Testing the Reliability of Optical Coherence Tomography to Measure Epidermal Thickness and Distinguish Volar and Nonvolar Skin

Abstract

In persons with limb loss, prosthetic devices cause skin breakdown, largely because residual limb skin (nonvolar) is not intended to bear weight such as palmoplantar (volar) skin. Before evaluation of treatment efficacy to improve skin resiliency, efforts are needed to establish normative data and assess outcome metric reliability. The purpose of this study was to use optical coherence tomography to (i) characterize volar and nonvolar skin epidermal thickness and (ii) examine the reliability of optical coherence tomography. Four orientations of optical coherence tomography images were collected on 33 volunteers (6 with limb loss) at 2 time points, and the epidermis was traced to quantify thickness by 3 evaluators. Epidermal thickness was greater (P < .01) for volar skin (palm) (265.1 ± 50.9 μm, n= 33) than for both nonvolar locations: posterior thigh (89.8 ± 18.1 μm, n= 27) or residual limb (93.4 ± 27.4 μm, n= 6). The inter-rater intraclass correlation coefficient was high for volar skin (0.887-0.956) but low for nonvolar skin (thigh: 0.292-0.391, residual limb: 0.211-0.580). Correlation improved when comparing only 2 evaluators who used the same display technique (palm: 0.827-0.940, thigh: 0.633-0.877, residual limb: 0.213-0.952). Despite poor inter-rater agreement for nonvolar skin, perhaps due to challenges in identifying the dermal-epidermal junction, this study helps to support the utility of optical coherence tomography to distinguish volar from nonvolar skin.