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Chapter 1 - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles History of Amputation Surgery and ProstheticsA. Bennett Wilson Jr., B.S.M.E.
No doubt artificial limbs of some type, such as a forked stick, have been used since the beginning of mankind, but the earliest recorded use of a limb prosthesis is that of a Persian soldier, Hegesistratus, who was reported by Herodotus to have escaped about 484 B.C. from stocks by cutting off one of his feet and replacing it with a wooden one. The oldest known artificial limb in existence was a copper-and-wood leg unearthed at Capri, Italy, in 1858, which was supposedly made about 300 B.C. Unfortunately, it was destroyed during a bombing of London in World War II.
Artificial hands made of iron were used by knights in the 15th century. The Alt-Ruppin hand, shown along with other hands from the 15th century in the Stibbert Museum, Florence, Italy, is a good example of the work of that age.
With respect to surgery, Hippocrates described the use of ligatures, but this technique was lost during the Dark Ages. It was reintroduced in 1529 by Ambroise Pare, a French military surgeon. As a result, amputations came to be used more and more as a lifesaving measure since the rate of survival was much higher when ligatures were used.
Morel introduced the tourniquet in 1674, which gave another impetus to amputation surgery. Parecarried out the first elbow disarticulation procedure in 1536. Sir James Syme reported his procedure for amputation at the ankle in 1843.
The introduction of antiseptic technique in 1867 by Lord Lister, a student and son-in-law of Syme, contributed greatly to the overall success of amputation surgery, as did the use of chloroform and ether about the same time.
The concept of kineplasty to power upper-limb prostheses directly by muscle contraction was introduced by Vanghetti in 1898 while trying to improve the function of Italian soldiers who had their hands amputated by the Abyssinians. Vanghetti's associate, Ceci,performed the first operation of this type on humans in 1900. In Germany, Sauerbruch and ten Horn (1916) developed the skin-lined muscle tunnel, and Bosch Arana in Argentina carried out clinical studies of this procedure in the 1920s.
Bier, about 1900, in an effort to make the distal end of the cut bone able to bear weight, recommended an osteoplastic procedure in which the cut end was covered with a flap of cortical bone connected by a periosteal hinge. This procedure never became widespread, but in the late 1940s, Ertl went a step further and developed a procedure for forming a bone bridge between the cut ends of the fibula and tibia. A few years later Mondry combined the bone bridge technique with myodesis, or attachment of the cut muscles to each other over the distal end of the stump. Dederich,Weiss et al., and others adopted and popularized these procedures in some areas.
Each major war seems to have been the stimulus not only for improvement of amputation surgical techniques but also for the development of improved prostheses. Toward the end of World War II, amputees in military hospitals in the United States began voicing their disappointment about the performance afforded by their artificial limbs. To ensure that they received the best care possible, Surgeon General of the Army Norman T. Kirk, an orthopaedic surgeon by training, turned to the National Academy of Sciences (NAS) for advice.
A COORDINATED PROGRAM FOR AMPUTEES
A conference of surgeons, prosthetists, and scientists organized by the NAS early in 1945 revealed that little modern scientific effort had gone into the development of artificial limbs, and a "crash" research program was launched later in 1945 through the NAS. This effort was initially funded by the Office of Scientific Research and Development (OSRD). At the end of the war when the OSRD was disbanded, the Office of the Surgeon General of the Army continued support that was later assumed by the Veterans Administration, which had also inherited the responsibility for the care of military amputees after discharge from the armed services.
For the first 2 years the NAS, through the Committee on Artificial Limbs (CAL), actually initiated and administered the program through subcontracts with several universities and industrial laboratories. On June 30, 1947, the CAL was discharged, and the role of the NAS became an advisory one to the Veterans Administration, which contracted directly with various research groups. In 1947, the Veterans Administration also established its own testing and development laboratory in New York City. The army and navy cooperated and contributed by supporting prosthetics research laboratories within their respective organizations. From July 1, 1947, to Dec 1, 1955, the group within the NAS was known as the Advisory Committee on Artificial Limbs. The Prosthetics Research Board was created to carry out the NAS responsibility from Dec 1, 1955, to June 30, 1959. In July 1959, the Committee on Prosthetics Research and Development (CPRD) and the Committee on Prosthetics Education and Information (later called the Committee on Prosthetics and Orthotics Education [CPOE]), both subgroups of the board, assumed this role until their dissolution by the parent NAS in 1976. The reason for the dissolution of these bodies has never been made completely clear.
The Artificial Limb Program, as it came to be known, was started initially with the idea that physicians and surgeons could provide engineers with design criteria for components such as ankle and knee joints and that good engineering design based on these criteria coupled with modern materials would result in devices that could solve many of the problems of the amputee. Although some progress was made early in the program by this approach, it soon became apparent that fundamental information on how human limbs function was needed before adequate design criteria could be formulated. To provide such information on lower-limb function, a project was established at the University of California, Berkeley, as a joint responsibility of the Engineering School in Berkeley and the Medical School in San Francisco. Eberhart et al., who had collaborated previously in a biomechanical analysis of the shoulder, directed this program, which began by using the latest technology to refine and add to the existing knowledge of human locomotion. A concurrent program was initiated under Taylor in the Engineering School at the University of California at Los Angeles on the function of the upper limbs.
At the same time design and development projects were being carried out at Northrop Aviation, Inc.; Cat-ranis, Inc.; the Army Prosthetics Research Laboratory (APRL); the U.S. Naval Hospital, Mare Island (which later became the Navy Prosthetics Research Laboratory, Oakland Naval Hospital); and a U.S. Army Air Force unit at Wright Field. New York University was engaged in 1947 to evaluate the devices that resulted from the research and development program. The Veterans Administrations laboratory in New York also performed evaluations primarily by means of mechanical and chemical testing projects; later this laboratory became part of the Veterans Administration Prosthetics Center (VAPC), which contributed heavily to development and evaluation projects established within the program. Although progress was made with new devices and substitutions of materials, more significant advances were in the areas of socket design and alignment of the various types of prostheses.
As a result of a visit by a commission to Europe in 1946, a study of the suction socket for transfemoral (above-knee) prostheses was made by the University of California, Berkeley. The results of this study, coupled with information derived from the locomotion studies at the University of California, Berkeley, led to a biomechanical rationale for the design and fabrication of the socket and the alignment of transfemoral prostheses.
Innovative techniques for providing improved prostheses for Syme (ankle disarticulation), hip disarticulation, and transpelvic (hemipelvectomy) amputees were developed by McLaurin and his associates while working at Sunnybrook Hospital, Toronto, under the auspices of the Department of Veterans Affairs of Canada. Much of this work was carried to fruition at the University of California, Berkeley, after Foort transferred there in 1955 from Toronto. Variations on the early designs of ankle disarticulation prostheses were made by VAPC prosthetists. Thus a body of knowledge of management of ankle and hip disarticulation (and transpelvic) amputees was developed and then disseminated to clinicians through a formal education program.
Concurrently, on the basis of a number of innovations in transtibial (below-knee) socket designs made by practitioners in various parts of the country, Radcliffe and Foort developed the rationale and techniques of fabrication for what is now known as the "patellar tendon-bearing" (PTB) prosthesis. Education in fabrication and application was first offered through university education programs in 1960. A number of variations in technique are now used successfully in practice, but the principles set forth originally by Radcliffe and Foort have stood the test of time.
In 1963, Weiss, an orthopedic surgeon in Poland,visited the United States under the auspices of the Office of Vocational Rehabilitation and the CPRD, at which time he described techniques he was using in management of lower-limb amputees. These included fitting of temporary prostheses immediately after surgery, a procedure adapted from Berlemont et al., and osteoplasty and myoplasty techniques adapted from Ertl, Mondry, and Dederich.
Weiss' presentations prompted the Veterans Administration to initiate in 1964 in Seattle under Burgess and colleagues a study to determine the feasibility of immediate postsurgical fitting, osteoplasty, and myoplasty. Projects were also started at the Navy Prosthetics Research Laboratory and the University of Miami. Just prior to this a team at Duke University had been studying the effects of early fitting, that is, providing the patient with temporary prostheses with well-defined sockets within a month after the amputation.
As a result of these efforts many amputees are fitted with rigid dressings immediately after surgery and with definitive prostheses much earlier than was previously considered possible. These procedures result in significantly lower hospital and training costs.
Pedersen and others began, about 1958, to promote the idea that knee joints in many elderly patients with vascular disease could be saved if proper care were given postsurgically. Until then the classic instruction was to amputate transfemorally when circulation was impaired so that healing could be ensured. Weiss agreed with the view that knees could be saved and pointed out that the use of a rigid dressing should improve healing by reducing edema. Consequently, the ratio of transfemoral to transtibial amputations in the United States between 1965 and 1975 was almost reversed from 70:30 to 30:70. This continues to have a profound effect on the rehabilitation potential of dys-vascular and geriatric amputees.
Although the Veterans Administration had no direct responsibility for children, it did provide indirect support to the Children's Bureau in adapting some of the devices and techniques developed for adults. Frantzand Aitken and the Michigan Crippled Children's Commission initiated a project to develop methods of management for child amputees in Grand Rapids in 1952. A similar project was launched at the University of California, Los Angeles, in 1955, and New York University was funded to further evaluate the devices and techniques emanating from these projects. The Children's Bureau also provided the NAS with some funds for coordination of activities in child prosthetics. From this emerged the Child Amputee Clinic Chiefs Program, which has held meetings nearly every year since 1958, and the Inter-Clinic Information Bulletin (ICIB), a small monthly publication that has proved to be useful for the dissemination of results of research and development.
After the dissolution of the CPRD (Committee on Prosthetics Research and Development) in 1976, the Child Amputee Clinic Chiefs formed the Association of Children's Prosthetic and Orthotic Clinics to continue the educational activities of the Chiefs' group.
AMPUTEE PROGRAMS IN OTHER COUNTRIES
In Great Britain, the Limb Fitting Centre at Queen Mary's Hospital, Roehampton, expanded its research effort shortly after the end of World War II and became known as the Biomechanical Research and Development Unit.
The Scottish Department of Home and Health Services has sponsored research and development at the Limb Fitting Centre, Dundee; University of Strath-clyde; and Princess Margaret Rose Hospital, Edinburgh. The work in Edinburgh was devoted mainly to children. At the University of Strathclyde there is a 4-year Bachelor of Science program in prosthetics and orthotics.
Work concerning children's problems is also being carried out in other places in Great Britain, namely, at Chailey Heritage and the Nuffield Clinic, Oxford. Suppliers of artificial limbs in Great Britain also support research and development within their own organizations.
Support of research in prosthetics in Canada has been sporadic, but some of the results have been important. The work of Scott at the University of New Brunswick and Sauter at the Hugh MacMillan Medical Centre (formerly Ontario Crippled Children's Centre) has made significant contributions to externally powered artificial arms, and Foort's team at the University of British Columbia have been the leaders in the development of computer-aided design and computer-aided manufacturing (CAD/CAM) techniques in lower-limb prosthetics.
A number of research and development efforts were started in Germany after World War II, but there appears to have been little coordination of these efforts. The work at the University of Münster in body-powered upper-limb prosthetics has influenced practice elsewhere, as has the work at the University of Heidelberg with severely involved child amputees.
Since the early 1970s research in Germany seems to have moved from the universities to the private manufacturers. The manufacturers have had a significant influence on prosthetics and orthotics practice throughout much of the world by providing innovative hardware.
A formal education program for prosthetists has been in operation in Germany for many years.
The thalidomide tragedy prompted the Swedish government to expand its research and development work in technical aids for the handicapped to include artificial limbs in 1962. This program continues today.
During the 1960s and early 1970s, the French government expanded its support of artificial limb research mainly through the Ministre des Anciens Combattants et Victimes de Guerre.
Research and development in artificial limbs in Italy have a long history. A research unit has been in operation at the University of Bologna for many years, and a group at the Prosthetic Centre in Budrio is very active in the development of externally powered upper-limb prostheses.
Not a great deal is known about activities in Russia, but research units are located in Leningrad and Moscow. Their contribution has been the first clinically useful myoelectrically controlled hand.
The U.S. government, through the Surplus Agricultural Commodity Act (P.L. 480), supported work in Poland, Yugoslavia, Israel, Egypt, India, and Pakistan from the early 1960s until funds were depleted in the early 1980s.
Some prosthetic research has been carried out in Japan but as yet has had little effect on practices in the United States.
RELATED ORGANIZATIONS
The American Orthotics and Prosthetics Association (AOPA) is an organization primarily of privately operated prosthetics and orthotics facilities in the United States and Canada to assist its members in providing the best possible services. The parent group was organized in 1917 as the Artificial Limb Manufacturers' Association. The name was changed in 1946 to the Orthopedic Appliance and Limb Manufacturers' Association when orthotists were invited to join, and the present name was adopted in 1958.
The American Board for Certification in Prosthetics and Orthotics was established in 1948 as an accreditation body to certify the professional competence of practitioners and facilities in these disciplines. In addition to its accreditation activities, the board also seeks to advance the highest levels of competency and ethics in the prosthetic/orthotic profession.
In 1952, the International Society for the Rehabilitation of the Disabled (now called Rehabilitation International) appointed an International Committee on Prosthetics and Orthotics (ICPO) to promote the dissemination of knowledge of prosthetics and orthotics throughout the world. The chairman was Knud Jansen, and headquarters for the committee was established in Copenhagen, where a number of very successful international seminars were conducted in the late 1950s and 1960s. The committee also sponsored courses and conferences at other locations during this period, and in 1971, with the concurrence of Rehabilitation International, the members of the committee and others formed the International Society for Prosthetics and Orthotics (ISPO) "to promote high quality prosthetics and orthotics care to all people with neuromuscular and skeletal disabilities." ISPO, an organization of all professionals associated with prosthetics and orthotics, conducts an international congress at 3-year intervals to bring together clinicians, educators, research personnel, and administrators to exchange information and ideas and to make plans for cooperative programs.
The American Academy of Orthotists and Prosthe-tists (AAOP) was founded in 1970 by practicing prosthe-tists and orthotists as a professional society to promote the advancement of knowledge in the field of prosthetics and orthotics. Its goals and organization relate primarily to education.
Through the years amputees have formed clubs for the purpose of exchanging experiences and views. Their initiation was accompanied by a good deal of enthusiasm, but few seem to have survived for any appreciable time.
However, in recent years there has been a proliferation of well-organized amputee support groups across the country that have the potential for influencing amputee rehabilitation. By working closely with rehabilitation personnel, especially clinicians, the amputee groups, in addition to providing psychological and other support to individual amputees, can provide clinicians, researchers, and administrators with information that will eventually improve the delivery system as well as prosthesis design and methods of therapy.
This new amputee movement is probably the result of a public that is more informed about medical problems in general and eager to acquire a better understanding of medical problems.
ENGLISH-LANGUAGE PERIODICALS
Although several periodicals were devoted to artificial limbs prior to 1946, they were directed toward amputees. The first English-language periodical written for practicing prosthetists was the Orthopedic and Prosthetic Appliance Journal. This journal began publication in 1946 when the Artificial Limb Manufacturers' Association became the Orthopedic Appliance and Limb Manufacturers' Association, the immediate predecessor of the American Orthotic and Prosthetic Association (AOPA). The journal's name was changed in June 1967 to Orthotics and Prosthetics.
The next prosthetics publication to appear was Artificial Limbs-A Review of Current Developments in 1954, published two or three times each year by the Advisory Committee on Artificial Limbs-later called the CPRD (Committee on Prosthetics Research and Development)-of the NAS, to provide recent results of the U.S. program to clinical personnel.
In 1972, the CPRD staff felt that Orthotics and Prosthetics had matured to the point that it was appropriate for it to be responsible for publishing clinically useful results of research, and publication of Artificial Limbs was terminated.
In 1964, the Prosthetics and Sensory Aids Service of the Veterans Administration (now the Department of Veterans Affairs) began semiannual publication of the Bulletin of Prosthetics Research, with emphasis on reports of research activities and results. In 1983, the name was changed to the Journal of Rehabilitation Research and Development. In addition to three issues per year devoted to technical reports, a separate issue is dedicated to progress reports from the majority of the research projects in prosthetics, orthotics, and sensory aids in the English-speaking world. From time to time the Department of Veterans Affairs also publishes "clinical supplements" to the journal to provide clinicians with current practice in selected areas such as "recreation for the handicapped" or "wheelchairs."
During the late 1950s, the CPRD organized a network of Child Amputee Clinics throughout the United States as a means of improving prosthetics services for children. To encourage rapid interchange of information among the clinics, publication of the ICIB (Inter-Clinic Information Bulletin) was begun in 1961. Primary responsibility for putting the bulletin together was initially assigned to New York University, then was transferred to CPRD, and is now published under the auspices of the Association of Children's Prosthetic and Orthotic Clinics.
The ICIB was received with such enthusiasm that in 1969 the CPOE (Committee on Prosthetics and Orthotics Education) applied the same concept to adult prosthetics and orthotics with the publication of Newsletter-Amputee Clinics. This bulletin continued until the dissolution of CPRD and CPOE in 1976. Because Newsletter-Amputee Clinics was sorely missed, the AAOP (American Academy of Orthotists and Prosthe-tists) initiated publication in 1976 of Newsletter-Prosthetic and Orthotic Clinics. In 1982, the title was changed to Clinical Prosthetics and Orthotics. In 1988, the AOPA and AAOP combined Orthotics and Prosthetics and Clinical Prosthetics and Orthotics to create a new quarterly entitled Journal of Prosthetics and Orthotics.
In the late 1950s, the ICPO (International Committee on Prosthetics and Orthotics) of the International Society for the Rehabilitation of the Disabled began publication of a technical journal that was published sporadically until 1970. At that time the ICPO was reformed into the ISPO (International Society for Prosthetics and Orthotics) and became a separate entity. After volume 1, the ICPO publication was renamed Prosthetics International. Volume 2, number 1 is dated simply "1964." From 1972 through 1976, the ISPO published the ISPO Bulletin four times a year, primarily to keep the membership informed of administrative and technical developments. As the ISPO grew, it was able in 1977 to replace the Bulletin with Prosthetics and Orthotics International, a scientific journal published three times a year that contains research reports and results of clinical evaluation of new devices and techniques.
DEVELOPMENTS IN LOWER-LIMB PROSTHETICS
Sockets and Suspension
Prior to the U.S. research program, the most common approach to the design of the transfemoral socket was the carved "plug fit" wooden socket with a conical interior shape. The weight of the amputee during the stance phase of walking and during standing was transferred to the skeletal system through the muscles about the thigh.
The transfemoral socket design introduced by the University of California, Berkeley, about 1950 was shaped to permit use of the remaining musculature. It contained well-defined walls and became known as the "quadrilateral socket." The posterior wall was shaped to provide ischial-gluteal weight bearing. Following the German practice, an air space was left between the distal end of the stump and the bottom of the socket, and an air valve was installed in the medial wall in this area. Most of the patients used this system successfully, but a sufficient number experienced edema and dermatologic problems to warrant further study.
The University of California, Berkeley and San Francisco, undertook studies of the problems of transtibial amputees as well as those of transfemoral amputees. The result was the PTB (patellar tendon-bearing) prosthesis, which involved total contact between stump and socket. Further analysis of problems with transfemoral amputation and experience with the PTB prosthesis resulted in the total-contact quadrilateral transfemoral socket, which minimized the problems of terminal edema.
Because it was felt that the education programs strayed from the fundamental principles of the quadrilateral design or for other reasons, some prosthetists began to feel by 1980 that a second generation of transfemoral sockets was needed. In the early 1980s Long, Sabolich, and others introduced designs known variously as NS/NA (normal shape-normal alignment), CAT-CAM (contoured, adducted trochanter/controlled alignment method), and narrow ML (medial-lateral). These widely publicized designs caused confusion in the field because not only was it difficult to explain their rationale and thus difficult to teach but their advocates also produced many variations. However, the one common feature was that the support of the amputees body relied less on the ischial "seat" than the original quadrilateral design specified. Two conferences sponsored by the ISPO in 1987 helped to clear up most of the confusion. The "ischial containment" sockets, as they are now called, are used in many areas with a better understanding of the underlying principles, but more study is needed if they are to be prescribed properly.
Fabrication Materials and Methods
Immediately after World War II the vast majority of lower-limb prostheses were constructed of a combination of wood and leather. These materials, alone and together, have many properties desirable for the construction of artificial limbs, but they also possess properties that make them a good deal less than perfect. Wood requires the skill of carving and shaping, and leather absorbs perspiration and is difficult to keep clean.
To overcome some of the deficiencies of wood and leather, Northrop Aviation, Inc., introduced the use of thermosetting resins for laminating tubular stockinette-over-plastic replicas of the stump to form sockets and structural components of upper-limb prostheses. The Veterans Administration Prosthetics Center conducted extensive demonstrations to encourage prosthetists to use plastic laminates over wood, thereby furthering the trend toward the use of plastics.
McLaurin and his coworkers in Toronto coupled the plastic laminating technique with a good engineering analysis of the problem to produce the "Canadian Syme prosthesis," which was a significant improvement over former practices. This design and variations developed by the Veterans Administration Prosthetics Center were adopted worldwide as prosthetists learned to use plastic laminates. (Experience with the foot of this prosthesis led to the development of the solid ankle, cushion heel [SACH] foot.) The same group also conceived and developed the plastic socket "Canadian hip disarticulation prosthesis" about 1955, which was also soon adopted worldwide.
Plastic laminating techniques made total-contact sockets practical; most of the prostheses used throughout the world now are total-contact sockets made essentially of either a plastic laminate or thermoformed plastic.
The search for a practical method of making transparent sockets was highlighted in 1972 when Mooney and Snelson developed a method for vacuum-forming a polycarbonate sheet over a positive model of the stump to provide the first practical transparent test sockets. Polycarbonate has been replaced by several cheaper materials, and today use of transparent check sockets is the rule rather than the exception. Vacuum-forming polypropylene, the properties of which seemed to make it appropriate for definitive use, was introduced in 1975 by the Moss Rehabilitation Hospital in Philadelphia,and today polypropylene sockets used with endoskele-tal systems are considered to be the norm.
The introduction of socket designs based on sound biomechanical analyses to take full advantage of the functions and properties of the stump in conjunction with a rationale for alignment undoubtedly represents the greatest achievement in prosthetics since World War II.
Suspension of the Prosthesis
Prior to the development of socket designs based on biomechanical principles, suspension of most lower-limb prostheses presented formidable problems. Until the introduction of the pelvic band about the time of World War I, over-the-shoulder suspenders were used almost universally for keeping transfemoral prostheses in place. Until the development of the PTB prosthesis, the side bars of the thigh lacers, or corset, of the trans-tibial prosthesis were bent to conform to the medial and lateral surfaces of the thigh to provide suspension. This arrangement was often supplemented by a waist belt.
The quadrilateral design not only permits the use of suction for suspension but makes the suspension problem easier because the muscle action of the stump within the intimately fitting socket also helps to hold the prosthesis in place.
Until the past few years suction was seldom used to suspend the transtibial prosthesis. The intimate fit of the transtibial socket makes it possible in most cases to achieve quite adequate suspension by a supracondylar strap. Variations of the original PTB prosthesis design (supracondylar or supracondylar-suprapatellar) employ more proximal brims that are contoured to make the supracondylar straps unnecessary.
Nevertheless, retention of the transtibial prosthesis by suction is considered desirable, and the efforts by Kristinsson and Durr-Fillauer have resulted in the so-called 3-S transtibial socket, which uses a closely fitting elastomeric sleeve as an inner socket to provide the adherence needed for adequate suspension.
It has been recognized for many years that if the flexibility of socket walls could be varied to match the properties of the underlying tissues of an amputation stump, the result would be a more comfortable and functional socket. The most successful approach to this problem was initiated by Kristinsson in the early 1980s, who used a semiflexible liner in a rigid outer structure, or frame, shaped so as to provide rigidity where it is required. The concept was adopted by a group in Sweden and then by New York University and Durr-Fillauer. Each added slight variations.
These sockets have been well received but not widely used because the materials currently available are not sufficiently durable when made thin enough to provide the desired flexibility.
The ultimate arrangement for achieving suspension would seem to be attaching the prosthesis directly to the bone. The first recorded efforts in what is often called "skeletal attachment" seem to have been made in Germany in the 1940s. Some work was considered at the University of California, but the first experimental work in the United States was probably that of Es-slinger in Birmingham, Michigan, during the 1960s, which was undertaken on a small scale with support from the Veterans Administration. Results with dogs were encouraging. Hall et al. of Southwest Research Institute continued this work for several years as a result of some experiences he had with horses, and Mooney carried out some investigations at Rancho Los Amigos Hospital, Downey, California, in the early 1970s. In spite of encouraging results, interest in "skeletal attachment" seems to have waned.
Computer-Aided Design/Computer-Aided Manufacturing
To accelerate the process of fitting and fabrication of artificial limbs, in the 1960s James Foort of the University of British Columbia proposed the use of numerically controlled milling machines with data supplied by stereophotography to produce a positive model of the stump ready for the molding of a socket. Progress was slow until the introduction of computer-aided design procedures and personal computers. The University College London in the late 1970s developed an automated process for molding polypropylene sockets, called Rapidform, and it seemed logical to develop a system that would include computer-aided design, numerically controlled production of a positive model of the stump, and automated production of the socket. Workers there also envisioned automated fabrication of the entire artificial limb if alignment data could be fed into the system.
In the early 1980s University College London introduced a system that requires taking a loose cast of the transtibial amputation stump, transferring the inside contours to a personal computer by means of a digitizer to produce an image of a positive model, modifying on the screen the shape of the positive model, and feeding this information into a numerically controlled milling machine that carves a positive model from a blank of plaster of paris or wax. At this point the positive model is ready for use in fabrication of a socket by any method desired, but vacuum-forming of polypropylene or similar sheet plastic is the rule.
In the mid-1980s the Veterans Administration began funding several projects in the United States to further the application of the CAD/CAM process in the fabrication of artificial limbs. Not a great deal of progress is apparent, although the interest generated by these projects and the availability of hardware and software for two systems from England based on the University College London work has induced several U.S. prosthetics facilities to experiment with the introduction of CAD/CAM on a routine basis in spite of the fact that in its current state of development the advantages do not seem to outweigh the disadvantages. Undoubtedly, further development will make CAD/CAM a useful tool in providing improved service to amputees.
Prosthetic Knees
Locomotion studies at the University of California showed that swing-phase control of the shank is as important as stance-phase control in lower-limb prosthetics. Until that time, control of the shank during swing phase in most transfemoral prostheses was provided by introducing friction about the knee bolt, the so-called constant-friction knee, an arrangement that provides a smooth gait at only one cadence for a given amount of friction.
The Navy Variable Cadence Knee Unit was designed to overcome the shortcoming of the constant-friction unit to some degree by increasing the friction toward the end of the swing phase. The Navy design, introduced about 1950, did indeed permit improvement in the gait pattern, but the materials available at that time soon failed as a result of wear, and maintenance became a problem. The same principle is employed in the Northwestern University variable-cadence knee, which was available commercially for some years.
In 1949 the Vickers Corporation in Detroit requested assistance from the government through the NAS in perfecting the Stewart-Vickers Hydraulic Above-Knee Leg, a design by Jack Stewart, who had had an amputation through the thigh. This system used hydraulic principles to lock the knee on heel contact and to provide coordinated motion between the knee and ankle during the swing phase. Laboratory and clinical trials at New York University with a dozen units showed that the prosthesis was well accepted by a significant proportion of amputees, apparently because of the swing-phase control resulting from the hydraulic system that had been provided primarily for stance-phase control and not because of the stance-phase control itself. It was learned later that the degree of resistance to plantar flexion of the ankle during the early stages of stance phase was beneficial in providing stability during the stance phase of walking.
Results of the New York University evaluation program and other efforts prompted the United States Manufacturing Company to make a version of the Stewart-Vickers design available commercially. Known as the Hydra-Cadence, this unit retained the swing phase and hydraulic ankle features, but because of the high cost, the stance-phase control feature was not included.
Mauch, who along with Henschke had been developing a hydraulically actuated stance-phase control unit under the auspices of the U.S. Air Force since 1946, was persuaded in 1951 to concentrate his efforts on the use of hydraulic principles for control of the shank during swing phase. The result was the model "B" Hen-schke-Mauch Knee Unit. The swing-phase feature was later incorporated into the stance-phase system (model A) and called the Mauch S 'n' S System, which is the unit available today. Many hydraulic swing-phase units are now available as a result of the research program.
To overcome the high costs involved in manufacturing hydraulic units and yet retain the advantages, a pneumatically controlled system designed at the University of California, Berkeley, is now available and known as the UC-BL Pneumatic Swing Control.
To eliminate the bulk usually associated with knee disarticulation prostheses, Lyquist in 1973 designed the OHC (Orthopaedic Hospital, Copenhagen) knee unit, which uses a four-bar linkage within the shank to provide an effective knee axis that approximately matches the normal knee axis. The OHC unit, by virtue of the four-bar linkage, is quite stable during stance phase, and it is available with a hydraulically controlled swing-phase system. This principle has been adopted by several manufacturers, and knee units similar to the OHC are used in many transfemoral prostheses as well as knee disarticulation limbs.
Other stance-phase controls have been developed by commercial organizations. These are essentially mechanical systems with an incremental resistance added upon weight bearing.
Prosthetic Feet
Throughout the years great attention was devoted to the design of artificial feet to provide better function than allowed by the standard single-axis wood foot. Considerable effort in the early years of the program was given to the design of articulated feet with the expectation that such designs would enhance the amputee's ability to walk. An outstanding achievement of the early years was the "Navy ankle" developed by the Naval Prosthetic Research Laboratory in Oakland, California. This ankle contained a block of rubber with variable stiffness to control motions in all three planes. However, excessive maintenance prevented it from being a commercial success. The Greissinger foot, developed in Germany to offer the kind of function provided by the Navy unit, has commonly been used to provide "three-way action." Meanwhile the introduction of the SACH (solid ankle, cushion heel) foot with the PTB prosthesis represented the ultimate in simplicity while providing acceptable function for most patients. The SACH foot has had outstanding success in the marketplace primarily because of its simplicity.
To retain most of the simplicity of the SACH foot while providing some of the function of three-way feet, John Campbell developed and introduced in the late 1970s the SAFE (stationary attachment-flexible en-doskeletal) foot, which proved to be well accepted in spite of a slight increase in weight over the SACH foot.
The Prosthetic Research Study at the University of Washington, in an effort to provide the athletic lower-limb amputee with more function, pioneered the concept of energy-storing feet with the introduction of the "Seattle" foot in the early 1980s. In this system energy is stored in an elastic keel as the foot rolls over during stance phase to be released just prior to toe-off. This feature was appreciated by less active users as well, and several competitive designs are now available and used widely, especially the Carbon Copy II. The Flex-Foot employs the same concept but is a radical departure from artificial foot design in that the endoskeletal shank and keel of the foot are one piece of carbon graphite flat stock.
Endoskeletal Prostheses
During the first decade of the U.S. research program the use of temporary prostheses was discouraged because it was believed that more harm than good would result from the use of crudely made, poorly fitting sockets mounted on peg legs. However, after the rationale for socket configuration was fully developed and plastics had proved to require less time but resulted in a better fit than earlier methods of fabrication, the idea of temporary prostheses was revived.
Pylons, or endoskeletal prostheses, with adjustment features began to appear about 1960. Staros established the criteria for their use as temporary limbs. Their use was then accelerated by immediate postsurgical fitting studies, and various designs began to appear on both sides of the North Atlantic, the ultimate concept being an adjustable endoskeletal structure that could be carried over into the definitive prosthesis, the "pylon" being covered with a resilient foam shaped to match the contralateral leg.
These designs, usually referred to as modular en-doskeletal limbs, have gradually had more and more success despite the difficulty in shaping and maintaining their foam covers. They have become the norm rather than an alternative.
DEVELOPMENTS IN UPPER-LIMB PROSTHETICS
Early in the Artificial Limb Program it was decided that the best approach to take at that time for upper-limb replacement was to develop a variety of components, socket designs, and harnessing methods that could be assembled to best meet the needs of individual patients rather than trying to develop special systems for each level of amputation.
The primary assignment to the APRL (Army Prosthetic Research Laboratory) was the development of artificial arms with emphasis on artificial hands. Out of this effort came the voluntary-closing APRL hand and the APRL hook. These devices were well received by a significant proportion of the amputee population, but it was difficult for the manufacturer to produce quality devices at a competitive price because of the close mechanical tolerances required. These devices are still available today, but the high costs preclude widespread use.
Although the APRL hand and hook are not used widely, the basic research required led to the development of the sizes and configurations that are now standard for most artificial hands produced today. The manufacture of nearly all of the cosmetic gloves provided for artificial hands is based on techniques developed at the APRL.
Northrop Aviation, Inc., produced many ingenious designs for artificial arms in addition to introducing plastic laminating techniques. The alternating-lock elbow unit operated from the harness for transhumeral amputees was first developed by Northrop in 1947. After becoming available commercially, it soon replaced other available units, all of which required use of the contralateral hand or motion against a fixed object to activate the lock. This basic design is in use throughout the world.
Northrop also initiated a study in harness design that was later taken over by the University of California at Los Angeles. UCLA also developed socket designs for all levels of upper-limb amputation that were based on anatomic and physiologic principles. Refinements of these basic socket and harness designs are still the standard for body-powered upper-limb prosthetics.
The hardware, socket, and harness designs produced by Northrop, APRL, UCLA, and others between 1946 and 1950 made it practical and desirable for the surgeon to save all length possible in amputation through the upper limb. Unfortunately, except for externally powered systems, no major advances that have found widespread use have been made in upper-limb prosthetics since the early 1960s.
External Power
Although some work was done in Germany earlier,it was Alderson who, with support from the United States government and International Business Machines, developed the first working model of an electrically powered artificial arm, which appeared about 1949. Demonstrations were impressive, but evaluations at New York University and UCLA in 1953 revealed that amputees could not operate any of the designs without conscious thought, primarily because the sensory feedback so necessary for automatic or semiautomatic operation was not adequate. For this reason, the development of devices was discontinued at that time, and some effort was put into a study of sensory feedback.
In 1958 Russian workers announced that a "thought-controlled" artificial arm had been perfected, which proved to be an electric hand controlled by myoelectric signals from the flexors and extensors of the wrist and was suitable only for transradial amputees. Again, adequate feedback signals were lacking.
Rights to manufacture these devices were purchased by groups in Canada and Great Britain, but these units were never widely accepted. However, Otto Bock Orthopaedic Industry, Inc., in Germany and Viennatone in Austria made versions of the Russian design available that they marketed with some success. An interesting design was proposed in Yugoslavia but was never carried to fruition. Mason of the Veterans Administration Prosthetics Center and Childress and Billock at Northwestern University provided refined designs in which the batteries were located within the hand or wrist unit. New socket designs for transradial amputees that provide self-suspension were developed, thus eliminating the need for any wiring or harness above the elbow.
The thalidomide tragedy created a great deal of interest in externally powered prostheses, especially in Germany, | 
