Skin Epidermal and Microvascular Properties at the Sacrum and Heel Assessed with Optical Coherence Tomography

The sacrum and posterior heel are two common areas where skin is exposed to pressure and shear forces which could lead to damage in the form of pressure ulcers. Despite their vulnerability, relatively few studies have explored their structural and physiological properties which predispose them to damage. The aim of this study was to characterise age and anatomical site differences in the skin epidermal properties and microvasculature using optical coherence tomography (OCT), in younger and older adults.

Twenty-two younger (18-35 years) and 19 older healthy adults (55-70 years) completed three experimental visits, comprising non-invasive OCT imaging to characterise skin epidermal properties and microvascular density. Extracted parameters from the captured images were optical attenuation coefficient, dermal brightness, epidermal thickness, surface roughness, microvascular plexus depth (µm), and vascular density (%).

There were significant differences in the epidermal structural properties between the sacrum and heel across all parameters (p < 0.001), except for roughness (p > 0.05). The vascular density profiles plotted against skin depth were also significantly different between anatomical sites (p < 0.001), with peak vascular density being more superficial in the heel: ∼0.2 mm vs. sacrum: ∼0.4 mm (p < 0.001). The sacrum had a greater maximum vascular density (∼9%) compared to the heel (∼7%; p < 0.001). No significant differences were observed between the age groups (p > 0.05).

Distinct differences were observed for epidermal and vascular density measurements between heel and sacral skin sites. However, there were no age-related differences, which may be associated with the older adult range (55-70 years) and healthy status. The structural and microvasculature insights could aid in the design of therapeutic interventions to promote tissue viability and health such as site-specific dressing and textiles.