Chapter 24 Shoes and shoe modifications
With few exceptions, the efficient function of virtually all lower extremity orthotic devices depends heavily on appropriate footwear.15 The efficacy of an assistive device can be greatly enhanced through good footwear selection and/or shoe modifications. If a patient is unable to find a shoe to accommodate his or her ankle–foot orthosis (AFO), the brace is rendered useless. To complicate matters, many people are accustomed to purchasing and wearing ill-fitting shoes. Of note is a study by the AOFAS Women’s Footwear Committee of 356 women, which found that nearly 90% wore improperly fitting shoes.4 This chapter explores shoe anatomy and construction techniques; discusses shoe selection and the importance of proper shoe fit; and explains some of the most common shoe modifications and their corresponding indications for use.
Choosing the proper footwear for use with or as an assistive device requires a basic understanding of shoe anatomy and construction. This section describes the parts of the shoe and lays the groundwork for future discussion. The following shoe components are common to all shoes; specific features individual to special shoes are excluded.
The most important parts of the shoe are illustrated in Figure 24-1. The terms used to describe parts of the upper include (1) toe box—part of the shoe that covers the toes; (2) vamp—part of the upper that covers the instep; (3) counter—section of the shoe anterior to the heel; (4) tongue—piece that covers the dorsum of the foot; and (5) throat—section where the tongue meets the vamp. The two basic types of throat openings are the blucher and the balmoral; one common variation is the modified balmoral (Fig. 24-2).
Figure 24-3 depicts a cross-section of the shoe. It illustrates the different layers of the sole: (1) insole—layer of sole closest to the foot; (2) midsole—layer directly below the insole that adds extra support, stability, and comfort to the shoe (not all shoes have a midsole); (3) outsole—bottommost part of the sole that comes into contact with the ground; (4) foot bed, some shoes have an additional removable foot bed inside the shoe, on top of the insole, for added comfort; and (5) shank—bridge between the heel and the ball area of the shoe; the shank portion of the shoe may be reinforced with a steel shank, a strip of spring steel between the outsole and insole.
The two main components of interest in shoe construction are (1) the technique used to attach the sole to the upper, which can be accomplished in a number of ways depending on the type of shoe and its intended use; and (2) the shoe materials used in the construction of both the upper and the sole.12
The manner in which a sole is attached to the upper defines some of its functional properties and its appearance and can affect the fit of the shoe. Six major types of sole attachment techniques are considered (Fig. 24-4).
The Goodyear welt takes its name from the Goodyear sole-stitching machine that was invented in the late 1880s.17 This technique is distinguished by its prominent use of a welt. A welt is a narrow strip of flat leather that is chain stitched to both the upper and the insole. The outsole then is lock stitched to the welt. Use of this technique yields a strong and structurally sturdy shoe. In order to provide a flat tread surface, the space between the insole and outsole is filled with ground cork or some other lightweight material. Shoes constructed with a Goodyear welt tend be less flexible and not as lightweight as other types. The Goodyear welted shoe lends itself to the attachment of a metal bracing system better than any other type of shoe.
The Littleway and McKay are two different attachment techniques wherein the upper is fastened to the sole via staples and the outsole then is attached with either lock stitches (Littleway) or chain stitches (McKay).17 This construction leads to the formation of a very flexible shoe, such as a moccasin or deck shoe.
In the stitchdown process, the upper is flanged outward and then stitched directly to the outsole. This is a simple construction technique and is quite cost effective. The stitchdown may or may not utilize a welt or midsole.
With the cement method, the upper is attached to the insole using a strong glue or cement. In a manner similar to that used in the Goodyear welt construction, the space between the insole and the outsole if filled with material. These types of shoes are lightweight and flexible. Many athletic shoes use this type of sole attachment.
Sliplasting is a technique whereby the upper is sewn to an insole made of a similar material. The outsole then is attached through a cementing process. Sliplasted shoes can be quite flexible and provide maximum shock absorption. Many athletic shoes, such as running shoes and court shoes, are constructed using sliplasting.
With injection molding, shoes are manufactured using a heat-sealing process. The outsole is made from a thermoplastic, which liquefies when heated. Using a special machine, the hot liquid plastic is injected into a form and heat sealed to the upper, rapidly hardening and forming an outsole. These types of shoes are fairly inexpensive to make, but they typically are not available in a wide range of sizes and widths and are not easy to modify or attach braces to. For injection-molded and unit bottom cemented soles, most manufacturers do not use a separate bottom for each last width. Typically, two or three different widths of uppers are used per unit bottom width.
Dozens of base materials and literally hundreds of variations of those base materials are used in the manufacture of shoes. In this section, discussion is limited to general categories of materials found in shoes used in conjunction with orthoses and with or as assistive devices.
Upper materials are important because they affect the way the shoe fits, feels, and performs as well as the longevity of the shoe. Cowhide, or leather, is one of the most commonly used materials. Leather probably is the most durable upper material. It is easily stretched or modified.
Some shoe uppers are formed with a lining that is heat moldable. These types of uppers can be molded to an individual foot. They are an especially useful alternative to custom shoes in patients with severe forefoot deformities who otherwise would not need custom shoes.
Shoe uppers are also frequently made of man-made materials such as fabric, nylon, canvas, and plastic. Uppers made of man-made materials sometimes are more durable than uppers made of leather or deerskin but generally are difficult to stretch or modify. A recent development in shoe upper technology is the use of elastic materials (e.g., neoprene) that will easily stretch around deformities.
Materials used in the construction of shoe soles vary greatly and have significantly different properties with regard to weight, durability, shock absorption and attenuation, flexibility, and support. The following is an examination of a handful of the most commonly used soling materials.
Leather at one time was the soling material of choice. Nowadays, it is reserved primarily for high-end men’s and women’s dress shoes. Leather soles are extremely durable. They tend to be stiff and heavy and offer little or no shock absorption. They can be slippery in wet conditions. Leather soles do allow for relatively simple attachment of AFOs.
Hard rubber is a great alternative to leather, especially when attaching an AFO, because it does not become slippery when wet. When used on welted shoe, a hard rubber outsole presents no real obstacle to attaching an AFO.
Crepe is a rubber compound that contains additives that give it a cellular structure. Crepe-soled shoes typically offer a great combination of shock absorption and traction. A shoe with a crepe sole still can have an AFO attached to it, although it is not as easy as with a leather- or rubber-soled shoe. Crepe outsoles are lightweight and lend themselves well to being modified. Crepe is the most commonly used material in after-market shoe modifications.
Vibram is a dense microcellular rubber. It has many of the good qualities of crepe but is more durable and can be even lighter and more shock absorbing than crepe. Vibram is used in work boots, hiking boots, walking shoes, and even stylish dress shoes.
Ethylene vinyl acetate (EVA) is used in the manufacture of almost every type of shoe today. This popular material is a blend of ethylene and acetate. It is shock absorbing, moldable, lightweight, and flexible. It is seen in the manufacture of foot beds, insoles, midsoles, and outsoles.
The most important adage in shoe fitting is “Fit the shoe to the foot, not the foot to the shoe.”3,8,10,13,18 Both the shape of the sole and the shape of the upper must be considered. Some shoes have pointed toe boxes; others have rounded, or oblique, toe boxes. Some shoes are wide in the shank area whereas others are very narrow. Shoes that are considered to be in-depth shoes have extra room throughout the shoe, an extra deep toe box, and one or more removable foot beds. There are nearly as many variations of shoe shapes as there are foot shapes.
The shape of a shoe is determined entirely by the last upon which it is made. Each differently shaped last produces a differently shaped shoe. The last is a solid, three-dimensional plastic or wooden model. If a shoe is made to be available in multiple true widths, then the manufacturer must use a different last for each size and width combination. The exorbitant cost of manufacturing the large number of lasts necessary to make shoes in multiple widths is a primary deterrent to many popular shoe companies producing shoes that are available in different widths. A last is measured at as many as 10 points, including the heel-to-toe measurement, heel-to-ball measurement, and circumferential measurements at the ball, waist, instep, and heel.17 Each time one of these measurements increases, the other measurements increase proportionally to create larger lasts. Different style shoes made on different lasts, even shoes made by the same company, fit differently.17
As variable as last shape is from manufacturer to manufacturer, shoe sizing is just as confusing. There is little or no regulation of sizing in the footwear industry.5,17 The most widely used scale in U.S. shoe manufacturing is the “common” scale, but what value the manufacturers choose as their baseline size is up to the individual manufacturer. To compound matters, the system itself makes little sense and could be considered archaic.
The shoe sizing system currently used by the majority of U.S. shoe manufacturers today is an evolution of a system developed in England in the mid-1300s AD by King Edward II. King Edward declared that three barleycorns, plucked from the center of the ear and laid end to end, would equal 1 inch. He decreed that 39 barleycorns would be equal to the size of the largest man’s foot, or 13 inches, thereby a size 13. Going backward from size 13, each size would equal one barleycorn, or approximately ⅓ inch. A child’s size 0 was equal to the width of a man’s knuckles, or 13 barleycorns (Edward decided that when an infant’s foot was equal to the width of a man’s knuckles, the time was appropriate for the infant to begin wearing shoes). After going up 13 sizes (or barleycorns) the sizes start over. Therefore, a baby’s foot (13 barleycorns) plus all 13 sizes of children’s shoes (13 more barleycorns) plus 13 sizes of men’s shoes (another 13 barleycorns) equals the length of 39 barleycorns, or a men’s size 13.7,17
Until the Civil War, mass-produced shoes were not available in “lefts” and “rights”; they were straight lasted shoes that could be worn on either foot.7 Twenty years later, Edwin Simpson of New York introduced a variation on the scale that, for the first time, included widths and half-sizes.19
Depending on the manufacturer, as the width of the shoe increases by one width (e.g., from an A to a B), the total interior girth (or the girth of the last) at the ball of the foot increases by to ¼ inch.
Many other sizing system are in use around the world. In most of Europe (except for the United Kingdom), shoes are sized according to the Continental, or Euro, scale. The Euro scale evolved from a French scale called Paris points. One Paris point equals ⅔ cm. The system begins at 0 cm and increases. There are no half sizes. The Euro scale is a unisex metric system whereby each shoe size is ⅔ cm, less than an American full size but more than an American half-size. To review, a US men’s size 9 equals a US women’s size 10½ equals a Euro size 43.17
The three primary considerations for shoe selection are (1) shoe shape and fit; (2) purpose, duration, and level of activity for which the shoe will be used; and (3) ease with which the shoe can be modified. Secondary considerations are upper material selection based on patient’s level of protective sensation; cost and insurance coverage or lack thereof; and lifestyle considerations such as fashion consciousness or workplace dress codes.
The first objective when choosing a shoe is proper fit. This can be a challenge if the patient is using foot orthoses or a molded AFO that is to be worn inside the shoe. These extra devices may consume a lot of space inside the shoe and must be considered. If a bulky device is being used unilaterally, the shoes may need to be mismated. Regardless, the shape of the shoe must be appropriate for the shape of the patient’s foot. If no off-the-shelf shoe fits the patient’s foot as is, the shoe may need to be modified to fit. If the shoe cannot be modified enough to fit, use of a custom shoe may be necessary.
Once shoes that do not match the foot shape have been ruled out, the next criterion to consider is the purpose or function the shoes will be asked to serve or perform. If the patient is fully ambulatory, then the shoe should be able to provide adequate support and control and have an outsole that will be durable. If the patient is essentially nonambulatory and footwear will be used only to protect the feet and aid in transferring, then a lightweight flexible shoe may be appropriate. If the patient will need to use some additional device, the shoe needs to have enough room to accommodate the device. This typically means a shoe with a deep toe box, high counter, blucher opening, and removable foot bed.
For athletic patients, activity-specific shoes are a necessity. One pair of sports shoes will not be appropriate for every activity. For example, running shoes are designed for forward motion. They have rocker soles and ample padding in the forefoot and hindfoot and often are designed to control excessive pronation. Therefore, running shoes are completely inappropriate for playing tennis, which requires lateral stability and a wide flat base of support. Similarly, it would be uncomfortable, if not outright detrimental, for a patient to attempt jogging in a basketball shoe that is flat on the bottom and lacks sufficient shock absorption under the heel and ball of the foot.
The modifiability of a shoe is an important consideration when discussing orthotic devices. With the constant development of new and better adhesives and techniques, there is nary a shoe that cannot be modified. It is merely a matter of the degree of difficulty with which a shoe can be modified and the practitioner’s level of ambition. However, there are some shoes to which attachment of a metal AFO is not possible or is extremely difficult. If the prescription and/or the goal of the treatment plan will require shoe modifications, then the sole material and method of construction must be given serious contemplation, as well as the overall quality of the shoe. Shoes that are designated for attachment to braces must be durable; simply put, they must be worth the effort and cost of attaching the brace to them.
It is generally accepted that there are seven basic types of shoes; the rest are considered variations of these basic styles.17 The seven basic shoe types are as follows: (1) boot—any footwear that extends proximal to the ankle; (2) clog—thick, wooden-soled, backless, slip-on shoe; (3) oxford—low-cut shoe fastened with laces; (4) moccasin—oldest form of shoe, low-vamp loafer, originally made entirely of one piece of leather; (5) mule—backless shoe or slipper with low or no heel; (6) sandal—shoe with an upper consisting of an arrangement of straps; and (7) pump—thin-soled, slip-on shoe with varying heel heights.
For orthotics and prosthetics, the two shoe types most frequently used are the boot and the oxford. Shoes that have emerged from the oxford family tree include today’s modern walking, running, athletic and lace-up comfort, dress, and in-depth shoes.