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A Manual for Above-Knee Amputees The Amputation Amputations are caused by accidents, disease, and congenital disorders. Approximately 74% are due to peripheral vascular disease (poor circulation of the blood) and cancer; 23% are due to accidents, and 3% are due to a problem found at birth. The accidents most likely to result in amputation are traffic accidents, followed by farm and industrial accidents. Amputations in the case of disease are performed as a lifesaving measure. The diseases that cause the most amputations are peripheral vascular disease (poor circulation of the blood) and cancer. A congenital disorder or defect of a limb present at birth is not an amputation, but rather a lack of development of part or all of a limb. A person born with a limb deficiency usually can be helped by use of an artificial limb. Sometimes amputation of part of a deformed limb or other surgery may be desirable before the application of an artificial limb. Above-knee (trans-femoral) amputees form the second largest group of amputees. Surgeons preserve as much length in thigh amputations as is medically feasible because longer stumps provide better control over the prosthesis. Experienced surgeons avoid leaving unnecessary skin and muscle. Disarticulation at the knee preserves the entire thigh, and, in addition, permits "end-bearing", or the ability of the stump to carry a substantial portion of the body weight over the end. The Immediate Post-surgical Period Nearly every amputee feels quite depressed immediately after the surgery, except possibly those who have suffered intense pain for a period just prior to the amputation. This depression is usually replaced early by a will to resume an active life. The dressing applied by the surgeon is either "rigid," usually made of plaster- of-Paris, or "soft," using ordinary cotton bandaging techniques. When a rigid dressing is used it is left on for 10 to 14 days during which time most of the healing has taken place. When the soft dressing is used, elastic bandages are used soon after surgery to aid circulation. The bandages are removed and reapplied throughout the day. (Instructions for application of elastic bandages are given in the next section) Regardless of the type of dressing used, exercises are extremely important to prevent tightening of the muscles, or contractures, which, when present prevent efficient use of a prosthesis. Some DON'Ts that will prevent muscle tightening, or contractures, are shown below. Fitting the Prosthesis In general, the earlier a prosthesis is fitted, the better it is for the amputee. One of the most difficult problems facing the amputee and the treatment team is edema, or swelling of the stump, owing to the accumulation of fluids. Edema will be present to some extent in all cases, and it makes fitting of the prosthesis difficult, but certain measures can be taken to reduce the amount of edema. The use of a rigid dressing seems to control edema. After the rigid dressing has been removed and when a prosthesis is not being worn, elastic bandages are used to keep edema from developing. The amputee is taught the proper technique for bandaging and is generally expected 'to do this for himself as shown on the next page. For the average adult two or three elastic bandages six inches wide are used. During application, the bandages should be stretched to about two-thirds of the limit of the elastic, and the greatest tension should be around the end of the stump. The stump should be kept bandaged at all times, but the bandage should be changed every four or six hours. It must never be kept in place for more than 12 hours without rebandaging. If throbbing should occur, the bandage must be removed and rewrapped. Edema occurs rapidly when the stump is left unbandaged so it is very important to replace the bandage without delay. Special elastic "shrinker" socks are available for use instead of elastic bandages, and while not considered by some to be as effective as a properly applied elastic bandage a shrinker sock is better than a poorly applied elastic bandage. Whether elastic bandage or shrinker sock is used, it should be removed at least three times daily and the stump should be massaged vigorously for 10-15 minutes. The bandage or sock must reapplied immediately after the massage. 1. Begin by placing one end of a rolled 6-inch wide elastic bandage on the upper part of the thigh and wrap it around the stump toward the rear. 2. Bring the roll through the legs and over the end of the front of the thigh. 3. Bring the roll across the back and on across the lower stomach area. 4. Continue to wrap around the thigh, across the back and lower stomach area until the roll is suspended. Attach the end of the roll with the metal clips that are included with the bandage. 5. With a second roll of elastic bandage, begin to wrap the stup from the upper outer surface diagonally toward the lower inner surface. 6. Bring the roll of bandage around the back of the stump and upward diagonally. 7. Bring the roll of bandage behind the uper part of the stump. 8. Continue to wrap the stump in an overlapping fashion until the entire stump is covered. Fasten the end of the second roll of bandage to the first bandage. The Preparatory Prosthesis Fitting a prosthesis as soon alter surgery as possible helps to combat edema. A preparatory prosthesis is frequently used for several weeks or months until the stump has stabilized before the "permanent" or definitive prosthesis is provided. The socket of the preparatory prosthesis may be made of either plaster-of-Paris or a plastic material, and is attached to an artificial foot by a lightweight tube or strut, often called a "pylon." When indicated, a suction socket is used. Most pylons are designed so that the alignment of the foot with respect to the socket can' be changed when it is needed. Although a variety of shoes may be worn with artificial limbs, the patient should consult with the prosthetist before selecting shoes to be used with the prosthesis, because heel height is a major factor in alignment of the artificial leg. A belt about the waist is usually used to help keep the preparatory prosthesis on the stump properly. At least one prosthetic sock is worn between the socket and stump to provide for ventilation and general comfort. Most prosthetic socks are woven of virgin lamb's wool, but socks of synthetic yarns are available also. Prosthetic socks are used to prevent skin abrasion and to provide ventilation. They are available in several thicknesses - most commonly 1-ply, 3-ply, 5-ply, and 6-ply. Additional socks can be used to compensate for stump shrinkage if the amount of shrinkage is not too great. The prosthetist and therapist can suggest the sock or socks to be used, but only the patient can determine the proper selection. Prosthetic socks must be changed daily to reduce the chance of skin irritation or dermatitis. Prosthetic socks require special care in laundering. Instructions are provided by each manufacturer. A special woven nylon sock known as a prosthetic sheath is used by many amputees between the skin and regular prosthetic sock to provide additional protection from abrasion. The sheath also allows perspiration to escape to the prosthetic sock and thus to the atmosphere. Special Note: Regardless of the functions provided by the most sophisticated mechanical devices, the most important factors in the usefulness of an artificial leg are fitting of the socket and alignment of the various parts with respect to the body and to each other. Fitting and alignments are difficult procedures that require a great deal of skill on the part of the prosthetist and a great deal of cooperation on the part of the patient. During fitting and alignment of the first prothesis, it is necessary for the prosthetist to train the amputee in the basic principles of walking. Fitting affects alignment, alignment affects fitting, and both affect comfort and function. Extensive training is carried out later by the physical therapist. The Definitive Above-Knee Prosthesis The above-knee prosthesis has four major parts: the socket; the knee system; the shank; and the foot-ankle system. A variety of sockets, knees, shanks, feet, and ankles are available and can be combined to produce a prosthesis that best meets the needs of each individual amputee. A Description of the components most used in the United States is given in the following sections. The Socket The socket is the basis for the connection between the user and the prosthesis. It always provides the means for transferring the weight of the amputee to the ground by way of the rest of the prosthesis. The shape of the socket is critical to comfort and function. The socket must not restrict circulation, yet it cannot be loose. Most sockets for above-knee prostheses cover the entire stump. There are several designs available to take maximum advantage of the muscles in the stump of the individual amputee for control of the prosthesis and for transferring the weight of the amputee to the floor. Most sockets are made of a rigid plastic, but some amputees prefer a flexible socket supported by a rigid frame because comfort during walking and sitting seems to be improved. For most patients, the prosthesis can be held in place by "suction", or a vacuum, provided by a close fit between stump and socket. This is known as a suction socket. Nothing is worn between the stump and socket. when circulation is marginal or precarious, a looser fit is provided, a woolen sock is worn over the stump, and the socket is held in place by a "Silesian Bandage". The Knee System If the above-knee amputee is to have a normal appearance while walking, the prosthesis must have a knee joint that will not buckle as he rolls over the artificial foot during the stance phase of walking. The simplest way to achieve this is to use mechanical friction about a bolt that connects the socket (thigh) to the shank. The bolt is located behind the path of the weight of the body to the floor so that it will not buckle when the user is standing straight. The mechanical friction, which may be a simple adjustable brake, keeps the shank from swinging forward too fast as the user swings the artificial leg through to the next step. The chief limitation in the single-axis, constant friction design is that appearance is normal at only one speed of walking for a given setting of friction, The amputee must be very careful in walking, especially on uneven surfaces, to avoid stumbling. A great deal of effort has been spent over the Years developing knee systems which overcome the limitations of the single-axis, constant friction knee. Many designers have been successful to some degree, but because of the simplicity of the constant friction design, no new system has totally displaced it. Weight Actuated Knee Brake The second level of complexity in knee systems is the use of a weight-actuated brake with constant friction. Two bolts are used at the knee, so that when one pivots about the other when the amputee is standing, the force of the body weight engages a brake that keeps the knee from buckling. Polycentric Knees To provide better control of the above-knee prosthesis during standing and the stance phase of walking than can be provided with a single axis knee, designers have used mechanical linkages between the socket and shank that, in effect provide for a moving center of rotation. Such designs are known as polycentric knees. Used originally for the knee-disarticulation case, polycentric knees now also used in prostheses for higher levels, especially when stability at heel strike is desirable. The swing phase control may be either mechanical friction or hydraulic resistance. The one limitation of the polycentric design is that range of motion about the knee may be restricted to some degree but not enough for it to be objectionable to most users. Hydraulic Knees To allow the amputee to vary his speed of walking, a number of hydraulic devices are available. In the simplest system, the piston is attached to a pivot in the thigh section of the prosthesis behind the knee bolt, and the cylinder is attached to a pivot in the shank. Because of the way oil acts when forced through a small hole the amount of resistance required for a given velocity of walking is provided automatically. The most complex knee systems of those available are those which control of both swing and stance phase with a single hydraulic cylinder. Braking of the knee is brought about automatically when the knee begins to buckle, without interfering with normal flexion and extension of the knee. The same system permits the velocity of walking to be varied at will. These features are appreciated most by very active amputees. The prescription for the prosthesis is based on activity level and particular needs of each amputee. Shanks The primary purpose of the shank is to transfer the vertical loads caused by the weight of the amputee to the foot and on to the floor. Two types are available: Crustacean, or exoskeletal, where the forces are carried through the outside walls of the hollow shank which is shaped like a leg; and endoskeletal, or pylon, where the forces are carried through a central structure, usually a tube and the shape of the leg is provided by a foam covering. Each design has advantages and disadvantages. The endoskeletal systems offer the most life-like appearance and "feel", but require more care to maintain. The crustacean design is suitable for heavy duty. Most endoskeletal parts are designed for moderate or light duty, but heavy duty systems are available. Another advantage of some of the endoskeletal systems is that knee units of greater complexity can be introduced as the amputee becomes more proficient or his functional needs change. Ankle-Foot Systems A variety of artificial foot designs is available, each having its advantages and disadvantages. Feet currently available can be divided into two classes: articulated -those with moving joints, and non-articulated. Those with moving joints generally require more maintenance and are slightly heavier than most of the non-articulated kind. Articulated feet may have one or more joints. The single-axis foot (one-joint) provides for ankle action that is controlled by two rubber bumpers either of which can be changed to permit more or less motion as needed. It is often used to assist in keeping the knee stable. A multi-axis foot is often recommended for people who have to walk on uneven surfaces because it allows some motion about all three axes of the ankle. It is, of course, slightly heavier than the other types of feet and is apt to require more maintenance as well. The simplest type of non-articulated foot is the SACH (solid ankle- cushion heel) Foot. The keel is rigid. Ankle action is provided by the soft rubber heel which compresses under load during the early part of the stance phase of walking. The rubber heel wedges are available in three densities: soft, medium, and hard. The SAFE (solid ankle-flexible-endoskeletal) Foot has the same action as the SACH plus the ability for the sole to conform to slightly irregular surfaces and thus makes it easier for the amputee to walk over uneven terrain. Feet of this type make walking easier because of the flexibility, and are sometimes called "flexible keel" feet. In recent years, there has been a proliferation of new designs for artificial feet. Most are capable of absorbing energy in a "flexible" keel during the "roll-over" part of the stance phase of walking and springing back immediately to provide push-off, or assistance in getting the toe off of the ground, to start the swing phase of walking. Although the original idea was to provide the active athlete with more function, amputees who are a lot less active have found these designs useful. These designs are often called "dynamic response" feet. Most of the non-articulated feet are available with toes molded in to provide a very realistic appearance. There are available still other ankle-foot systems that incorporate the shank and eliminate the need for a mechanical connection between the foot and shank. The shank-ankle-foot is usually made of a specially developed plastic composite that responds nicely to the forces created during the stance phase of walking. These lightweight systems seem to have most of the advantages of more conventional designs, while providing an additional function. Transverse Rotation Device A transverse rotation unit allows some rotation about the long axis of the shank when it is installed in the shank between the ankle and the socket. The idea of providing this function seems to be sound, but the difficulty in designing and manufacturing a unit that is reliable has restricted its acceptance. Above-Knee Prosthesis Fabrication Whether the prosthesis is to be a crustacean or an endoskeletal (often called "modular") type, the prosthetist begins by wrapping the stump with plaster-of-Paris bandages to obtain a negative mold. A positive model is made by filling the negative mold with a mixture of plaster-of-Paris and water, and allowing it to harden. After modification of the model to provide the proper characteristics in the finished socket, a plastic socket is formed over it. The first socket is usually transparent for use as "test" or "check" socket to determine if further modifications are needed. A new method being used by some prosthetists for obtaining a modified model of the stump involves use of a computer and automatic machinery. Known as CAD/CAM, (Computer-Aided Design \ Computer-Aided Manufacturing), this system permits prosthetists to modify the model more easily since it does not require making and carving an actual plaster model. The socket is mounted on an adjustable leg for walking trials, and when both the prosthetist and the amputee are satisfied, the limb is ready for the finishing procedures. The crustacean shank may be of plastic-covered wood or all plastic. The endoskeletal type uses carved foam rubber over the supporting tube and the entire prosthesis is encased in a latex or fabric stocking. Steps in the fabrication of a plastic prosthesis for the trans-femoral amputee are: 1. A negative mold of the stump is made by wrapping it with a wetted plaster-of-Paris bandages. 2. The cast is filled with a mixture of plaster of Paris and water to make a positive model. 3. After modifications have been made to the positive model to make sure that the pressure on the stump will be distributed properly, a check, or test, socket is made by forming a heated sheet of a clear plastic over the modified model. 4. The clear plastic socket is tried on to make sure that it fits properly. 5. A new positive model is made by filling the clear test socket with a mixture of plaster of Paris and water. 6. The socket to be used on the definitive prosthesis is formed over the model either by using a mixture of plastic resin and cloth or by forming a heated sheet of plastic over the model. 7. The definitive socket is attached to an adjustable leg for alignment and walking trials. 8. The finished prosthesis may be either the crustacean or the endoskeleton type. Donning the Sucton Socket A number of methods of donning the suction socket have been devised through the years. Each amputee needs to experiment to determine the method that seems easiest for him. The three most popular methods seem to be: 1. Use of a nylon stocking or a single layer of tubular stockinet over the stump and removing it through the valve hole as the stump is "pumped" into the socket. 2. Use of tubular stockinet that has been doubled over the stump and removing the stockinet by pulling the end of the outer layer through the valve hole as the stump is "pumped" into the socket. 3. Use of an elastic bandage that has been wrapped tightly around the upper half of the stump and then pulled through the valve hole as the stump is "pumped" into the socket. Various devices have been made available from time to time with the purpose of making the donning of the prosthesis easier, but none seem to have been used widely. Air bubbles between the socket and stump result in discomfort. The valve is opened as the stump is forced into the socket to expel any air bubbles that may develop and to reestablish suction when it is lost after sitting or for any reason. Care of the Stump The stump must be washed daily to avoid irritations and infection. A mild soap and warm water are recommended. The interior of the socket must be kept clean as well by washing daily with warm water and a mild soap. Use of detergents should be avoided. Some amputees have found a hair dryer to be very useful in drying the stump and the inner walls of the socket. When prosthetic socks are used, they should be replaced daily with newly laundered ones; more often, in warm humid weather. The socks should be washed in warm water with a mild soap. Manufacturers recommend that socks be rotated on at least a three or four-day schedule to allow the fibers to retain their original position. Prosthetic socks must be applied carefully to avoid wrinkles which can cause skin problems. Reductions in the size of the stump can be accommodated by adding one or more prosthetic socks. Prosthetic socks are woven especially for their intended use and are available in three thicknesses and a variety of sizes. The thicknesses generally available are 3-ply, 5-ply, and 6-ply. With this combination, various thicknesses can be obtained as follows: One 3-ply = 3 plies One 5-ply = 5 plies Two 3-ply = 6 plies One 3-ply + One 5-ply= 8 plies One 6-ply sock can be used instead of two 3-ply socks. Some amputees have found that use of a one-ply cotton cast sock provides a satisfactory way to obtain still finer adjustment in thickness. When the amputee has trouble in obtaining comfort by a combination of prosthetic socks, he should consult with his prosthetist immediately. Training Extensive training in the use of an above-knee prosthesis is usually necessary if optimum gait and comfort are to be obtained. Early training is provided by the prosthetist during fitting trials. Physical therapists usually provide the additional training as required. The new prosthesis should be worn initially for short periods and wearing time increased each day depending upon individual situations. One of the greatest problems in obtaining good performance and maximum comfort is overweight of the amputee, especially the above knee. Fluctuations in body weight are reflected in the stump where changes in volume result in poor fit, discomfort, and consequently poor performance. A reasonable exercise program and a sensible diet are important factors in the health and well being of every one, but even more so in the case of the amputee. Slight reduction in size of the stump can be accommodated by adjustments to the socket, but the prosthetist can do little about expanding the size of a socket and almost any increase in size of the stump means a new prosthesis, or, at the least, a new socket. Knee-Disarticulation Prostheses The knee-disarticulation prosthesis is very similar to the above-knee prosthesis, except for the lower part of the socket and the knee mechanism. Before the introduction of the present day polycentric knee units, sockets for the prosthesis were usually made of leather and metal hinges were used to attach the socket to the shin. This type of prosthesis is still preferred by a few preferred even though it is bulky and control of the leg during the swing phase is difficult. However, most prefer one of the polycentric designs where the knee mechanism can be installed within the shin due to its special design. The major objection to the polycentric units is that the knee protrudes slightly beyond the front of the shank when the amputee is sitting or kneeling. Leather sockets are held on by a lacing. Plastic sockets usually have a foam liner in the lower part for the bulbous end of the stump to slip by so as to keep the socket in place. All of the instructions given about use of the above-knee apply equally to the Knee-Disarticulation prosthesis. Hip-Disarticulation and Hemipelvectomy Prostheses Most of the components designed for above-knee prostheses are suitable for amputees who have lost function about the hip due to amputation just below the hip joint, at the hip joint (hip-disarticulation), or hemipelvectomy (when half of the pelvis has been removed.) To provide good control of the leg, the artificial hip joint is placed on the front of the socket rather than opposite the anatomical hip joint, an arrangement that provides better control of the prosthesis. For these prostheses, the socket is either of laminated plastic or a thermoplastic, and the construction is usually modular that is, pylon, or endoskeletal, because this type of construction results in a relatively lightweight prosthesis. The hemipelvectomy prosthesis presents an added problem to the prosthetist because there is no ichial bone present to aid in weight bearing. All of the instructions given about use of the above-knee prosthesis apply equally to the hip-disarticulation and hemipelvectomy prostheses. Maintenance of the Prosthesis When one of the non-articulating feet is used, there is very little maintenance required for the below-knee prosthesis other than keeping it clean inside and out. Articulated feet generally need to be lubricated at regular intervals. The heel height of the shoe is an important factor in the alignment of the prosthesis. Therefore, when shoes are changed, it is important that the effective heel height be the same as the ones used previously. The effective heel height is obtained by subtracting the thickness of the sole of the shoe from the apparent heel height as shown below. For the same reason, the heels of the shoes should be replaced frequently so that wear will not result in alignment changes. Also, a badly worn shoe will increase the wear on a prosthetic foot. Prostheses should not be worn without shoes. Not only will it cause excessive stress on the stump and knee joint, but the wear on the foot will result in permanent malalignment. Most prostheses are water-resistant but few are waterproof. If the foot becomes wet, the shoe should be removed as soon as possible to facilitate drying. If the amputee has any doubt about the fit, alignment, or condition of the prosthesis or stump, he should consult his prosthetist immediately. Maintenance requirements for knee units vary. Prosthetists will give instructions for maintenance except for hydraulic units which must be taken care of by the prosthetist or manufacturer. An exchange unit can be provided when a hydraulic unit has to be removed for repair. Definitions Preparatory Prosthesis. An unfinished functional replacement for an amputated limb, fitted and aligned in accordance with sound biomechanical principles, which is worn for a limited period of time to accelerate the rehabilitation process. Pylon. A rigid member, usually tubular, between the socket or knee unit and the foot to provide support. Rigid Dressing. A plaster wrap over the stump, usually applied in the operating or recovery room immediately following surgery, for the purpose of controlling edema (swelling) and pain. It is preferable, but not necessary, that the rigid dressing be shaped in accordance with the basic biomechanical principles of socket design. Early Prosthetic Fitting. A procedure in which a preparatory prosthesis is provided for the amputee immediately after removal of the sutures. Modular Prosthesis. An artificial limb assembled from components, usually of the endoskeletal type where the supporting member, or pylon, is covered with a soft foam or other light material shaped and finished to resemble the natural limb. Definitive, or "Permanent", Prosthesis. A replacement for a missing limb or part of a limb which meets accepted check-out standards for comfort, fit, alignment, function, appearance, and durability. Check or Test Socket. A temporary socket, often transparent, made over the plaster model to aid in obtaining a proper fit.