Lower extremity orthoses range from shoes used for clinical purposes to THKAFOs. Characteristics and functions of the principal FOs, AFOs, KAFOs, HKAFOs, and THKAFOs, and trunk orthoses, together with the clinically important attributes of shoes, will be described. Although physical therapists also encounter KOs, HOs, and orthoses for special purposes, such as management of Legg-Calvé-Perthes disease, these orthoses are not included because they are used less frequently than the appliances that do appear in this chapter. Similarly, orthoses for the upper limb are omitted from this chapter because they are less commonly prescribed and in most instances are used only for a brief duration.
The shoe is the foundation for most LE orthoses. Each part of the shoe contributes to the efficacy of orthotic management and offers many options for selection. Shoes transfer body weight to the ground and protect the wearer from the terrain and the weather. The ideal shoe should distribute bearing forces so as to provide optimum comfort, function, and appearance of the foot. For the individual with an orthopedic disorder, footwear can serve two additional purposes: (1) it reduces pressure on sensitive deformed structures by redistributing force toward pain-free areas; and (2) it serves as the foundation for AFOs and more extensive bracing. Unless the shoe is correctly fitted and appropriately modified, the alignment of the orthosis will not provide the designed pattern of weight-bearing. The major parts of the shoe are the upper, sole, heel, and reinforcements. These features are found in both the dress leather shoe (Fig. 30.1A) and the athletic shoe (Fig. 30.1B).
(A) Parts of a low quarter shoe with a Blucher lace stay. Note that the counter and toe boxing are internal reinforcing structures of the shoe. (B) Parts of a low-quarter running shoe.
The portion of the shoe over the dorsum of the foot is the upper. It consists of an anterior component called the vamp and the posterior part, the quarter. If the shoe is to be used with an AFO having an insert as its foundation, then the vamp should extend to the proximal portion of the dorsum to secure the shoe and thereby the rest of the orthosis onto the foot. In a laced shoe, the vamp contains the lace stays, which have eyelets for shoelaces (Fig. 30.2). Laces provide more precise adjustment over the entire opening than do strap closures. The latter, however, enable individuals with limited manual dexterity to manage the shoe more easily. For most orthotic purposes, a Blucher lace stay is preferable; it is distinguished by the separation between the anterior margins of the lace stays and the vamp. The alternate design is the Bal, or Balmoral, lace stay, in which the lace stay is continuous with the vamp. The Blucher opening permits substantial adjustability, an important feature for the patient with edema. It also offers a large inlet into the shoe, so that one can determine whether paralyzed toes lie flat within the shoe. An extra-depth shoe is one having an upper contoured with additional vertical space. The shoe is manufactured with a second inner sole that can be removed to accommodate an insert or thick surgical dressing.
Low-quarter shoes: (A) Blucher (open lace) and (B) Bal (Balmoral) (closed lace). The Blucher lace stay is generally preferred for orthotic use owing to ease in donning (provides greater foot entry space to accommodate orthosis) and adjustability.
Quarter height is another consideration in shoe prescription. The low-quarter terminates below the malleoli and is satisfactory for most clinical purposes. This style does not restrict foot or ankle motion. If the patient will be wearing a plastic orthosis molded about the ankle, it is not necessary to go to the additional expense of providing a high-quarter shoe for ankle support. A high-quarter shoe, covering the malleoli, is indicated to cover the foot having rigid pes equinus. It is also appropriate to augment foot stability in the absence of an AFO. The high-quarter shoe, however, is more difficult to don and more expensive than a comparable low-quarter one.
The sole is the bottom portion of the shoe. For use with a riveted metal attachment between shoe and orthosis, the sole should have an outer and an inner sole. Between the two lies a metal reinforcement that receives the rivets. This type of shoe, however, is heavier than an athletic shoe with a single sole. Leather soles absorb little impact shock and provide minimal traction as compared to natural or synthetic rubber soles. To absorb shock, the shoe may have a resilient outer sole, inner sole, or insert. Older people should wear shoes with firm, slip-resistant outsoles to reduce the risk of falling.3,4
Regardless of material, the outer sole should not contact the floor at the distal end; the slight rise of the sole is known as toe spring (see Fig. 30.1), which allows a rocker effect at late stance. If a lift is added to the sole to compensate for leg length discrepancy, the lift should be beveled to achieve toe spring.
The heel is the portion of the shoe adjacent to the outer sole, under the anatomical heel. A broad, low heel provides greatest stability and distributes force between the back and front of the foot most evenly. For adults, a 1-in (2.5-cm) heel tilts the center of gravity slightly forward to aid transition through stance phase, but does not disturb normal knee and hip alignment significantly. Slight heel lifts increase the contraction of the medial gastrocnemius and the tibialis anterior.5 A higher heel places the ankle in greater plantarflexion range and forces the tibia forward. The wearer compensates either by retaining slight knee and hip flexion or by extending the knee and exaggerating lumbar lordosis. The high heel transmits more stress to the metatarsals6 and knee.7 Nevertheless, transferring load anteriorly may be desirable if the patient has heel pain. The higher heel also reduces tension on the Achilles tendon and other posterior structures and accommodates rigid pes equinus. Although most heels are made of firm material with a rubber plantar surface, a low resilient heel is indicated to permit slight plantarflexion if the ankle cannot move because of orthotic or anatomical limitation.
Reinforcements located at strategic points preserve the shape of the shoe. Toe boxing in the vamp protects the toes from stubbing and vertical trauma; it should be high enough to accommodate hammer toes or similar deformity. The shank piece is a longitudinal plate that reinforces the sole between the anterior border of the heel and the widest part of the sole at the metatarsal heads. A corrugated steel shank is necessary if an orthotic attachment is to be riveted to the shoe. The counter stiffens the quarter and generally terminates at the anterior border of the heel. The patient with pes valgus, however, should have a shoe with a long medial counter that provides reinforcement along the medial border of the foot to the head of the first metatarsal, thus resisting the tendency of the foot to collapse medially.
The last is the model over which the shoe is made. The last, whether of traditional wood, custom-made plaster, or computer-generated design, remains with the manufacturer; the shoe shape duplicates the last's contour. A given shoe size may be achieved with many lasts, each transmitting different forces to the foot. Consequently, the physical therapist should ascertain that the shoe shape fits the foot satisfactorily, rather than relying on a particular shoe size. The patient with a markedly deformed foot requires a shoe made over a special last, either a factory- or custom-made one.
Foot orthoses are appliances that apply forces to the foot. These may be an insert placed in the shoe, an internal modification affixed inside the shoe, or an external modification attached to the sole or heel of the shoe. They can enhance function by relieving pain. This may be accomplished by transferring weight-bearing stresses to pressure-tolerant sites, protecting painful areas from contact with the shoe, correcting alignment of a flexible segment, or accommodating a fixed deformity. Inserts can also improve the wearer's transition during stance phase, by altering the rollover point in late stance and by equalizing foot and leg lengths on both limbs. In many instances, a particular therapeutic aim can be achieved by a variety of devices.
Generally, the closer the modification is to the foot, the more effective it is. Biomechanically, inserts and internal modifications are identical. Both inserts and internal modifications reduce shoe volume, so proper shoe fit must be judged with these components in place. An insert permits the patient to transfer the orthosis from shoe to shoe, if the shoes have the same heel height; otherwise, a rigid insert may rock in the shoe. Most inserts terminate just behind the metatarsal heads; thus, they may slip forward, particularly if the shoe has a relatively high heel. Some inserts extend the full length of the sole, preventing slippage, but occupying the often limited space in the anterior portion of the shoe. Internal modifications are fixed to the shoe's interior, guaranteeing the desired placement, but limiting the patient to the single pair of modified shoes.
Inserts made of resilient materials, such as the rubber, viscoelastic plastics (e.g., Sorbothane and Viscolas), or polyethylene foam, reduce impact shock and shear, thus protecting painful or insensitive feet.8 Inserts are also constructed of semirigid or rigid plastics and metal, often with a resilient overlay. A full-length insert tends to reduce gait unsteadiness by improving proprioception from the increased foot contact area.9 A heel-spur insert orthosis (Fig. 30.3), for example, may be made of vis-coelastic plastic or rubber.10 The orthosis slopes anteriorly to reduce load on the painful heel. In addition, the orthosis has a concave relief to minimize pressure on the tender area.
(Left) Plastic tapered heel spur cushion with concave relief to reduce pressure (available in multiple densities as well as with a removable central plug). Courtesy of Silipos, Inc., Niagara Falls, NY 14304-3731. (Right) The shaded area of the shoe on the right indicates the relative position of the heel spur cushion when placed in a shoe.
Longitudinal arch supports are intended to prevent depression of the subtalar joint and flattening of the arch (pes planovalgus, pes planus). The orthosis may include a wedge (post) to alter foot alignment. The minimum support is a resilient scaphoid pad (Fig. 30.4) positioned at the medial border of the insole with the apex between the sustentaculum tali and the navicular tuberosity. Flexible flat foot can be realigned with a semirigid plastic University of California Biomechanics Laboratory (UCBL) insert.11 It is molded over a plaster model of the foot, taken with the foot in maximum correction. It controls hindfoot valgus and limits subtalar motion. The insert encompasses the heel and midfoot. Corrective alignment includes a three-point counterpressure system and force couple for control of calcaneal eversion; forefoot abduction is controlled by a second three-point counterpressure system (Fig. 30.5).12 A full-length insert reduces motion at the first metatarsophalangeal joint, resulting in pain reduction.13,14 Wearing arch supports is associated with increased activation of the tibialis anterior and peroneus longus.15 With regard to the effect of inserts on proximal joints, the evidence is equivocal; some investigations show that orthoses alter the onset of erector spinae and gluteus medius activity16 and support the positive effect of FOs on reducing knee pain,17,17,18,19,20,21 whereas others show little or no effect.22,23 Some adults with plantar fasciitis also respond favorably to foot or-thoses.24,25,26,27,28 Children with pes planus may also benefit from wearing longitudinal arch supports, although the evidence is weak.29,30
Scaphoid pads (left) are available with self-adhesive backing. They are positioned (middle) medial and plantar to the longitudinal arch; scaphoid pad (right) positioned inside of shoe.
University of California Biomechanics Laboratory (UCBL) foot orthosis exerts control at the subtalar joint via a force couple (A) and three-point counterforces to control calcaneal eversion (B). A second counterforce system (C) restricts forefoot abduction. From May and Lockard,12, p. 239 with permission.
Insert orthoses are also used to relieve pain and activity limitation associated with pes cavus.31,32,33 The metatarsal pad (Fig. 30.6) is a convex component that may be incorporated in an insert or may be a resilient domed piece glued to the inner sole so that its apex is under the metatarsal shafts. The pad transfers stress from the metatarsal heads to the metatarsal shafts and is effective in reducing plantar pressure particularly in patients with diabetic neuropathy.34,35,36
Rubber metatarsal pad. Whether used as an internal modification or as part of an insert, the pad should be oriented as shown on the skeletal model.
Occasionally, modifications are sandwiched between the inner and outer soles; for example, the patient with marked arthritic changes in the front of the foot probably will be more comfortable if the shoe has a steel band between the soles to eliminate motion at the painful joints. The same effect can be achieved with a rigid insert.
An external modification ensures that the patient wears the appropriate shoes and does not reduce shoe volume, but will erode as the individual walks and is somewhat conspicuous. In addition, the client is limited to wearing the modified shoe, rather than being able to choose from a wide selection of shoes.
A heel wedge (Fig. 30.7) is a frequently prescribed external modification. It alters alignment of the rearfoot. A medial heel wedge, by applying laterally directed force, can aid in realigning flexible pes valgus or can accommodate rigid pes varus by filling the void between the sole and the floor on the medial side. A medial wedge is incorporated in a Thomas heel, intended for flexible pes valgus (Fig. 30.8 [middle]). The anterior border of the Thomas heel extends forward on the medial side to augment the effect of the medial wedge in supporting the longitudinal arch. A cushion heel is made of resilient material to absorb shock at heel contact. Because it provides slight plantarflexion, the cushion heel is indicated when the patient wears an orthosis with a rigid ankle. Sole wedges alter medial–lateral forefoot alignment. A lateral wedge shifts weight-bearing to the medial side of the front of the foot. It compensates for fixed forefoot valgus, allowing the entire distal foot to contact the floor.
Illustrated here are (left) a metatarsal bar and standard heel, (middle) a rocker bar with a Thomas heel (note the medial extension), and (right) pivot point of rocker bar.
A metatarsal bar (see Fig. 30.8 [left]) is a flat strip of firm material placed posterior to the metatarsal heads. At late stance, the bar transfers stress from the metatar-sophalangeal joints to the metatarsal shafts. A rocker bar (see Fig. 30.8 [middle and right]) is a convex transverse band affixed to the sole proximal to the metatarsal heads. It reduces the distance the wearer must travel during stance phase, improving late stance, as well as shifting load from the metatarsophalangeal joints to the metatarsal shafts.37,38
The patient with leg length discrepancy of more than 1/2 in (1 cm) will walk better with a shoe lift made of cork or other lightweight material. Approximately 3/8 in (0.8 cm) of the elevation can be accommodated on the insole at the heel of a low-quarter shoe.
The AFO is composed of a foundation, ankle control, foot control, and a superstructure.
The foundation of the orthosis consists of the shoe and a plastic or metal component.
A plastic or metal insert or foot plate foundation (Fig. 30.9) has several advantages. Because internal modifications can be incorporated in it, the insert provides good control of the foot. It must be worn with a shoe that closes high on the dorsum of the foot to retain the orthosis. The insert facilitates donning the orthosis because the shoe can be separated from the rest of the brace. The insert also permits interchanging shoes, assuming that all shoes have been made on the same last. Less expensive shoes, such as sneakers, can be worn, because the foundation does not need to be riveted to the shoe. Because the insert is usually made of a thermoplastic material, such as polyethylene or polypropylene, the orthosis with an insert is relatively lightweight. The orthotist creates a plaster model of the patient's leg, then modifies the model, removing plaster in areas where the orthosis is to apply substantial pressure, and adding plaster where pressure relief is required. Thermoplastic is then heated and molded over the modified plaster model.
An insert foundation, however, is inappropriate if the patient cannot be relied on to wear the orthosis with a shoe of proper heel height. If the orthosis is placed in a shoe with too low a heel, the uprights would incline posteriorly, increasing the tendency of the wearer's knee to extend. Conversely, if the orthosis is worn with a higher heeled shoe, the patient might experience knee instability. The insert reduces interior shoe volume, and thus must be used with suitably spacious shoes. Custom-molded foot plates may be more expensive than other types of foundations. If the orthosis is to be used by a very obese or exceptionally active individual, a plastic foot plate may not provide adequate support.
An older foundation for the AFO is the steel stirrup, a U-shaped fixture, the center portion of which is riveted to the shoe through the shank. The arms of the stirrup join the brace uprights at the level of the anatomical ankle, providing congruency between orthotic and anatomical joints. The solid stirrup (Fig. 30.10) is a one-piece attachment that provides maximum stability of the orthosis on the shoe. The split stirrup (Fig. 30.11) has three segments. The central portion has a transverse rectangular opening. Medial and lateral angled side pieces fit into the opening. The split stirrup simplifies donning the orthosis because the wearer can detach the uprights from the shoe. If a central piece is riveted to another shoe, the shoes can be interchanged. The extremely active client may dislodge a side piece from its receptacle unintentionally. The split stirrup is bulkier and heavier than a solid stirrup.
Solid stirrup. The stirrup in the foreground is as it comes from the manufacturer before it is U-shaped and fitted to the patient and shoe.
Most AFOs are prescribed to control ankle motion by limiting plantarflexion and/or dorsiflexion, or by assisting motion. The patient with dorsiflexor weakness or paralysis risks dragging the toe during swing phase. Dorsiflexion assistance can be provided by a posterior leaf spring that arises from a plastic insert (Fig. 30.12). During early stance, as the patient applies force to the braced foot, the upright bends backward slightly. When the patient progresses into swing phase, the plastic recoils forward to lift the foot. Thinner, narrower plastic permits relatively greater motion. Motion assistance can also be achieved with a steel dorsiflexion spring assist (Klenzak joint) (Fig. 30.13) incorporated into each stirrup. The coiled spring compresses in stance and rebounds during swing. The tightness of the coil can be adjusted. An orthosis with a dorsiflexion spring assist is noticeably bulkier than the posterior leaf spring model. Both types of spring assists yield slightly into plantarflexion at heel contact, affording the wearer protection against inadvertent knee flexion. Other AFO designs which control toe drag are presented in Figures 30.14 and 30.15. Healthy subjects wearing a posterior leaf spring AFO exhibited less hip extension and ankle plantarflexion during the transition from stance to swing phase.39 AFOs with flexible ankle control altered the stance phase transition between rear- and forefoot among nondisabled adults.40
Plastic insert on posterior leaf spring AFO.
Steel dorsiflexion spring assist.
ToeOFF® ankle-foot orthosis. This fiber glass, carbon fiber, and Kevlar orthosis is designed to provide dorsiflexion assistance in the presence of mild to severe foot drop accompanied by mild to moderate ankle instability. This orthosis is contraindicated in the presence of moderate to severe spasticity or edema. Courtesy of CAMP Scandinavia AB. SE 254 67 Helsingborg, Sweden.
Ypsilon™ ankle-foot orthosis. This carbon composite AFO is designed to provide dorsiflexion assistance in the presence of mild to moderate isolated drop foot. It promotes free ankle movements (medial, lateral, and rotational movement). The proximal Y-shape provides tibia crest clearance. This orthosis is contraindicated for an unstable ankle joint or in the presence of moderate to severe spasticity or edema. Courtesy of CAMP Scandinavia AB. SE 254 67 Helsingborg, Sweden.
The alternate approach to prevent toe drag is plan-tarflexion resistance, which stops the ankle from plan-tarflexing so that the patient with weak dorsiflexors will not catch the toes and stumble during swing phase. A joint placed in a plastic hinged AFO (Fig. 30.16) or a steel posterior stop (Fig. 30.17) can be incorporated in the stirrup. The posterior stop also imposes a flexion force at the knee during early stance, preventing the knee from hyperextending. Healthy adults walking with the ankle fixed in plantarflexion consumed more oxygen than when walking with AFOs which kept the foot in neutral position.41
Plastic hinged ankle-foot orthoses. Courtesy of Otto Bock, Minneapolis, MN 55447.
Steel stirrup (left) with posterior stop at its proximal end (arrow). Posterior stop (right) incorporated into a stirrup. A posterior stop is designed to allow dorsiflexion and prevent or stop plantarflexion.
An anterior ankle stop limits dorsiflexion, aiding the individual with paralysis of the triceps surae to achieve propulsion during late stance.
Limiting all foot and ankle motion can be done with a plastic solid ankle-foot orthosis (Fig. 30.18); its trimlines are anterior to the malleoli. Able-bodied adults fitted with solid ankle AFOs descended stairs more slowly than when walking without orthoses.42 The solid ankle orthosis may be divided transversely at the ankle, with the two sections hinged, creating the hinged ankle-foot orthosis (see Fig. 30.16). It permits slight sagittal motion, facilitating progression to the foot-flat position in early stance. The joint at the hinge may be a plastic overlap or a flexible plastic rod. A versatile option is a pair of metal hinges that can be adjusted to alter the excursion of ankle motion. An alternative to the plastic solid ankle AFO is a metal joint that resists both plantarflexion and dorsiflexion, known as a limited motion joint. One type of limited motion joint is a pair of bi-channel adjustable ankle locks (BiCAALs) (Fig. 30.19) that consist of a pair of joints, each of which has an anterior and a posterior spring. The springs may be replaced by metal pegs (or pins), the lengths of which determine the amount of motion provided by the orthosis. To compensate for lack of plantarflexion in early stance, the shoe worn with the solid AFO or the orthosis with a limited motion stop should have a resilient heel. Similarly, to facilitate rollover in late stance, the shoe sole should have a rocker bar. Hinged AFOs reduced frontal plane motion during ramp descent exhibited by subjects who have subtalar osteoarthritis.43
Plastic solid AFO. Courtesy of Otto Bock, Minneapolis, MN 55447.
Bi-channel adjustable ankle locks (BiCAALs). Note that this ankle joint includes two channels. A spring placed in the posterior channel (shown) provides a dorsiflexion assist. A peg (or pin) placed in the anterior channel (shown) provides a dorsiflexion stop. A peg placed in the posterior channel creates a plantarflexion stop. From May and Lockard12, p. 254 with permission.
Adults with hemiplegia who wore AFOs demonstrated increased cadence, walking speed, step length, and ankle dorsiflexion,44 and the AFO enabled some patients to walk with increased stride length and cadence.45,46,47,48,49,50 Other subjects with stroke improved their scores on the Berg Balance Scale when wearing AFOs51 and improved weight transfer during stance phase.52 Balance improvement was also achieved by those wearing an anterior AFO,53,54 while other subjects demonstrated better function with a posterior leaf spring AFO.55 Orthoses may either contribute to improved compensatory functions of the nonparetic limb,56 or may be less important during swing phase of the paretic limb as compared with pelvic obliquity.57
A hinged AFO with full-length insert and posterior stop improves early stance stability for subjects with hemiplegia.58 The alignment of a solid AFO should be individualized to achieve optimal function.59
Limited investigation of energy expenditure of adults with hemiplegia wearing AFOs suggests that wearing orthoses results in more efficient gait.60,61,62
Adults with hemiplegia complicated by plantarflexor contracture walk with less plantarflexion and greater knee flexion when wearing either an AFO with posterior stop or a solid AFO.63
Functional electric stimulation is an alternative to an AFO for some adults with stroke and other central neuropathies. Various commercially available systems all incorporate a cuff on the proximal leg; the interior of the cuff contains a skin electrode over the peroneal nerve. The electrode is stimulated by a self-contained electrical unit. As compared to walking with an AFO, subjects report more positive results, particularly during swing phase.64,65,66,67,68
Children with hemiplegic cerebral palsy improved weight-bearing on the paretic limb while wearing either a posterior leaf spring AFO or a hinged AFO with plan-tarflexion stop.69 Other children with similar disability showed slight gait improvement.70,71,72 Energy expenditure lessened when children wore a hinged AFO.73,74,75,76 Other investigators found that hinged AFOs were preferable to other designs for level walking77,78 and stair climbing.79
Some young patients with excessive knee flexion achieved better gait when wearing AFOs with anterior band (floor reaction orthosis).80,81,82 The desirable effect occurred only if the child did not have knee flexion contracture.
Medial–lateral motion can be controlled with a solid ankle AFO. The rigidity of the orthosis can be increased by using thicker or stiffer plastic, corrugating the plastic, forming the edges with a rolled contour, or embedding carbon fiber reinforcements. A solid ankle AFO (see Fig. 30.18) or a hinged solid ankle AFO (see Fig. 30.16) also controls frontal and transverse plane foot motion of children with cerebral palsy to a limited extent.83 Less effective is a metal and leather orthosis to which a leather valgus (or varus) correction strap is attached. The valgus correction strap (Fig. 30.20) is sewn to the medial portion of the shoe upper near the sole, and buckles around the lateral upright, exerting a laterally directed force to restrain pronation. The varus correction strap has opposite attachments and force application. Either strap, although adjustable, complicates donning.
Valgus correction strap (also called a "T-strap"). Arrows indicate the three-point pressure system created by the corrective forces (right lower extremity).
The proximal portion of the orthosis, the superstructure, consists of one or two uprights, and a shell, band, or brim. Plastic AFOs usually have a single upright or shell. Both the solid ankle and the hinged solid ankle AFOs have a posterior shell extending from the medial to the lateral midline of the leg, thus providing excellent medial-lateral control and a broad surface to minimize pressure. The posterior leaf spring AFO (see Fig. 30.12) has a single posterior upright that does not contribute to frontal or transverse plane control.
The spiral AFO (Fig. 30.21) is a design in which a single upright spirals from the foot plate around the leg, terminating in a proximal band. It may be made of polypropylene, nylon acrylic, or carbon fiber. The spiral orthosis controls, but does not eliminate, motion in all planes. Orthoses with plastic shells or uprights are molded over a cast of the patient's leg and are designed to fit snugly for maximal control and minimal conspicuousness. Such AFOs are contraindicated for the individual whose leg volume fluctuates markedly, because the orthoses cannot be adjusted readily.
Metal and leather orthoses usually have medial and lateral uprights to maximize structural stability. Occasionally, a single side upright will suffice when the patient insists on a less conspicuous orthosis and the person is not expected to exert undue force. Some AFOs shear stress on the calf and Achilles tendon. Aluminum uprights are typically used because they are lighter in weight than steel. Carbon graphite and titanium uprights weigh appreciably less than aluminum and rival the strength of steel; however, orthoses made of these materials are more expensive.
Most orthoses have a posterior calf band made of rigid plastic or leather-upholstered metal. The band has an anterior buckled or pressure closure strap (Fig. 30.22). The farther the band is from the ankle joint, the more effective the leverage of the orthosis; however, the band must not impinge on the peroneal nerve. An anterior band that is part of a solid ankle AFO imposes posteriorly directed force near the knee, enabling the AFO to resist knee flexion. Such an orthosis is known as a floor reaction orthosis (Fig. 30.23). In fact, all LE orthoses are influenced by the floor reaction when the wearer stands or is in the stance phase of gait. If the AFO is to reduce the amount of weight transmitted through the foot, it may have a patellar-tendon-bearing brim (Fig. 30.24), resembling a transtibial (below-knee) prosthetic socket. The plastic brim has a slight indentation over the patellar tendon, and is hinged to facilitate donning. The brim must be used with a plastic solid ankle or a steel limited-motion ankle joint.
Conventional AFO with stirrup attachment, limited motion ankle joints, bilateral uprights, and uphol-
Floor reaction AFO with anterior band provides a knee extension moment in stance without preventing flexion during swing. From May and Lockard,12, p. 276 with permission.
(Left) AFO with stirrup, hinged ankle joint, steel uprights, and plastic patellar-tendon-bearing brim. (Right) Plastic AFO with patellar-tendon-bearing brim to reduce weight-bearing on foot. Courtesy of Ortho-Bionics Laboratory, Inc., South Ozone Park, NY 11420.
Individuals with more extensive paralysis or limb deformity may benefit from KAFOs, which consist of a shoe, foundation, ankle control, knee control, and superstructure. KAFOs often include foot control. The shoe, foundation, ankle control, and foot control of the KAFO may be selected from the components already described. Patients with poliomyelitis who wore carbon-composite KAFOs walked better than with leather/metal or plastic/metal KAFOs.84,85,86 Donning a plastic and metal KAFO is appreciably faster than putting on a metal and leather orthosis because the shoe can be separated from the rest of the orthosis.
The simplest knee joint is a hinge. Because most KAFOs include a pair of uprights, the orthosis has a pair of knee hinges that provide medial–lateral and hyperextension restriction while permitting knee flexion.
The offset joint (Fig. 30.25 [left and middle]) is a hinge placed posterior to the midline of the leg. When the weight line falls anterior to the offset joint, stabilizing the knee in extension during the early stance phase of gait. The offset joint does not hamper knee flexion during swing or sitting. The joint may, however, flex inadvertently when the wearer walks on ramps.
Two examples of offset knee joints (left and middle) and one of a drop ring lock (right).
The most common knee control is the drop ring lock (Fig. 30.25 [right]). When the client stands with the knee fully extended, the ring drops, preventing the uprights from bending. Although both medial and lateral joints should be locked for maximum stability, manipulating a pair of drop ring locks is inconvenient, unless each upright is equipped with a spring-loaded retention button. The button permits the wearer to unlock one upright, then attend to the other one without having the first lock drop. The buttons also enable the physical therapist to give the patient a trial period of walking with the knee joints unlocked.
The pawl lock with bail release (Fig. 30.26) provides simultaneous locking of both uprights. The pawl is a spring-loaded projection that fits into a notched disk. The patient unlocks the brace by pulling upward on the posterior bail. Some people are agile enough to be able to nudge the bail by pressing it against a chair. The bail is bulky and may release the locks unexpectedly if the wearer is jostled against a rigid object.
Knee joint hinge with pawl lock: basic component (A) and pawl lock installed in KAFO with bail
The offset joint and knee joints with basic drop ring or pawl locks are contraindicated in the presence of knee flexion contracture. If one cannot achieve full passive knee extension, an adjustable knee joint such as the fan lock, serrated lock (Fig. 30.27), or ratchet lock is required. Such joints usually have a drop ring lock for stability in the partially flexed attitude.
Knee joint hinge with serrated knee lock. Note the location of the knee hinge and the serrated disk. From Fishman, S, et al: Lower extremity orthoses. In American Academy of Orthopaedic Surgeons: Atlas of Orthotics, ed 2. Mosby, St. Louis, 1985, p 213, with permission.
Sagittal stability is augmented by a kneecap (Fig. 30.28A) or an anterior band or strap that completes the three-point pressure system necessary for stability. The cap or band applies a posteriorly directed force to complement the anteriorly directed forces from the back of the shoe and the thigh band. The leather knee cap has four straps buckled to both uprights above and below the knee. The knee cap requires the patient to buckle two straps when donning the orthosis. When the straps are tight enough to stabilize the knee, the cap is likely to restrict flexion when the wearer sits. A more practical alternative is a rigid anterior band, either a pretibial band or a suprapatellar band, both of which apply posteriorly directed force, but do not interfere with sitting and are easier to don. The bands generally are molded of plastic and thus not readily adjustable. The prepatellar band rests over the bony proximal portion of the leg and requires careful contouring to be comfortable. The suprapatellar band fits over the fleshy anterodistal thigh. Examples of combined metal and plastic KAFOs are presented in Fig. 30.28 (B and C).
(A) Conventional KAFO with knee cap. (B) Plastic KAFO pictured on a subject together with schematic of same orthosis. Courtesy of Orthomerica Products, Inc., Orlando, FL 32810. (C) This orthosis allows conversion between an AFO and KAFO based on patient requirements. The knee component that provides more proximal alignment and stability is detachable to create an AFO. Courtesy of Orthomerica Products, Inc., Orlando, FL 32810.
Another means of obtaining sagittal stability involves a KAFO with an electronic stance control mechanism that prevents knee flexion during stance phase and permits knee flexion during swing phase. By moving a lever on the side of the joint, the patient can select the mode of action: (1) stance control that is disengaged during swing phase, (2) no stance control, and (3) lock in full extension. Preliminary investigation indicates that adults with LE paralysis walked faster and more efficiently, with increased cadence and step length, and fewer compensatory trunk movements, as compared with use of a locked KAFO.87,88,89,90,91,92,93,94,95 KAFOs with computer-controlled knee joints are also available96 (Fig. 30.29). A KAFO with electronic knee control enables some patients with stroke and other neuropathies to walk97 (Fig. 30.30).
(A) Computer-controlled KAFO. (B) Closeup of knee joint. The E-Knee" pictured here is a force-activated, computer-controlled knee unit powered by a lithium battery. The pressure-sensitive footplate signals the microprocessor to lock knee when pressure is applied and to unlock in the absence of pressure. The unit is recharged using a standard electrical outlet. Becker E-Knee, Becker Orthopedic, Troy, MI 48083.
Patient moving from sit-to-stand wearing the Tibion Bionic Leg (Tibion Corporation, Sunnyvale, CA 94085). This is a KAFO with electronic knee control designed to support the rehabilitation process. A computer allows the therapist to program the amount of support the orthosis is providing during various tasks.
Frontal plane control may be achieved with plastic calf shells shaped to apply corrective force for genu valgum or genu varum. To reduce genu valgum, the medial portion of the shell extends proximally in order to apply laterally directed force at the knee. The semi-rigid shell is more effective than a valgum correction strap, which is a knee cap with a fifth strap designed to be buckled around the lateral upright. The opposite force application is indicated for the patient who has genu varum. The shell does not require time in donning and applies force over a broad area without impinging on the popliteal fossa.
Thigh bands provide structural stability to the orthosis. If the distal portion of the limb cannot tolerate full weight-bearing, then the proximal thigh band may be shaped to form a weight-bearing brim. To eliminate all weight-bearing through the lower extremity, the orthosis must include a weight-bearing brim, a locked knee joint, and a patten bottom. The patten is a distal extension that keeps the foot on the braced side off the floor (Fig. 30.31). To maintain a level pelvis, the patient must also wear a lift on the opposite shoe; the height of the lift should equal the height of the patten.
The patten bottom is the distal component of an orthosis designed to eliminate weight-bearing from the limb. The patten bottom prevents the foot from contacting the floor.
Addition of a pelvic band and hip joints converts the KAFO to an HKAFO.
The usual hip joint is a metal hinge (Fig. 30.32) that connects the lateral upright of the KAFO to a pelvic band. The joint prevents abduction and adduction, as well as hip rotation. If the patient requires only control of hip rotation, a simpler alternative to the hip joint and pelvic band is a webbing strap. To reduce internal rotation, the strap resembles a Silesian belt on a prosthesis. The center of the strap is riveted to the rear of a waist belt. Each end of the strap is attached to the proximal end of the lateral upright. To reduce external rotation, a strap joins the lateral uprights of the KAFOs, passing anteriorly at the level of the groin. If flexion control is required, a drop ring lock is added to the hip joint. A two-position lock stabilizes the patient in hip extension for standing and walking, and at 90 degrees of hip flexion for sitting.
Hip joint with drop ring lock.
An upholstered metal band (Fig. 30.33) anchors the HKAFO to the trunk. The band is designed to lodge between the greater trochanter and the iliac crest on each side. HKAFOs are not used very often because they are much more awkward to don than KAFOs, and, if the hip joints are locked, they restrict gait to the swing-to or swing-through pattern. The pelvic band may be uncomfortable when the wearer sits.
(Left) Conventional HKAFO with stirrup; uprights; hinged ankle, knee, and hip joints; drop ring locks at the knee and hip; and pelvic band. (Right) Plastic and metal HKAFO with hip and knee joints unlocked. Courtesy of Orthomerica Products, Inc., Orlando, FL 32810.
Patients who require more stability than provided by HKAFOs may be fitted with THKAFOs (Fig. 30.34), which incorporate a lumbosacral orthosis attached to KAFOs. The pelvic band of the trunk orthosis serves as the pelvic band used on HKAFOs. Because the THKAFO is very difficult to don and is heavy and cumbersome, it is seldom worn after the client is discharged from the rehabilitation program. Alternative orthoses providing standing stability, with or without provision for walking, are available for some individuals with paraplegia.
Conventional THKAFO without upholstery. This image illustrations the foundational structure of these cumbersome orthoses. To this large heavy metal frame, the additional weight of the upholstery, needed straps and pads, and shoes was added. Patients once leaving the rehabilitation setting often discarded such extensive bracing.
Orthotic Options for Patients with Paraplegia
Orthoses are often prescribed for patients with spina bi-fida, spinal cord injury, or other disorders that result in paraplegia. The functional goals for such people include standing to maintain skeletal, renal, respiratory, circulatory, and gastrointestinal function and some form of ambulation. Upright posture also affords the individual important psychological benefits.
Several appliances are marketed for children who have spina bifida or other disorders resulting in paraplegia. The mass-produced orthoses provide the youngster with considerable function and are less expensive and easier to don than many custom-made devices. The stabilizing points on these orthoses are the same, namely a means of securing the shoes to the base, an anterior knee band, posterior dorsolumbar band, and an anterior chest band. The orthoses permit the wearer to stand without crutch support, freeing the hands for play or vocational activities.
Standing Frame and Swivel Walker
The standing frame (Fig. 30.35) consists of a broad base, posterior nonarticulated uprights extending from a flat base to a midtorso chest band, and a posterior thoracolumbar band. Anterior leg bands contribute to stability. A similar orthosis is the swivel walker, which is made in both child and adult sizes. The major difference is the base. The swivel walker has two distal plates that rock slightly to enable a swiveling gait. Standing frames offering a variety of features are commercially available (Fig. 30.36).
Standing frame. Courtesy of Variety Village, Electro Limb Production Centre, Scarborough (Toronto), Ontario, Canada.
Adult standing frame. Courtesy of Altimate Medical, Inc., Morton, MN 56270.
The parapodium (Fig. 30.37) is manufactured in child sizes, and permits the wearer to sit. The base is flat. One version of parapodium has a provision for keeping the knees locked while the child unlocks the hips in order to lean forward to pick up objects from the floor. With some of these devices, the child can move from place to place by rotating the upper torso to shift weight, causing the frame to rock and rotate alternately on one edge then the other. For walking longer distances, the youngster uses crutches or a walker in the swing-to or swing-through pattern. The appliances are worn on the outside of clothing, which school-age children eventually find cosmetically objectionable.
Parapodium. Courtesy of Variety Village, Electro Limb Production Centre, Scarborough (Toronto), Ontario, Canada.
Although the mass-produced devices afford considerable function to their users, many individuals seek more streamlined orthoses. Custom-made AFOs, KAFOs, and THKAFOs provide sufficient rigidity, either by metal joints or orthotic alignment, to enable selected individuals to stand. Ambulation requires crutches or similar aids, together with well-coordinated use of the trunk and upper limbs. Some patients may not realize the extent of the physical conditioning program required to prepare them for ambulation. Consequently, a trial period is advisable using mass-produced, adjustable, temporary orthoses.
AFOs designed for adults with paraplegia include a pair of stabilizing boots molded to conform to the patient's legs and feet (Fig. 30.38). The foot plate is angled at approximately 15° plantarflexion to shift the wearer's center of gravity anterior to the ankles. The plastic component is inserted into leather boots which have flat soles. The legs are thus inclined posteriorly to keep the knees extended. The patient maintains standing stability by leaning backward, with the iliofemoral ligaments resisting a backward fall. A pair of crutches or a walker is needed for two- or four-point gait. Ambulation requires shifting the upper torso diagonally forward to allow one leg to swing ahead. The orthoses are easy to don and do not restrict sitting. The candidate must not have any hip or knee flexion contractures, and must be able to extend the hips and lumbar spine by trunk motion.
Stabilizing boots. From Kent, HO: Vannini-Rizzoli stabilizing orthosis (boot): Preliminary report on a new ambulatory aid for spinal cord injury. Arch Phys Med Rehabil 73: 302, 1992, p 304, with permission.
A pair of Craig-Scott KAFOs (Fig. 30.39) may be prescribed for adults with paraplegia. Each orthosis includes either a shoe reinforced with transverse and longitudinal plates and BiCAAL ankle joints set in slight dorsiflexion or a plastic solid ankle section, as well as a pretibial band, a pawl knee lock with bail release, and a single thigh band. The orthoses enable the patient to stand with sufficient backward lean so as to prevent untoward hip or trunk flexion. The gait pattern usually is swing-to or swing-through, with the aid of crutches or a walker. Although the orthoses do not restrict hip motion, the patient with thoracic spinal injury cannot control the hips, and the orthosis has no mechanism to aid single-leg progression. Some individuals perform a two- or four-point gait by shifting the trunk enough to allow the leg to swing forward in a pendular manner.
The Walkabout orthosis consists of a pair of KAFOs with a hinge mechanism joining the medial uprights of the two orthoses. The mechanism permits hip flexion and extension, but restricts hip abduction, adduction, and rotation.
Reciprocating Gait Orthoses
Children and adults can be fitted with a reciprocating gait orthosis (RGO) (Figs. 30.40 and 30.41). The RGO is a THKAFO in which the orthotic hip joints are connected by one or two metal cables or rods. The knees are stabilized with knee locks, and the feet are encased in solid ankle orthoses. To walk, the wearer follows a four-stage procedure: (1) shift weight to the right leg, (2) tuck the pelvis by extending the upper thorax, (3) press on the crutches, and (4) allow the left leg to swing through. For the next step, one shifts to the left leg, tucks, presses, and then allows the right leg to swing. The steel cable(s) or rods prevent inadvertent hip flexion on the supporting leg. Reciprocal four- or two-point gait is stable, because one foot is always on the floor, but the pace is slow. For sitting, the wearer releases the cable(s) to enable both hips to flex. RGOs require substantial energy expenditure on the part of the wearer.98,99,100,101
Reciprocating gait orthosis. Courtesy of Fillauer Companies, Inc., Chattanooga, TN 37406.
ARGO reciprocating gait orthosis. This system includes pneumatic struts at the knee that extend the knees and ensure locks are engaged on standing. Courtesy of RSL Steeper, Rochester Kent ME2 4DP, United Kingdom.
Alternatives for patients with thoracic level spinal cord injury are the ParaWalker and the ParaStep. The ParaWalker is a THKAFO with massive hip joints. The clinician can limit the flexion and extension excursion of the hip joints. Gait is similar to that with an RGO. Subjects who wore the ParaWalker had fewer pressure sores and no fractures.102 The ParaStep is a system combining AFOs with skin electrodes over the quadriceps and glutei maximus. Energy expenditure with either device is very high.103