certain deaf people to hear. These do not make sounds louder like hearing aids. Instead, an electrode in the inner ear bypasses the damaged part of the ear and creates a nerve impulse that stimulates the hearing part of the brain.

While some of these devices are astounding in the new or regained capabilities they provide, future systems presently being researched will be truly revolutionary. The goal of today's designers is to build an active device that works very much as our own muscles do. This means that for controlling movement, the ultimate goal is to tap into the nervous system itself and move naturally what are basically artificial muscles. Doing this is very difficult since it means being able to stimulate or detect signals from individual nerve cells. If this type of linkage is ever achieved, humans will be truly melded with a machine.

Besides the difficult problem of connecting with the brain's control system, the other great challenge is providing the power to run these bionic (pronounced by-ON-ik) implants. The energy requirements of any prosthesis are very important, and it appears that for decades to come, batteries of all types will still be used. However, continued battery improvements suggest that future prostheses will use electricity both to power and to control the artificial body part. Today, amputees are able to run races, peddle bicycles, and ski. In England, a man was fitted with the first fully powered electrical shoulder. Continued research and development in prosthetics suggests that life for an amputee will be closer to normal than ever before.

Prosthetics

Definition

Prosthetics is the branch of surgery concerned with the replacement of missing body parts with artificial substitutes.

Description

While prosthetics is defined as a branch of surgery, those involved in this profession include the surgeon, nurse, prosthetist, and physical therapist. Others involved in treatment can include a prosthetics technician, prosthetics assistant, rehabilitation counselor, and social worker.

The goal of prosthetics is to replace all or part of a missing limb so that a patient can function. This replacement can involve fitting a man with an artificial leg so that he can walk, or equipping a woman with an artificial hand so that she can hold objects. An artificial appliance is often called a "prosthetic" or a "prosthesis." Prosthesis can also refer to the replacement of a missing part with a prosthetic.

Historical perspective

The practice of prosthesis dates back to ancient times. During the sixteenth century, a German knight was known as Gotz of the Iron Hand because of his prosthetic. The appliance's movable fingers enabled the knight to hold a sword.

Wood, however, served as the primary material for prosthetics until the twentieth century. In the aftermath of two world wars, research led to the development of prosthetics made of aluminum alloys, metals, and fiber material.

Throughout the centuries, prosthetics were made with mechanical devices and rubber band-type material to allow their wearers to grip objects and move more easily. Movement devices in prosthetics now include hydraulic knees and computer-programmable hands that sense muscle movement.

Legs, arms, feet, and hands are the most commonly known artificial appliances. Other prosthetics include artificial eyes, hip joints, breasts, and heart valves. Prosthodontics is the branch of dentistry concerned with the replacement of teeth.

Contemporary prosthetic care

Patients requiring prosthetic care range from children born with missing limbs to elderly adults requiring hip joint replacement surgery. Trauma such as an automobile accident may cause the loss of a limb, and conditions such as diabetes may lead to the amputation of a limb.

Health care roles

Patients are seen by a prosthetics health care team, which can include a surgeon, nurse, prosthetist, prosthetics technician, prosthetics assistant, and physical therapist.

Prosthetics is sometimes also grouped with orthotics in allied professions. Orthotics is concerned with producing and fitting braces (orthoses) for patients' limbs and spines.

Work settings

Members of the prosthetics health care team work in hospitals, rehabilitation facilities, medical centers, medical schools, colleges, and universities. Prosthetics technicians may work in those settings or in labs and facilities that manufacture prostheses.

The prosthetist designs and fits prostheses. When surgery is planned, the prosthetist consults with the surgeon about where a limb is to be amputated. The prosthetist's input includes recommendations about fitting the prosthesis after surgery.

Pre-operative preparation

For some members of the health care team, patient contact begins before surgery. The doctor examines the patient to determine if more treatment is needed. If amputation is required, those who counsel the patient may include the doctor, nurse, and social worker. They will try to help the patient prepare emotionally and physically for surgery and rehabilitation.

The prosthetics health care team

Prosthetists may supervise several staff members. In some workplaces, the prosthetics assistant assists the prosthetist and may fabricate, repair, and maintain artificial appliances. However, prosthetics may be made by the prosthetics technician, an allied health worker who takes direction from the prosthetist and the prosthetics assistant. The technician also repairs and maintains prostheses. In some settings, the technician may have no contact with patients.

After surgery, the patient may be seen by the surgeon or primary care doctor. During the rehabilitation phase, the prosthetist and therapist will help the patient adjust to the prosthetic. The nurse and social worker may provide patient education and support. If needed, the patient may be referred to a rehabilitation counselor or a vocational counselor.

In addition, the patient will see the prosthetist, prosthetics assistant, or prosthetics technician if the prosthetic needs adjusting.

The early stages of all prosthetic treatment usually involves the prosthetist working with the physical therapist. The therapist can evaluate factors such as the patient's strength and ability to wear a prosthetic.

Education and training

Members of the health care team, such as surgeons, nurses, physical therapists, and social workers, may receive training in the use of prosthetics while studying for their respective professions. Prosthetists earn a four-year bachelor of science degree that includes specialized prosthetic training. They also serve a clinical residency. Programs for prosthetics assistants and technicians range from six months to two years. In addition, people working in these allied health professions can receive certification through the American Academy of Orthotics and Prosthetics. Board certification is based on education, employment, completion of certification of program modules (continuing education courses), and membership in the academy.

Advanced education and training

The name of the American Academy of Orthotics and Prosthetics reflects the relationship between the fields of orthotics and prosthetics. While orthotics usually focuses on temporary treatment with a brace, prosthetics involves permanent replacement of a body part with an artificial appliance. However, some patients require both prosthetics and orthotics, so schools offer degrees and certificates in both disciplines. Allied health professionals with education and experience in both disciplines will be twice as employable as those with degrees or certificates in only one of the professions.

Education is the key to career advancement for an allied health employee with only one specialty. A prosthetics technician can advance to assistant and then prosthetist by completing more classes.

The American Academy of Orthotics and Prosthetics offers continuing education courses and forums so that allied health workers remain knowledgeable about new developments in their professions.

Future outlook

The need for prosthetists, prosthetics assistants, and prosthetics technicians is expected to increase with the aging of the baby boomer generation. The existence of a rapidly growing senior population is a global trend, and prosthetics care should be in increasing demand worldwide. Among the needs for older populations are hip replacement and replacement of limbs amputated because of diabetes and other conditions.

Resources

BOOKS

Lusardi, M. M., and C. C. Nielsen. Orthotics and Prosthetics in Rehabilitation. Butterworth-Heinemann, 2000.

May, Bella. Amputations and Prosthetics: A Case Study Approach. Philadelphia, PA: F. A. Davis Co., 1996.

Wilson, A. Bennett. A Primer on Limb Prosthetics. Springfield, IL: C.C. Thomas, 1998.

ORGANIZATIONS

American Academy of Orthotists and Prosthetists. 526 King Street, Suite 201, Alexandria, VA 22314. (703) 836-0788. 〈http://www.oandp.org〉.

American Board for Certification of Orthotics and Prosthetics. 330 John Carlyle Street, Suite 200, Alexandria, VA 22314. (703) 836-7114. 〈http://www.opoffice.org〉.