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COMMON FOOT PROBLEMS

Callouses and Bunions, Corns, and other Hyperkeratotic Lesions

Lesions made of focally thickened keratotic tissue may be caused by abnormal pressure or shearing forces. The body responds by trying to protect itself through the formation of hyperkeratosis, which causes increased pressure and pain when thickened or nucleated enough. Common areas in which this occurs are over bony prominences such as the medical aspect of the head of the first metatarsal (bunion) and the lateral aspect of the fifth metatarsal head (tailor's bunion), over contracted digits (corns), or under prominent, lesser metatarsal head plantarly (Callouses) bunion, corns. If there is a contracture of bony prominence that causes increased pressure between the toes, a nucleated hyperkeratotic lesion develops.

Evaluation of these lesions should include an assessment of the size, depth, color, and relationship to bony prominences or weight-bearing areas. It is common to encounter a deep nucleation over areas that receive a large amount.

It is important to differentiate between mechanically induced hyperkeratoses and lesions caused by other conditions such as viral infections (plantar warts) or blocked sweat glands (porokeratoses). These other lesions may not present on areas of weight bearing or pressure. Plantar warts caused by the human papilloma virus.

Treatment of the mechanically induced hyperkeratotic lesions includes sharp debridement of the thickened tissue to relieve pain and alleviate the overlying pressure. Changes in footwear, accommodative padding, or footor thoses may be effective ways to decrease the rate of reformation of the lesion and, at times, may allow the lesion.

Treatment of verruca plantaris usually involves the debridement of hyperkeratotic tissue and the use of topical salicylic acid preparations that lyse the tissue until it becomes macerated enough to debride to the base of the wart, which extends no deeper than the dermis. These agents are available without a prescription, are priced reasonably.

Bleomycin also has been used as an injectable agent that is deposited in multiple areas of the wart in an attempt to cause an inflammatory reaction and eventual resolution, but this treatment may be painful.

Finally, sublesional injection of local anesthetic with epinephrine and blunt curettage of the lesion can be effective. Any initially successful treatment for verruca plantaris,however, carries a risk of recurrence up to 30%, so it is helpful to inform the patients of this before initiation of therapy. In immunocompromised patients, rapid recurrence or formation of new lesions makes it difficult to eradicate this infection completely, so topical salicylic acid combined with periodic debridement affords relief of pressure.

Dermatoses

The skin of the feet is especially susceptible to fungal infection (tineapedis) because it usually is encased in a shoe that provides a dark, warm, moist environment for most of the day. Therefore, those patients who have a tendency for hyperhydrosis are at increase risk for these infections. There apparently is familial predilection for this condition.

TOENAIL ABNORMALITIES

Pain in the toenail area can be caused by thickening of the nail plate or incurvation of the nail border. A thick nail plate can cause pressure on the nail bed, especially when wearing shoes, which causes pain and sometimes ulceration of the nail bed. An incurvated nail border causes pressure on the skin adjacent to the are (the ungualabia) and may erode into the tissue, causing a local inflammation or infection commonly known as paronychia.

Thickening of the nail plate most commonly is caused by a fungal infection (onyuchomycosis) or traumatic injury to the nail matrix. Less commonly the nail matrix is damaged by chronic dermatoses such as psoriasis or eczema.

VASCULAR ABNORMALITIES

Vascular problems of the lower extremity fall into three categories: (1) arterial, (2) venous, and (3) lymphatic. Abnormalities of these systems may cause ulcerations but by different mechanisms.

Arterial disease can have devastating consequences on the lower extremity and can cause severe debilitating pain, ulceration, and loss of limb. The most common cause of this in the foot and leg is diabetes, which is discussedlater in this article. Other causes include hypercholesterolemia, arteriosclerosis obliterans (Buerger's disease), and vasospasm caused by Raynaud's disease or Raynaud's phenomenon secondary to collagen vasculardiseases such as systemic lupus erythematosus.

The occlusive disease cause ulceration by decreasing blood flow enough to allow even minor areas of pressure, shearing force, or skin irritation to break down. Usually preceding this are symptoms of intermittent claudicationor rest pain. Therefore, if these symptoms can be recognized and if the physical examination is consistent with ischemia, a prompt referral to an aggressive vascular surgeon could possibly decease the patient's pain.

NEUROLOGIC PROBLEMS

Metabolic, radicular, and locally compressive neuropathies commonly manifest in the foot and ankle area and can cause considerable pain and dysfunction. Taking a careful history and a concise neurologic screening examination of thelower extremity can be helpful in differentiating between these problems.

Local compression neuropathies are common in the foot because most of the sensory nerves lie directly under the skin, there is little fat to protect the nerves, there are many bony protuberances, and the foot commonly isenclosed in a somewhat rigid shoe for most the day. Areas commonly affected are the medial dorsal cutaneous nerve as it courses over the first metatarsal cuneiform joint and the first dorsal digital proper nerve to the medial aspect of the hallux as it courses over the first metatarsal head.

MUSCULOSKELETAL PROBLEMS

Any musculoskeletal deformity of the foot can cause pain with ambulation or footwear. Some deformities are present from birth, but the majority are secondary to biomechanic abnormalities and are acquired as adults. Patients typically state that the deformity has been present only as long as the pain has, but usually acquired deformities.

Digital Deformities

Digital deformities usually are caused by an imbalance of the muscles that govern their function. This imbalance is usually secondary to abnormal function of the foot in fair, inflammatory arthritis can be classified as reducible, semireducible, or rigid and can involve the metatarsophalangeal joint, the proximal interphalangeal joint.

If the toe is dorsiflexed at the metatarsophalangeal joint and plantar flexed at the proximal interphalangeal joint, it is termed a hammertoe.Plantar flexion at only the distal interphalangeal joint is called a mallet toe,and deformity at all three joints consisting of dorsiflextion at the metatarsophalangeal joint and plantar flexion at the proximal and distal interphalangeal joints.

Treatment of the hammertoe depends on the flexibility of the deformity. A flexible hammertoe can be treated conservatively with a dynamic digital sling that planter flexes the digit at the metatarsophalangeal joint in stance and gait. This does not correct the deformity permanently but decreases the pressure.

Claw toe deformity frequently causes painful callosities at the dorsal aspect of the proximal interphalangeal joint and the distal aspect of the end of the digit. The padding techniques mentioned may be used, or another the of padding that planter flexes the digit at the metatarsophalangeal joint while dorsiflexing at the proximal and distal interphalangeal joints may be effective, again if the deformity is flexible.

Deformity of the hallux frequently involves contracture at the interphalangeal joint, commonly known as hallux malleus. This commonly is associated with a high-arched or cavus-type foot, and patients have pain caused by rubbing of the shoe over the prominent interphalangeal joint. Dynamic splinting rarely is effective in this instance.

Metatarsal Deformities

Pressure areas and callosities frequently occur plantar to the lesser metatarsal heads that are adjacent to digital deformities. The dorsal contracture at the metatarsophalangeal joint causes retrograde pressure.

Metatarsal-Cuneiform Exostosis

This relatively common exostosis cause a bony bump dorsally on the midfoot area. Symptoms can be caused by shoe pressure and entrapment of the medial dorsal cutaneous never as it passes over the exostosis. This commonly is associated with the cavus foot type or the foot that exhibits a large amount of plantar flexion at the metatarsal-cuneiform joint. Weight bearing and gait cause retrograde "jamming" at the metatasal-cuneiform joint.

The Acquired Cavus Foot

If a patient presents with a high-arched foot, it is important to interview him or her carefully to ascertain whether this is the foot type the patient was born with or the foot has been deforming gradually over months.

If the latter is true, a thorough neurologic and musculoskeletal examination is required to look for signs of neurologic deficit or muscular weakness. Common conditions that can cause this deformity are cerebrovascular accidents, Charcot-Marie-Tooth disease, Friedreich's ataxia, and Duchenne's muscular dystrophy.

The Pronated Foot (Flatfoot)

An abnormally pronated foot can exhibit multiple symptoms, including digital deformities, hallux valgus, plantar facilities, and posterior tibial tendinitis. When evaluating a symptomatic flatfoot, it is important again to interview the patient to see if this is a recently acquired deformity. If so, evaluation of the function of the posterior tibial tendon.