The foot and ankle specialist is expected by patients and fellow healthcare providers to be familiar with bracing biomechanics and the effects of footwear components on the lower extremity. A successful bracing treatment outcome for pathological conditions is the result of an evolution to the final product based on history and physical examination characteristics coupled with feedback from both the patient and treating clinician. An experienced orthotist may see the patient and modify the brace multiple times during the brace manufacturing and fitting process. This chapter discusses fundamentals of orthosis design with updates on recent footwear trends. Knowledge of these topics will help clinicians more effectively communicate with orthotists regarding patient-specific clinical goals and anticipated outcomes.

The footwear industry has been recently characterized by engineering of a more specialized shoe driven by marketing and consumer demand. Foremost, shoes protect the feet from the environment. However, certain modifications may offer protective advantages in specific settings or sometimes may even compromise safety to enhance performance. For example, a steel-toe, stiff-sole shoe may protect a manual laborer, whereas a soft-soled, cushioned shoe can prevent skin ulcers in patients with diabetes. Athletic shoes are now often designed to be sport-specific and sometimes even customizable. A recent survey of adolescent cross-country runners revealed that 73% identified arch-type compatibility with shoe design as the most important factor in choosing a shoe. Seventy-four percent reported not knowing how many miles they had logged in a single pair of running shoes before replacement, even though loss of midsole cushion recoil is know to be a risk factor for overuse injuries.¹ With injury prevention and playing surface type now major topics in professional sports, organizations such as the National Football League have provided financial support for shoe research and development, with an emphasis on performance and protection for athletes. Although further research is needed on shoe design including cleat properties on a variety of playing surfaces, athletic footwear is now considered an integral piece of protective equipment rather than simply an extension of uniform apparel.² Some evidence suggests that artificial surfaces may increase the rate of injury by failing to release the shoe cleat from the surface; the same cleat designs tend to lose friction on natural grass surfaces and sheer more quickly thereby decreasing torque transferred to the lower extremity.³

Running sports have expanded with marketing efforts now increasing the popularity of “barefoot-style” running shoes and the latest trend of “maximalist
cushioned” running shoes (Figure 1). Safety and efficacy of these shoe design concepts are not yet backed by scientific validity. In the case of barefoot-style running, well-designed studies are necessary to prove whether this minimalist running style is beneficial or harmful to overall foot and ankle health. There is some evidence to support the notion that peak ground forces are reduced as a runner changes his gait pattern from a hindfoot strike typical of shod runners to a forefoot and midfoot strike typical of barefoot runners.⁴ When switching from running in cushioned shoes to minimalistic shoes, runners showed increased pressures in the forefoot and therefore may be acutely at risk for stress fractures during the transition phase.⁵ Proponents of minimalist running reference studies that show decreased exertional compartment syndrome and anterior knee pain.⁶ A 2011 study⁷ evaluated barefoot runners, runners in a minimalist shoe, and runners in a cushioned running shoe. Runners could estimate direction and amplitude of terrain more accurately with a minimalist shoe model. No substantial differences were found between runners using the minimalist shoe model and those who ran completely barefoot. The authors claimed that cushioned shoes substantially impair foot position and awareness compared with less-structured shoes or barefoot conditions. Some proponents claim that minimalist running advantages include increased coordination and improved intrinsic muscle foot strength.⁸ Another proposed benefit of minimalist shoe running is increased intrinsic foot muscle strength. When comparing 18 runners transitioning to minimalist shoes with 19 control runners who did not switch, the abductor hallucis muscle cross-sectional area increased by 10.6%, but all other muscles tested did not change. Eight of the minimalist runners developed bone marrow edema while only one control runner developed edema.⁹ A prospective survey followed 107
barefoot runners and 94 shod runners over the course of a 1-year period. Both groups had similar injury rates although different types of injuries depending on the running style.¹⁰ The different patterns or injuries observed may be due to different lower limb muscle activity. Electromyography studies have been used to evaluate the effects of habitual minimalist running on muscle activation. When running barefoot as compared with shod running, during stance phase minimalist runners had greater muscle activity in the gastrocnemius medialis and gluteus maximus and lower activity in the tibialis anterior. During swing phase, minimalist running exhibited increased muscle activity in the vastus lateralis and gastrocnemius medialis.¹¹

Increasing variability of running sports has led to another popular alternative of an extreme running shoe. Running in a thickly cushioned rocker shoe has been termed maximalist running. Multiple maximalist running shoe companies such as Hoka and Altra have entered the global footwear market. Proponents of maximalist running style suggest it may prevent lower extremity injuries particularly in long-distance running by increasing shock absorption in the sole of the shoe. A recent study evaluated energy expenditure between minimalist, maximalist, and standard running shoes. Oxygen consumption with maximalist rocker shoes was found to be 4.5% higher than with standard shoes and 5.6% higher than with minimalist shoes, but this may be due to the larger mass effect of the rocker soles.¹²

A 2011 study¹³ reported that thicker soles evoke a stronger protective eversion response from the peroneal muscles to counter the increasing moment arm at the ankle-subtalar joint complex following sudden foot inversion. The study’s authors suggested that thicker soles are likely to increase risk for lateral ligament injury at the ankle when the protective response of the peroneal tendons is overwhelmed.

The influence of high-fashion footwear on foot and ankle biomechanics and pathoanatomy has long been a subject of concern. A 2013 study¹⁴ found that habitual high-fashion shoe wearers showed decreased range of motion in dorsiflexion and eversion compared with flat-shoe wearers. The study’s authors recommended intensive ankle stretching exercises for habitual high-heeled shoe wearers. In 2013, investigators¹⁵ performed electromyography of different muscle groups in high-heeled shoe wearers and found that high heels adversely affect muscle control and reduce loads in the quadriceps and spine musculature. These authors suggested that the addition of a total-contact insert to a shoe might improve comfort rating and foot stability.

Despite continued evolution and specialization of footwear, many of the basic components that make up a shoe remain the same (Table 1).

Historically, commercial shoes were designed to protect the sole of the foot from the environment with few anatomic or pathologic considerations. Research and development driven by the consumer demand and industry marketing has resulted in a multitude of shoe options. Now patients with subtle anatomic deviations or pathologic foot conditions may be able to achieve pain relief through strategic footwear selection. A mild forefoot malalignment can be accommodated by a wide toe-box shoe to relieve pressure points on the foot. Many running shoe companies market styles with varied degrees of arch support to accommodate runners with either pes planus or pes cavus. These shoes may increase comfort and stability during activity in patients with over or under pronation. Patients with diabetes now have easier access to therapeutic in-depth shoes with soft uppers and cushioned insoles, designed to relieve pressure over bony prominences. In-depth shoes feature an additional 0.25 to 0.375 inches of insole cushioning and can be easily modified by removing the factory inlay and inserting a custom foot orthosis without affecting overall fit.¹⁶

Shoes can be modified to increase ambulation efficiency or compensate for decreased motion secondary to pain, fusion, arthritis, or deformity. They may
also incorporate features to increase stability or offload high-pressure areas.¹⁶ (Table 2). Modifications may delay the need for surgical intervention or provide temporal relief for poor surgical candidates. The upper portion of a shoe can be stretched with a “ball-and-ring stretcher” to soften the material and make room for bony prominences such as a hallux valgus deformity or a hammertoe. The vamp of the shoe may cause increased pain in midfoot arthritis by compressing the sensory nerves over osteophytes and this can sometimes be relieved with simple alterations such as alternate lacing patterns or elastic laces. Modifications to offload bony prominences also may be made to sole of the shoe. A factory insole can be supplemented or removed and replaced with a commercially available insole or a custom insole. A metatarsal bar pad may additionally offload the ball of the foot during gait. Pads and insoles are manufactured in multiple sizes and shapes, which can easily be further modified before shoe insertion.