Mechanical Hyperkeratosis: Let the Corn and Callus Do You No Harm!
Abnormal mechanical stresses on the skin will result in the formation of an accumulation of several horny layers of epithelium (hyperkeratosis).
A corn is a confined hyperkeratotic lesion with a central conical core of keratin that causes pain and inflammation. The conical core in a corn, which is a thickening of the stratum corneum, is a protective response to the mechanical trauma. This central core distinguishes the corn from the callus.
A callus is a broad-based or diffuse hyperkeratotic lesion of relatively even thickness, usually found under the metatarsal heads at a site of friction, irritation, and pressure. Unlike corns, the margins of a callus are undefined. They are rarely painful and are often larger than corns.
Abnormal mechanical stresses can result from a variety of intrinsic factors (bony prominences or hammertoe deformities) or extrinsic factors (tight shoes, irregularities within the shoe, or high activity levels). As mechanical stresses on the skin increase, the body attempts to protect irritated skin by forming a hyperkeratotic lesion, such as a corn or a callus; however , this lesion will increase the pressure in a tight shoe, thus creating a vicious cycle: increased pressure increases the formation of corns or calluses, which further increases the pressure.
You may have a corn or callus if you notice:
- A thick, rough area of skin
- A hardened, raised bump
- Tenderness or pain under your skin
- Flaky, dry or waxy skin
Pressure and friction from repetitive actions cause corns and calluses to develop and grow. Some sources of this pressure and friction include:
- Wearing ill-fitting shoes
- Skipping socks
- Playing instruments or using hand tools
These factors may increase the risk of corns and calluses:
- Bunions: A bunion is an abnormal, bony bump that forms on the joint at the base of your big
- Hammertoe: A hammertoe is a deformity in which your toe curls like a
- Other foot deformities: Certain conditions, such as a bone spur, can cause constant rubbing inside your
- Not protecting your Using hand tools without wearing gloves exposes your skin to excessive friction.
Hyperkeratotic lesions are secondary to increased mechanical stress and are not a disease of the skin. The principles of treatment should be to:
- Provide symptomatic relief,
- Determine the mechanical etiology,
- formulate a treatment plan that includes padding and modification of footwear,
- consider surgery if conservative measures fail.
- A mainstay of palliative treatment is sharp debridement to reduce the amount of hyperkeratotic tissue.
- A chisel blade may be used to pare down these lesions, providing almost complete relief to the area.
- A pad may be used to prolong the relief provided by sharp debridement.
- For diffuse hyperkeratotic lesions that are not painful, a pumice stone is used to reduce the lesion after first soaking the foot in warm water.
- Over-the-counter products that contain salicylic acid should be avoided because they may damage surrounding normal tissues, especially in neuropathic and immunocompromised patients.
Therapeutic padding can alleviate the patient’s symptoms by reducing the amount of mechanical irritation to the site of the corn or callus.
- For hard corns: foam pads or silicone toe sleeves offer the cushioning and protection needed after adequate debridement of the
- For soft corns: After debridement of soft corns, relief can be provided by padding the web space with a foam toe spacer or a small amount of lamb’s
- for calluses: Plantar calluses caused by weight-bearing stresses on the metatarsal heads may be relieved or eliminated by accommodative metatarsal padding may be applied directly on the foot or within the shoe.
Most mechanical lesions can be conservatively managed with an adequate shoe.
- Patients should be advised to wear low-heeled shoes with a soft upper portion and a roomy
- Patients with hammertoe deformities may need a shoe with an extra depth to accommodate hard corns that often occur on the top of the deformed
- Patients with soft or hard corns on the fifth toe may benefit from a shoe that has extra
Surgery should concentrate on correcting the abnormal mechanical stresses and should only be considered after conservative measures have failed.
- The goal of surgical correction of a hammertoe deformity, claw toe deformity, or mallet toe deformity is to reestablish a rectus alignment of a toe that is also free of painful
- Hard corns on the fifth toe and soft interdigital corns can be treated by resection of the prominent condyles or excision arthroplasty of the proximal phalanx of the fifth
- Calluses under the metatarsal heads are best managed conservatively because metatarsal osteotomies have unpredictable results, and the callous may transfer to an adjacent metatarsal
These approaches may help you prevent corns and calluses:
- Wear shoes that give your toes plenty of room.
- Use protective coverings.
- Wear padded gloves when using hand tools.
- Keep hands and feet moisturized.
The formation of corns and calluses can be caused by mechanical stresses from faulty footgear, abnormal foot mechanics, and high levels of activity. Corns and calluses result from hyperkeratosis , a normal physiologic response of the skin to chronic excessive pressure or friction. Treatment should provide symptomatic relief and alleviate the underlying mechanical cause. The lesions will usually disappear following the removal of the causative mechanical forces. Most lesions can be managed conservatively by the use of properly fitting shoes and padding to redistribute mechanical forces. Surgery is only indicated if conservative measures fail and should be aimed at correcting the abnormal mechanical stresses.
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