Chapter 31: Prosthetics

Physical therapists are concerned with the care of individuals with lower- and upper-limb amputations. Patients are often fitted with a prosthesis to replace the absent part of the leg or arm. In the broadest sense, prostheses also include dentures, titanium femoral heads, and plastic heart valves. A prosthetist is a health care professional who designs, fabricates, and fits limb prostheses.

The major causes of amputation are peripheral vascular disease, trauma, malignancy, and congenital deficiency. In the United States, vascular disease accounts for most leg amputations, particularly among patients with diabetes.¹ Individuals older than 60 constitute the largest group of people with amputation. Trauma is responsible for the majority of amputations in younger adults and adolescents. Men are more likely to sustain amputation because of trauma and vascular disease. Bone and soft tissue tumors are sometimes treated by amputation, with adolescence the period of peak incidence. Congenital deficiency refers to the absence or abnormality of a limb evident at birth.

This chapter focuses on the lower extremity (LE) because many more people have lost a portion of the LE, as compared with the upper extremity (UE). Physical therapists are key members of the rehabilitation team, working with prosthetists, physicians, occupational therapists, and others to foster the patient's welfare. For individuals with LE amputation, physical therapists have the major role in assisting the person to regain function. Lower extremity prostheses will be described, together with a program for training patients in their use. For patients with UE amputation, physical therapists may play a lesser role, cooperating with occupational therapists, depending on the administrative organization of the health care facility.

Historic records confirm that the concept of replacing a missing limb is very old. A forked stick that formed a peg leg to support a transtibial (below-knee) amputation limb was known in antiquity. Today, most individuals with LE amputation are provided with a prosthesis because function with one LE is very different from maneuvering with two.

The principal LE prostheses are partial foot, Syme's, transtibial, and transfemoral, as well as knee and hip disarticulation. The physical therapist should be familiar with their characteristics and maintenance, as well as the rehabilitation of patients fitted with these devices.

The purposes of partial foot prostheses are to (1) restore, as much as possible, foot function, particularly in walking; and (2) simulate the shape of the missing foot segment. The patient who has lost one or more toes may simply pad the toe section of the shoe to improve the appearance of the upper portion of the shoe. Standing will not be affected, assuming the metatarsal heads remain. When the individual walks, late stance will be less forceful, particularly if both phalanges of the great toe are absent. An arch support foot orthosis helps to maintain alignment of the amputated foot, especially if one or more proximal phalanges have been amputated.²

Transmetatarsal amputation disturbs foot appearance more noticeably. A prosthesis prevents the shoe from developing an unnatural crease in the forefoot area. The patient bears most weight on the heel and reduces the amount of time spent on the affected foot during walking. A particularly useful prosthesis consists of a plastic socket for the remainder of the foot. The socket is affixed to a rigid plate that extends the full length of the inner sole of the shoe. The plate has a cosmetic toe filler. The socket protects the amputated ends of the metatarsals, and the rigid plate restores foot length so that the person can spend more time during the stance phase of gait on the affected side than would otherwise be the case. To aid late stance, the bottom of the prosthesis or the sole of the shoe may have a convex rocker bar.³

Amputation or disarticulation through the tarsals, such as Lisfranc and Chopart disarticulations,⁴ poses the additional problem of retaining the small foot segment in the shoe during swing phase. Foot length is apt to be diminished further by an equinus deformity of the amputated limb, resulting from unbalanced contraction of the triceps surae. Consequently, the prosthesis described for the transmetatarsal amputation may be augmented with a plastic calf shell, which is strapped around the leg.^5,6

Syme's amputation involves surgical sectioning through the distal tibia and fibula, removal of the entire foot, and preservation of the calcaneal fat pad. The patient can usually bear significant weight through the distal end of the amputation limb.^7,8 The socket (Fig. 31.1) trimlines (edges) are located in the proximal portion of the lower leg. The socket has a relief (concavity) for the tibial crest. If the distal end of the Syme's limb is markedly bulbous, the lower part of the medial wall can be made removable; the patient dons the socket, and then fastens the wall section in place. The socket for an amputation limb having relatively vertical contours does not need a removable section; this design has a resilient liner that assists entry of the bulbous distal end of the amputated limb, enabling the wearer to don the prosthesis easily. The prosthesis includes a foot specifically designed to accommodate the long socket (Fig. 31.2). The Syme's prosthesis is suspended by the contour of its brims and socket walls, ordinarily without any other suspension mechanism.

The transtibial level, formerly known as below-knee, refers to an amputation in which the tibia and fibula are transected. The patient retains the anatomical knee with its motor and sensory functions. This is the predominant site of amputation, particularly for individuals with vascular disease.⁹ Prostheses for transtibial amputations include a foot-ankle assembly, shank (lower leg), socket, and suspension component.

Foot-Ankle Assemblies

A foot-ankle assembly restores the general contour of the patient's foot, absorbs shock at heel contact, plantarflexes in early stance, and simulates metatarsophalangeal (MTP) hyperextension (toe-break action) in the latter part of stance phase; patients appear to prefer a foot with a relatively rigid forefoot.¹⁰ The foot is in the neutral position during swing phase. Many assemblies also provide slight motion in the frontal and transverse planes, attempting to mimic physiological foot action.^{11,12,13,14,15,16} Newer feet are often made of carbon fiber, which is lighter and stronger than wood.

Nonarticulated Feet

In the United States, the most popular foot type is nonarticulated, without a space between the foot and lower portion of the shank. As compared with articulated feet, nonarticulated components are lighter in weight and more durable; some versions are made to suit high-heeled shoes.

SACH Foot

The nonarticulated solid ankle cushion heel (SACH) assembly is commonly prescribed (Fig. 31.3A). The longitudinal portion is a wooden or metal keel, which terminates at a point corresponding to the metatarsophalangeal joints. The keel is covered with rubber; the posterior portion is resilient, to absorb shock and permit plantarflexion in early stance. Anteriorly, the junction of the keel and the rubber toe sections allows the foot to hyperextend in late stance. The SACH foot is manufactured in a wide range of sizes to accommodate infants, adolescents, and adults. It is available with heel cushions of varying degrees of compressibility for those who strike the heel with different amounts of force. SACH feet can be ordered in several plantarflexion angles to fit shoes with diverse heel heights. The heel cushion allows a very small amount of medial–lateral and transverse motion.

Other Nonarticulated Feet

A newer version of the SACH foot is the stationary attachment flexible endoskeleton (SAFE) foot (Fig. 31.3B). It has a rigid ankle block joined to the posterior portion of the keel at a 45° angle, which is comparable to that of the anatomical subtalar joint. The junction permits the wearer to maintain contact with moderately uneven terrain, because of the relatively great range of medial– lateral motion permitted in the rear foot. The SAFE foot, however, is somewhat heavier and more expensive than the SACH foot.

Feet that have a springy sole store energy in early and midstance as the wearer moves over the foot, bending it slightly. In late stance, as the wearer transfers loading to the opposite foot, the spring in the prosthetic foot recoils, returning some of the stored energy. Such feet are described as energy storing/energy releasing, or dynamic.¹¹ Both the Flex-Foot and the Springlite foot (Fig. 31.4) include a long band of carbon fiber, extending from the toe to the proximal shank, as well as a posterior heel section. The long band acts as a leaf spring, enabling the foot to store considerable energy in early and midstance, and then to release energy at the end of stance phase. Active wearers, such as those who play basketball or run, utilize the energy-storing and energy-releasing capacity of these feet. The C-Walk^® (Fig. 31.5) is another example of an energy-storing foot. Other energy storing prosthetic feet are shown in Figure 31.6. They are more expensive than SACH feet. Many of these feet can be sheathed in a cosmetic cover (Fig. 31.7). Athletes may opt to interchange the basic prosthetic foot for one designed for sprinting (Fig. 31.8).

Articulated Feet

Manufactured with separate foot and lower shank sections, articulated feet have the sections joined by a metal bolt or cable. Rubber bumpers usually control the ease of foot motion. Articulated feet are subject to eventual loosening, which may be signaled by a squeaking noise.

Single-Axis Feet

The most common example of an articulated foot is the single-axis foot (Fig. 31.9). A rear bumper absorbs shock and controls plantarflexion excursion; it is easy for the prosthetist to substitute a firmer or softer bumper, depending on the force that the patient applies in early stance. A heavy or very active client requires a firm bumper, whereas a frail individual needs a bumper that is soft enough to permit the foot to plantarflex with minimal loading. At early stance, bearing-weight on the heel causes the foot to plantarflex, ensuring that the wearer achieves the stable foot-flat position. Anterior to the ankle bolt is firmer rubber or similar material, the dorsiflexion stop, which resists dorsiflexion as the wearer transfers weight forward over the foot. The single-axis foot does not allow medial–lateral or transverse motion. Some people prefer this simplicity of control.

Multiple-Axis Feet

These components move slightly in all planes to aid the wearer in maintaining maximum contact with the walking surface, even if the surface slopes or has slight irregularities (Fig. 31.10). A recent version of the multiple-axis foot is the ProprioFoot^® (Fig. 31.11), which includes electronic sensors to detect when the wearer needs dorsiflexion; it also provides greater ankle excursion than other foot-ankle assemblies and reduces pressure on the amputation limb.^17,18 Multiple-axis feet are heavier and less durable than single-axis or nonarticulated feet.

Selection of the appropriate foot is based on the needs of the individual, considering the wearer's activity level, weight, and level of amputation, as well as the length and shape of the residual limb. The patient may also benefit from a rotator and a vertical shock absorber.

Rotators and Shock Absorbers

A rotator is a component placed above the prosthetic foot to absorb shear stress in the transverse plane. A shock absorber reduces vertical impact. These components protect the user from skin chafing, which would otherwise occur if the socket were permitted to slide against the skin.^19,20,21 Rotators and shock absorbers are most often used with single-axis feet and by very active individuals, especially those with transfemoral amputations. A rotator with or without a shock absorber may be contained within a prosthetic foot, such as Ceterus^® (Fig. 31.6C), or may be installed in the shank, such as the Delta Twist^® (Otto Bock, Minneapolis, MN 55447) (Fig. 31.12).

Shank

The shank is the substitute for the human leg, restoring leg length and transmitting body weight from the socket to the prosthetic foot. The shank is located between the foot-ankle assembly (or rotator) and the socket in a transtibial prosthesis. The two types of shank are exoskeletal and endoskeletal.

Exoskeletal Shank

The exoskeletal shank (Fig. 31.13 [left]), sometimes called crustacean, is typically made of rigid plastic (older versions are made of wood). The rigid exterior is shaped to simulate the contour of the anatomical leg. Although the shank is usually finished with plastic tinted to match the wearer's skin color, some individuals opt for a multicolored or patterned shank. The exoskeletal shank is very durable and, with the plastic finish, is impervious to liquids. Because they are less lifelike and do not permit changes in alignment of the prosthesis, exoskeletal shanks are less frequently prescribed.

Endoskeletal Shank

The endoskeletal shank (Fig 31.13 [right] and Fig. 31.14), or modular shank, consists of a central aluminum or rigid plastic tube (called a pylon) usually covered with foam rubber and a sturdy stocking or similar finish. With its cover, the endoskeletal shank is more natural in appearance than the shiny exoskeletal shank. In addition, the pylon has a mechanism that permits making slight adjustment of the alignment of the prosthesis; this may contribute to comfort and ease of walking. A variety of prosthetic foot-ankle assemblies, such as the Flex Foot^®, incorporate an endoskeletal shank. Some patients wear prostheses without a cover over the pylon.

Socket

The amputation limb fits into a plastic receptacle called the socket (Fig. 31.15). Although the original name for the modern transtibial socket was the patellar-tendon-bearing (PTB) socket, the socket is designed to contact all portions of the amputated limb for maximum distribution of load, as well as to assist venous blood circulation and provide maximum tactile feedback. The PTB socket features a prominent indentation over the patellar ligament, sometimes known as the patellar tendon. A newer socket variation is total surface bearing, which has a shallower anterior indentation.²²

Sockets are custom made of plastic molded over a model of the patient's amputation limb. The model may be produced from a plaster cast of the amputation limb or by computer-aided design/computer-aided manufacture (CAD-CAM). The latter involves an electronic sensor, which transmits a detailed map of the limb to a computerized program consisting of socket-shape variations; the prosthetist selects the appropriate shape, which is transmitted to an electronic carver that creates the model over which the plastic is shaped. Whether the model is made by hand or by computer, it provides reliefs, concavities in the socket over areas contacting sensitive structures, such as bony prominences; reliefs are located over the fibular head, tibial crest, tibial condyles, and anterior–distal tibia. The posterior brim is shaped to provide adequate room for the medial and lateral hamstring tendons, so that the patient is comfortable when sitting. Build-ups are convexities in the socket over areas contacting pressure-tolerant tissues, such as the belly of the gastrocnemius; patellar ligament; proximomedial tibia, corresponding to the pes anserinus; and the tibial and fibular shafts (see Fig. 31.15).

When viewed from above, the socket resembles a triangle, the apex of which is formed by the relief for the tibial tubercle and crest, and the base angles of which are the hamstring reliefs. The anterior wall terminates at the mid-patella, or above. The medial and lateral walls extend at least to the femoral condyles. The posterior wall lies across the popliteal fossa.

The socket is aligned on the shank in slight flexion to enhance loading on the patellar ligament, prevent genu recurvatum, and resist the tendency of the amputation limb to slide too deeply into the socket. Flexion also facilitates contraction of the quadriceps muscle. The socket is also aligned with a slight lateral tilt to reduce loading on the fibular head.^23,24

Lined Socket

The transtibial socket generally includes a resilient liner, made of polyethylene foam,²⁵ polyurethane,²⁶ silicone,²⁷ or similar materials. In addition to cushioning the amputation limb, the removable liner facilitates alteration of socket size; the prosthetist can add material to the outside of the liner, reducing the volume of the socket while preserving smooth interior contours. The liner, however, adds to the bulk of the prosthesis and is a heat insulator, which the wearer may find uncomfortable in hot weather. Individuals with Syme's and transtibial amputations usually wear cotton, wool, or synthetic fabric socks to ensure a snug socket fit. An alternative to the polyethylene liner is a sheath made of silicone or similar material, which fits so snugly that the wearer has little risk of abrasion between the socket and skin.

Socks, Sheaths, and Liners

All individuals with LE amputations, except those wearing transfemoral prostheses suspended by total suction or those using a sheath, require a supply of clean socks of appropriate material, size, and shape. It is expeditious to order at least a dozen socks at the time the prosthesis is prescribed, so that third-party payment may cover this relatively inexpensive but important accessory.

Fabric socks are woven in various thicknesses, referred to as ply, designating the number of threads knitted together. Cotton socks absorb perspiration readily and are the least allergenic; they are made in two-, three-, and five-ply, the last being the thickest. Wool socks provide good cushioning, woven in three-, five-, and six-ply; they are expensive and must be laundered carefully. Orlon/Lycra socks are manufactured in two- and three-ply thicknesses. They can be washed easily without shrinking. This synthetic fabric combination affords considerable resilience, but does not absorb much perspiration.

A nylon sheath creates a smooth surface over the skin, thereby reducing the risk of chafing, especially in hot weather and among those with much scarring. Some transtibial prosthesis wearers are able to use a woman's knee-high nylon stocking if the amputated limb is slender. Because nylon does not absorb sweat, liquid passes through the weave to be absorbed by an outer sock of cotton or wool. Silicone, urethane, and other synthetic sheaths provide excellent shock absorption and abrasion resistance; they also can aid in suspending the socket on the patient's limb, and are designed to be worn next to the skin. They are, however, more expensive than fabric socks or sheaths.

It is common practice to add more socks as the amputation limb volume reduces. Nevertheless, when the patient requires a total of 15-ply of socks to achieve snug fit, the socket should be altered or replaced by the prosthetist. Excessive sock padding distorts the weight-bearing characteristics of the socket, losing the effect of strategically placed build-ups and reliefs.

Regardless of material, the shape of the sock or sheath is important for comfort. An interface of proper size fits smoothly without wrinkling or undue stretching. The sock or sheath should be long enough to terminate above the most proximal part of the socket.

Silicone gel suspension liners are another form of socket-residual limb interface. These liners cushion the residual limb as well as function as a primary or secondary suspension system. Some include a nylon outer cover, with liner thickness tapering distally, and may be indicated for particularly active users and those with fragile or sensitive residual limbs. They are available in locking, custom, and seal-in designs (Fig. 31.16).

Unlined Socket

Although the unlined socket is sometimes referred to as a hard socket, that term is a misnomer, because the wearer has a soft interface provided by socks or a sheath worn with the unlined socket. Occasionally, a resilient pad is placed in the bottom of the unlined socket to cushion the distal end of the amputation limb. The unlined socket is a more satisfactory choice for the person whose limb has stabilized in volume, because it is easier to clean; however, it is more difficult to alter the shape of the unlined socket in comparison to the lined socket.

A newer type of unlined socket is made of thin thermoplastic in a rigid frame. The plastic can be spot-heated to facilitate alteration of socket fit. It adheres to the skin better than rigid plastic, thereby improving suspension. It contributes to comfort by dissipating body heat more effectively and responds to changes in amputation limb shape as the patient contracts and relaxes various muscles.

Suspension

During the swing phase of walking, or whenever the wearer is not standing on the prosthesis, such as when climbing stairs or jumping, the prosthesis requires some form of suspension to hold it in place.

Cuff Variants

The modern transtibial prosthesis originated with a supracondylar cuff (Fig. 31.17 [left]), which is still widely used. The cuff may be a leather, flexible plastic, or fabric-webbing strap. It encircles the thigh immediately above the femoral condyles, and permits the user to adjust the snugness of suspension easily. Some individuals, however, object to the profile of the distal thigh created by the cuff. Others who have severely arthritic hands or limited vision have difficulty engaging the buckle or pressure hook-and-loop closure on the cuff.

A fork strap and waist belt may be used to augment the cuff. The elastic fork strap extends from the outside of the anterior portion of the socket to a waist belt. The fork strap and waist belt may be indicated for individuals who climb ladders or engage in other activities during which the prosthesis is unsupported by the ground for long periods. Alternatives to the cuff include a rubber sleeve, a tubular component that covers the proximal socket and the distal thigh; or a sleeve that includes a distal pin to create a shuttle lock (Fig. 31.17 [right]), described in the following section titled Distal Attachments. The sleeve provides excellent suspension and a streamlined silhouette when the wearer sits. Donning the sleeve, however, requires two strong hands and a thigh that does not have excessive subcutaneous tissue.

Distal Attachments

Very secure suspension is achieved with the use of a silicone sheath with a distal metal pin (Fig. 31.18; see Fig 31.17 [right]). The sheath clings to the skin. The user inserts the sheathed limb into the prosthesis, guiding the attached pin into a receptacle, also called a shuttle lock, in the socket. During swing phase, the pin mechanism prevents the prosthesis from slipping.

Vacuum-assisted suspension is another alternative mode of suspension. The system (Fig. 31.19) combines a pump, liner, and sleeve to achieve elevated vacuum in an airtight environment. Vacuum promotes fluid exchange, reduces moisture buildup, regulates volume fluctuations, and increases proprioceptive awareness of the limb's position in space.

A surgical approach to distal attachment is known as osseointegration²⁸ in which the surgeon implants a metal post in the distal bone. The post protrudes through the skin and locks into a mechanism in the prosthesis. Osseointegration eliminates the need for other suspension apparatus; however, fluid drainage and infection at the skin/post interface are sometimes troublesome. The procedure was developed in Europe and is not yet readily available in North America.

Brim Variants

The socket walls may be extended proximally to suspend the prosthesis. With supracondylar (SC) suspension (Fig. 31.20 [left]), the medial and lateral walls extend above the femoral condyles. Some SC suspension designs include a plastic wedge on the medial wall (Fig. 31.20 [middle]). When donning the prosthesis, the client removes the wedge, places the amputation limb in the socket, and then places the wedge between the socket and the medial condyle to retain the prosthesis on the limb. Alternatively, the wedge can be incorporated in a liner; for donning, the patient applies the liner, and then inserts the limb, with liner, into the socket. Supracondylar suspension increases medial–lateral stability of the prosthesis, presents a pleasing contour at the knee, and eliminates the need to engage a buckle or hook-and-loop closure on a cuff. It is more difficult to fabricate (and, hence, more expensive), and it is not readily adjustable.

Presenting a contour of medial and lateral walls similar to the supracondylar suspension, the supracondylar/suprapatellar (SC/SP) suspension (Fig. 31.20 [right]) also features an anterior wall that terminates above the patella.

The short amputated limb is well accommodated by SC/SP suspension. The high anterior wall may interfere with kneeling and presents a conspicuous contour when the wearer sits.

Thigh Corset

Some individuals with very sensitive skin may benefit from thigh corset suspension (Fig. 31.21). Metal hinges attach distally to the medial and lateral aspects of the socket and proximally to a flexible plastic corset. Corset heights vary and may reach the ischial tuberosity for maximum weight relief on the amputation limb. The hinges increase frontal plane stability, and the corset increases area for weight-bearing load distribution. The resulting prosthesis, however, is heavier and apt to foster piston action because the hinges have a single pivot joint that does not articulate collinearly with the anatomical knee. Prolonged use of a thigh corset produces pressure atrophy of the thigh. A prosthesis with corset suspension is more difficult to don because the wearer must fasten a series of pressure closure hook-and-loop straps.

Individuals with amputation between the femoral condyles and greater trochanter are fitted with transfemoral (above-knee) prostheses. Those whose limbs retain the distal part of the femur can wear a knee disarticulation prosthesis, which differs from the transfemoral prosthesis in the type of knee unit and socket. If the amputation is proximal to the greater trochanter, the patient cannot retain or control a transfemoral prosthesis and is therefore a candidate for a hip disarticulation prosthesis. The transfemoral prosthesis consists of (1) foot-ankle assembly; (2) shank; (3) knee unit; (4) socket; and (5) suspension device.

Foot-Ankle Assemblies and Shanks

Although the SACH foot is often prescribed for transfemoral prostheses, the single-axis foot is more frequently used for transfemoral than for transtibial prostheses. The single-axis foot reaches the foot-flat position with minimal application of weight-bearing load. Nevertheless, almost any foot, including the energy storing/releasing designs, can be incorporated in a transfemoral prosthesis. As compared with wearers of transtibial prostheses, however, most wearers of transfemoral prostheses do not load the prosthesis as vigorously. Consequently, less energy would be stored and released in a dynamic response foot.

Either the sturdy exoskeletal shank or the more attractive endoskeletal shank may be used. The latter creates a more pleasing appearance, particularly in the knee area, is adjustable in alignment, and is lighter than an exoskeletal shank. Limited research is inconclusive regarding the merit of minimizing prosthetic weight.²⁹ Problems of durability remain, particularly at the knee, where constant bending of the joint, especially when the wearer is kneeling, accelerates deterioration of the rubber cover. A rotator with or without a shock absorber incorporated in the shank diminishes shear stress on the amputation limb.³⁰

Knee Units

The prosthetic knee enables the user to bend the knee when sitting or kneeling and, in most instances, also permits knee flexion during the latter portion of the stance phase and throughout the swing phase of walking. Commercial knee units may be described according to four features: (1) axis; (2) friction mechanism; (3) extension aid; and (4) mechanical stabilizer. Many combinations of features are available; not every knee unit has all four components.

Axis System

The thigh piece can be connected to the shank either by a single-axis hinge, which is a common arrangement, or by polycentric linkage. Polycentric systems (Fig. 31.22) have pivoting bars and provide greater stability to the knee, inasmuch as the momentary center of knee rotation is posterior to the wearer's weight line during most of stance phase.³¹ The polycentric knee provides mechanical swing control that allows a single optimal walking speed. For variable cadence, some polycentric knee units incorporate pneumatic or hydraulic swing control.

Friction Mechanisms

In the simplest sense, the leg of the transfemoral prosthesis is a pendulum swinging about the knee hinge. For the elderly individual who walks slowly for short distances, a basic pendulum is adequate. More energetic walkers, however, benefit from adjustable friction mechanisms that modify the pendulum action of the leg to reduce the asymmetry between the motions of the sound and prosthetic limbs. If the prosthetic knee does not have sufficient friction to retard its natural pendulum action, the person who walks rapidly experiences excessive knee flexion (high heel rise) at the beginning of swing phase and abrupt, often noisy, knee extension at the end of swing phase (terminal swing impact). Friction mechanisms change the leg swing by modifying knee motion during various parts of swing phase and by affecting knee swing according to walking speed. Two interrelated issues involved in friction mechanisms are the time during swing phase when friction affects the knee unit and the medium through which the mechanism operates.

Constant and Variable

The most commonly prescribed knee unit has constant friction (Fig. 31.23), generally a pair of clamps that grasp the knee bolt. The clamps resist shank motion throughout swing phase time, providing a constant amount of friction. The clamps are easy to loosen or tighten to change the ease of knee motion. A more sophisticated device applies variable friction, in which the amount of friction changes during a given portion of swing phase. At early swing, high friction is applied to retard excessive knee flexion; during midswing, friction diminishes to permit the knee to swing easily; at late swing, friction increases to dampen impact.

Medium

The medium through which friction is applied influences performance. The usual medium is sliding friction, contact of one solid structure on another. A clamp sliding about the knee bolt is simple and inexpensive, but it does not accommodate automatically to changes in walking speed. A more complex approach is fluid friction, either oil (hydraulic friction) (Fig. 31.24) or air (pneumatic friction). Unlike sliding friction, fluid friction varies directly with velocity. Thus with a hydraulic or pneumatic unit, if the wearer walks faster, the knee increases friction instantly to prevent excessive knee flexion and abrupt extension. Consequently, the movements of the prosthetic and sound limbs are less asymmetrical than would be the case with sliding friction. Oil or air is contained in a cylinder in the knee unit. A piston descends in the cylinder during early swing, causing the knee to flex. The speed of piston descent depends on the type of fluid and the walking speed. Later, the piston ascends, extending the knee. Hydraulic units provide more friction than do pneumatic devices. Both types are more expensive than the simpler sliding friction designs.

Microprocessor-controlled hydraulic units, such as the C-Leg^® (Fig. 31.25), utilize electronic sensors, which detect the rate and range of shank movement 50 or more times per second, providing almost instant friction adjustment to changes in the gait pattern.^{32,33,34,35,36,37,38,39,40,41} Units are programmed with a computer, and may provide stumble recovery, locking option, and accommodation to walking on various terrain and bicycle riding. An alternative to oil-filled hydraulic units is the Rheo^® knee (Ossur, Aliso Viejo, CA 92656), which has magnetized fluid and sensors that detect knee action in much smaller time units.⁴²

Extension Aids

Many knee units include a mechanism to assist knee extension during the latter part of swing phase. The simplest type is an external extension aid, consisting of elastic webbing in front of the knee axis. The elastic stretches when the knee flexes in early swing and recoils to extend the knee in late swing. Webbing tension is easily adjusted, but tends to pull the knee into extension when the wearer sits. The internal extension aid is an elastic strap or coiled spring within the knee unit. It functions identically to the external aid during walking, but unlike the external aid, the internal type keeps the knee flexed when the individual sits. Acute knee flexion causes the strap or spring to pass behind the knee axis, maintaining the flexed attitude. Fluid-controlled knee units incorporate an internal extension aid.

Although most extension aids affect the wearer's performance during late swing and early stance phases, the Power Knee^® (Fig. 31.26) also assists the user to ascend stairs step-over-step as well as to rise from a chair. The unit incorporates accelerometers, gyroscopes, a torque sensor, and an on-board computer.

Stabilizers

Most knee units do not have a special device to increase stability. The patient controls prosthetic knee action by hip motion, aided by the alignment of the knee in relation to other components of the prosthesis. The knee axis is usually aligned posterior to a line extending from the greater trochanter to the ankle (trochanter-knee-ankle [TKA] line). The patient who has excellent balance and muscular control may have the knee bolt placed on the line, thus creating TKA alignment. Some hydraulic knee units are aligned with the knee axis anterior to the trochanter-ankle line. Elderly or debilitated patients may benefit from a stabilizing mechanism, as do some people who walk on very rough terrain, such as hunters.

Manual Lock

The simplest mechanical stabilizer is a manual lock (Fig. 31.27), in which a rod lodges in a receptacle and is released only when the wearer manipulates an unlocking lever. When engaged, the manual lock prevents knee flexion. The user is secure not only during early stance when stability is desired, but also throughout the entire gait cycle. To compensate for difficulty in advancing the locked prosthesis, the shank should be shortened approximately 1/2 in (1 cm). The manual lock must be disengaged when the wearer sits. Nevertheless, some people with impaired balance prefer the stability of the locked knee.⁴³

Friction Brake

A more elaborate stabilizing system, the friction brake, provides very high friction during early stance as the wearer bears weight on the prosthesis, resisting the tendency of the knee to flex.⁴⁴ One design, incorporated in a sliding friction unit, involves the mating of a wedge and groove upon loading, assuming the knee is flexed less than 25 degrees. Another version of friction brake is found in some hydraulic units; during early stance, additional fluid resistance markedly retards piston descent within the fluid cylinder and thus stabilizes the knee. Microprocessor units include stance control and, in most instances, a manual lock option.

From midstance through heel contact, friction brakes do not interfere with knee motion. In addition, they do not impede the patient who transfers from sitting to standing. Such devices add to the cost of the prosthesis and, if improperly used, may not protect the patient from falling.

Sockets

As with all prosthetic sockets, the transfemoral one should be a total-contact receptacle to distribute load over the maximum area, thereby reducing pressure. Total-contact fitting also provides counterpressure to assist venous return and prevent distal edema, and enhances sensory feedback to foster better control of the prosthesis.

Most transfemoral sockets are made of a flexible thermoplastic socket encased in a rigid frame. The frame enables the wearer to transmit weight through the distal components of the prosthesis to the ground. The flexible socket provides sensory input from external objects, such as chairs; it also dissipates body heat and facilitates alterations in socket fit. A polyester laminate socket is entirely rigid.

Transfemoral sockets are designed to emphasize loading on pressure-tolerant structures, such as the gluteal musculature, sides of the thigh, and, to a lesser extent, distal end of the amputated limb. The socket must avoid excessive pressure on the pubic symphysis and perineum.

Quadrilateral Socket

The basic transfemoral socket shape is quadrilateral when viewed from above (Fig. 31.28). The socket features a horizontal posterior shelf for the ischial tuberosity and gluteal musculature, a medial brim at the same level as the posterior shelf, an anterior wall 2.5 to 3 in (6 to 8 cm) higher to apply a posteriorly directed force to the thigh to retain the ischial tuberosity on its shelf, and a lateral wall the same height as the anterior wall to aid in medial–lateral stabilization. Concave reliefs are (1) anteromedial, for the pressure-sensitive adductor longus tendon and obturator nerve; (2) posteromedial, for the sensitive hamstring tendons and sciatic nerve; (3) posterolateral, to permit the gluteus maximus to contract and bulge without being crowded; and (4) anterolateral, to allow adequate room for the rectus femoris. The anterior wall has a convexity, Scarpa's bulge, to maximize pressure distribution in the vicinity of the femoral (Scarpa's) triangle. The lateral wall may have reliefs for the greater trochanter and the distal end of the femur.

Ischial Containment Socket

An alternate design type is the ischial containment socket (Fig. 31.29), sometimes called the contoured adducted trochanter-controlled alignment method.^45,46 Its walls cover the ischial tuberosity and part of the ischiopubic ramus to augment socket stability. To increase frontal plane stability and minimize bulk between the thighs, the mediolateral width of the socket is narrower than that of the quadrilateral socket. The anterior wall is lower than in the quadrilateral socket, whereas the lateral wall covers the greater trochanter. Weight-bearing occurs on the sides and bottom of the amputated limb.

Slight socket flexion is desirable for the following reasons: (1) to facilitate contraction of the hip extensors; (2) to reduce lumbar lordosis; and (3) to provide a zone through which the thigh may be extended to permit the wearer to take steps of approximately equal length. For wearers of quadrilateral sockets, socket flexion also enhances positioning of the ischial tuberosity on the posterior brim. Figure 31.30 presents a schematic of pelvic position within the ischial containment socket.

ComfortFlex^™ Socket

The ComfortFlex^™ (Hanger, Inc., Oklahoma City, OK 73118) is a soft flexible socket (plastic and silicone materials) placed in a carbon graphic frame (Fig. 31.31). This sockets design is available for various-level amputations (e.g., transfemoral, transtibial, hip disarticulation, hemipelvectomy). The carbon fiber frame provides structural support while the intimately fit flexible socket allows for muscle contraction and improved control of the prosthesis. The transfemoral socket is designed to "lock" the ischium and pubic ramus into the socket improving anterior/posterior and lateral stability and reducing socket rotation. The sockets are contoured to accommodate bone and soft tissue structures (e.g., muscles, tendons, nerves, vascular structures).

Suspensions

Three means are used to suspend the transfemoral prosthesis: (1) total suction, (2) partial suction, and (3) no suction (require auxiliary suspension).

Suction Suspension

Suction refers to the difference between pressure inside and outside the socket. With suction suspension, internal socket pressure is less than external pressure; consequently, atmospheric pressure causes the socket to remain on the thigh. A one-way air-release valve located at the bottom of the socket enables residual air to be expelled.

Total Suction

Maximum control of the prosthesis, without any encumbering auxiliary suspension can be achieved only when the socket brim fits very snugly. Some people add a transfemoral suspension sleeve (Fig. 31.32), especially when engaging in vigorous activities. If the patient experiences reduction in amputation limb volume, suction will be lost and an auxiliary suspension will be required.

Partial Suction

A socket that is slightly loose may provide partial suction suspension combined with auxiliary suspension; the socket has a valve. The patient wears one or more socks, or a synthetic liner. Because air enters the space between the sock's fibers, auxiliary suspension is needed, either a fabric Silesian belt (Fig. 31.33), or a rigid plastic or metal hip joint and pelvic band. These aids encircle the pelvis. The Silesian belt also controls the transverse plane orientation of the prosthesis on the thigh, while the hip joint restricts transverse and frontal motion at the hip. The pelvic band adds weight to the prosthesis and may impose uncomfortable pressure against the torso when the wearer sits.

No Suction

If the socket has a distal hole without a valve, then no pressure difference exists between the inside and the outside of the socket. The client wears one or more socks and requires a pelvic band. The pelvic band has a rigid metal or nylon single-axis hip joint attached to a leather belt, which encircles the pelvis. The relatively loose socket makes donning easy, but hinders control of the prosthesis and may make sitting uncomfortable.

Osseous integration is another less common suspension alternative. A metal post implanted in the femur locks into a fixture embedded in the distal portion of the socket.⁴⁵

Individuals with knee or hip disarticulation wear prostheses that include the same distal components as prostheses for lower levels. Any prosthetic foot can be used with either an endoskeletal or exoskeletal shank. The major distinction, therefore, is in the proximal portion of the prostheses.

Knee Disarticulation Prostheses

When amputation is at or distal to the femoral condyles, the patient should have excellent prosthetic control because (1) thigh leverage is maximum; (2) most of the body weight can be borne through the distal end of the femur; and (3) the broad condyles provide rotational stability.^46,47 The problem presented by knee disarticulation is primarily cosmetic; when the individual sits, the thigh on the amputated side may protrude forward of the sound knee. The knee disarticulation prosthesis has a streamlined knee that minimizes protrusion, as well as a specially designed socket.

Knee Units

Several units are specifically manufactured for knee disarticulation. All have a thin proximal attachment plate to minimize added thigh length. One may choose among hydraulic, pneumatic, and sliding friction units, with or without polycentric linkage. Even with a special knee unit, the thigh will be slightly longer. Consequently, the shank is shortened equivalently, so that when the person stands, the pelvis is level. When the individual sits, the thigh on the prosthetic side will project slightly.

Sockets

Two types of sockets are currently in use. Both are made of plastic and usually terminate below the ischial tuberosity. Generally, no additional suspension aids are needed. One version features an anterior opening to accommodate a bulbous amputation limb. After the limb is inserted, the wearer closes the socket with lacing or hook-and-loop closure. The other design has no anterior opening and is suitable for limbs that are not bulbous.

Hip Disarticulation Prostheses

A hip disarticulation prosthesis^48,49 (Fig. 31.34) is fitted to a person with amputation above the greater trochanter (very short transfemoral), removal of the femoral head from the acetabulum (hip disarticulation), or removal of the femur and any portion of the pelvis (transpelvic amputation, also known as hemipelvec-tomy). The modern prosthesis was developed in Toronto and is sometimes called the Canadian Hip Disarticulation Prosthesis. Prostheses for proximal levels share common hip, knee, and foot assemblies, but differ with regard to socket design. The endoskeletal thigh and shank predominate because they save appreciable weight in these massive prostheses. The prosthesis may be shortened slightly, to aid clearance during swing phase, encourage the wearer to apply maximum weight to the prosthesis, and increase stability.

Sockets

The basic socket is plastic molded to provide weight-bearing on the ipsilateral ischial tuberosity and buttock (gluteal musculature). The person with transpelvic amputation who does not retain the ipsilateral tuberosity or iliac crest has a socket with a higher proximal trimline, sometimes encompassing the lower thorax. This individual supports weight on the remainder of the pelvis, on the abdomen, and perhaps on the lower ribs.

Hip Units

The prosthetic hip joint has an extension aid to bias the prosthesis toward the stable neutral position. Positioning the mechanical hip anterior to a point corresponding to the anatomical hip also contributes to hip stability. The joint is set below the normal hip, so that when the wearer sits, the prosthetic thigh will not protrude unattractively. All hip joints provide hip flexion; some also allow transverse rotation.^50,51

Knee Units

Although virtually any knee unit can be incorporated into the hip disarticulation prosthesis, the unit should have an extension aid to resist knee flexion during stance phase. The prosthetic knee is aligned relatively posteriorly to contribute to stability.

Bilateral amputations occur either simultaneously, as in the case of trauma or congenital limb deficiency, or sequentially, as is seen with peripheral vascular disease. In the latter instance, previous experience with a unilateral prosthesis is invaluable in determining whether the patient will benefit from a pair of prostheses.

Bilateral Syme's and Transtibial Prostheses

Any foot design can be worn, although both prosthetic feet must be the same design from the same manufacturer to reduce the likelihood of gait asymmetry⁵². Ideally, foot and shoe size should be shorter than the person's preamputation size to facilitate transition through stance phase; wider feet contribute to stability. Shanks, sockets, and suspensions need not match; each component should suit the characteristics of the individual amputation limb.

Bilateral Transfemoral Prostheses

Other than matching prosthetic foot design and size, each amputation limb is fitted on an individual basis^53,54. The patient will perform activities in a manner similar to someone with unilateral transfemoral amputation.

The patient may be fitted with short, nonarticulated prostheses. The lower center of gravity provides the individual with more stability. Gait is awkward, with exaggerated trunk rotation; crutches or canes need to be adjusted to suit the person's short stature. Transferring into an adult-size chair, as well as climbing stairs, is more difficult than with longer prostheses. Patients who object to the markedly altered appearance created by these short prostheses may refuse to wear them.

Longer prostheses should include a matched pair of feet. Endoskeletal shanks are highly desirable to reduce prosthetic weight and enable minute changes in alignment; typically the shanks are shortened by several inches to reduce the effort required to walk with the prostheses. Any type of knee unit may be worn; they need not be the same on both prostheses. Nevertheless, one should avoid a pair of manually locked knee units because they would make chair transfers and stair maneuvering very difficult. Sockets do not have to match; however, a pair of ischial containment sockets will minimize the walking base because the sockets have a relatively narrow mediolateral dimension, as compared with quadrilateral sockets. Any type of suspension may be worn.

Optimal function depends on proper care of socks or sheaths, prosthesis, amputation limb, and intact limb, as well as general health maintenance. Guidelines for personal hygiene are presented in Chapter 22, Amputation. In addition to ensuring cleanliness, the individual should wear a well-fitting sock and shoe on the sound foot. It must be the mate to the shoe on the prosthesis. Both shoes should be in excellent condition.

As with any appliance, the prosthesis benefits from simple regular maintenance, which generally avoids costly, time-consuming repairs. Printed instructions pertaining to the prosthesis and socks or sheath are helpful for patient education.

Foot-Ankle Assemblies

One should avoid getting the prosthetic foot wet, especially if the foot is an articulated model. If this happens, the shoe and sock should be removed to allow the foot to dry completely, away from direct heat. The wearer should also avoid stepping into sand and similar materials that might enter the cleft between the foot and shank section and restrict the excursion of the foot. The prosthetist will have to disassemble the foot to clean it.

The client should inspect the foot periodically to spot cracking at the toe-break or tip of the keel; such a crack will curl the toes and prevent smooth transition during late stance. A deteriorated heel cushion or plantar bumper will cause one to appear to be walking in a hole. Although most feet are now molded to simulate toes, the patient should not walk without a shoe because the sole of the prosthetic foot is not intended to resist much abrasion.

Foot socks wear much more quickly on the prosthetic side, because the hard foot-ankle assembly and shank rub against the fabric. Stair risers also scuff the sock. Some people find that wearing two socks helps cushion the outer one against premature formation of holes.

The individual must be instructed regarding wearing shoes of the same heel height as was the case when the prosthesis was aligned. Too low a heel interrupts late stance; an unduly high heel makes the knee less stable. If the prosthesis has the usual foot designed for low-heeled shoes, and the wearer wishes to wear flat-heeled shoes, a 1/2 in (1 cm) shim (a thin tapered wedge) should be placed inside both shoes at the heel. High-heeled shoes require that the foot be changed, either by unbolting it and replacing it with a foot with an appropriate plantarflexion angle, or by adjusting the heel-height feature found in certain models of feet (e.g., Runway^® [Freedom Innovations, Fayette, UT 84630]; Elation^® [Ossur, Aliso Viejo, CA 92656]). Boots and other footwear with stiff upper sections restrict the action of any foot assembly that is designed to provide substantial dorsiflexion and plantarflexion.

Removing the shoe is easier if the prosthesis is not worn. With the shoe unlaced completely, one grasps the rear of the shoe, then pulls the shoe off the back of the foot. Finally, the shoe is moved upward off the forefoot. The shoe should be put on the prosthetic foot with the aid of a shoehorn.

Shanks

The usual finish of exoskeletal shanks is polyester laminate, which is impervious to most liquids. It needs to be wiped only periodically with a cloth dampened with dilute detergent to remove surface soil. Marks can be gently removed with kitchen cleanser; excessive abrasion will dull the finish.

The soft foam cover of the endoskeletal prosthesis requires reasonable caution against exposure to direct heat, penetrating objects, and solvents. The outer covering will need replacement whenever it becomes unacceptably soiled or torn. The transfemoral version tends to deteriorate at the knee, especially if the wearer kneels a great deal.

Knee Units

Sliding friction mechanisms tend to loosen with walking and thus require periodic tightening to retain the original adjustment. The frequency of tightening depends on how much the wearer walks. Most units have a pair of screws in front or in the rear of the knee unit that can be turned clockwise with an Allen wrench (small L-shaped metal bar with hexagonal head at each end) or common screwdriver. After turning each screw a quarter turn, the client should walk for at least 5 minutes to ascertain the effectiveness of the adjustment.

Squeaking at the knee or articulated ankle usually indicates the need for oil. The rubber or felt extension bumper in the knee unit will erode after prolonged vigorous use, and the wearer will then notice that the knee begins to hyperextend. The bumper, visible when the knee is flexed, must be replaced by the prosthetist.

The external extension aid eventually loses its elasticity. The user will then experience high heel rise in early swing and slow knee extension at the end of swing phase. The simplest approach is to tighten the strap through its buckle. Eventually, the prosthetist will need to replace the elastic webbing. Internal elastic extension aids are not subject to rubbing from the trouser leg or skirt and thus do not lose elasticity as readily. Steel spring internal aids usually retain their effectiveness for the life of the prosthesis.

Pneumatic and hydraulic units must be protected against tears of the rubber shield protecting the piston. The piston must not be scratched, because this would allow air and debris to enter the cylinder. Air bubbles in the unit will cause a spongy feeling, and possibly noise with walking. At night, the prosthesis should be stored upright, with the knee extended to exclude air from the cylinder.

Electronic units must not be immersed or used in a particle-filled environment, such as a commercial bakery or lumberyard (sawdust).

Sockets and Suspensions

Plastic sockets should be washed with a cloth dampened in warm water that has a very small amount of mild soap dissolved in it. The socket is then wiped with a damp, soap-free cloth, and dried with a fresh towel. In warm climates, the socket should be washed every evening so that it will be completely dry when the patient dresses the following morning. Socket liners made of polyethylene foam can be washed by hand in tepid water with mild soap, rinsed, and air-dried overnight. They should not be subjected to direct sunlight when removed from the prosthesis. Other sheaths and liners should be maintained according to the manufacturer's instructions.

Leather corsets should be kept dry. Use of saddle soap will keep leather clean. If the patient is incontinent, the thigh corset should be made of flexible polyester laminate or polypropylene, which are impervious to urine.

The transfemoral suction valve should be brushed daily to remove talcum and lint, which might clog the tiny aperture. The valve should be inserted and removed only with one's fingers, because tools are apt to damage the internal mechanism or outer threads.

Physical therapists participate in the management of patients with amputation at several key stages: (1) preoperative; (2) postoperative–preprosthetic; (3) prosthetic prescription; (4) prosthetic examination; and (5) prosthetic training.

The first two stages are described in Chapter 22, Amputation. The following discussion emphasizes the responsibilities of the physical therapist with regard to the patient and prosthesis. Ideally, the therapist works as a member of a clinic team, together with the physician and prosthetist. Others, such as a social worker, vocational counselor, and psychologist may participate in the team on a regular basis or as needed. The clinic team provides the best environment for exchange of information and viewpoints regarding the patient and fostering efficient treatment;^55,56 the team meets to formulate the prosthetic prescription, examine the newly delivered prosthesis, and reexamine the patient and prosthesis upon completion of prosthetic training. The therapist, therefore, has an integral part to play in these critical points in rehabilitation, as well as conducting prosthetic training. If a formal clinic team is not established in the therapist's work setting, one must coordinate the recommendations of the physician and prosthetist.

With either administrative situation, the physical therapist:

• Addresses nonprosthetic considerations

• Contributes to prosthetic prescription

• Examines the prosthesis

• Facilitates prosthetic acceptance

• Instructs the patient in donning, use, and maintenance of the prosthesis

Preprescription Considerations

Successful prosthetic rehabilitation depends on matching the individual's physical and psychosocial characteristics to a prosthesis composed of carefully selected components. Although everyone who wears a prosthesis has an amputation or comparable limb deficiency, the reverse is not true. That is, some people with amputations are not candidates for prostheses or prefer not to use prostheses. Prostheses are contraindicated for patients with severe dementia or depression or advanced cardiopulmonary disease. If the person displays significant changes associated with organic brain syndrome, prosthetic fitting is contraindicated. Individuals with bilateral amputations who are unable to transfer independently or don underwear by themselves are unlikely to benefit from definitive prostheses. Similarly, a patient with bilateral amputations who had sustained unilateral amputation previously and was unable to don and walk with a unilateral prosthesis is not a candidate for a pair of prostheses. Some people with high amputations, especially hip disarticulation, find that a prosthesis is unduly cumbersome; they prefer to ambulate with a pair of crutches or depend on a wheelchair. Several sports, particularly swimming, are generally easier to perform without a prosthesis.

Physical Examination

The physical therapist should examine joint mobility and active and passive range of motion of all joints on both LEs. Knee and hip flexion contractures compromise prosthetic alignment and appearance. A knee lock may be needed in a transfemoral prosthesis. A patient with knee contracture requires an alternative transtibial socket design. Severe contractures may contraindicate provision of a prosthesis. The deleterious effects of contractures are especially serious with bilateral amputations.

The length of the amputation limb should be measured. The individual with a short transtibial amputation may require SC/SP suspension. Every attempt should be made to fit the patient with a short transfemoral amputation with suction or partial-suction suspension to retain the prosthesis on the thigh.

Strength of all limb and trunk muscles should be examined. Frequently, the elderly patient with vascular disease experiences reduced physical activity as LE pain and foot ulceration develop. Such an individual may present with marked debility, which would interfere with prosthetic use or necessitate use of a unit with a knee lock.

The therapist should inspect the skin, noting the status of the incision and any other lesions. The patient may require a nylon or silicone sheath to provide a smooth interface between socket and skin to avoid irritating tender or grafted skin.

An examination of sensory function should be performed. For example, someone with impaired proprioception at the knee will need extra prosthetic stability in the form of higher medial and lateral socket walls, or side joints attached to a thigh corset, on the transtibial prosthesis. Blindness does not preclude fitting, but it does pose problems with regard to selecting components that are easy to don, as well as altering the training program. If the patient complains of a neuroma, the problem must be addressed surgically or conservatively (e.g., cortisone injection) before fitting can proceed.

The therapist should examine the patient's ability to learn and retain new information, including both short- and long-term memory. Neurological conditions, such as cerebrovascular accident, complicate fitting and training. Ipsilateral hemiplegia is not as detrimental to prosthetic rehabilitation as contralateral paralysis. In both instances, the prosthesis should be designed for maximum stability. Patients with mild neurological impairments often respond favorably to altered training strategies, which the therapist designs on an individualized basis.

The circulation and anthropometric dimensions of the amputation and sound limbs require careful scrutiny. The physical therapist should teach the patient to inspect the intact foot, using a hand mirror to visualize the plantar surface. Inspection aims to identify skin lesions and incipient areas of abrasion so that corrective measures may be instituted before ulceration or infection ensues. In addition, the patient should be taught to keep the sound foot clean and should wear clean socks or stockings and a well-fitting shoe (see Chapter 14, Vascular, Lymphatic, and Integumentary Disorders, for additional guidelines for managing the patient with peripheral vascular disease). Sequential measurements of amputation limb circumference as well as palpation will indicate whether the individual has edema. Measures should be instituted to stabilize limb volume so that the patient can retain the fit of the prosthetic socket. The patient with vascular impairment may benefit from prosthetic fitting, which transfers some stress from the contralateral limb. In addition, should the person come to bilateral amputation, previous experience with donning and controlling a unilateral prosthesis is invaluable in adjusting to a pair of prostheses.

Prosthetic prescription is also based on the patient's aerobic capacity and endurance. The clinic team must formulate realistic goals based on the individual's physical capacity, particularly related to exercise tolerance and level of deconditioning. The person who is not expected to walk rapidly is an unlikely candidate for an energy-storing/releasing foot or a fluid-controlled knee unit. Nevertheless, a fluid-controlled knee unit that incorporates a braking mechanism is appropriate for selected patients with generalized weakness.

Obesity is another factor to be considered in the preprescription examination. The obese individual is more apt to fluctuate in body weight, necessitating provision of socket liners and several socks to compensate for changing limb circumference. Similarly, those who have renal disease, especially if requiring dialysis, experience volume changes that need prosthetic accommodation.

Arthritis affects prosthesis prescription. Diminished LE mobility or deformity may compromise prosthetic alignment. Patients with hip or knee arthroplasty, however, function quite well with a prosthesis. Hand and wrist function affects the mode of donning; a laced corset should be avoided. Canes and crutches may require modification.

Functional examination is an essential component of physical therapy management (see Chapter 8, Examination of Function). Among the most useful examination procedures involves observing the patient's ability to transfer from sit-to-stand and bed-to-wheelchair. To accomplish these maneuvers, the individual must have reasonable strength, balance, and coordination, as well as adequate comprehension.

Psychosocial Considerations

Ordinarily, the physical therapist treats the patient more frequently than any other member of the clinic team and thus is more likely to be attuned to changes in the individual's psychosocial status. Ample evidence supports the psychological, as well as physical, benefit of clinic team management.^55,56 Many people with amputation confront psychosocial issues, which should be recognized and addressed.^{57,58,59,60,61,62,63,64} For example, the patient who is excessively fearful may be served best by prosthetic rehabilitation beginning with a temporary (provisional) prosthesis.

Temporary Prostheses

Transtibial Temporary Prosthesis

Most transtibial temporary prostheses have sockets made of thermoplastic material that becomes malleable at temperatures low enough to permit forming directly on the patient. One can also obtain mass-produced adjustable sockets; it may be necessary to pad the socket bottom so that the amputation limb does not develop distal edema. Some temporary prostheses have a plaster socket molded to the amputated limb. Plaster is inexpensive, readily available, and easy to use. The resulting socket, however, is rather heavy and bulky. Suspension is usually by a cuff or thigh corset. The pylon can be an aluminum component manufactured for this purpose; such a pylon has a proximal fixture that permits small changes in prosthetic alignment. A simpler pylon can be made with polyvinylchloride piping, such as used for plumbing. The pipe is lightweight and can be spot-heated to enable slight alteration in alignment. A SACH foot is customarily used on temporary prostheses.

Transfemoral Temporary Prosthesis

The easiest approach is to use a polypropylene socket (Fig. 31.35), which is manufactured in several sizes and has straps for circumferential adjustment. The socket can be suspended with a Silesian bandage or pelvic band, and is mounted on a knee unit, which may include a manual lock. Alternatively, a custom-fabricated socket of plaster or low-temperature thermoplastic can be used. Some individuals with bilateral transfemoral amputations use a pair of short prostheses. These are nonarticulated prostheses; the sockets are mounted on short platforms, drastically reducing the wearer's height in order to increase balance stability. The platforms each have a rearward projection to protect the patient from a backward fall.

Motivation is a cardinal determinant of prosthetic outcome. Again, strong motivation demonstrated through use of a temporary prosthesis and adherence with other elements of the rehabilitation program is a reliable predictor of prosthetic success. One should guard against unrealistic expectations. Involving the patient and family in group situations with other persons with amputation in the physical therapy department and in social environments fosters constructive attitudes. The therapist should also weigh the likelihood that the individual will be able to care for complex prosthetic mechanisms and have the financial resources to obtain prosthetic servicing, especially of less durable components, such as the foam rubber covering of the endoskeletal shank.

Prosthetic Prescription

No prosthetic component is ideal for all clients. It is necessary to select components that are most apt to meet each individual's needs. Alternatives to every element of the prosthesis have advantages and disadvantages. The task of the physical therapist, in conjunction with other team members, is to judge the relative merits of various feet, shanks, and other components in light of objective and subjective information pertaining to the prosthetic candidate. In 1995, Medicare identified functional levels applicable to individuals with unilateral transtibial and transfemoral prostheses:⁶⁵

• K0: Not a candidate

• K1: Household ambulation

• K2: Limited community ambulation

• K3: Community ambulation and the ability to vary cadence with vocational, therapeutic, or exercise needs

• K4: High levels of activity such as demonstrated by active adults and athletes

These levels determine the medical necessity of knee and ankle-foot units.

Some people can be expected to function best with a sophisticated prosthesis that enhances the wearer's ability to engage in vigorous walking and athletics. Others are well served by simple, inexpensive devices. The most accurate predictor of future function is the patient's performance with a previous prosthesis. For the wearer who seeks a replacement prosthesis, the clinic team should consider the extent of use of the previous limb, together with any changes in the patient's health status and lifestyle. For example, if the person fitted with one prosthesis now returns with bilateral amputation, never having used the original prosthesis, that patient is a very poor candidate for bilateral prosthetic fitting. In contrast, another person who had been fitted with a simple transfemoral prosthesis expresses the wish to participate in sports. By demonstrating good use of the original prosthesis, that individual is likely to derive considerable benefit from a new prosthesis with a fluid-controlled knee unit and an energy-storing/releasing foot.

Prescription for the new patient is more difficult. Depending on the interval between amputation surgery and prescription, the amputation limb may not have stabilized in volume; the patient may not have achieved the maximum benefit from the preprosthetic program. The best criterion for prosthetic prescription in such an instance is performance with a temporary (provisional) prosthesis. As mentioned earlier, this appliance includes a well-fitting socket, suitable suspension, pylon, and foot; the transfemoral model usually has a knee unit. The temporary prosthesis allows preliminary gait and activities training. The major difference between the temporary and definitive (permanent) prosthesis is appearance. The temporary socket is designed for easy alteration to accommodate change in amputation limb volume. Ordinarily, little attention is paid to the color and exterior shape of the temporary prosthesis.

Prosthetic Examination/Evaluation

The prosthesis should be examined before the patient engages in prosthetic training and should be reexamined at the conclusion of training. The procedure is intended to determine the adequacy of prosthetic fit and function, as well as the wearer's opinion of appearance and overall satisfaction. This process typically follows a sequence of examining the prosthesis while the patient stands (static analysis), examining the patient's gait (dynamic analysis), and finally examining the prosthesis off the patient (additional static analysis). In many institutions, the physical therapist examines the prosthesis and presents a summary of findings to the clinic team. The team makes the final determination regarding the acceptability of the prosthesis.

No special materials are needed to examine the prosthesis, except for a checklist, a straight (armless) chair, a few sheets of paper, a ruler, lift blocks, and colored chalk. For final evaluation, stairs and a ramp are needed. The checklists referred to in the following sections can be found in Appendices 31.A and 31.B.

At initial evaluation, the team has three options: (1) pass, (2) provisional pass, or (3) fail. Pass indicates that no changes are needed in the prosthesis and the patient can proceed to training. Provisional pass signals that one or more minor problems require correction, none of which would interfere with training. Failure is the team's judgment that the prosthesis has a major fault that should be corrected to the team's satisfaction before commencement of prosthetic training. For example, poor finishing of the prosthetic foot merits a provisional pass, whereas a socket that abrades the amputation limb should be graded as fail. If the therapist intends to provide treatment to a patient who is not managed by a formal clinic team, it is especially critical that one examine the prosthesis before initiating instruction and training to discover any problems that would interfere with the future program. At the final evaluation, two ratings are available: pass indicates that no problems exist and the patient uses the prosthesis in a manner commensurate with that individual's physical capacity; fail means that major or minor problems remain.

Transtibial Examination

Most items on the checklist in Appendix 31.A are self-explanatory. Each contributes to forming an accurate judgment of the adequacy of the prosthesis.

Static Analysis

The prosthesis is examined while the wearer stands and sits. In addition, the amputation limb and details of the prosthesis are examined. The prosthesis should be compared with the prescription. The individual who authorized the prescription must approve departures from the original specifications.

The new wearer should stand in the parallel bars or other secure environment, attempting to bear equal weight on both feet. The therapist should solicit subjective comments about comfort. Estimates of anteroposterior and mediolateral alignment are aided by slipping a sheet of paper under various parts of the shoe. Ideally, the patient should stand with both heels and soles flat on the floor. Misalignment, indicated by excessive weight-bearing on one portion of the shoe, may be confirmed by subsequent analysis of gait.

Most prostheses are constructed so that when the individual stands, the pelvis is level;³⁶ if the pelvis tilts, the therapist should place lifts under the foot on the shorter side to restore a level pelvis. If the total lift measures 1/2 in (1 cm) or less, no attention is needed. For greater discrepancy, one should seek causative factors. An amputation limb that sinks too far into the socket will make the prosthetic side appear short, and the wearer will probably complain of discomfort.

Piston action refers to vertical motion of the socket when the patient elevates the pelvis. Slippage can be determined by chalk marking the sock at the posterior margin of the socket, and then having the patient elevate the ipsilateral pelvis. The socket should slip less than 1/4 in (0.5 cm). Looseness, inadequate suspension, or both cause socket slippage. Socket walls should fit snugly, as should the thigh corset if it is part of the prosthesis.

Comfortable sitting is a primary need for all people. The posterior brim should not impinge into the popliteal fossa, and hamstring reliefs should be adequate, especially on the medial side where the semitendinosus and semimembranosus insert relatively distally. Placement of the tabs of the cuff or the joints of the corset also influences sitting comfort.

Dynamic Analysis

Analysis of the gait pattern and performance of other ambulatory activities is an essential part of rehabilitation. For most patients, a major reason for prosthetic fitting is to resume walking. Nevertheless, no prosthesis eradicates entirely the anatomical and physiological changes produced by amputation. When walking, the person who wears a prosthesis compensates for anatomical and prosthetic deficiencies.^{66,67,68,69,70,71} Some are inherent to amputation; others are abnormalities of the body or the prosthesis. Because virtually all people walk with a prosthesis in a manner different from the nondisabled walking pattern, prosthetic gait represents compensation for the patient's altered locomotor apparatus. The term gait compensation may be a more accurate descriptor than the more commonly used gait deviation inasmuch as the patient with amputation is most unlikely ever to walk exactly like a nondisabled person.

No prosthesis restores sensation, skeletal continuity, muscle integrity, or full body weight. Anatomical deficiencies are aggravated in the presence of pain, contracture, weakness, instability, or incoordination. Similarly, prosthetic components do not replace every function of the missing limb. For example, prosthetic feet do not move through the full excursion of the human counterpart. Inadequacies in the prosthesis compel the wearer to adopt gait compensations. Such problems include a poorly fitted socket, prosthetic misalignment, malfunctioning components, and improper height of the prosthesis. Compounding the problem are incorrect donning of the prosthesis and wearing inappropriate shoes. The physical therapist must determine when gait compensation exists and the potential causes so that remedial action may be taken. Otherwise, the patient is compelled to expend more energy walking and to exhibit a more conspicuously abnormal gait. The new wearer will have had brief experience walking in the prosthesis during the course of prosthetic fabrication. Although a smooth gait is unlikely on the day of the initial examination, gross departure from the usual gait exhibited by others with similar prostheses should be noted and causes sought.

Transtibial analysis focuses on action of the knee on the amputated side during stance phase. Both knees should flex in a controlled manner during their respective early and late stance phases. Excessive flexion of the knee on the amputated side indicates that the socket is aligned too far anterior in relation to the foot or is excessively flexed; this deviation may cause the patient to fall. If the knee flexes too much only during early stance, the cause may be a heel cushion that is too firm for that wearer. Conversely, insufficient knee flexion results from posterior displacement of the socket or inadequate socket tilt. When viewed in the frontal plane, the socket brim should maintain reasonable contact with the leg; excessive lateral thrust of the prosthetic brim suggests that the prosthetic foot has been positioned too far medially. Table 31.1 summarizes the prosthetic and anatomical causes of transtibial gait compensations/deviations.

At the initial evaluation, performance on stairs and inclines may be omitted because the patient has not had training in these activities.

Inspection of the Prosthesis Off the Patient

The posterior wall should be approximately at the same level as the build-up for the patellar ligament (tendon) when the patient stands. To check this, the prosthesis is stood upright on a table; one end of a ruler is then placed on the anterior socket bulge and the opposite end on the posterior brim. In a well-constructed prosthesis, the ruler will slant upward toward the rear, indicating that when the individual stands in the prosthesis and compresses the heel cushion, the posterior wall will be at the proper height.

The amputation limb should be examined for signs of proper loading with respect to the type of prosthesis worn. Any straps or cuff should provide reasonable adjustability. Construction is a guide to future durability, as well as contributing to acceptable appearance of the prosthesis.

Transfemoral Examination

A similar checklist is used to evaluate the transfemoral prosthesis (Appendix 31.B). It is important to recognize that seldom is one item of major significance. The therapist and entire team should look for patterns that might herald future difficulty. For example, misalignment detected in static analysis should be confirmed during gait.

Static Analysis

The patient who has a flesh roll above the socket either did not don the socket properly or has a thigh that is larger than that for which the socket was made. Perineal pressure results from sharpness of the medial brim or insufficiency of the adductor longus relief in a quadrilateral socket.

The knee unit should be stable enough to withstand a blow delivered by the therapist to the posterior aspect of the unit when the patient stands. Stability is influenced by the alignment of the knee in relation to the hip and prosthetic ankle. The farther posterior the knee bolt, the more stable the knee will be. Polycentric linkage and mechanical stabilizers also contribute to stability. If the socket is opaque, the only way to judge its snugness is by palpating tissue protruding through the valve hole when the valve is removed.

The checklist is designed to help the clinician determine the fit of the socket, regardless of shape or material. If the prosthesis has a quadrilateral socket, proper location of the adductor longus tendon and ischial tuberosity ensures that the patient has donned the socket correctly. A horizontal posterior brim allows weight to be borne on the gluteal musculature as well as the ischial tuberosity. The ischial containment socket is intended to cover the ischial tuberosity, yet allows the client to move the hip in all directions comfortably, without socket gapping.

The lateral attachment of the Silesian belt should be superior and posterior to the greater trochanter for best control of prosthetic rotation. Anteriorly, the attachment should be at the level of the ischial tuberosity, or slightly below, to aid in adducting the prosthesis.

The pelvic joint and band should fit the torso snugly for optimum control of the prosthesis and to minimize bulkiness. The joint axis should be superior and anterior to the greater trochanter.

The patient should be able to sit comfortably with the prosthesis. Posterior discomfort may indicate inadequate hamstring relief, or a sharp or thick posterior brim.

Dynamic Analysis

Gait analysis gives the clinic team members the opportunity to determine the adequacy of socket fit and of prosthesis alignment and adjustment. The patient also influences the walking pattern by the timing and force of muscular contraction and the presence or absence of contractures. The goal of walking with a transfemoral prosthesis is a comfortable, safe, efficient gait, rather than duplicating the gait of someone wearing a transtibial prosthesis or one who does not have amputation.⁷² Table 31.2 summarizes the prosthetic and anatomical causes of transfemoral gait compensations/deviations.

Compensations/Deviations Best Viewed from Behind

Many individuals with transfemoral amputation abduct the prosthesis to improve frontal plane balance (abducted gait). Hip abduction contracture predisposes patients to this deviation, which is seen in stance phase. Inadequate socket adduction, socket looseness, or medial discomfort also causes the fault. Circumduction is a displacement exhibited in swing phase if the prosthesis is too long or if the patient is reluctant to allow the knee unit to bend. Socket looseness also may result in circumduction. The patient may shift the trunk excessively. Lateral trunk bending toward the prosthetic side during stance phase generally accompanies abducted gait. It should be noted, however, that all individuals with transfemoral amputation have an incomplete abductor mechanism, and tend to compensate by bending toward the prosthetic side, especially when fatigued. Although the anatomical hip and gluteus medius are usually in good condition, lack of skeletal continuity to the ground (imposed by the amputation) compromises the effectiveness of abductor contraction. If the prosthesis is too long, the patient will abduct; if it is too short, the patient will bend the trunk laterally.

Whips refer to medial or lateral rotation of the heel at late stance. If the socket does not fit well, contraction with bulging of the thigh musculature will cause the prosthesis to rotate abruptly as it is being unloaded at the end of stance phase. Although less likely, malrotation of the knee unit or foot-ankle assembly may contribute to whipping. Rotation of the foot on heel contact is a much more serious deviation. It indicates inadequate compression of the heel cushion or plantar bumper and can result in a fall.

Compensations/Deviations Best Viewed from the Side

Forward trunk shifting in stance phase is a compensation that some patients use to cope with knee instability. If the walker or crutches are too short, the individual will lean forward. Lumbar lordosis results from inadequate socket flexion and is aggravated by a hip flexion contracture.

Improper adjustment of the knee unit gives rise to uneven heel rise (excessive knee flexion) and terminal swing impact (abrupt knee extension). If both deviations are present, the probable cause is insufficient friction. If the knee exhibits impact without undue heel rise, it is more likely that the extension aid is too tight.

To compensate for reduced knee motion, the vigorous walker may demonstrate vaulting by excessively plantarflexing the sound ankle to afford extra room to clear the prosthesis during prosthetic swing phase. A less strenuous compensation for excessive actual or functional prosthesis length is hip hiking, when the patient elevates the pelvis on the prosthetic side.

Unequal step length will be evident if the patient has a hip flexion contracture or inadequate balance. A longer step taken with the prosthesis gives the person more time on the sound limb. A flexion contracture or insufficient socket flexion (limiting hip extension range) prevents the sound limb from passing the prosthetic side during swing phase on the sound side (i.e., shorter step length on the sound side).

Inspection of the Prosthesis Off the Patient

Following the static evaluation, the therapist should examine the prosthesis and amputation limb as indicated on the checklist. A resilient back pad (placed externally on the posterior wall) enables the patient to sit quietly without undue trouser or skirt abrasion. The pad is unnecessary with a flexible socket.

Facilitating Prosthetic Acceptance

Amputation generally is regarded as a grievous occurrence, with its visibility a constant reminder of the individual's abnormality. The physical therapist can help the patient and family accept the reality of amputation and the prosthesis by verbal and nonverbal communication. One's calm respect for the patient as a worthy human being, regardless of limb condition, should set a model for the attitudes of others. Clinic team management accords not only the benefits of better prosthetic provision but also brings the individual in contact with clinicians who convey experience and confidence in dealing with problems that the person may have considered unique.

As soon as possible, the hospitalized patient should be treated in the physical therapy department, rather than at bedside. The bustle of the department should help dispel despondency. Although postoperative mourning is expected, prolonged depression is not constructive. Peer support groups are often very effective in aiding acceptance of the prosthesis and in learning special procedures for accomplishing activities. Observation and eventual participation in specially designed sports programs is another way people learn to cope and gain the most from rehabilitation. The physical therapist, by virtue of close daily contact with the patient, is also in a position to recommend to the clinic those who might profit from psychological counseling or psychiatric services, particularly when pain is an issue. Appendix 31.C provides website-based prosthetic resources for clinicians, families, and patients.

Prosthetic Training

Learning to use a prosthesis effectively involves being able to don it correctly, develop good balance and coordination, walk in a safe and reasonably symmetrical manner, and perform other ambulatory and self-care activities. Anticipated goals and expected outcomes depend on the patient's physical and psychological status, preprosthetic experience, and quality of prosthesis. Using the prosthesis only to assist in transferring from the wheelchair to the toilet may be an appropriate outcome for an elderly person with multiple disabilities, whereas the program for the youngster with traumatic amputation might extend to a full range of sports.

Donning

Correct application of the prosthesis and frequent inspection of the amputation limb are very important, especially for the beginner and those with poor circulation. Patients with partial foot, Syme's, and transtibial amputations can don the prosthesis while seated, after having applied the correct number and sequence of socks or sheath. Then, in most instances, the individual simply inserts the amputation limb into the socket. With SC/SP suspension, one applies the liner to the amputation limb, then inserts the limb and liner into the socket. The initial entry into the socket with corset suspension may be made while sitting; however, final tightening of laces or straps should be done in the standing position to ensure that the limb is lodged suitably in the socket.

Those with transfemoral amputation also can begin the donning process while seated. Total suction wearers may use either a pulling or pushing method. To pull oneself into the socket, the patient applies a light dusting of talcum powder to the thigh to reduce friction. Then one applies a pulling sock, a tubular cotton stockinet approximately 30 in (76 cm) long, a roll of elastic bandage wound around the thigh, or a nylon stocking. Whatever the donning aid, it should be placed high in the groin to pull in proximal tissues. After placing the sock-encased thigh into the socket, one draws the distal end of the aid through the valve hole. Although it is possible to complete the donning process while seated, most people prefer to stand while pulling the sock or other aid out through the valve hole. By leaning forward, the body's weight line will prevent the prosthetic knee from flexing inadvertently. The patient alternately flexes and extends the sound hip and knee while tugging downward on the donning aid until it slips out from the prosthesis. Finally, one inserts the valve. Another approach to donning is to coat the thigh with lubricating lotion, push it into the socket, and then install the valve.

Patients who use partial suction apply a sock, making certain the proximal margin of the sock extends to the inguinal ligament. The patient then introduces the amputation limb into the socket, taking care that the thigh is correctly oriented; pulls the distal end of the sock down through the valve hole enough to ensure that the skin is smooth; tucks the sock back into the socket; and inserts the valve. Finally, one secures the pelvic band or Silesian belt. If suction is not used, donning is similar to the method used with partial suction, except that there is no valve.

Balance and Coordination

Exercises are similar for all patients with LE amputations, although the individual with a transfemoral or hip disarticulation prosthesis may be expected to encounter more difficulty controlling the mechanical knee, as compared to those with two anatomical knees. All must learn to balance on the amputated side.^{73,74,75,76,77} A graduated program for increasing prosthetic tolerance minimizes the danger of skin abrasion, particularly if the amputation limb presents skin grafts, poor circulation, or diminished sensation. The patient should alternately exercise and rest, with cardiopulmonary monitoring a routine part of the program, especially for high-risk individuals.

Some clinicians eschew parallel bars because the fearful patient pulls on them, which will be fruitless when progressing to a cane. When bars are used, the therapist should encourage the patient to rest the open hand on the bar for support, rather than using a viselike grip. A plinth or sturdy table offers the dual advantages of providing good support on only one side, ordinarily the contralateral side, and unidirectional control, because the patient can only push, never pull, for balance.

Static erect balance reintroduces the novice to bipedal posture. The patient should strive for level pelvis and shoulders, vertical trunk without excessive lordosis, and equal weight-bearing. The therapist should guard and assist the patient as necessary. When the physical therapist stands near the prosthesis, this encourages the patient to shift his or her weight onto it. To suggest symmetrical performance, refer to the limbs as "right" and "left," or "sound" and "prosthetic," rather than discouraging the patient with "good" and "bad." The client must learn to use proximal sensory receptors to maintain balance and perceive the position of the prosthesis without looking at the floor. Some patients respond well to increased use of visual feedback (e.g., using a mirror).

Dynamic exercises improve medial–lateral, sagittal, and rotary control. The patient learns that hip flexion causes the knee to bend, and hip extension stabilizes the knee during stance phase. Placing the sound foot ahead of the prosthesis makes the prosthetic knee more stable. Patients should be instructed in weight shifting in both symmetrical and stride positions and in stepping movements. Stepping on a low stool or step platform with the sound foot obliges the patient to shift weight onto the prosthesis and increases stance phase duration on the prosthesis. Having all exercises performed rhythmically with both the right and left LEs fosters symmetrical performance.

Gait Training

Walking is a natural progression from dynamic balance exercises as the patient takes successive steps. Patients tend to place greater load and exert more propulsive force on the intact side; consequently, gait training should emphasize symmetrical performance.^{67,68,69,70,71,72,73} Inas much as hamstrings become the main muscles of propulsion, strengthening exercises are indicated. Some people respond well to proprioceptive neuromuscular facilitation.⁷⁴ Rhythmic counting and walking in time with music in 2/4 time also improves gait symmetry and speed. In the physical therapy department, an apparatus that includes a suspension harness (partial body weight support) provides a protected environment for the patient to learn gradual weight-bearing on the prosthesis. A balance apparatus (e.g., Balance Master^®) providing electronic feedback with or without emphasis on psychological awareness of bodily position is another training option.

Either a cane or pair of forearm crutches is an appropriate aid for the client who is unable to achieve a safe gait without undue fatigue. Sometimes the cane is used only outdoors to aid in negotiating curbs and other ground irregularities and to signal oncoming traffic. Ordinarily the cane is used on the contralateral side to enhance frontal plane balance. If bilateral assistance is required, a pair of forearm crutches is preferable to two canes. The crutches remain clasped around the forearms when the user opens a door. Axillary crutches tempt the patient to lean on the axillary bars, risking impingement of the radial nerves; they are also inconvenient when climbing stairs. An aluminum walker provides maximum stability, which is particularly useful for patients with generalized weakness. The walker should be adjusted so that the user does not lean too far forward.

Patients with transtibial amputation walk faster with a two-wheeled walker as compared with a four-footed walker.⁷⁵ Fear of falling can undermine walking and social activity participation. Improving the patient's balance confidence is essential to lessen this concern.^76,77

Functional Training

The prosthesis wearer who is learning to walk also should gain experience in performing a wide variety of functional mobility skills. Activities such as transferring to various chairs add interest to the program and, for some patients, may be more important than long-distance ambulation.

The training program for vigorous individuals includes stair climbing, negotiating ramps, retrieving objects from the floor, kneeling, sitting on the floor, running, driving a car, and engaging in sports. The fundamental difference between these activities and walking is the way each LE is used. Walking implies symmetrical usage, but the other activities are done asymmetrically, with greater reliance on the strength, agility, and sensory control of the sound limb.

Generally, the patient should have the opportunity to analyze each new situation and arrive at a solution to the problem, rather than depending on directions from the therapist. Most tasks can be accomplished safely in several ways. The learner profits from practice in clinical decision making and observing other prosthesis wearers as well as from professional instruction.

Transfers

Rising from different chairs, the toilet, and car are primary skills even for people who are elderly or debilitated. Most patients enter the physical therapy department in a wheelchair. Initially, the patient can park the chair at the parallel bars or at a plinth. After locking the wheelchair and raising the footrests, the patient should sit forward and transfer weight to the intact leg, then push down on the armrests. The individual will find that placing the sound foot close to the chair enables rising by extending the knee and hip on the sound side. Sitting is accomplished by placing the sound foot close to the chair and lowering oneself by controlled hip and knee flexion on the sound side.

For both standing and sitting, the beginner should have the advantage of a chair with armrests that enables use of the hands to control and assist trunk movement. Later the person should practice sitting in deep upholstered sofas and low chairs, as well as benches, the toilet, and other seats that do not have armrests. Transfer into an automobile should be an integral part of the training activities; otherwise, the patient faces a gloomy future, confined to home or dependent on special transportation systems. To enter the right (passenger) side of an automobile, the prosthetic wearer faces toward the front of the car. The person with a right prosthesis puts the right hand on the door post and the left hand on the back of the front seat, then swings the left leg into the car, slides onto the car seat, and finally places the prosthesis in the car. The individual with a left prosthesis may find that sitting sideways with both feet out the car door is easiest. One then pivots on the seat while swinging the prosthesis into the car, then puts the intact right foot inside the car.

Climbing Stairs, Ramps, and Curbs

Patients with Syme's and transtibial amputations generally ascend and descend stairs and inclines with steps of equal length in step-over-step progression.^78,79,80 Those with unilateral transfemoral amputation, in contrast, usually ascend by leading with the sound foot and learn to descend by first placing the prosthesis on the lower step. A few individuals with transfemoral amputation subsequently learn to control prosthetic knee flexion in order to descend step-over-step. Those fitted with the Power Knee^® may be able to ascend stairs step-over-step.

Curbs present a slightly different problem, because there is no handrail. The techniques are basically the same, however.

Ramps may be difficult if the prosthetic foot does not have sufficient anteroposterior excursion.^81,82 With steep stairs, ramps, and curbs, the individual may climb diagonally or sidestep with the prosthesis kept on the downhill side. Patients should also learn how to maneuver over obstacles on the walking surface.⁸³

Final Evaluation and Follow-up Care

Economic strictures may compel the therapist to conclude the training program after the patient is able to walk and to negotiate basic transfers and stair climbing but before the full range of training activities is completed. Before discharge, the patient and prosthesis should be reexamined to make certain that socket fit, prosthetic appearance, and function are acceptable. The checklist used for initial evaluation can be used. The physical therapist should instruct the patient with regard to the patient's responsibility for reporting skin redness and any loose or missing parts from the prosthesis.

The new prosthesis wearer should return to the training site at regular intervals so that the clinic team may examine socket fit. Most will require major socket revision or replacement during the first year to accommodate amputation limb volume reduction. Follow-up visits are good opportunities to augment training and to encourage the individual to engage in the widest possible range of activities.

Functional Capacities

Functional capacities refer to the individual's ability to walk, transfer from chairs, climb stairs, and perform other ambulatory activities, including recreational endeavors. A primary responsibility of the clinic team is to predict the probable function of the person with a new amputation, to determine whether the individual would benefit from a prosthesis, and what degree of activity is likely. Because many people with LE amputation are elderly with several medical problems, the need for accurate forecasting and ongoing monitoring is especially critical.

Walking with a prosthesis increases energy cost.^{84,85,86,87,88} Compared with those people with two sound limbs, the individual with a unilateral transtibial prosthesis requires slightly more oxygen when walking at a comfortable speed;^89,90 the person wearing a transfemoral prosthesis consumes nearly 50% more oxygen than normal,⁹¹ al though selection of prosthetic feet and knee units usually modifies the energy demand.^92,93,94,95 The prosthesis wearer chooses a comfortable pace, because at a speed that is natural for the individual, the energy cost per minute is similar to that of the person who does not require a prosthesis, although speed is slower. The lower the amputation level, the less the metabolic disadvantage. Among persons with transtibial amputations older than 40, those with long amputation limbs average minimal increase in energy, but persons with shorter limbs work harder. Those with bilateral transtibial amputations expend less energy than those with unilateral transfemoral amputations. Individuals whose amputation was traumatic perform more efficiently than those whose amputation was caused by vascular disease at every amputation level. People who sustained trauma walk faster and use less oxygen than their dysvascular counterparts.

The increased metabolic expenditure results in part from the socket, which surrounds semifluid tissue, giving imperfect anchorage imposing challenges to limb control. The foot-ankle assembly transmits no plantar tactile or proprioceptive sensation, does not move through as large an excursion as the anatomical foot, and does not initiate the dynamic propulsion characteristic of normal gait. The transfemoral prosthesis also incorporates a knee unit that provides no proprioception to the wearer. The problem is aggravated by the fact that a prosthesis is operated by remotely located muscles that contract longer and more forcefully than in normal gait. With transfemoral amputation, for example, the wearer positions the prosthetic foot by hip motion. The resulting alteration of motion is reflected in asymmetry of timing, further disturbing gait smoothness. Individuals with prostheses walk with greater vertical movement, inasmuch as the knee, whether mechanical for the transfemoral prosthesis wearer or anatomical in the transtibial wearer, does not flex as much as the contralateral knee during stance phase.

Use of a hip disarticulation prosthesis demands considerable energy expenditure.⁹⁶

People wearing bilateral prostheses consume even more oxygen and walk more slowly than those with unilateral amputation at a given level.⁹⁷

With the exception of patients on beta-blockers, heart rate response is an important indication of the metabolic cost of prosthetic use for most individuals. Overall, strength, balance ability, etiology of amputation, and level of amputation predict the extent of impairment.⁹⁸

Other measures of functional capacities include utilization of prostheses^{99,100,101,102} and quality-of-life surveys.^{103,104,105,106,107,108,109,110,111,112,113,114,115,116} Return to work^117,118 and ability to drive an automobile^119,120 are other indicators of rehabilitation success.

Sports participation (Fig. 31.36) is an excellent extension of rehabilitation for patients of all ages.^{121,122,123,124,125,126,127,128,129,130,131,132,133,134} Older adults may enjoy fishing, golfing, dancing, Tai Chi Chuan, and shuffleboard, and younger people may add basketball, tennis, archery, and track events to their range of activities. Most sports do not require any adaptation to the prosthesis. Horseback riding is a superb activity that fosters trunk control and seated balance. The hiker should pack extra amputation limb socks or a sheath to protect the skin; a well-fitting, comfortable hiking boot is essential. Bowling and participating in shot put are facilitated by emphasizing balance on the intact LE. For sports that involve running, an energy-storing/releasing foot is most suitable. The socket should fit snugly with very secure suspension to minimize abrasion of the amputation limb. Clients with Syme's or transtibial amputations usually run with reasonably symmetrical step lengths, although they will favor the sound limb, which has greater propulsive ability.⁷ Those with a knee disarticulation or transfemoral amputation will derive most of the propulsive force from the sound leg and use the prosthesis as a momentary prop. Many marathon competitions have a category for people with disabilities. Jumping, as in basketball, requires the athlete to generate a substantial upward force with the sound leg; landing is more comfortable on the sound leg, particularly for those who wear transfemoral prostheses. Some activities are facilitated by minor modification of the equipment, such as a toe loop on a bicycle pedal or an adapted prosthesis.

Other activities are generally performed without a prosthesis, such as swimming and skiing. The skier will probably use ski poles equipped with small rudders, in a "three-track" manner. Soccer is usually played without a prosthesis, with the player using a pair of crutches. Some individuals enjoy playing tennis and field events in a wheelchair. Equipment and techniques developed for individuals with paraplegia usually can be adapted for people with amputations.

Recreational programs designed for adults with amputations help the participants to return to active lifestyles. The physical therapist should be able to refer patients to convenient recreational clubs and sporting events. The desired outcome is to maximize each person's functional capacity and quality of life.

This chapter has focused on the prosthetic management of adults with lower-limb amputations. Characteristics and function of the principal lower-limb prostheses and prosthetic components have been discussed. In addition, the responsibilities of the physical therapist in prosthetic management have been emphasized. Successful prosthetic rehabilitation depends on close collaboration among the patient, physical therapist, physician, prosthetist, and other team members. This will provide an environment for information exchange and foster coordinated management. The result will be an optimum match between the patient's physical and psychosocial characteristics and a prosthesis capable of fulfilling its intended purposes.

1. What are the principal causes of amputation in the elderly? In the young?

2. Describe appropriate prostheses for individuals with the following partial foot amputations: phalangeal, transmetatarsal, and Syme's.

3. Distinguish between the Syme's and the transtibial amputation limbs and prostheses.

4. What prosthetic feet are especially suitable for elderly patients? Why?

5. Name the reliefs and build-ups in the transtibial socket.

6. Contrast the modes of suspension for the transtibial prosthesis. Which suspension is indicated for an individual with a very short amputation limb?

7. Classify knee units according to friction mechanisms.

8. Compare the quadrilateral and the ischial containment transfemoral sockets.

9. Describe the modes of suspension of the transfemoral prosthesis. In which type(s) does the client wear a sock?

10. How is the wearer of a hip disarticulation prosthesis prevented from inadvertently flexing the prosthetic hip and knee?

11. Outline a maintenance program for a transfemoral prosthesis with hydraulic knee unit and endoskeletal shank.

12. What factors should be considered before formulating a prosthetic prescription?

13. How can the physical therapist determine and improve the patient's psychological status?

14. What features of the transtibial prosthesis are considered in static evaluation? In dynamic evaluation?

15. Delineate the training program for a patient with a transfemoral prosthesis.

The patient is a 67-year-old man with diabetic arteriosclerosis. He sustained a right transtibial amputation 5 months ago. He was treated in the inpatient physical therapy department for 3 weeks. The wound healed satisfactorily. His physical therapist taught him to transfer independently and ambulate using a temporary prosthesis and a walker. He was discharged with a home program consisting of exercises to promote strength, joint mobility, and endurance. He was also told to keep an elastic shrinker sock on his amputation limb whenever he was not wearing the temporary prosthesis. In addition, the physical therapist instructed the patient in care of the left foot, including thorough foot washing every evening; inspecting all surfaces of the foot, using a mirror; wearing a clean sock and well-fitting shoe each day; and careful nail trimming. He was fitted with a permanent prosthesis 3 months after surgery. The prosthesis consisted of a SACH foot, endoskeletal shank, total contact socket, and cuff suspension. He returned to the rehabilitation department today complaining of difficulty keeping his balance on the irregular terrain on the golf course where he had gone for the first time since his surgery. He also mentioned that his golf score was poorer than it had ever been.

PAST MEDICAL HISTORY

The patient was in fairly good health until 6 months ago, when he went on a long-awaited trip to Europe. On the trip he did much more walking than usual, even though he had to stop every 50 feet because of cramping pain in his legs. His wife noticed that the hallux and second toe on his right foot were discolored. The discolored area became painful. After his return home, he was examined by his primary care physician and was diagnosed with gangrene and adult-onset diabetes. Despite aggressive wound care, the gangrene progressed to involve the entire foot. An amputation was required. His diabetes is now stabilized with diet and medication.

SOCIAL HISTORY

The patient is a retired accountant who lives with his wife. For years, he played golf on vacations. Upon retirement last year, he had looked forward to more frequent golfing.

PHYSICAL THERAPY EXAMINATION FINDINGS

• Cognitive status: Alert, oriented, memory intact

• Vision: Intact with corrective lens

• Cardiopulmonary:

  • Vital signs seated at rest: Blood pressure 140/86, heart rate 84, respiration within normal limits (WNL)

  • Endurance: Fair, tolerance to activity is approximately 30 minutes (with some fluctuation); occasional rest periods required

• Integumentary: Incision well healed without adherent scar

• Neuromuscular:

  • Sensation: Both upper and lower extremities: sharp/dull, light touch, temperature, and proprioception all WNL bilaterally

  • Reflexes: WNL

Range of Motion

• Goniometric examination of both LEs: WNL

Observational Gait Analysis (General Findings)

• Overall decrease in speed of movement

• Diminished, awkward weight transfer

Hip/Pelvis (Bilateral)

• Decreased pelvic rotation

• Diminished hip flexion

Knee

• Diminished right knee flexion

Foot/Ankle

• Minimal medial–lateral motion of the right prosthetic foot

Gait

The patient is a functional ambulator using a transtibial prosthesis. Gait is slow, with longer steps on the right side; without the cane he leans to the right side. When outdoors he uses a cane in the left hand. He can climb stairs slowly, using the handrail. On uneven surfaces, he widens his walking base and walks slowly.

Strength

Prosthetic Examination

• Socket is loose, as indicated by piston action

Balance

Standing

• Static: Good; able to maintain static position for unlimited period

• Dynamic: Fair +; difficulty maintaining balance on uneven terrain

Sitting

• WFL

Examination of Function

• Patient independent in transfers: bed, chair (FIM level = 7); requires minimal assistance in floor-to-stand transfers.

• Patient is independent in all basic activities of daily living (BADL).

• Patient is independent in approximately 80% of instrumental activities of daily living (IADL) (limitations imposed by fatigue and low ambulatory tolerance).

PATIENT DESIRED OUTCOMES

• Play golf at previous level of proficiency

• Walk without depending on cane when outdoors

• Improve endurance

1. Formulate a clinical problem list, including impairments, activity limitations, and participation restrictions.

2. Formulate a patient asset list.

3. Establish anticipated short-term goals and expected long-term outcomes, with regard to impact on:

   • Impairments

   • Activity limitations

   • Participation restrictions

   • Risk reduction/prevention

   • Health, wellness, and fitness

   • Patient/client satisfaction

4. Formulate a plan of care, with reference to Guide to Physical Therapist Practice.

5. Identify three impairments to address initially to improve this patient's activity limitations and participation restrictions.

6. Describe three treatment interventions focused on functional outcomes that could be used during the first weeks of therapy, indicating how you could progress each intervention.

7. What important safety precautions should be observed during treatment of this patient?

8. Describe strategies that can be used to develop self-management skills and promote self-efficacy in achieving goals and outcomes.

1. Is the prosthesis as prescribed?

2. Can the client don the prosthesis easily?

Standing

• 3. Is the client comfortable when standing with the heel midlines 6 in (15 cm) apart?

• 4. Is the anterior–posterior alignment satisfactory?

• 5. Is the medial–lateral alignment satisfactory?

• 6. Do the contours and color of the prosthesis match the opposite limb?

• 7. Is the prosthesis the correct length?

• 8. Is piston action minimal?

• 9. Does the socket contact the amputation limb without pinching or gapping?

Suspension

• 10. Does the suspension component fit the amputation limb properly?

• 11. Does the cuff, fork strap, or thigh corset have adequate provision for adjustment?

Sitting

• 12. Can the client sit comfortably with hips and knees flexed 90°?

Walking

• 13. Is the client's performance in level walking satisfactory?

• 14. Is the client's performance on stairs and ramps satisfactory?

• 15. Can the client kneel satisfactorily?

• 16. Does the suspension function properly?

• 17. Does the prosthesis operate quietly?

• 18. Does the client consider the prosthesis satisfactory as to comfort, function, and appearance?

Prosthesis Off the Client

• 19. Is the skin free of abrasions or other discolorations attributable to this prosthesis?

• 20. Is the socket interior smooth?

• 21. Is the posterior wall of the socket of adequate height?

• 22. Is the construction satisfactory?

• 23. Do all components function satisfactorily?

1. Is the prosthesis as prescribed?

2. Can the client don the prosthesis easily?

Standing

• 3. Is the client comfortable when standing with the heel midlines 6 in (15 cm) apart?

• 4. Is any flesh roll above the socket minimal?

• 5. Is the client free from vertical pressure in the perineum?

• 6. Do the contours and color of the prosthesis match the opposite limb?

• 7. Is the prosthesis the correct length?

• 8. Is the knee stable?

• 9. When the socket valve is removed, is the distal tissue firm?

Quadrilateral Socket

• 10. Does the ischial tuberosity rest on the posterior brim?

• 11. Is the posterior brim approximately parallel to the floor?

• 12. Is the adductor longus tendon located in the anterior–medial corner?

Ischial Containment Socket

• 13. Does the posterior–medial corner of the socket cover the ischial tuberosity?

• 14. Can the client hyperextend the hip on the amputated side comfortably?

• 15. Can the client flex the hip 90° comfortably, without socket gapping?

• 16. Can the client abduct the hip on the amputated side comfortably, without socket gapping?

Suspension

• 17. Does the Silesian bandage control prosthetic rotation and adduction adequately?

• 18. Does the pelvic band conform to the torso?

Sitting

• 19. Can the client sit comfortably with hips and knees flexed 90°?

• 20. Does the socket remain securely on the thigh, without gapping or rotating?

• 21. Are both thighs approximately the same length and height from the floor?

• 22. Can the client lean forward to touch the shoes?

Walking

• 23. Is the client's performance in level walking satisfactory?

• 24. Is the client's performance on stairs and ramps satisfactory?

• 25. Does the suspension function properly?

• 26. Does the prosthesis operate quietly?

• 27. Does the client consider the prosthesis satisfactory as to comfort, function, and appearance?

Prosthesis Off the Client

• 28. Is the skin free of abrasions or other discolorations attributable to this prosthesis?

• 29. Is the socket interior smooth?

• 30. With the prosthesis fully flexed on a table, can the thigh piece be brought to at least the vertical position?

• 31. If the socket is totally rigid, is a back pad attached?

• 32. Is the construction satisfactory?

• 33. Do all components function satisfactorily?