Chapter 167

Socrates once said “To him whose feet hurt, everything hurts.” Patients with foot pain and deformities are commonly seen in the Emergency Department complaining of compromised mobility. The frequency of these disorders increases with age. This chapter addresses common presentations and procedures for the management of the painful foot. A number of other podiatric procedures (e.g., local anesthesia, ingrown toenails, plantar warts, puncture wounds, toe fractures) are addressed in other chapters of this book.

### Introduction

The skin on the sole of the foot is the thickest skin on the entire body. It is especially adapted to protect the internal structures from environmental demands. A 150-lb person has dissipated 60 tons of force with each foot after walking a mile.1 Hyperkeratosis (callosity) occurs when the process of keratinization, which maintains the outer layer of epithelium as a horny protective cover, becomes overactive due to shearing forces and pressure points over bony prominences. This is a normal protective response as the body attempts to protect the irritated skin. It may be seen on the hands of a laborer or on the plantar surfaces of feet in those who walk barefoot. Over time, a vicious cycle begins. The hyperkeratotic area becomes a prominence, increases the pressure in a tight shoe, produces further discomfort, and results in further keratinization.

The ubiquitous verruca virus can invade the plantar skin of the foot and produce a wart or a hyperkeratotic response. It is sometimes difficult to differentiate this condition from other hyperkeratoses (calluses or corns). Warts may occur at any site on the plantar skin, unlike a pressure or friction-induced callus or corn. Warts are less likely to occur on the digits and seldom occur on the dorsal skin. The surface appearance of all of these conditions may be identical, yet their treatment strategies are radically different. The wart is treated with epidermal eradication (Chapter 165), whereas other hyperkeratoses are treated with simple paring and rebalancing of the weight-bearing surfaces.

A corn, also known as a helomata or a clavus, represents a well-circumscribed traumatic hyperkeratosis caused by friction or pressure on the skin. It has a visibly translucent core that presses deeply into the dermis. Corns may be so painful as to be disabling.2 A hard corn (heloma durum) forms primarily on the exposed surfaces of the toes from extrinsic pressure of footwear.3–6 It is commonly found on the dorsolateral aspect of the fifth toe or the dorsum of the interphalangeal joints of toes 2 to 5.

Hammertoes occur when the intrinsic muscles of the foot lose their stabilizing effect on the interphalangeal joints, allowing the extrinsic muscles of the leg to overpower and flex the interphalangeal joints. This deformity may be associated with the formation of painful hyperkeratotic lesions. These lesions may be overlying or adjacent to any or all of the interphalangeal joints or on the distal tip of the ...

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