Corns (Clavus) 

Updated: Jan 10, 2019
Author: Nanette B Silverberg, MD; Chief Editor: Dirk M Elston, MD 

Overview

Background

A corn (also termed clavus) is a thickening of the skin due to intermittent pressure and frictional forces. These forces result in hyperkeratosis, clinically and histologically. The extensive thickening of the skin in a corn may result in chronic pain, particularly in the forefoot; in certain situations, this thickening may result in ulcer formation. The word clavus has many synonyms and innumerable vernacular terms, some of which are listed in the Table below; these terms describe the related activities that have induced clavus formation.

Synonyms for clavus include callosity, a hyperkeratotic response to trauma; corn, heloma, or a circumscribed hyperkeratotic lesion that may be hard (ie, heloma durum) or soft (ie, heloma molle); and callous, callus, or a diffusely hyperkeratotic lesion. Localized callosities of the soles, which do not resolve, are termed plantar callus, heloma, tyloma, keratoma, or plantar corn. When callosities occur over one or more lateral metatarsals, they are termed intractable plantar keratoses.[1]

Corns are often seen in athletes and in patient populations exposed to uneven friction from footwear or gait abnormalities, including elderly persons, diabetic patients, and amputees.[2] Abnormal foot mechanics, foot deformities, high activity level, and more serious conditions such as peripheral neuropathy also contribute to the formation of corns.[3] Corns are associated with considerable morbidity secondary to pain; fortunately, many treatment and preventative options are available that provide a high rate of mitigation.[4]

Clinically, all these lesions look like hyperkeratotic or thickened skin. Maceration and secondary fungal or bacterial infections are a common overlying feature in heloma molle and diabetes. Plantar helomas tend to have a central keratin plug, which, when pared, reveals a clear, firm, central core. The most common sites for clavus formation are the feet, specifically the dorsolateral aspect of the fifth toe for heloma durum, in the fourth interdigital web of the foot for heloma molle, and under the metatarsal heads for calluses. Clinically, three types of corns have been described. The first is a hard corn, or heloma durum, notable for its dry, horny appearance. It is found most commonly over the interphalangeal joints. The second is a soft corn, or heloma molle, described as such because of its macerated texture secondary to moisture. It is generally found in interdigital locations.[5, 6] The third type is a periungual corn, and this type occurs near or on the edge of a nail.[7] Note the image below.

Hard corn over the proximal interphalangeal joint Hard corn over the proximal interphalangeal joint of second toe. Courtesy of James K. DeOrio, MD.

Corns are often misdiagnosed as calluses, which are also hyperkeratotic skin lesions resulting from excess friction. However, calluses develop from forces distributed over a broad area of skin, whereas corns develop from more localized forces.[8] Calluses are often considered desirable for some activities (eg, gymnastics, weightlifting), and they lack a central core, which is characteristically revealed in corns upon removal of the upper hyperkeratotic layer of skin. Corns can occur within an area of callus,[9] such as on the plantar surface. Note the image below.

Calluses on the palmar surface of the hands of a b Calluses on the palmar surface of the hands of a body builder. Courtesy of James K. DeOrio, MD.

Table. Clavus Formation Named for Specific Etiology or Location (Open Table in a new window)

Vernacular Term

Location

Association

Jeweler's callus, cherry pitter's thumb,[10] cameo engraver's corn[11]

Thumb

Digital changes, including callosities related to repetitive use of fine jeweler's instruments, which also may be seen with the use of cherry-pitting tools

Weight lifter's callus[12]

Callosities over the palmar metacarpophalangeal joints

Caused by the friction of weight-lifting apparatus (This also may be seen in athletes who participate in crew.)

Prayer callus[13, 14]

Callosity on the forehead

From kneeling prayer with the hands on the forehead

Cigarette lighter's thumb[15]

Hyperkeratosis of the radial aspect of the thumb

Caused by excessive cigarette lighter flicking

Knuckle pads[16]

Hyperkeratosis over the knuckles

Caused by boxing training

Russell sign[17]

Callosities of the dorsum of the hand over the metacarpophalangeal and interphalangeal joints

Caused by the friction involved with self-induced emesis in bulimia nervosa

Screwdriver operator's clavus[18]

Palmar surface of the hand

Occurs at the site of contact with a screwdriver handle

Spine bumps

Hyperkeratosis over the spinal column

Caused by dancing with spinning on one's back

Hairdresser's hand

First finger on dominant hand

Callus formation at the site of friction caused by scissors around the first finger on the dominant hand

Sucking calluses[19]

Lip, hand, or foot of a newborn

Callus formation at the site of an area of suction on the lip, hand, or foot of a newborn

Vamp disease[20]

Feet

Clavus formation due to wearing tight high-heeled shoes

Muay Thai kickboxers[21]

Feet

Callosities on the forefoot (77.5%), on the plantar first metatarsal (55.3%), and on the big toe (33.3%)

A clinical image of a screwdriver operator's clavus is below.

Screwdriver operator's callus (ie, clavus). Screwdriver operator's callus (ie, clavus).

Pathophysiology

Corns are the result of mechanical trauma to the skin culminating in hyperplasia of the epidermis. Most commonly, friction and pressure between the bones of the foot and ill-fitting footwear cause a normal physiological response—proliferation of the stratum corneum. One of the primary roles of the stratum corneum is to provide a barrier to mechanical injury. Any insult compromising this barrier causes homeostatic changes and the release of cytokines into the epidermis, stimulating an increase in synthesis of the stratum corneum. When the insult is chronic and the mechanical defect is not repaired, hyperplasia and inflammation are common.[26] With corns, external mechanical forces are focused on a localized area of the skin, ultimately leading to impaction of the stratum corneum and the formation of a hard keratin plug that presses painfully into the papillary dermis, which is known as a radix or nucleus.[6, 8]

The shape of the hands and feet are important in corn (clavus) formation. Specifically, the bony prominences of the metacarpophalangeal and metatarsophalangeal joints often are shaped in such a way as to induce overlying skin friction. As corn formation ensues, friction against the footwear is likely to perpetuate hyperkeratosis. Repetitive motion can produce callosities, as would be seen in musicians.[22]

Toe deformity, including contractures and claw, hammer, and mallet-shaped toes, may contribute to pathogenesis. Deformity of the feet from underlying conditions such as rheumatoid arthritis can contribute to clavus formation.[23] Bunionettes, ie, callosities over the lateral fifth metatarsal head, may be associated with neuritic symptoms due to compression of the underlying lateral digital nerves. Furthermore, Morton toe, in which the second toe is longer than the first toe, occurs in 25% of the population; this may be one of the most important pathogenic factors in a callus of the common second metatarsal head, ie, an intractable plantar keratosis.

Long-term or repetitive motion may also induce clavus formation, as is seen in computer users and text messengers (ie, "mousing" callus).[24] Callosities can also form from excessive leg crossing.[25]

Etiology

Both hard and soft corns are caused by pressure from unyielding structures.[5] Abnormal mechanical stress may be intrinsic or extrinsic. Intrinsic factors include foot deformities (eg, hammer toe, bunion)[27] ; abnormal foot mechanics (acquired or hereditary); and peripheral neuropathy. Extrinsic factors include poorly fitting footwear and heavy activity (athletics).

A 2005 study conducted by Menz et al reported that in older populations, plantar pressures are significantly higher under callused regions of the foot.[28] These data support the idea that increased pressures are related to a hyperkeratotic response and that the target for treatment should be eliminating excess pressures on the foot.

Conditions associated with clavus formation include the following:

Faulty mechanics play a role. Irregular distribution of pressure and repetitive motion injury (especially in athletes) are believed to be the main inciting causes; however, inappropriately shaped or constrictive footwear in the presence of bony prominences (eg, talar bone prominences[35] ) may exacerbate corn formation. Furthermore, some disorders may alter the shape or sensation of the soles of the feet. Bony prominences and faulty foot mechanics then allow clavus formation to continue.[36, 37, 38, 39, 40]

  • Rheumatoid arthritis [41] : About 17% of patients with rheumatoid arthritis present with intractable foot pain. Chronic arthritis leads to foot deformities and consequent callus formation. Bleeding into callosities in patients with rheumatoid arthritis may be a sign of rheumatoid angiitis.
  • Diabetes mellitus with associated peripheral neuropathy [42] : In patients with diabetes, chronic callosities in the presence of neurovascular deterioration may lead to ulcerations and superinfections.
  • Obsessive-compulsive disorder (pseudo-knuckle pads)
  • Ectopic nail

Epidemiology

Frequency

United States

Corns are one of the most common foot conditions in the United States, particularly amongst older patients. It is a common disorder because of the frequency of usage of occlusive footwear and participation in repetitive activities, such as running.

International

Corns are common worldwide. Any weight-bearing human is susceptible to the development of corns.

Race

An epidemiological study evaluating the prevalence of foot conditions amongst a diverse sample of adults from the northeastern United States revealed a significant difference in rates of corns amongst ethnic groups. African Americans had a significantly higher rate of corns and calluses compared with non-Hispanic white and Puerto Rican participants (70% vs 58% vs 34.1%).[43]

Sex

Amongst elderly populations, both men and women have been reported to wear shoes too narrow for their feet. Women have been reported to wear shoes that are also shorter than their feet. Both narrow and short footwear can lead to the development of corns, in addition to foot deformities.[44] They are more common in women than in men because of this use of occlusive and poorly fitted footwear.

Age

Hyperkeratotic lesions of the foot (including corns and calluses) have been reported to affect 20-65% of people aged 65 or older.[43, 45, 46]  

Anyone can have a clavus, but most individuals acquire the risk factors for clavus formation after puberty because of the onset of traumatic footwear use, repetitive motion injuries, and progressive foot deformities.

Prognosis

Recurrence is common. The most common symptoms associated with corns are pain upon ambulation and restriction of activity secondary to pain. Corns are generally not associated with mortality; however, recognizing the potential for a maltreated corn, soft corns in particular, to develop into a life-threatening secondary infection (bacterial or fungal) is important in patients with diabetes mellitus or immunosuppression.

The prognosis depends on the underlying cause of the callous formation and whether interventions can successfully be introduced to eliminate the repetitive motion. Chronic clavus generally occurs because of the difficulty in removing inciting factors in most situations. Extensive thickening of the skin may result in chronic pain, particularly in the forefoot; in certain situations, ulcer formation may result. Clavus may be a sign of underlying neuropathy due to diabetes or neuroborreliosis, or owing to the deformities of rheumatoid arthritis. In the case of neuropathy, a clavus may hide ulceration or denote abnormal neurovasculature of the feet. In the case of rheumatoid arthritis, corns may enhance the pain of deformed joints.

See Type 1 Diabetes Mellitus, Type 2 Diabetes Mellitus, and Diabetic Foot Infections for follow-up information.

Patient Education

Patients must be taught to wear less traumatic footwear, such as shoes with a wide toe space. Using inner soles, lowering the heel (if second metatarsal head lesions are present), and preventing the repetitive injuries that cause occupational clavus formation may be helpful. Review of proper footwear and trauma reduction may reduce disease severity over time.

For patient education resources, see the patient education article Corns and Calluses.

 

Presentation

History

Commonly, a patient reports the development of a localized growth on their foot or toes that causes pain with ambulation or when wearing shoes.[4, 7]

A clavus forms because of inappropriate distribution of pressure onto a specific site, usually of the foot. A localized callosity of the soles, which does not resolve, is termed plantar callus, heloma, tyloma, keratoma, or plantar corn. When callosities occur over one or more lateral metatarsals, they are termed intractable plantar keratoses.

Physical Examination

Clinically, all variants of clavus lesions look like hyperkeratotic or thick skin; maceration and secondary fungal or bacterial infections are a common overlying feature in heloma molle and diabetes. Plantar helomas tend to have a central keratin plug, which, when pared, reveals a clear, firm, central core. The most common sites for clavus formation are the feet, specifically the dorsolateral aspect of the fifth toe for heloma durum, in the fourth interdigital web of the foot for heloma molle, and under the metatarsal heads for calluses.

Corns are typically located between toe clefts, on the plantar aspect beneath prominent metatarsals, or on the dorsal aspect of toe joints.[8] The patient’s gait should be observed to identify irregular mechanics.[6] Additionally, surrounding erythema and heat may be present if the corn is acutely irritated.[5] Multiple physical signs, as follows, can be evaluated in order to differentiate between a clavus, callus, and wart:

  • Both plantar warts and hard corns can be tender, and both occur on the pressure points of the sole.

  • Direct pressure generally causes tenderness in a callus and corn. Warts are tender with pressure applied from side to side.[7, 9]

  • Calluses have a waxy appearance after being pared, whereas corns produce a central keratin plug.[7] Plantar warts do not have a central core.

  • The absence of capillary dotting after paring hard corns distinguishes them from plantar warts.[6, 47]

  • Skin markings can be seen crossing the surface of calluses, but not warts or corns.[47]

A hard corn is a firm, dry, and tender lesion with a shiny polished surface. If the upper layers are pared, a small, 1- to 2-mm translucent central core may be seen within the base of the lesion. Hard corns usually occur on the dorsolateral aspect of the fifth toe.[5] A plantar corn is a type of hard corn most commonly associated with a central core. These corns are located beneath the metatarsal heads of the toes.[5] Plantar corns that do not respond to conservative medical treatment are referred to as intractable plantar keratosis.[48] Note the image below.

Hard corn on the lateral surface of fifth toe. Cou Hard corn on the lateral surface of fifth toe. Courtesy of James K. DeOrio, MD.

A soft corn is boggy and macerated so that it appears white. Soft corns usually occur in the fourth interdigital space.[5]

Examination of patients should include assessment of the types of footwear worn, activities performed, gait, and current home therapy or previously prescribed therapy.

Lesions should be palpated and pared to look for underlying blood vessels (black dots or pinpoint bleeding), which are seen in warts, and to look for underlying ulcerations, as seen in neurovascular ulcerations (especially in patients with diabetes).

Paring of callosities or corns, as opposed to plantar warts, should reveal normal dermatoglyphics.[49]

Callosities are generally more painful with direct pressure, whereas warts are more painful with lateral pressure.[50]

Pedobarographic studies are pressure assessments that may be used to detect an altered distribution of foot pressure. MRI may delineate diabetic foot problems more clearly.

Biopsy of lesions reveals hyperkeratosis and, occasionally, mucin deposition.

Complications

Complications include secondary bacterial or fungal infection in patients with diabetes or in patients with immunosuppression. With deep paring, be aware of the risk of bleeding and infection.[7]

Corns are often in close proximity to joints and bones, increasing the chances for septic arthritis or osteomyelitis to occur if left untreated.

Patients, particularly patients with diabetes, may have ulcerations from chronic pressure. This can lead to infection and cellulitis.

Maceration and tinea pedis also may occur.

 

DDx

Diagnostic Considerations

Other considerations include the following:

Differential Diagnoses

 

Workup

Laboratory Studies

No routine laboratory tests are necessary to evaluate a patient with corns (clavus).[6] Diabetes mellitus, tertiary lues, and other causes of neuropathy should be excluded.

Blood glucose testing is required when paring of a clavus reveals an ulcer or when diabetes mellitus is suspected. In the setting of neuropathy, neuroborreliosis should be considered, and testing is performed with Lyme titers. Rheumatoid factor testing for deformities consistent with rheumatoid arthritis may be indicated. Also see Lyme Disease and Rheumatoid Arthritis.

Imaging Studies

Imaging studies are required in clavus patients only to detect underlying bony abnormalities. Studies may include radiography and, occasionally, CT scanning of the affected area with bone window settings.[51] Radiographs of the feet in a weight-bearing position are useful for identifying bony prominences and the presence of underlying pathology contributing to foot pain.[34] However, a physical examination may be sufficient to evaluate smaller toe abnormalities.[34]

Other Tests

Pedobarographic studies are pressure assessments that may be used in clavus patients to detect an altered distribution of foot pressure.

Procedures

Dermoscopic examination before and after trimming can be helpful with the differential diagnosis of plantar warts, corns, calluses, and healed warts. The translucent central core known as a nucleus may be visualized more easily in a corn using dermoscopy.[49]

Biopsy of the lesions reveals hyperkeratosis and, occasionally, mucin deposition. Paring of the corn can relieve pressure temporarily. Biopsy may be helpful in considering some of the other differential diagnoses, such as warts. Additionally, biopsy can be performed to differentiate clavus from porokeratosis palmoplantaris et disseminatum or discreta. These disorders occur in those aged 20-40 years who have hyperkeratotic plaques on the palms and soles. Biopsy shows a cornoid lamella.

Histologic Findings

Corns demonstrate epidermal hyperplasia with a thick and compact stratum corneum. Whereas calluses demonstrate only orthokeratosis, parakeratosis may be present in corns, and biopsy specimens demonstrate an endophytic cup shape. The granular cell layer may be decreased or absent.[8, 9] The dermis may occasionally show fibrosis with hypertrophied nerves and scar tissue replacing subcutaneous fat.[8]

 

Treatment

Medical Care

When treating hard corns (clavi), the primary objective is to debulk or pare the lesion without drawing blood. Treatment should be aimed at reducing symptoms such as pain and discomfort with walking. Paring of the lesions immediately reduces pain. Following preparation of the skin with alcohol or iodine, a No. 15 surgical blade can be used with or without anesthesia to gradually remove sequential layers of keratin.[6] Once the etiology of the foot pressure irregularity is determined, attempts at pressure redistribution should be made. The final treatment goals are to remove the central keratin core for short-term pain relief and to reshape the skin to provide long-term prevention of excess friction.[7, 8] Regular debridement in high-risk populations, such as diabetic patients, may decrease the incidence of ulceration and, consequently, the need for surgical intervention.[52]

The use of orthotics and conservative footwear with extra toe space are often beneficial. When all else fails, surgery may be performed.

If abnormal dermatoglyphics or pinpoint bleeding is seen, wart therapy is initiated. If normal dermatoglyphics are noted, salicylic acid compounds and orthotics may be beneficial. Relief of symptoms may be achieved by thinning and cushioning of the involved lesions.

Paring of the lesions immediately relieves pain, especially with helomas. Lesions may be maintained in this state if the patient uses short soaks and pumice stone debridement at home. Debridement may be enhanced with the use of keratolytic agents, such as ureas, alpha-hydroxy acid (eg, glycolic, malic, or lactic acid), or beta-hydroxy acid (eg, salicylic acid).[53] Garlic extracts have also been described as being helpful.[54]

Self-adhesive pads are most effective for reducing thick lesions, whereas lotions, creams, and medicaments in petrolatum are best for maintenance. Most salicylic acid compounds are 10-17%. High concentrations of salicylic acid (eg, 40%) may lead to severe maceration, and in patients with diabetes, it may lead to frank foot ulcerations.[55] Intralesional triamcinolone and topical vitamin A acid compounds also may reduce localized hyperkeratosis. Triamcinolone can lead to localized hypopigmentation.[56]

A statistically significant reduction in pain at 6 months with complete and partial resolution rates of 26% and 50%, respectively, were seen with electrosurgery compared with resolution rates of 4% and 28%, respectively, with sharp debridement in one study.[57]

Soft corns are often difficult to treat because they develop from underlying pressures in between the fourth and fifth digit, caused by bony prominences.[5] Soft corns are best treated with properly fitting footwear and better foot hygiene in order to decrease the likelihood for infection. Applying an antifungal or antibacterial powder after washing the area and using lamb’s wool or a toe spacer are additional techniques used to treat soft corns.[8] A good option in patients with coexisting dermatophytosis complex is 20% aluminum chloride hexahydrate solution (Drysol).

Reduced friction may be accomplished with the use of silicone-lined sleeves on the toes, padding, and, in select cases, silicone[58] or collagen injections[6] over the bony prominence in question.

Lamb's wool may be beneficial in interdigital corns. Pads or permanent insoles, which place pressure proximal to the metatarsal head, relieve stress on the region. Insoles may be made of silicone or soft plastics.

Shoes with extra length are required for toe deformity, and shoes with extra width are required for lateral toe callosities. Shoes should be soft inside without seams that rub or press. Orthotics can be placed in the shoe for patients with abnormalities of the foot, such as cavovarus. Orthotics can be created by using insoles made to correct deformities noted on dynamic pressure molds. Reduction of heel height may be helpful for patients with metacarpal head callosities.[59]

Vacuum orthoses have been described to aid in lesional clearance for diabetic patients with plantar callosities.[60]

Following are additional treatment modalities:

  • Keratolytics: Products that can be applied to affected areas include 40% salicylic acid pads and plaster, 40% urea cream, and 12% lactic acid cream.[8, 61] However, patients with peripheral neuropathies should avoid topical salicylic acid or use it with caution.[55, 62]

  • Filler injections: A retrospective evaluation of the use of fluid silicone in treating loss of plantar fat reveals a unique treatment option for corns and calluses.[58, 63, 64] Balkin reports he treated more than 1500 patients from 1964-2005 with silicone injections to digital and plantar sites. He found that 60-80% experienced some form of pain relief and elimination of calluses. Booster treatments are often needed, and the only complication reported was skin discoloration.[64] Injection of 0.1 mL of medical-grade liquid silicone below a clavus and above the bone has been reported to have good results,[65] but it is not presently approved by the US Food and Drug Administration.[59] Whether other filler substances can achieve the same success is unknown; a case report suggests hyaluronic acid gel injections may be beneficial.[66]

  • Laser: A carbon dioxide laser can be used to pare deep lesions.[67]

  • Combination products: A combination product to be applied by physicians consisting of 1% cantharidin, a vesicant, mixed with 30% salicylic acid and 5% podophyllin has been described as effective for most people after just one session. In a study looking at 72 patients, 90.3% with callosities on the feet demonstrated that application of this agent after paring with a No. 15 blade effected clearance in 79.2%, 12.5%, 6.9%, and 1.4% after 1, 2, 3, and 4 sessions, respectively, with only one recurrence at 1 year follow-up.[68]

  • Botulinum toxin: Injection of botulinum toxin into the plantar area of two patients with pachyonychia congenita has been described as beneficial for the reduction of clavus formation and blisters.[69]

Overall, removing or adjusting the mechanical stress causing the corn—finding footwear that matches the length and width of a foot—is the first step towards treatment of this condition.[6, 70] Patient awareness of his or her footwear is critical to the prevention of future corns. Conservative treatment can be continued at home and may consist of using a pumice stone for minor debridement, practicing good foot hygiene, and using soft spacers or a silicone sleeve, which can be bought at most retail stores.[5, 61]

Further inpatient care

Further inpatient care usually is not required unless surgical adjustments are needed.

A patient with diabetes who has neuropathic ulcers and overlying clavus formation may require further care.

Rheumatoid arthritis patients may benefit more from surgical interventions than callous debridement. Forefoot arthroplasty and first metatarsophalangeal joint implants may improve clavus formation and rheumatoid foot pain over the long term.

Measurement of the foot for orthoses is beneficial in the case of multiple clavi.

Surgical Care

Surgery to remove the bony prominences is indicated only if all conservative measures fail.[6, 7, 27] Surgical procedures include bunionectomy, syndactylization, osteotomy, and arthroplasty.[5, 27] Long-term improvement for lateral fifth-toe corns and interdigital corns has been achieved with partial and complete condylectomy.[27]

Chronic foot pain despite conservative therapy is the number one indication for surgery.

Hallux valgus correction may aid in reduction of painful callosities over the long term.[60]

Surgical corrections for claw, hammer, and mallet toes are simple procedures.

Shaving of prominent condyles of bony prominences may be beneficial, particularly on the fifth digit.

Arthroplasty of the fifth toe interphalangeal joint also may be performed.

Metatarsal condylectomy or chevron osteotomy may be performed to relieve metatarsal head pressure.[71]

Mann and DuVries described the use of a combination of arthroplasty and condylectomy. This combination results in 95% clearance, with only a 13% occurrence of transfer lesions.[72]

When thinning of the plantar fat pads is contributory to the formations of callosities, injectable silicone can be used on the soles underneath the callosities and corns to reduce pressure-related callous formation.

Description of excision followed by either grafting, use of flaps, or grafting using split-thickness graft with or without a collagen/elastin matrix graft has been described as effective in a single resistant case.[72]

Consultations

If patients do not respond to conservative treatment, further evaluation by a podiatrist or orthopedic surgeon is recommended. Extensive orthoses are available to help remove mechanical stresses on the foot, and an orthopedist or podiatrist should be consulted.

An orthopedist and a podiatrist also can be helpful in adjusting abnormalities of gait or pressure distribution.

In cases of suspected arthritis, a rheumatologist can be consulted.

Dermatologists are best consulted to assess for the possibility of other disorders in the differential diagnosis, especially warts and keratoderma.

Diet

Weight loss may reduce pain from corns and improve biomechanics in patients who are obese.

Activity

Patients are advised to reduce or eliminate certain mechanical forces or motions. However, certain activities, particularly work related, may be unavoidable or patients may be reluctant to make the necessary changes.

Adjustment of the footwear and the use of special insoles aid in the maintenance of full mobility and eliminate the need for activity limitation.

Prevention

Deterrence and prevention includes the use of corn pads, web spacers, and properly fitting shoes (see Pathophysiology and Medical Care). Patients can treat their corns at home using a pumice stone to regularly debulk the lesion after a shower, when the skin is soft.

Long-Term Monitoring

Follow-up care is important to ensure control of the hyperkeratosis because patients may require regular, repeated applications of keratolytic agents in conjunction with careful paring.

Patients with special health concerns, including diabetic patients, amputees, and elderly persons, may require more frequent follow-up visits in order to decrease the likelihood of a more catastrophic complication, particularly secondary bacterial infection, from the initial lesion.

Numerous contributory factors may result in thickened skin on the feet. Factors such as occupation, athletic pursuits, footwear, underlying bony abnormalities, and problems with general health may contribute to clavus formation.

Etiologic factors must be carefully assessed before treatment can be given.

Symptomatic relief can be achieved by thinning the hyperkeratotic lesions and by using cushions or insoles, which reduce pressure on the affected areas.

Surgery can be an adjunctive treatment in those patients with intractable clavus formation and chronic foot pain.

Using a combination of modalities and reducing the pressure of footwear ultimately reduces the appearance and discomfort of the clavus.

 

Medication

Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Debridement may be enhanced with the use of keratolytic agents, such as ureas, alpha-hydroxy acid (eg, glycolic, malic, or lactic acid), or beta-hydroxy acid (eg, salicylic acid). The use of these agents is not recommended in pregnant women and young children. Most salicylic acid compounds are 10-17%. High concentrations of salicylic acid (eg, 40%) may lead to severe maceration and frank foot ulcerations in patients with diabetes. Self-adhesive pads are most effective for reducing thick lesions, whereas lotions, creams, and medicaments in petrolatum are best for maintenance. Intralesional triamcinolone and topical vitamin A acid compounds also may reduce localized hyperkeratosis. Triamcinolone may be injected during pregnancy because of its limited absorption; however, it can lead to localized hypopigmentation. Topical vitamin A derivatives are not intended for use in women who are pregnant or intending to become pregnant because their safety ranges from category C to category X.

A combination product to be applied by physicians consisting of 1% cantharidin, a vesicant, mixed with 30% salicylic acid and 5% podophyllin has been described as effective for most people after just one session.[68]

Keratolytic agents

Class Summary

These agents cause the cornified epithelium to swell, soften, macerate, and then desquamate. Commonly used agents include urea, alpha-hydroxy acids (eg, lactic acid, glycolic acid), and beta-hydroxy acids (eg, salicylic acid).

Salicylic acid topical (Clear Away, Compound W, Dr. Scholl's Corn Removers)

Topical salicylic acid is a keratolytic, bacteriostatic, and fungistatic agent. Its main clinical use is as a keratolytic agent and as an agent that increases the percutaneous absorption of combined drugs by removing the stratum corneum. The keratolytic activity results from solubilization of the intercellular ground substance in the stratum corneum and shedding of the scales, which are bound by it.

Salicylic acid topical can be compounded in petrolatum at any percentage and is usually used at 5-20%, beginning with a lower percentage. It can be purchased over the counter as a liquid or pad preparation, ranging from 17-40% (multiple companies make these). It can be irritating or cause blistering.

Ammonium lactate (AmLactin, Lac-Hydrin, Lactinol)

Ammonium lactate may loosen the adhesion of the keratinocytes in the stratum corneum, thereby thinning the skin. Ammonium lactate provides beneficial effects on dry skin and severe hyperkeratotic conditions. It is indicated for moisturizing and softening dry, scaly skin.

Urea (Aquadrate, Calmurid, Carmol, Nutraplus)

Urea is a a keratolytic, bacteriostatic, bactericidal, and fungistatic agent. It is topical treatment for dry skin and ichthyosis and is also used as a skin moisturizer. Urea promotes the hydration and removal of excess keratin in conditions of hyperkeratosis.

Corticosteroids

Class Summary

These drugs have anti-inflammatory properties and cause profound and varied metabolic effects. Corticosteroids modify the body's immune response to diverse stimuli.

Triamcinolone (Aristospan, Kenalog IV, Trivaris)

An injectable version of triamcinolone is available in concentrations of 3-40 mg/mL. Generally, this compound is diluted to 1-4% for injection into lesions, such as a clavus.

Retinoids

Class Summary

These agents are not specifically approved for use in corn (clavus) therapy. Only tretinoin has been shown to be useful for clavus therapy in the topically applied form. These agents cause the skin to peel by loosening of keratinocyte adhesion. Irritation and discomfort are limiting adverse effects.

Tretinoin topical (Atralin, Avita, Refissa)

Tretinoin topical inhibits microcomedo formation and eliminates lesions. It makes keratinocytes in sebaceous follicles less adherent and easier to remove. It is available as 0.025%, 0.05%, and 0.1% creams and 0.01% and 0.025% gels.