Assessment of Hair Density and Sub-epidermal Tissue Thickness in Burn Scars Using High-Definition Ultrasound Imaging

Burn scars show significant differences in structure, pigment, and hair density/sparsity from unburned skin, yet no formal documentation of these changes can be found in the literature. Evaluation of these differences is essential to assessing future intervention outcomes. The study was a prospective controlled clinical trial. Included were 19 adult burn survivors (18-63 years old, average age 47; 15 male, 4 female, 14 Caucasian, 2 African American, 1 Hispanic; 11 flame burns, 5 scald burns, 2 grease burns and 1 electrical burn, 2%-60% TBSA) with conspicuous, mature scars. All study subjects had either skin-grafted or nongrafted scars, as well as healthy skin in the same body area, to control for intraindividual variability. All scars were at least 9 months old and at a minimum 2 × 2 cm2 in size. On each individual, at least one nongrafted scar or one grafted scar and healthy skin was imaged with a high-definition ultrasound device (Longport, Inc., Glen Mills, PA, 35MHz probe, 1500 m/s). Vancouver scar scale was assessed. Although scarred skin had significantly fewer follicles than healthy skin in both grafted (P < .0001) and un-grafted sites (P = .0090), there were even significantly fewer follicles in grafted scars than un-grafted scars (P = .0095). In thickness of the sub-epidermal layer, there was no difference between grafted and un-grafted scars (P = .1900). Both kinds of scars had a significantly thicker sub-epidermal layer than healthy skin (P = .0010). Vancouver scar scale was 7.4 for grafted and 4.6 for nongrafted scars with grafted flame burn scars ranging higher than all others (5-11). There was no discomfort during the imaging, and no adverse events occurred during the study period. Our study demonstrates two clear morphologic differences between scars and healthy skin: thickness of the sub-epidermal layer and hair follicle density. Grafted burn scars were shown to contain fewer hair follicles than un-grafted scars.