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Corns and Calluses
Neil J. Feldman, DPM, FACFAS
image BASICS
DESCRIPTION
  • A callus (tyloma) is a diffuse area of hyperkeratosis, usually without a distinct border.
    • Typically, the result of exposure to repetitive forces, including friction and mechanical pressure; tend to occur on the palms of hands and soles of feet (1).
  • A corn (heloma) is a circumscribed hyperkeratotic lesion with a central conical core of keratin that causes pain and inflammation. The conical core in a corn is a thickening of the stratum corneum.
  • Hard corn or heloma durum (more common): more often on toe surfaces, especially 5th toe (proximal interphalangeal [PIP]) joint
  • Soft corn (heloma molle): commonly in the interdigital space (1)
  • Digital corns are also known as clavi.
  • Intractable plantar keratosis is usually located under a metatarsal head (1st and 5th most common), is typically more difficult to resolve, and often is resistant to usual conservative treatments.
EPIDEMIOLOGY
Corns and calluses have the largest prevalence of all foot disorders.
Incidence
Incidence of corns and calluses increases with age. Less common in pediatric patients. Women affected more often than men. Blacks report corns and calluses 30% more often than whites.
Prevalence
  • 9.2 million Americans
  • ˜38/1,000 people affected
ETIOLOGY AND PATHOPHYSIOLOGY
Increased activity of keratinocytes in superficial layer of skin leading to hyperkeratosis. This is a normal response to excess friction, pressure, or stress.
  • Calluses typically arise from repetitive friction, motion, or pressure to skin.
  • Soft corns arise from increased moisture from perspiration leading to skin maceration, along with mechanical irritation, especially between toes.
  • Hard corns are an extreme form of callus with a keratin-based core. Often found on the digital surfaces and commonly linked to bony protrusions, causing skin to rub against shoe surfaces.
Genetics
No true genetic basis was identified because most corns and calluses are due to mechanical stressors on the foot/hands.
RISK FACTORS
  • Extrinsic factors producing pressure, friction, and local stress
    • Ill-fitting shoes
    • Not using socks, gloves
    • Manual labor
    • Walking barefoot
    • Activities that increase stress applied to skin of hands or feet (running, walking, sports)
  • Intrinsic factors
    • Bony prominences: bunions, hammertoes
  • Enlarged bursa or abnormal foot function/structure: hammertoe, claw toe, or mallet toe deformity
GENERAL PREVENTION
External irritation is by far the most common cause of calluses and corns. General measures to reduce friction on the skin are recommended to reduce incidence of callus formation. Examples include wearing shoes that fit well and using socks and gloves.
Geriatric Considerations
In elderly patients, especially those with neurologic or vascular compromise, skin breakdown from calluses/corns may lead to increased risk of infection/ulceration. 30% of foot ulcers in the elderly arise from eroded hyperkeratosis. Regular foot exams are emphasized for these patients as well as diabetic patients (2).
COMMONLY ASSOCIATED CONDITIONS
  • Foot ulcers, especially in diabetic patients or patients with neuropathy or vascular compromise
  • Infection: look for warning signs of:
    • Increasing size or redness
    • Puslike drainage
    • Increased pain/swelling
    • Fever
    • Change in color of fingers or toes
  • Signs of gangrene
image DIAGNOSIS
  • Most commonly a clinical diagnosis based on visualization of the lesion
  • Examination of footwear may also provide clues.
PHYSICAL EXAM
  • Calluses
    • Thickening of skin without distinct borders
    • Often on feet, hands; especially over palms of hands, soles of feet
    • Colors from white to gray-yellow, brown, red
    • May be painless or tender
    • May throb or burn
  • Corns
    • Hard corns: commonly on dorsum of toes or dorsum of 5th PIP joint
      • Varied texture: dry, waxy, and transparent to a hornlike mass
      • Distinct borders
      • More common on feet
      • Often painful
    • Soft corns
      • Often between toes, especially between 4th and 5th digits at the base of the webspace
      • Often yellowed, macerated appearance
      • Often extremely painful
P.233

DIFFERENTIAL DIAGNOSIS
  • Plantar warts (typically a loss of skin lines within the wart), which are viral in nature
  • Porokeratoses (blocked sweat gland)
  • Underlying ulceration of skin, with or without infection (rule out especially with diabetic patients)
DIAGNOSTIC TESTS & INTERPRETATION
Initial Tests (lab, imaging)
  • Radiographs may be warranted if no external cause is found. Look for abnormalities in foot structure, bone spurs.
  • Use of metallic radiographic marker and weight-bearing films often highlight the relationship between the callus and bony prominence.
Diagnostic Procedures/Other
Biopsy with microscopic evaluation in rare cases
Test Interpretation
Abnormal accumulation of keratin in epidermis, stratum corneum
image TREATMENT
GENERAL MEASURES
  • Débridement of affected tissue and use of protective padding
  • Low-heeled shoes; soft upper with deep and wide toebox
  • Extra-width shoes for 5th-toe corns
  • Avoidance of activities that contribute to painful lesions
  • Prefabricated or custom orthotics
MEDICATION
  • Most therapy for corns and calluses can be done as self-care in the home (1).
  • Use bandages, soft foam padding, or silicone sleeve over the affected area to decrease friction on the skin and promote healing with digital clavi.
  • Use socks or gloves regularly.
  • Use lotion/moisturizers for dry calluses and corns.
  • Keratolytic agents, such as urea or ammonium lactate, can be applied safely.
  • Use sandpaper discs or pumice stones over hard, thickened areas of skin.
Geriatric Considerations
Use of salicylic acid corn plasters can cause skin breakdown and ulceration in patients with thin, atrophic skin; diabetes; and those with vascular compromise. The skin surrounding the callus will often turn white and can become quite painful. Aggressive use of pumice stones can also lead to skin breakdown, especially surrounding the callus.
ISSUES FOR REFERRAL
  • May benefit from referral to podiatrist if use of topical agents and shoe changes are ineffective
  • Abnormalities in foot structure may require surgical treatment.
  • Diabetic, vascular, and neuropathic patients may benefit from referral to podiatrist for regular foot exams to prevent infection or ulceration.
SURGERY/OTHER PROCEDURES
  • Surgical treatment to areas of protruding bone where corns and calluses form
  • Rebalancing of foot pressure through functional foot orthotics
  • Shaving or cutting off hardened area of skin using a chisel or 15-blade scalpel. For corns, remove keratin core and place pad over area during healing.
COMPLEMENTARY & ALTERNATIVE MEDICINE
  • Many over-the-counter topical creams, ointments, and lotions are available for calluses (Kera brand, CalleX, Urea, Lac-Hydrin). Do not use on broken skin.
  • Warm water/Epsom salt soaks.
INPATIENT CONSIDERATIONS
Admission Criteria/Initial Stabilization
  • Admission usually not necessary, unless progression to ulcerated lesion with signs of severe infection, gangrene
  • May require aggressive débridement in operating room should an abscess or deep space infection be suspected. Deep-space infections can develop where an abscess can penetrate into tendon sheaths and/or deep compartments within the foot or hand, potentially leading to rapid sepsis. Vascular status must be assessed and vascular referral considered.
Nursing
Wound care, dressing changes for infected lesions
image ONGOING CARE
PATIENT EDUCATION
  • General information: http://www.mayoclinic.org/diseases-conditions/corns-and-calluses/basics/definition/con-20014462
  • American Podiatric Medical Association: http://www.apma.org
PROGNOSIS
Complete cure is possible once factors causing pressure or injury are eliminated.
REFERENCES
1. Freeman DB. Corns and calluses resulting from mechanical hyperkeratosis. Am Fam Physician. 2002;65(11):2277-2280.
2. Pinzur MS, Slovenkai MP, Trepman E, et al. Guidelines for diabetic foot care: recommendations endorsed by the Diabetes Committee of the American Orthopaedic Foot and Ankle Society. Foot Ankle Int. 2005;26(1):113-119.
Additional Reading
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Theodosat A. Skin diseases of the lower extremities in the elderly. Dermatol Clin. 2004;22(1):13-21.
Codes
&NA;
ICD10
L84 Corns and callosities
Clinical Pearls
&NA;
Most therapy for corns and calluses can be done as self-care in the home using padding over the affected area to decrease friction or pressure. However, if simple home care is not helpful, then removal of the lesions is often immediately curative.