Chapter 183. Soft Tissue Problems of the Foot

Calluses represent a dermatologic reaction to focal pressure. Ongoing pressure results in calluses developing into corns. Corns can be differentiated from warts when incised; warts will bleed, corns will not. The differential diagnosis includes syphilis, psoriasis, lichen planus, rosacea, arsenic poisoning, basal cell nevus syndrome, and malignancy. Treatment for corns is paring with a No. 15 blade to include removal of central keratin plug.

Plantar warts are common, contagious, and caused by the human papillomavirus. The diagnosis is clinical and the differential diagnosis includes corns and undiagnosed melanoma. Topical treatment with 15% to 20% salicylic acid is most effective. Nonhealing lesions should be referred to a dermatologist or podiatrist.

Onychocryptosis is characterized by increased inflammation or infection of the lateral or medial aspects of the toenail. This occurs when the nail plate penetrates the nail sulcus and subcutaneous tissue (usually in the great toe). Patients with underlying diabetes, arterial insufficiency, cellulitis, ulceration, or necrosis are at risk for amputation if treatment is delayed. Treatment depends on the type of inflammation. If toenail is uninfected, sufficient results will often be obtained with elevation of the nail with a wisp of cotton between the nail plate and the skin, daily foot soaks, and avoidance of pressure on the area. A second option (requiring digital block) is to remove a spicule of the nail and debride the nail groove. If granulation tissue or infection is present, partial removal of the nail is indicated. If the toenail is infected perform digital block and cut one-fourth or less of the nail with a longitudinal incision (including beneath the cuticle). A nonadherent bulky dressing should be placed, and the wound should be checked in 24 to 48 hours.

Pathologic bursae of the foot are categorized as follows: (1) noninflammatory, (2) inflammatory, (3) suppurative, and (4) calcified. Noninflammatory bursae become painful as a result of direct pressure, whereas inflammatory bursitis results from gout, syphilis, or rheumatoid arthritis. Suppurative bursitis results from spread of pyogenic organisms (often Staphylococcus aureus) from adjacent wounds. Complications include hygroma, calcified bursae, fistula, and ulcer formation. Treatment for severe septic bursitis includes intravenous antibiotics such as nafcillin 500 milligrams qid or oxacillin 500 milligrams qid. For further discussion, see Chapter 180 Acute Disorders of the Joints and Bursae.

The plantar fascia is connective tissue anchoring the plantar skin to the bone protecting the arch of the foot. Plantar fasciitis is the most common cause of heel pain due to overuse. Patients have point tenderness over the anterior–medial calcaneus, that is, worse on arising and after activity. The differential diagnosis includes abnormal joint mechanics, poorly cushioned shoes, Achilles tendon pathology, and rheumatoid disease. Treatment includes rest, ice, and nonsteroidal anti-inflammatory drugs (NSAIDs). Most cases are self-limited. Glucocorticoid injections are not indicated in the ED. Severe cases may require a short-leg walking cast and should be referred to a podiatrist or orthopedist.

Tarsal Tunnel Syndromes

Tarsal tunnel syndrome involves heel and foot pain due to compression of the posterior tibial nerve as it courses inferior to the medial malleolus. Causes include running, restrictive footwear, edema of pregnancy, posttraumatic fibrosis, ganglion cysts, osteophytes, and tumors. Pain is worse at night and located at the medial malleolus, the heel, the sole, and the distal calf.

The differential diagnosis includes plantar fasciitis and Achilles tendonitis. Tinel sign is positive, and eversion and dorsiflexion worsen symptoms. The pain of tarsal tunnel syndrome involves the more medial heel and arch and worsens with activity. Ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) may aid in diagnosis. Treatment includes NSAIDs, rest, and possible orthopedic referral.

Deep Peroneal Nerve Entrapment

Entrapment of the deep peroneal nerve occurs most frequently where it courses beneath the extensor retinaculum. Recurrent ankle sprains, soft tissue masses, and restrictive footwear represent the most common causes. Symptoms include dorsal and medial foot pain as well as sensory hypoesthesia at the first web space.

Pain and tenderness can be elicited by plantar flexion in inversion of the foot. Plantar fasciitis should also be considered. Ultrasound, CT, and MRI may aid in diagnosis. Treatment includes NSAIDs, rest, and possible orthopedic referral.

A ganglion is a benign synovial cyst attached to a joint capsule or tendon sheath near the anterolateral ankle. Typically a firm, nontender, cystic lesion is found on examination. The diagnosis is clinical, but MRI or ultrasound can be used if in doubt. Treatment includes aspiration and injection of glucocorticoids, but most require surgical excision.

Tenosynovitis and Tendinitis: Tenosynovitis or tendonitis are usually due to overuse, and present with pain over the involved tendon. Treatment includes ice, rest, and NSAIDs.

Tendon Lacerations: Tendon lacerations should be explored and repaired if the ends are visible in the wound. Due to the high complication rate, specialty consultation is recommended. After repair, extensor tendons are immobilized in dorsiflexion and flexor tendons in equinus.

Tendon Ruptures: Achilles tendon rupture presents with pain and a palpable defect in the area of the tendon. Patients have an inability to stand on tiptoes, and an absence of plantar flexion with squeezing of the calf (Thompson test). Treatment is generally surgical in younger patients and conservative (casting in equinus) in the elderly. Anterior tibialis tendon rupture results in a palpable defect and mild foot drop. Posterior tibialis tendon rupture is usually chronic and presents with a flattened arch and swelling over the medial ankle. Examination may show weakness on inversion, a palpable defect, and inability to stand on tiptoes. Flexor hallucis longus rupture presents with loss of plantar flexion of the great toe and must be surgically repaired in athletes. Disruption of the peroneal retinaculum occurs after a direct blow during dorsiflexion, and causes localized pain behind the lateral malleolus; there is clicking during walking, as the tendon is subluxed. Treatment is surgical.

Neuromas are thought to occur from entrapment of the plantar digital nerve due to tight-fitting shoes; the third interspace is most commonly affected. Patients often present with burning, cramping, or aching over the affected metatarsal head. Diagnosis is clinical, but ultrasound or MRI may be helpful. Conservative treatment includes wide shoes and glucocorticoid injections. Local glucocorticoid injections may be curative. Surgical neurolysis is occasionally required.

The foot has 9 compartments. Compartment syndromes in the foot are associated with high-energy crush injuries. Other causes include bleeding disorders and postischemic swelling after arterial injury, ankle fractures, burns, and chronic overuse. Patients should be considered at-risk if there is increasingly severe pain exacerbated with active and passive motion, coupled with paresthesias or neurovascular deficits.

At-risk patients must have compartment pressures checked. Any difference of less than 30 mm Hg between the Stryker STIC Device (Stryker, Kalamazoo, MI) and diastolic blood pressure is considered positive. Prompt consideration of emergent fasciotomy.

Plantar fibromatosis (Dupuytren contracture of the plantar fascia) involves small, asymptomatic, palpable, slowly growing, firm masses on the plantar surface of a (nonweightbearing) foot. MRI may be helpful for diagnosis. Toe contractures do not occur. Lesions tend to reabsorb spontaneously, and treatment is conservative.

Melanoma of the foot, which accounts for 15% of all cutaneous melanomas, may present as atypical nonpigmented or pigmented lesions; the nail may be included. Vigilance is key as these lesions often mimic more benign conditions. The differential diagnosis includes fungal infections, plantar warts, and foot ulcers. All atypical or nonhealing lesions should be sent for biopsy.