Clinically known as Heloma Durum, a hard corn is a small, dense, round nucleus of skin within the epidermis which is often covered with layers of callus.
The corns were roughly 5mm in diameter under the 3rd metatarsal head and went quite deep into the epidermal layer. On the plantar surface, they are usually found on the plantar metatarsal heads and the calcaneus.
Cause: Caused by the human papillomavirus infection of epidermal (stratum germinativum) cells and is transmitted by direct contact, possibly through small cuts or abrasions in the stratum corneum layer of the skin. (Mooney, 2009:419).
Aetiology and Pathology
They are associated with structural deformities, pressure and excessive mechanical stress. (Neale’s p200, 2010). The normal keratinisation process is accelerated. They present with a hard, glassy and dense texture and the classic formation is cone shaped with the point deep to the wider surface. Under greater trauma the papillary capillaries may be extruded into the epidermis and will appear as brown/black stains. If the corn forms over a bursa, it may indicate the formation of a sinus into the bursal sac which may result in infection (Merriman & Turner p231, 2002).
Enucleate the corn with a suitable scalpel blade, eg number 15, then use padding to redistribute the mechanical stress. Provide footwear advice. Address and treat any underlying causes. Consider the use of orthotics to alter any stresses caused by the gait pattern.
Frowen, Paul; Maureen O'Donnell; Lorimer, Donald; Burrow, Gordon (2010). Neale's Disorders of the Foot. London: Churchill Livingstone. p200.
Merriman, Linda M: Turner, Warren (2002) Assessment of the Lower Limb 2nd ed. London: Churchill Livingstone p231