The Characterization of Plantar Skin Across Environmental Condition and Time

In the presence of pathologic conditions such as diabetes or neuropathy and activity-related forces, the plantar surface of the foot is a common place for skin breakdown. With this risk, foundational knowledge of typical plantar skin behavior is needed. The purpose of this study was to characterize the plantar skin properties (tangential stiffness, normal compliance, and thickness) across environmental condition and time.

Nonexperimental laboratory design.

Sixteen individuals participated (age range, 19-78 years; mean age, 48.5 ± 19.23 years; mean body mass index, 31.5 ± 7.61 kg/m).

Tangential stiffness, normal compliance, and thickness were assessed with the Tissue Interrogation Device (TID), Myotonometer, and ultrasound, respectively. Measurements were taken at 5 anatomic locations over 4 visits across a day (morning and afternoon), week, and month. Measurements were taken in standard (20° C to 24° C, 35%-50% relative humidity) and shoe conditions (32° C, 66% relative humidity).

Tangential stiffness (P = .000), normal compliance (P = .000), and thickness (epidermis, P = .000; dermis, P = .044) all varied by location. No main effect differences were noted across visits or environment across devices. Reliability varied across visits.

All 3 skin properties were found to vary across location and people. Given skin property consistency over time and device reliability, it is reasonable to take and compare measurements within a week. Environmental conditions should be reported and controlled in research assessing plantar skin.