Introduction
Background
Clavus is a thickening of the skin due to intermittent pressure and frictional forces. These forces result in hyperkeratosis, clinically and histologically. This extensive thickening of the skin 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 include the following: 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
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Table
| Vernacular Term | Location | Association |
| Jeweler's callus, cherry pitter's thumb, 4 cameo engraver's corn 5 | 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 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 |
| Vernacular Term | Location | Association |
| Jeweler's callus, cherry pitter's thumb, 4 cameo engraver's corn 5 | 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 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 |
Screwdriver operator's callus (ie, clavus).
Pathophysiology
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. Toe deformity, including contractures and claw, hammer, and mallet-shaped toes, may contribute to pathogenesis. 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 (ie, "mousing" callus).15
Frequency
United States
The clavus is a common disorder because of the frequency of usage of occlusive footwear and participation in repetitive activities, such as running.
Mortality/Morbidity
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.
Race
Any race may be affected.
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.
Clinical
History
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.
Physical
Clinically, all these 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.16
- Callosities are generally more painful with direct pressure, whereas warts are more painful with lateral pressure.17
- 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.
Causes
- Conditions associated with clavus formation include the following:
- Advanced patient age
- Amputation (ie, stump callosities)
- Use of a brace or orthopedic stabilizing product
- Bulimia nervosa11
- Diabetes mellitus with associated peripheral neuropathy18
- Doxorubicin toxicity19
- Keratoderma palmaris et plantaris
- Obesity
- Pachyonychia congenita20
- Rheumatoid arthritis21
- Sensory neuropathies, including neuroborreliosis
- Tethered spinal cord syndrome22
- Vascular occlusion syndromes23
- Warts (ie, verruca vulgaris)1
- Faulty mechanics: 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 prominences24 ) 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.25,26,27,28,29
- Rheumatoid arthritis: 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: 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
More on Clavus |
 Overview: Clavus |
| Differential Diagnoses & Workup: Clavus |
| Treatment & Medication: Clavus |
| Follow-up: Clavus |
| Multimedia: Clavus |
| References |
| Further Reading |
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References
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Heyl T, Raubenheimer EJ. Sucking pads (sucking calluses) of the lips in neonates: a manifestation of transient leukoedema. Pediatr Dermatol. Aug 1987;4(2):123-8. [Medline].
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Murray HJ, Young MJ, Hollis S, Boulton AJ. The association between callus formation, high pressures and neuropathy in diabetic foot ulceration. Diabet Med. Nov 1996;13(11):979-82. [Medline].
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Lemont H, Ravick A. Hemorrhage within plantar callus. A cutaneous sign of rheumatoid angiitis. J Am Podiatry Assoc. Jan 1980;70(1):22-5. [Medline].
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Further Reading
Clinical guidelines
Dermatologic manifestations.
New York State Department of Health - State/Local Government Agency [U.S.]. 2004. 15 pages. NGC:003931
Guidelines for the management of actinic keratoses.
British Association of Dermatologists - Medical Specialty Society. 2007 Feb. 9 pages. NGC:005656
Clinical trials
Potential Research Study Participant Registry
Study to Compare Different Light Therapies (Narrowband Ultraviolet B Vs PUVA) for Hand and Foot Skin Diseases.
Related eMedicine topics
Corns (Dermatology)
Arsenical Keratosis
Warts, Nongenital Warts, Plantar
Keywords
callosity, corn, heloma, heloma durum, heloma molle, callous, callus, plantar callus, heloma, tyloma, keratoma, plantar corn, plantar callus, intractable plantar keratoses, jeweler's callus, cherry pitter's thumb, cameo engraver's corn, weight lifter's callus, prayer callus, cigarette lighter thumb, knuckle pads, Russell's sign, Russell sign, screwdriver operator's clavus, spine bumps, hairdresser's hand, sucking callus, Vamp disease, mousing callus
