Ms Christine Andrews1, Ms Margit Kempf1, Prof Roy Kimble2, Dr Leila Cuttle3
1Centre for Children’s Burns and Trauma Research, The University of Queensland, Child Health Research Centre, Brisbane, Australia, 2Centre for Children’s Burns and Trauma Research, Child Health Research Centre, The University of Queensland, Queensland University of Technology, Children’s Health Queensland, Lady Cilento Children’s Hospital, Brisbane, Australia, 3Centre for Children’s Burns and Trauma Research, Queensland University of Technology, Institute of Health and Biomedical Innovation at Centre for Children’s Health Research, Brisbane, Australia
Ultrasonographic measurement of skin and burn scar thickness for clinical and research purposes is gaining popularity. However, the relationship between in vivo ultrasound measurements and histologically determined (biopsy) values for skin thickness is poorly understood. This study investigates the influence of excision and biopsy processing procedures on skin thickness measurements.
Skin thickness was measured in six large white pigs (35kgs) from cranial and caudal locations on both flanks. Using ultrasound (22MHz hockey stick probe), skin was scanned in vivo, excised and rescanned ex vivo. Excised skin was processed for histological analysis using three techniques; (1) 10% formalin for 24-36 hours, (2) skin stretched to in vivo dimensions and pinned, 10% formalin for 24-36 hours, (3) snap frozen.
Mean shrinkage after excision was 12% for length and 19% for width. Ex vivo ultrasound measurements were 5% thicker than in vivo. The dermis and total skin were significantly thicker (p < 0.0001) after histological analysis of routinely processed formalin and frozen sections than in vivo. Mean relative thickening was: 54% (dermis) and 41% (total skin) for formalin-fixed; 66% (dermis) and 51% (total skin) for frozen-fixed sections. Pinning the sample to approximate in vivo size/tension during processing resulted in values most comparable to those in vivo.
The substantial disparity between in vivo and ex vivo thickness measurements highlights caution when absolute and to a lesser extent relative values for depth are compared. Overestimation of depth as a result of processing artefact must be considered by researchers examining skin samples.
Christine is a PhD student from the University of Queensland working with the Children’s Burns and Trauma Research group at the Lady Cilento Children’s Hospital. She commenced her studies in May 2014, prior to this she worked as a veterinarian in private practice for over 15 years. Her field of interest is the pathophysiology of burns. Her research examines the relationship between temperature, duration of contact and tissue injury severity for scald burns.