A 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 clavus 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.[1] When callosities occur over 1 or more lateral metatarsals, they are termed intractable plantar keratoses.[2]
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, reveal 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.[3]
Table. Clavus Formation Named for Specific Etiology or Location
View Table
See Table
A clinical image of a screwdriver operator's clavus is below.
The shape of the hands and feet are important in 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 clavus formation ensues, friction against the footwear is likely to perpetuate hyperkeratosis. Repetitive motion can produce callosities, as would be seen in musicians.[16]
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.[17] Bunionettes, ie, callosities over the lateral fifth metatarsal head, may be associated 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.
Chronic or repetitive motion may also induce clavus formation, as is seen in computer users and text messengers (ie, "mousing" callus).[18] Callosities can also form from excessive leg crossing.[19]
Clavus is a common disorder because of the frequency of usage of occlusive footwear and participation in repetitive activities, such as running.
Race
Persons of any race may be affected by clavus.
Sex
Clavus is more common in women than in men because of their use of occlusive and poorly fitted footwear.
Age
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.
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 due 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, clavus may enhance the pain of deformed joints.
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 excellent patient education resources, see eMedicineHealth's patient education article Corns and Calluses.
A clavus forms because of inappropriate distribution of pressure onto a specific site, usually of the foot. A localized callosity 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.
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, reveal 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.
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.[20]
Callosities are generally more painful with direct pressure, whereas warts are more painful with lateral pressure.[21]
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.
Conditions associated with clavus formation include the following:
Advanced patient age
Amputation (ie, stump callosities)
Use of a brace or orthopedic stabilizing product
Bulimia nervosa
[11]
Costa acrokeratoelastoidosis[22]
Doxorubicin toxicity[23]
Keratoderma palmaris et plantaris
Obesity
Pachyonychia congenita
[24]
Sensory neuropathies, including neuroborreliosis
Tethered spinal cord syndrome[25]
Vascular occlusion syndromes[26]
Warts (ie, verruca vulgaris)[1]
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[27] ) may exacerbate clavus 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.[28, 29, 30, 31, 32] Note the association with the following disorders:
Rheumatoid arthritis[33] : 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[34] : In patients with diabetes, chronic callosities in the presence of neurovascular deterioration may lead to ulcerations and superinfections.
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 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.[35]
Biopsy of the lesions reveals hyperkeratosis and, occasionally, mucin deposition. Paring of the clavus 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 occurred in those aged 20-40 years who have hyperkeratotic plaques on the palms and soles. Biopsy shows a cornoid lamella.
Treatment of a clavus should be aimed at reducing symptoms such as pain and discomfort with walking. Paring of the lesions immediately reduces pain. Once the etiology of the foot pressure irregularity is determined, attempts at pressure redistribution should be made. 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).[36] Garlic extracts have also been described as being helpful.[37]
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.[38] Intralesional triamcinolone and topical vitamin A acid compounds also may reduce localized hyperkeratosis. Triamcinolone can lead to localized hypopigmentation.[39]
A carbon dioxide laser can be used to pare deep lesions.[40]
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 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.[41]
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.[42]
Reduced friction may be accomplished with the use of silicone-lined sleeves on the toes, padding, and, in select cases, silicone[43] or collagen injections[3] 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.[44]
Vacuum orthoses have been described to aid in lesional clearance for diabetic patients with plantar callosities.[45]
Further inpatient care
Further inpatient care 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 long-term.
Measurement of the foot for orthoses is beneficial in the case of multiple clavi.
Surgical options for clavus should be used when only conservative measures fail.
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.[45]
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.[46]
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.[47]
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.[47]
Clavus formation is a common painful frictional disorder that results in hyperkeratosis. Multiple methods to reduce friction and thus prevent recurrences are described in Medical Care and Long-Term Monitoring.
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.
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 Kenalog and topical vitamin A acid compounds also may reduce localized hyperkeratosis. Kenalog 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.[41]
Clinical Context:
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.
These agents cause 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).
Clinical Context:
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.
Corticosteroids cause the skin to thin, and this beneficial side effect can be used to reduce the thickness of a clavus. However, overusage also can lighten the skin and cause atrophy.
These drugs have anti-inflammatory properties and cause profound and varied metabolic effects. Corticosteroids modify the body's immune response to diverse stimuli.
Clinical Context:
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.
Retinoids decrease the cohesiveness of abnormal hyperproliferative keratinocytes, and they may reduce the potential for malignant degeneration. Retinoids modulate keratinocyte differentiation.
These agents are not specifically approved for use in 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.
Nanette B Silverberg, MD, Clinical Professor of Dermatology, Icahn School of Medicine at Mount Sinai; Chief, Pediatric Dermatology, Mt Sinai Health Systems, Mount Sinai St Luke's-Roosevelt Hospital and Mt Sinai Beth Israel Medical Centers
Disclosure: Nothing to disclose.
Specialty Editors
David F Butler, MD, Section Chief of Dermatology, Central Texas Veterans Healthcare System; Professor of Dermatology, Texas A&M University College of Medicine; Founding Chair, Department of Dermatology, Scott and White Clinic
Disclosure: Nothing to disclose.
Jeffrey J Miller, MD, Associate Professor of Dermatology, Pennsylvania State University College of Medicine; Staff Dermatologist, Pennsylvania State Milton S Hershey Medical Center
Disclosure: Nothing to disclose.
Chief Editor
William D James, MD, Paul R Gross Professor of Dermatology, Vice-Chairman, Residency Program Director, Department of Dermatology, University of Pennsylvania School of Medicine
Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Naked Biome<br/>Received income in an amount equal to or greater than $250 from: Elsevier; WebMD<br/>StatPearls; Editor.
Acknowledgements
Smeena Khan, MD Private Practice, Adult and Pediatric Dermatology Associates
Smeena Khan, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology
Atlan M, Naouri M, Lorette G, Estève E, Zakine G. [Original treatment of constitutional painful callosities by surgical excision,collagen/elastin matrix (MatriDerm(®)) and split thickness skin graft secured by negative wound therapy]. Ann Chir Plast Esthet. April 2011. 56:163-9.
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[6]
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[7, 8]
Callosity on the forehead
From kneeling prayer with the hands on the forehead
Cigarette lighter's thumb[9]
Hyperkeratosis of the radial aspect of the thumb
Caused by excessive cigarette lighter flicking
Knuckle pads[10]
Hyperkeratosis over the knuckles
Caused by boxing training
Russell sign[11]
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[12]
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[13]
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[14]
Feet
Clavus formation due to wearing tight high-heeled shoes
Muay Thai kickboxers[15]
Feet
Callosities on the forefoot (77.5%), on the plantar first metatarsal (55.3%), and on the big toe (33.3%)
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