Corns and Calluses

Corns (clavi) are localised, conical thickenings of the stratum corneum with a central core, painful on pressure, and calluses are broader, diffuse thickened plaques, from repeated friction or pressure. They develop on the feet and sometimes the hands.

• Causes: ill fitting footwear, bony deformity (hammer toe, bunion, claw toe, pes cavus), loss of fat pad, abnormal gait, high heels, barefoot walking, manual work.
• High risk groups: diabetes with neuropathy, rheumatoid arthritis, peripheral vascular disease, older adults.

Hard corn: small, well demarcated, over bony prominences of the toes; soft corn: whitish macerated between toes (fourth web space); callus: yellow plaque on the ball of the foot and heel.

• Pain with pressure; no black dots; skin lines are preserved.
• Differential diagnosis: plantar wart, foreign body, porokeratosis, verruca, melanoma (acral), squamous cell carcinoma, hyperkeratotic eczema, keratoderma.
• Complications: ulceration beneath a callus, haemorrhage into callus, infection, osteomyelitis in diabetes, gait disturbance, falls.

Clinical; paring shows a translucent central core without capillary dots.

• Foot examination: sensation (10 g monofilament), pulses, deformity, footwear, gait.
• Plain radiograph for bony prominence or suspected osteomyelitis.
• Glucose and ankle brachial index in at risk patients.

Offload the pressure and remove the keratin.

• Supportive: well fitting wide toe box footwear, cushioning (silicone toe sleeves, felt padding), soak and pumice gently, daily moisturiser, treat the biomechanical cause, daily foot inspection in diabetes.
• Pharmacological: urea 10 to 25 percent cream twice daily; salicylic acid 40 percent plaster for 48 to 72 hours or 10 to 20 percent paint daily (avoid in diabetes, neuropathy and vascular disease); antibiotic therapy for infection with flucloxacillin 500 mg four times daily for 7 days (or amoxicillin clavulanate 625 mg three times daily for diabetic foot infection).
• Procedures: paring of keratin with a scalpel by a podiatrist or trained clinician, custom orthoses, correction of toe deformity or bony prominence surgically for recurrent or painful disease.
• Special groups: diabetes, neuropathy or ischaemia, never use corn plasters, acids or blades at home and refer to podiatry; pregnancy, topical urea and footwear changes; children, look for orthopaedic cause; rheumatoid arthritis, specialist footwear.
• Red flags: ulceration, bleeding under callus, signs of infection, erythema extending beyond the lesion, loss of sensation, absent pulses.
• Follow-up: review at 4 to 6 weeks; regular podiatry every 3 to 6 months in high risk feet.