FLORENCE, ITALY — Shove variably shaped human feet into uniformly shaped shoes, some with pointy toes and impossibly narrow widths, and the result will be toenail trauma, one of the most common etiologies of toenail disorders.
Friction of a patient's foot against his or her shoe may cause hyperkeratosis, nail fractures, onycholysis, and/or hematomas, said Bertrand Richert, M.D., a specialist in the nail unit of the department of dermatology at the University of Liege, Belgium, at the 13th Congress of the European Academy of Dermatology and Venereology.
But although shoes get all the bad press, sometimes the anatomy of a patient's foot adds to the problem, Dr. Richert said.
For example, in a classic Greek-type foot, the second toe is longer than the first.
Because most shoes don't accommodate this foot pattern, the second toe has to bend to fit, causing frictional onycholysis, hyperkeratosis of the nail, and sometimes, hemorrhages of the second toe.
“All forces while walking are exerted on the tip of the second toe,” he said.
Another common but often-overlooked foot variation causes a shiny dermatosis at the hyponychium and onycholysis with hyperkeratosis on the great toenail.
“Check the foot on a lateral view and you've got the answer. This is hallux erectus,” Dr. Richert explained.
In this condition, the great toe veers upward, where it rubs against the roof of any shoe. The resulting clinical picture can look like psoriasis of the nail or onychomycosis, when the actual culprit is the shape of the foot.
“If you clip off the onychoclavus, you'll reveal the hyperkeratotic process,” he said. “This condition is sometimes really painful. People are just unable to wear shoes [until the lesion is trimmed].”
Dr. Richert urged colleagues to carefully examine their patients' bare feet and their shoes before reaching a conclusion about a toenail diagnosis.
What looks like melanoma may actually be a hematoma caused by pressure on the toe by footwear.
Frictional melanonychia can be present on the fifth, fourth, or third toes.
Joggers, tennis players, and squash players often present with lateral nail fractures caused by forceful pressure exerted by the tip of the shoe. Forceful pressure exerted over time can activate melanocytes.
“Be very careful not to miss a melanoma in situ,” he said.
Hallux valgus, the abnormal angulation of the great toe, can cause overlapping of the second toe over the first, or occasionally the first toe over the second, he added.
Surgical excision of hyperkeratotic tumors or lateral horns may be necessary to resolve traumatic toenail issues, but the first and most important treatment approach is conservative, consisting of selection of proper footwear and use of silicon prosthetic devices that can accommodate anatomic foot variations within patients' shoes.