Anatomical and histological study to determine the border of sole skin

Transfer of a free skin graft from the submalleolar or plantar instep area to the palmoplantar area and finger defects is widely performed; however, the sites and the border of plantar skin have yet to be examined in detail. The aim of this study was to determine the border of sole skin.

Twelve paraformaldehyde-fixed cadavers were examined. Skin specimens were harvested from an area from the top of the medial malleolus extending to the top of the lateral malleolus of the right foot. The paraffin-embedded skin specimens were analyzed using histological (hematoxylin and eosin, Fontana-Masson, and elastica van Gieson stains) and immunohistochemical (cytokeratin 9) techniques.

CK9-positive cells were present at the points between 21 and 78 % of the intermalleolar distance measured from the tops of the medial and lateral malleoli. The melanin index abruptly changed at the points 25 ± 7.1 and 75 ± 4.2 %. The skin thickness and amount of elastic fibers changed greatly at the points between 20 and 30 % and between 70 and 80 % of the intermalleolar distance.

Submalleolar skin is quite different from sole skin. The border of sole skin lies at the points between 20 and 25 % of the intermalleolar distance from the medial malleolus, which macroscopically corresponds to the border of skin maceration. It would be better to use the submalleolar area for grafts for the dorsum of the fingers or toes, and the plantar instep area for the ventral areas of the fingers or toes.