Chapter 285: Soft Tissue Problems of the Foot

This chapter discusses the common foot disorders that are likely to present to the ED. Patients with chronic or complicated foot problems generally should be referred to a dermatologist, orthopedist, general surgeon, or podiatrist, depending on the disease and local resources. Tinea pedis, foot ulcers, and onychomycosis are discussed in Section 20, "Skin Disorders," in chapter 253, "Skin Disorders: Extremities." Puncture wounds of the foot are discussed in Section 6, "Wound Management," in chapter 46, "Skin Disorders: Extremities.", "Puncture Wounds and Bites." Foot ulcers and osteomyelitis are discussed in Section 17, "Endocrine Disorders," in chapter 224, "Type 2 Diabetes Mellitus."

Calluses are a thickening of the outermost layer of the skin and are a result of repeated pressure or irritation. Corns (clavus) develop similarly, but have a central hyperkeratotic core that is often painful. The causes can be external (poorly fitted shoe) or internal (bunion).

Calluses are protective and should not be treated if they are not painful. Calluses grow outward but may be pushed inward by continued pressure and become corns. Corns also develop in areas of scarring and between toes. Corns are classified as hard or soft. Hard corns are seen over bony protuberances where the skin is dry. Soft corns are seen between toes where the skin is moist. Corns may be painful or painless, but pressure on the corn usually produces pain. Diagnosis is based on clinical appearance. Corns interrupt the normal dermal lines and can thus be differentiated from calluses, which do not interrupt the normal dermal lines. Hard corns may resemble warts. However, when warts are pared, warts contain black seeds, which are thrombosed capillaries and may bleed, while corns do not bleed. Soft corns resemble tinea, and identifying tinea is important for proper treatment (see chapter 253).^1,2

Keratotic lesions may indicate more severe underlying disease, deformity, local foot disorder, or mechanical problem. Differential diagnosis of keratotic lesions includes syphilis, psoriasis, arsenic poisoning, rosacea, lichen planus, basal cell nevus syndrome, and, rarely, malignancies.²

TREATMENT OF CORNS

Treatment of symptomatic corns often necessitates referral to a podiatrist because the treatment may involve repeated paring, use of keratolytic agents, and possibly surgery to correct any underlying source of pressure (bunion).^1,2,3,4 Salicylic acid treatments are more effective than paring with a scapel.⁵ Recurrence can be prevented by weekly gentle trimming with a pumice stone or emery board after soaking in warm water for 20 minutes. Placing a pad on or around the lesion relieves pressure, and avoiding constrictive footwear also provides benefit.

Plantar warts are caused by the human papillomavirus. Plantar warts are most common in children, young adults, and butchers or fishmongers. Infection occurs by skin-to-skin contact, with maceration or sites of trauma. The incubation period is 2 to 6 months. Spontaneous remission may occur in up to two thirds of patients within 2 years.⁶ Recurrence is common. Single lesions are endophytic and hyperkeratotic. A mother-daughter wart is similar to a single lesion except for a small vesicular satellite lesion. Mosaic warts are often painless, closely grouped, and may coalesce. Diagnosis is clinical. The wart will obscure normal skin markings. If in doubt, use a #15 scalpel blade to pare down the lesion to expose thrombosed capillaries, called seeds. The only two effective treatments for warts are salicylic acid and liquid nitrogen (cryotherapy).^7,8 Some salicylic acid preparations are available without a prescription. Duct tape (silver or clear) as an adjunct provides no benefit.⁸ Adequate paring is required for larger lesions.⁷ Plantar warts may require prolonged treatment (several weeks or months) as well as cryotherapy, so refer to a dermatologist or podiatrist for follow-up.⁸ Nonhealing lesions require referral to a specialist because they may represent undiagnosed melanoma.^7,9 Instruct patients to avoid touching warts on themselves or others, to wear slippers in public showers, and to not use paring down tools (pumice stone, file) on normal skin or nails.

Normal nail function requires maintenance of a small space between the nail and the lateral nail folds. Ingrown toenails occur when irritation of the tissue surrounding the nail causes overgrowth, obliterating the space.^10,11,12 Causes include improper nail trimming, using sharp tools to clean the nail gutters, tight footwear, rotated digits, and bony deformities.^10,12 Curvature of the nail plate is another predisposing factor.¹² Symptoms are characterized by inflammation, swelling, or infection of the medial or lateral aspect of the toenail. The great toe is the most commonly affected. In patients with underlying diabetes or arterial insufficiency, cellulitis, ulceration, and necrosis may lead to gangrene if treatment is delayed.

TREATMENT OF INGROWN TOENAILS

If infection or significant granulation is absent at the time of presentation, accepTable treatment is daily elevation of the nail with placement of a wisp of cotton or dental floss between the nail plate and the skin.¹³ Daily foot soaks and avoidance of pressure on the nail help.¹³ Another option, if no infection is present, is to remove a small spicule of the nail (Figure 285-1).¹²

A digital nerve block is placed (see Section 5, "Analgesia, Anesthesia, and Procedural Sedation," and chapter 36, "Local and Regional Anesthesia"). Cleanse the area and prepare the skin for an antiseptic procedure. Trim an oblique portion of the affected nail about one to two thirds of the way back to the posterior nail fold. The nail groove should then be debrided and a nonadherent dressing placed.^10,11

If granulation or infection is present, a larger partial removal of the nail plate is indicated (Figure 285-2). Preprocedure antibiotics are not needed unless the patient is systemically ill.¹⁴ First, perform a digital nerve block and prepare the area for antiseptic technique. Longitudinally, cut the entire affected area, base-to-tip, cutting about one fourth of the nail plate, including the portion of the nail beneath the cuticle. Cutting the nail is made easier by first sliding mosquito forceps or small scissors between the nail and nail bed on the affected side, freeing the nail from the bed below. Rotate the forceps, turning up the portion of the nail on the affected side. A nail splitter is the optimal instrument for cutting the nail; however, sturdy scissors are a reasonable alternative. Then grasp the affected cut portion of the nail with a hemostat and, using a rocking motion, remove it from the nail groove. Then debride the nail groove.¹⁰ Once the procedure is completed, place a nonadherent gauze or antibiotic ointment on the wound and a bulky dressing over that, covering the toe. Check the toe in 24 to 48 hours.^10,12 If phenol is used for chemical matricectomy, massage the involved nail matrix vigorously with a cotton-tipped swab dipped in an aqueous solution of phenol 88%, with a rotation directed toward the lateral nail fold, for 1 minute. Irrigate the nail matrix using isopropyl alcohol to neutralize completely the phenol solution.^15,16 Do not expose normal skin or tissues to the phenol solution. Postprocedure antibiotics are not needed unless cellulitis is proximal to the toe.¹¹

For recurrent ingrown toenails, refer to a podiatrist for permanent nail ablation, which may require a combination of surgical excision plus chemical matricectomy (phenol ablation).^15,16

Other common toenail afflictions include paronychia (see Section 23, "Musculoskeletal Disorders," chapter 283, "Nontraumatic Disorders of the Hand") and subungual hematoma (see Section 6, "Wound Management," chapter 43, "Arm and Hand Lacerations"), which are treated similarly to when they occur in the fingers. Hyperkeratotic toenails can be a problem in the elderly. These may become so severe as to affect gait and cause ulcerations and infections. Refer such patients to podiatry for repeated trimming or nail plate removal.

Calcaneal bursitis causes posterior heel pain that is similar to Achilles tendinopathy^17,18; however, the pain and local tenderness are located at the posterior heel at the Achilles tendon insertion point. In contrast, Achilles tendinopathy causes symptoms 2 to 6 cm superior to the posterior calcaneus. Pathologic bursae can be divided into noninflammatory, inflammatory, suppurative, and calcified. Noninflammatory bursae are usually pressure induced and are found over bony prominences. Inflammatory bursitis is commonly due to gout or rheumatoid arthritis. Suppurative bursitis is due to bacterial invasion of the bursae (primarily staphylococcal species), usually from adjacent wounds. Acute bursitis can lead to the formation of a hygroma or calcified bursae. Diagnosis can be aided by the use of US and MRI¹⁷ but is not indicated for evaluation in the ED. Treatment of the bursitis depends on its cause. For nonseptic bursitis, symptoms usually resolve with simple measures including heel lifts, comforTable footwear, rest, ice, and nonsteroidal anti-inflammatory drugs.¹⁹ Management of septic bursitis is discussed in Section 23, "Musculoskeletal Disorders," in chapter 284, "Joints and Bursae." Diagnosis of these lesions is dependent on analysis of bursal fluid, which can be obtained by large-bore needle aspiration.¹⁷

Plantar fasciitis, inflammation of the plantar aponeurosis, is the most common cause of heel pain.^20,21,22 Peak age incidence is usually between 40 and 60 years old, but it has a younger peak in runners.^23,24 Plantar fasciitis is common among ballet dancers and those performing aerobics. The plantar fascia anchors the plantar skin to the bone and provides support to the foot during gait. The cause is usually overuse. Other causes of heel pain include abnormal joint mechanics, tightness of the Achilles tendon, shoes with poor cushioning, abnormal foot position and anatomy, and obesity.^17,20 In the younger patient, autoimmune and rheumatic diseases can be considered.

The symptom of plantar fasciitis is pain on the plantar surface of the foot that is worse when initiating walking. Examination usually reveals a point of deep tenderness at the anterior medial aspect of the calcaneus, the point of attachment of the plantar fascia. Pain and tenderness tend to be increased upon dorsiflexion of the toes. Diagnosis is clinical. Radiographic studies are not indicated unless other causes are being considered. The presence of heel spurs is of no diagnostic value because many patients without plantar fasciitis have this finding on imaging. For resistant cases, US and MRI may aid in diagnosis but are not indicated for evaluation in the ED.¹⁷

Plantar fasciitis is generally a self-limited disease. Eighty percent of cases resolve spontaneously within 12 months. Initial treatment consists of rest, ice, nonsteroidal anti-inflammatory drugs, heel and arch support shoe inserts, taping or strapping of the foot, and dorsiflexion night splints (molded ankle-foot orthotics that holds the plantar fascia and Achilles tendon stretched). Plantar-specific stretch exercises are the most beneficial treatment in the acute phase: with the ankle dorsiflexed, the patient uses one hand to dorsiflex the toes and with the other hand palpates the plantar surface of the foot, confirming tension.²⁵ Patients should be taught Achilles tendon stretching exercises and be told to avoid the use of flat shoes and barefoot walking.¹⁷ In severe cases, a short-leg walking boot may be useful to unload and rest the plantar fascia. Corticosteroid injections provide short-term benefit, up to 1 month,²⁵ but are associated with plantar fascia rupture,¹⁷ and are best left to the orthopedist.^20,21 Refer patients to a podiatrist, orthopedist, or primary care physician for follow-up care.^20,21

TARSAL TUNNEL SYNDROME

Tarsal tunnel syndrome is an uncommon source of foot pain and numbness in runners due to compression of the posterior tibial nerve as it courses behind the medial malleolus.^26,27 The cause is usually from prior injury (scar tissue, bone or cartilage fragments, or bony spurs) and overpronation during running.^26,27 Overpronation (inward rotation) makes the nerve more vulnerable both to direct trauma from stretch and to indirect trauma from inflammation of the surrounding structures, resulting in compression.^26,27 Other causes include activities requiring restrictive footwear (ski boots, skates), edema from pregnancy, ganglion cysts, and tumors, but frequently, no inciting event is known.²⁸

Symptoms include numbness or burning pain of the sole and may be limited to the heel, mimicking plantar fasciitis. Distal calf pain may be due to retrograde radiation (Valleix phenomenon). Weakness is uncommon. Pain is often worse with running, at night, and after standing, and often leads to the desire to remove the shoes. Tinel sign is positive with percussion inferior to the medial malleolus yielding pain radiating to the medial or lateral plantar surface of the foot. Simultaneous dorsiflexion and eversion of the ankle exacerbates symptoms. Diagnosis is aided by nerve conduction studies or MRI,^26,27 but these are not routinely ordered from the ED.

The differential diagnosis includes plantar fasciitis and, if limited to the heel, Achilles tendinitis. Plantar fasciitis will cause point tenderness over the plantar heel, and pain is worse upon morning standing. Tarsal tunnel syndrome causes greater medial heel and arch pain due to involvement of the abductor hallucis muscle. Tarsal tunnel pain worsens with ambulation throughout the day. In addition, tarsal tunnel syndrome may produce distal calf pain, whereas plantar fasciitis does not.

Initial treatment includes avoidance of the exacerbating activities, nonsteroidal anti-inflammatory drugs, shoe modification, and occasionally orthotics. If there is no improvement or symptoms recur after a few weeks, then orthopedic evaluation is recommended.^26,27

DEEP PERONEAL NERVE ENTRAPMENT

Deep peroneal nerve entrapment occurs most commonly at the location where the nerve courses under the inferior extensor retinaculum²⁹ (Figure 285-3). Recurrent ankle sprains, soft tissue masses, trauma (both acute and repetitive),³⁰ chronic biomechanical misalignment, edema, and tight-fitting footwear (ski boots) are the most common causes. Symptoms are dorsal and medial foot pain and sensory hypoesthesia at the first toe web space. There may be loss of the ability to hyperextend the toes due to wasting of the extensor hallucis brevis and extensor digitorum brevis muscles. Pain and tenderness can be elicited on palpation of the peroneal nerve at the site of entrapment and by plantar flexion with inversion of the foot. Pain is exacerbated by activity and relieved by rest. Nighttime pain is common. Treatment is the same as for tarsal tunnel syndrome.

A ganglion is a common benign synovial cyst. Ganglions are 1.5 to 2.5 cm in diameter and are often attached to a joint capsule or tendon sheath. Although ganglions typically occur in the wrist or hand, they may also occur in the foot. Ganglions typically arise in the anterolateral aspect of the ankle, but can occur in many areas of the foot. The cause is unknown. Ganglions may appear suddenly or gradually, may enlarge and diminish in size, and may be painful or asymptomatic. On examination, a ganglion is a firm, cystic lesion. Diagnosis is usually made clinically, although US or MRI may exclude other causes when serious pathology is suspected. Aspiration and instillation of glucocorticoids by an orthopedist lead to the complete resolution of ganglions in some cases,³¹ with surgical excision required for persistence.^32,33

TENOSYNOVITIS AND TENDINITIS

Tenosynovitis and tendinitis may occur in the foot, usually due to overuse. Patients present with pain over the involved tendon (Figure 285-3). The flexor hallucis longus, posterior tibialis, and Achilles tendon are most commonly involved.³⁴ Treatment consists of rest, ice, and oral nonsteroidal anti-inflammatory drugs.³⁴

Flexor hallucis longus tenosynovitis classically affects ballet dancers, but can also be seen in runners and nonathletes. Presentation is similar to plantar fasciitis and tarsal tunnel syndrome. Posteromedial ankle pain, medial arch pain, and a positive Tinel sign (see earlier description in "Tarsal Tunnel Syndrome") are seen. Conservative management (rest, mobilization, orthotic shoe implant, nonsteroidal anti-inflammatory drugs) is usually successful. Surgery is reserved for refractory cases.

TENDON LACERATIONS

Tendon lacerations can result from penetrating injuries to the dorsal or plantar aspect of the foot. Tendon repairs in the foot are complex, and orthopedic consultation is needed for repair.³⁴

The foot should be casted in dorsiflexion after the repair of extensor tendons and in equinus after repair of flexor tendons.

TENDON RUPTURES

Spontaneous rupture of the Achilles tendon is common. Rupture of the anterior tibialis and posterior tibialis tendons may also occur.³⁴ Age and chronic corticosteroid and fluoroquinolone use are risk factors for spontaneous rupture. Diagnosis is usually clinical but is aided by US or MRI studies in difficult cases.

Achilles tendon rupture occurs when a sudden shear stress, such as sudden pivoting on a foot or rapid acceleration, is applied to an already weakened or degenerative tendon. Many patients report immediate sharp pain, and some hear an audible "pop." The peak age for rupture is 30 to 40 years, and rupture is four to five times more common in men than women.³⁵ Over 80% of ruptures occur during recreational sports ("weekend warrior"). Patients often present with pain, a palpable defect in the area of the tendon, and inability to stand on tiptoes. A minority of patients with complete tendon ruptures are able to ambulate and may be misdiagnosed as having an ankle sprain. Squeezing the calf of the prone patient whose knee is flexed at 90 degrees will normally cause the foot to plantar flex (calf squeeze or Thompson test. The absence of plantar flexion indicates a positive test indicative of rupture. Initial ED treatment consists of ice, analgesics, immobilization of ankle/foot in plantar flexion, crutches, and referral to an orthopedic surgeon. Definitive treatment is generally surgical in younger patients and conservative (casting in equinus or plantar flexion) in older patients.^34,36,37 For further discussion, see chapter 44, "Leg and Foot Lacerations," and Figure 44-1 (Thompson test) in that chapter, in Section 6, "Wound Management."

Ruptures of the anterior tibialis tendon are rare. Ruptures usually occur after the fourth decade and are not excessively painful. Patients present with varying degrees of foot drop and a palpable defect distal to the ankle joint in the area of the tendon. In most cases, disability is minimal, and surgery is not necessary.³⁴

Spontaneous ruptures of the posterior tibialis tendon also occur after the fourth decade. Two thirds of these cases occur in women. The presentation is usually chronic and insidious. Patients notice a gradual flattening of their arch, with modest discomfort and swelling over the medial ankle. Examination reveals absence of the tendon's normal prominence and weakness on inversion of the foot. Patients find it impossible to stand on tiptoes. Treatment may be conservative or surgical, depending on the duration of the tear and activity of the patient.²²

Flexor hallucis longus rupture presents as a loss of plantar flexion of the great toe. The need for surgery will depend on the patient's occupation and lifestyle.³⁴

Disruption of the peroneal retinaculum can occur as a result of direct trauma during dorsiflexion of the foot. Besides pain localized to the peroneal tendon behind the lateral malleolus, the patient complains of a clicking when walking as the tendon subluxes. Peroneal tendon injuries may lead to lateral ankle instability. Treatment is generally surgical repair.³⁴

Neuromas may form in a plantar digital nerve, usually proximal to its bifurcation. Neuromas may occur in any of the digital nerves but are most common in the third interspace. The cause is thought to be local irritation of the nerve due to entrapment, usually from tight-fitting shoes. Women between the ages of 25 and 50 years old are the most commonly affected group. Patients present with pain located in the area of the metatarsal head. The pain is described as burning, cramping, or aching. Pain is worsened by ambulation and resolved by rest and removal of shoes. The pain may radiate to the affected toes, and patients may note numbness in the toes. Pain is usually easily reproduced upon palpation of the area, and at times, a mass is felt. Diagnosis is usually made clinically, but nerve conduction studies, electromyograms, US, and MRI may be helpful at times. Conservative treatment consists of wearing wide shoes with good metatarsal head supports and metatarsal head off-loading inserts.³⁸ Local glucocorticoid injections can sometimes be curative. Surgical removal may be necessary for refractory symptoms.

The foot has up to nine compartments. Compartment syndrome occurs when an elevation of tissue pressure within one of these nonyielding fascial compartments impedes vascular flow. The cause of compartment syndrome is a high-energy injury (crush injury)³⁹ associated with multiple fractures. Compartment syndromes have been reported in association with foot and ankle fractures (especially calcaneal and Lisfranc's fracture/dislocation), burns, contusions, bleeding disorders, postischemic swelling after arterial injury or thrombosis, venous obstruction, snakebites, exercise, and prolonged pressure to the affected area (e.g., cast immobilization, prolonged abnormal positioning).⁴⁰ Diagnosis begins with a high index of clinical suspicion based on the mechanism of injury. Pain out of proportion to injury is one of the early findings. Additional symptoms include pain that is worsened on active or passive movement, paresthesias, and neurovascular deficits. An absent pulse and complete anesthesia are late findings and may be difficult to assess due to underlying swelling. The only reliable objective method to diagnose compartment syndrome is by obtaining compartment pressures using an intracompartmental pressure monitoring system (Stryker STIC Device [Stryker, Kalamazoo, MI] or similar equipment). A difference between diastolic blood pressure and intracompartmental pressure of <30 mm Hg is an indication for fasciotomy.⁴¹ Once the diagnosis is made, fasciotomy should be performed emergently. In the ED, elevate the extremity to the level of the heart pending fasciotomy. The sequelae of compartment syndrome range from transient neurologic compromise to complete myoneural necrosis, fibrosis, and ischemic contractures. The prognosis of compartment syndrome is directly related to the time delay in diagnosis and treatment (see Section 22, "Injuries to Bones and Joints," chapter 278, "Compartment Syndrome").⁴¹

Chronic exertional compartment syndrome is due to overuse.⁴² Symptoms occur with exertion and are relieved by rest. Patients should be instructed to avoid overexertion and be referred for further investigation and treatment.

Malignant melanoma of the foot accounts for up to 15% of all cutaneous melanomas. Melanomas can present as an atypical, pigmented, or nonhealing lesion of the foot, including the nail. These malignancies often imitate more common foot disorders such as fungal infections, foot ulcers, and plantar warts. Because prognosis is directly related to early diagnosis, maintain a high index of suspicion for the diagnosis. Acral lentiginous melanoma is an aggressive malignant tumor that more commonly affects nonwhites. This tumor has a predilection for the plantar surface of the foot. It may present with atypical features leading to a delay in diagnosis and poor outcome. All skin lesions that are either atypical or not healing despite treatment should be referred for biopsy.⁴³

For heel pain, the Journal of Foot and Ankle Surgery published a guideline, "The Diagnosis and Treatment of Heel Pain: A Clinical Practice Guideline–Revision." This can be found online at http://www.acfas.org/Research-and-Publications/Clinical-Consensus-Documents/Clinical-Consensus-Documents/.