Protective footwear is the second line of defense after skin and toenail care for prevention of new and recurrent wounds (Figure 1).1,2 Any patient who has one or more of the conditions recognized as risk factors for wound development — such as deformity, peripheral vascular disease, history of a previous wound, previous amputation and/or neuropathy — and is ambulatory requires intelligent decision-making for the selection of protective footwear. This line of defense is so important that in 1993, Medicare (Center for Medicare/ Medicaid Services) under the direction of Congress, initiated the “Therapeutic Shoe Bill” benefit for diabetic Medicare beneficiaries with risk factors for wounds. Undoubtedly this decision was based on the assumption that the potential benefits to prevent diabetic foot problems outweighed the costs to provide protective footwear.3,4 Essentially, it is less expensive to prevent a diabetic foot problem from arising by providing therapeutic footwear than it is to treat the complications that arise from not using appropriate footwear. In recognition of this, benefits for protective footwear for diabetic patients were established and will be delineated later in this article.
FIGURE 1. Appropriate footwear selection is the second line of defense against developing new or recurrent foot wounds.
Legend: Selection of appropriate footwear depends on findings from the evaluation. Footwear selection choices lie on a continuum from least expensive/less complex to most expensive/most complex. Medicare provides benefits for diabetic patients who require prescription footwear.
Selection of protective footwear is not a matter of fashion. It requires knowledge, insight and experience. There are a large number of options to consider when recommending and prescribing protective footwear including individual adjustments such as casts, orthotics, wedges, fillers, lifts, cut outs, relief areas, bars or other modifications. To simplify matters, the selection of protective footwear can logically be placed in a hierarchy from least to most complex (Figure 2). Factors that determine complexity include availability ranging from off-the-shelf to custom-molded and modifications from simple inserts to specifically placed reliefs and pads. As the complexity increases, the costs increase proportionately. The hierarchy has five levels: 1) quality walking or athletic shoes, 2) off-the-shelf diabetic shoes with cushioned plantar inserts, 3) custom prescriptions added to off-the- shelf diabetic shoes, 4) custom-molded diabetic shoes and 5) Charcot restraint orthotic walkers (CROW boots).
SHOE COMPONENTS AND SOCK CHARACTERISTICS
To appropriately prescribe protective footwear, it is helpful to be aware of the various components of a shoe, its functions, what alternatives exist for each component and what complications may arise from them. Surprisingly, many options also exist for sock choices. The following is a summary of major shoe components and sock compositions:
1.Covering materials (outer portions) are what the outer component of the shoe is made of, give the shoe above the sole portion its shape, and often give the shoe its common name such as leather, house, tennis, athletic, boot, etc. Common components include leather, cloth, netting comprised of various materials, canvas, rubber, synthetic fibers (rigid or flexible) or plastic. Multiple combinations may be used, as is often found in tennis shoes. Leather is desirable for its durability, breathability and malleability to accommodate deformities. Flexible synthetic fibers are desirable because they accommodate changes in foot size due to swelling and are pliable enough to avoid pressure concentrations. Rigid plastic coverings, such as those used in the Charcot restraint orthotic walkers (CROW boot), require padded inner linings.
2. Fasteners are the devices that help to keep the shoe on the foot. There are three basic choices: 1) string ties, 2) elastic bands and 3) Velcro® straps. String ties tend to be more secure but require agility and good proprioception to tension properly and tie. If the knot becomes untied, the shoe may loosen, subjecting the patient’s skin to shear stresses and the foot and ankle ligaments to sprains. Another hazard of string ties is they can become untied and can cause the patient to trip over a shoelace. Elastic bands or Velcro® straps are more user-friendly and the preferred choice for many patients with comorbidities such as arthritis, obesity and hemiparesis, etc. In patients who retain fluid, the elastic bands may indent the edematous skin and interfere with venous return.
3. Heels are elevations that may be are elevations that may be added to the back thirds of the shoe sole (discussed below). They may be thick, thin, wedged on either side, extend medially (Thomas heels) or absent, depending on the perceived needs of the hindfoot. Whereas some of the heel modifications are of dubious value, those used to counteract equinus deformities and position the ankle during Achilles tendon healing are of value
4. Heel counters are the parts of the shoe that come in contact with the back of the shoe heels. They may be low profile, barely covering the back of the heel, or enough to extend proximal along the back of the Achilles tendon. The higher the heel the greater is the control of the hindfoot. The inside portion of the heel counter may be padded with foam or soft cloth or merely lined with cloth or leather to provide a cosmetic appearance for the shoe covering material. Semirigid plastic inserts may be placed between the layers to add increased rigidity to the heel counter and control of the hindfoot.
5. Inner lining may or may not be present. They may increase the cushioning properties of the shoe, absorb moisture or help with the fit of the shoe. In stylish shoes, most are thin leather and added only for their cosmetic effect. In addition to lining materials may be cloth or various types of foam.
6. Lasts refer to the shape of the sole portion of the shoe. Usually the last is slightly concave along its medial aspect. For angular deformities (especially metatarsus adductus in children), the lasts may be straight or reversed, that is convex along their medial border.
7. Shanks are devices inserted into the sole portion of the shoe to control flexibility. Most often they are rigid steel bars and used for specific occupational needs rather than as modifications for protective footwear.
8. Shoe heights (upper portion) designate the portion of the shoe that is attached to the sole and extends over the foot, ankle or leg. Low-cut shoes such as moccasins and flats may cover only the bottom half of the foot. Consequently, they provide minimal support and stability. Intermediate cut shoes, the most frequently prescribed protective footwear, enclose the feet and extend to just below the level of the ankle malleoli. High-top shoes extend above the malleoli, with boots being a good example of this type of footwear. With increasing height of the upper portion of the footwear, protection, support and stability increase. Conversely, the greater the height of the upper portion of footwear, the more difficult it is to don, fasten and remove the shoe. Velcro® straps help to mediate the difficulties of tying the shoes. Specially designed footwear such as CROW boots help to mitigate the difficulty of donning and removing the shoe.
9. Shoe soles are the part of the shoe that makes contact with the ground or floor. They may be rigid or flexible. Typically, they may be flat, with or without the addition of a heel portion. Materials used for the soles of shoes include leather, plastic composite materials, wood and rubber. The rocker-bottom sole is a modification that facilitates walking in the presence of severe deformities or joint mobility problems.
10. Shoe tongues may or may not be present in protective footwear. Tongues, when present, are usually a separate component that attaches to the toe box (described next). Tongues serve several purposes, including providing protection between the laces and the top of the foot, and improved fit and comfort. Tongues may or may not be padded. Shoes that do not have tongues usually have overlapping flaps secured with Velcro® straps. These make the shoe easier to don and remove.
11. Toe boxes are the portions of the shoe top that cover the forefoot. For most protective footwear, the toe boxes are spacious enough to prevent pressure sores developing from clawed toes and other forefoot abnormalities. Of course, the antithesis of the large toe box is the pointed-toe shoe. In comparison to protective footwear, pointed-toe shoes have many undesirable features that contribute to bunion deformities, hallux valgus, hyperpronation of the great toe, varus plus supination deformities of the little toes and cross-over toes. In conjunction with high heels, pointed-toe shoes contribute to clawed toe deformities, hyperextension contractures of the toes at the metatarsal-phalangeal joint levels, proximal migration of the forefoot fat pads, as well as calluses, bone spurs and ulcerations under the metatarsal heads. When toes or a distal portion of the foot are absent, a filler (or spacer) is usually inserted in the toe box to help with shoe fit and prevent shearing stresses on the skin with movements of the foot.
12. Sock options should not be overlooked in conjunction with footwear selection. Knee-length compression stockings with 20- to 30 mmHg tensions are recommended for all patients who have had foot surgeries, lower-extremity edema, mobility problems, venous stasis disease or spend extended periods of time with their feet immobile in the dependent position. Sock fiber choices include cotton, wool, acrylic, polyester, polypropylene or combinations of these fibers. Cotton socks are the least expensive, do not provide very good padding and manage moisture poorly. Wool socks provide good insulation and manage moisture fairly well. Acrylic socks fit well, reduce shear, cushion well and handle moisture well. The other synthetic fibers manage moisture well but do not provide good padding. Blends of these fibers can combine the desirable features of several fiber types. White stockings are especially desirable for those patients with risk factors for wound development because a stain on a white sock will not likely be ignored, as it might be if the patient was wearing dark-colored socks. Finally, stocking cleanliness is desirable, preferably with changes being made daily. Socks from synthetic fibers tend to retain odors and pile with repeated wear.
PROTECTIVE FOOTWEAR OPTIONS
Although nearly a dozen components, as just described, may be considered when prescribing protective footwear, choices can be reduced to five principle types in a hierarchy that ranges from off-the- shelf, least expensive to custom-molded, most expensive (Figure 2). Knowledge of the footwear options and what protective footwear. Considerations include the following:
patient’s functional capacity
characteristics of the foot problem
modifications available for the five principle protective footwear choices
- patient goals
In most circumstances this information, except for knowledge of the available modifications, is already available from the patient’s initial evaluation or becomes readily obvious with the reevaluation preceding the footwear prescription. The actual protective footwear selection, addition of modifications and fitting should be done by the pedorthotist or orthotist, who is the health-care professional most knowledgeable in this aspect of protective footwear. The following information describes the five principle choices for protective footwear in the hierarchy of complexity and costs. For each upward step in the hierarchy, the costs increase two- to threefold.
FIGURE 2. Hierarchy of prescription footwear
Level 1 — Quality walking or athletic shoes:
Theses shoes can be purchased without a prescription and usually do not qualify for Medicare Therapeutic Shoe Bill benefits. They are the least expensive and the best looking of the footwear options (Figure 3). Not only is the construction of the highest quality, but they are also usually available in a variety of lengths and widths to accommodate a wide range of foot sizes. The insides of these shoes are typically well-padded and the soles fairly rigid. The shoes are generally secured by lace-up ties or Velcro® straps. Many choices have large toe boxes that provide room for clawed or hyperextended toe deformities. This footwear choice is ideal for patients without foot deformities and/or who have only minimal, if any, risk factors for wound development. Prices of quality walking or athletic shoes range from $100 to $200.
FIGURE 3. Quality walking and athletic shoes vs. a high-fashion
Legend: Quality walking and athletic shoes can be stylish as well as functional, but contrast markedly with the shoe in the right hand figure, which has pointed toes, a thin side, compressed toe box, and slip-on (moccasin style) fixation to the foot.
Level 2 — Off-the-shelf diabetic shoes with cushioned plantar inserts:
As the name implies, these are production model (i.e., mass-produced) shoes that generally are available in most well- stocked specialty footwear and orthotic- prosthetic providers. The shoes are similar to the descriptions given above for quality walking or athletic shoes with the major difference being that there is enough room to accommodate extra- depth inserts (Figure 4). Although these shoes with the prescribed orthotics can be purchased without a prescription, a prescription by a physician is necessary for patients with diabetes to receive Medicare Therapeutic Shoe Bill benefits. There are advantages in obtaining these shoes from sales people trained in the fitting of protective footwear, including 1) improved likelihood of proper size selection, 2) experience with the choices available to comply with the footwear prescription, 3) recognition and management of special needs such as different sized shoes for each foot, 4) preparation and fitting of multidensity inserts (Table 1), 5) ability to stretch and relieve pressure areas that are noted after using the shoes and 6) recourse such as exchanges or refunds if the patient is not satisfied with the footwear that was selected.5 In general, patients who enter the footwear selection hierarchy at this level have minimal deformities, although they have risk factors for the development of foot wounds.
FIGURE 4. Off-the-shelf shoes with cushioned plantar inserts for diabetics
Legend: These shoes have the desirable features of the quality walking and athletic shoes (Figure 3) in addition to providing additional room for inserts.
Note the relief areas in the orthotic under the first metatarsal head and lateral side of the midfoot (⇔) in the left half of the figure.
TABLE 1. Materials commonly used for shoe inserts and/or orthotics
Durability of Level 2 protective footwear: For household and limited community ambulation needs, off- the-shelf diabetic shoes should remain effective for approximately a year. The Medicare Therapeutic Shoe Bill allows for shoe replacement yearly. With use and time the shoes stretch, become easier to don and remove and, according to the patients, feel more comfortable. Unfortunately, these may be clues that it is time to replace the shoes. Other signs of shoe deterioration include wearing down of the heels or soles so they no longer keep the foot plantigrade, shifting of the upper portion of the shoe on the sole, wearing away of the inner linings especially over bony prominences, separation of seams, and excessive wear and tear of the upper portions. Consequently, if the shoe fits, it does not always mean it should be worn. Multidensity inserts quickly lose their cushioning ability with use. The Medicare Therapeutic Shoe Bill provides for replacement inserts as frequently as every four months if they are no longer effective. Prescription footwear with inserts usually costs about two to three times as much as quality walking or athletic shoes or in the $300–$500 range.
Level 3 — Custom prescriptions added to off-the shelf diabetic shoes:
This is the third level in the footwear selection hierarchy (Figure 5). This step of the hierarchy is typically associated with a single fixed (static) or dynamic deformity of the foot or ankle. Generally, shoes from the previous level are used as the foundation for the prescription modifications. A large number of options exist; essentially every shoe component previously discussed can be modified in one way or another (Table 2). When shoe modifications are prescribed, several requirements need to be met. First, the modification should address the structural deformity. The deformity can be as simple as mildly depressed metatarsal heads that require placement of a simple metatarsal pad to associated with Charcot neuroarthropathy.6 Second, the modification needs to provide a stable, plantigrade platform for the bottom of the foot to transfer the patient’s body weight to the underlying walking surface. Third, the modification needs to reduce focal areas of pressure as typically found over deformities. Fourth, the modification needs to eliminate shear stresses. For example, the indication for prescribing a filler or spacer for the forefoot after a transmetatarsal amputation (Figure 6).
FIGURE 5. Custom prescriptions added to off-the-shelf diabetic shoes
Legend: Major customized modifications to control severe lateral instability of the foot and ankle. These modifications made to an off-the-shelf athletic shoe. Note normal height of the medial side of the athletic shoe heel in the photo inset in the upper right side of the figure.
FIGURE 6. Custom prescription for a transmetatarsal amputation
Legend: Extra-depth plastizote insert plus filter for missing forefoot added to an off-the-shelf diabetic shoe that has a large toe box. The filter prevents the shortened foot from sliding forward in the shoe when walking.
Note the slight ridge at the heel portion (long black arrow) of the insert. This helps stabilize the heel. Also, note the darkened spot on the heel portion of the insert. This "dirty" area confirms that the patient has been an active ambulator with the prescription protective footwear.
TABLE 2. Foot problems manageable by footwear modifications
Bracing for protective footwear
Another prescription addition that may be required at this level of protective footwear is the use of the metal double upright brace (Klenzak). Whereas plastic ankle foot orthoses (AFOs) have many desirable features such as lightness and ease of application, they do not control angular and rotation deformities very well. They are most suitable for drop foot (peroneal nerve palsy) problems where a single (i.e., lack of foot dorsiflexion), nonangular deformity is present. In addition, AFOs may cause ulcerations not initially perceived by the patient due to their sensory deficits. The Klenzak brace with its distal insertion into a high- quality shoe (frequently with prescribed adjustments) can control angular, rotation, static and dynamic deformities simultaneously. In this respect, despite its weight and unattractiveness, it is a valuable asset in the armamentarium of protective footwear alterations.
Successful use of protective footwear: Although prescription modifications may be the logical choice for the problem observed in the foot and ankle, they are not always successful. Maintaining the ability to walk and the prevention of new wound problems confirm successful use of the footwear. This is achieved only in conjunction with patient education and proper skin and toenail care. Often revisions and adjustments are needed to make the protective footwear function optimally. Even then, they may be able to only maintain the status quo — that is, prevent the wound from worsening while maintaining the patient’s mobility such as in a chronic, stable wound. A second corollary of successful protective footwear modifications is that they may require ongoing adjustments. Frequently, the shape of the foot changes with time. This is especially noted with Charcot neuroarthropathies, posterior tibial tendon insufficiencies and motor neuropathies. The third corollary is to establish whether or not the deformity is static, that is present even when not weight bearing or dynamic, that is it is present only with weight bearing. In general, static deformities are harder than dynamic deformities to control with prescription adjustments. Prescription adjustments for dynamic deformities, however, have a propensity to generate shear stresses when walking and thus are more prone to cause skin ulcers. Shoe modifications/adjustments are another provision of the Medicare Therapeutic Shoe bill for diabetic patients. In general, adding prescription modifications to off-the-shelf shoes triples the costs of the unmodified shoes.
Level 4 — Customized molded protective footwear: This is the fourth level in the hierarchy of footwear options and is especially suited for patients with multiple deformities that have dynamic as well as static components (Figure 7). These shoes, as the title implies, are custom molded to accommodate unique foot and ankle deformities. Common features of these shoes are their unattractive appearance, their high- topped lengths and their asymmetry with the opposite shoe. Typically, the deformities are unilateral and so severe that the footwear selections from the first three levels of the selection hierarchy are not able to protect (from new ulcerations) and maximize function of the foot and/or ankle. Examples include Boyd amputations (all the foot bones are removed except for the talus and calcaneus), rigid foot deformities in which the majority of the foot bones have fused into a solid mass, and the splayed forefoot in which the medial and lateral toes and rays are widely divergent. The costs of custom-fabricated shoes and/or double upright braces attached to prescription shoes is in the $1,000 to $1,500 range or two to three times the costs of shoes with prescription adjustments.
FIGURE 7. Custom molded protective footwear
Legend: Custom molded shoes to manage major deformities of the feet and ankles. Note the asymmetry of the shoe lasts and upper portions. Regardless of the appearances of the shoes, the patients were thankful that these protective footwear devices allowed them to remain ambulatory and gainfully employed while not developing new wounds.
Charcot restraint orthotic walker (CROW) boots: The CROW boot represents the ultimate in the hierarchy of prescription footwear (Figure 8). When multiple fixed and dynamic deformities are present in the foot and ankle, uncontrollable by other means and the leg is at risk of a below-knee amputation because of them, a CROW boot is indicated. The CROW boot consists of a rigid posterior foot and leg shell that is filled with an injection molded rubberized foam material that conforms to the foot and ankle deformities. The patient steps into the posterior shell with the rubberized lining conforming exactly to the shape of the foot and leg. A padded anterior splint is placed over the front aspect of the foot and leg to close the boot and completely encircle the extremity. The anterior portion of the boot is held securely to the posterior shell with three Velcro® straps. With the uniform contact of the foam lining material, dynamic rotational problems between the foot and leg are controlled. With the elasticity of the lining material and the leeway the Velcro® straps provide in closing the CROW boot, leg swelling from fluid retention can be accommodated. The sole of the CROW boot has a rocker- bottom shape to facilitate walking with its rigid construction.7 Typically it is 3-4 cm thick, so a thick-soled shoe may be needed on the other foot to equalize lower-extremity lengths.
FIGURE 8. Charcot restraint orthotic walker (CROW) boot
Legend: The CROW boot is at the apex of the protective footwear hierarchy. Features include a thick rocker bottom sole, a rigid posterior-plantar shell, an injected molded rubberized foam lining that conforms to the patient's foot/ankle deformity, a padded anterior splint that make with the posterior shell and Velcro® straps.
Indications for a CROW boot: A CROW boot is usually not prescribed until other levels of the footwear hierarchy have been tried and found to be unsuccessful. With the most severe foot and ankle deformities such as those associated with severe deformities from Charcot neuroarthropathy, however, a CROW boot becomes a first line defense to prevent new and recurrent foot wounds and to maximize the patient’s walking ability. Clinical judgment is required to make the decision. If the patient has little or no potential for ambulation, there is little indication to order a CROW boot. In this situation, the ambulation goal would be mobility with a wheelchair. If the deformity is controllable by cast wear and the cast makes it possible for the patient to do limited walking, a CROW boot is indicated. As with the other levels of the protective footwear hierarchy, the CROW boot may require adjustments and replacements with time and use as the foot shape changes and the device wears.
Considerations regarding CROW boots: As desirable as the CROW boot is as a functional device for ambulation in patients with the severest of foot and ankle deformities, it has undesirable features. These include its appearance, weight and contraindication for wear when any but the smallest wounds are present. CROW boots cost $1,500 to $2,000. Even when CROW boots are prescribed with the indications given in the previous paragraph, about one-fourth of the patients do not use them. Reasons, in addition to those mentioned above, include worsening infirmities that negate walking and development of new wounds. When sizable wounds are present and/or new wounds develop, surgical options such as complex foot reconstruction or lower-limb amputation must be considered.
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