VALIDATION OF A VERTICAL PROGRESSION PORCINE BURN MODEL

Abstract

Background

A major potential goal of burn therapy is to limit progression of partial to full-thickness) burns. To better test therapies, we developed and validated a vertical progression porcine burn model in which partial thickness burns treated with an occlusive dressing convert to full thickness burns that heal with scarring and wound contraction.

Methods

Forty contact burns were created on the backs and flanks of two young swine using a 150 gm aluminum bar preheated to 70°, 80°, or 90°Celsius for 20 or 30 seconds. The necrotic epidermis was removed and the burns were covered with a polyurethane occlusive dressing. Burns were photographed at 1, 24, and 48 hours as well as at 7, 14, 21, and 28 days post injury. Full thickness biopsies were obtained at 1, 4, 24, and 48 hours, as well as at 7 and 28 days. The primary outcomes were presence of deep contracted scars and wound area 28 days after injury. Secondary outcomes were depth of injury, reepithelialization, and depth of scars. Data were compared across burn conditions using ANOVA and χ ² tests.

Results

Eight replicate burns were created with the aluminum bar using the following temperature/contact-time combinations: 70/20, 70/30, 80/20, 80/30, and 90/20. The percentage of burns healing with contracted scars were 70/20–0%, 70/30–25%, 80/20–50%, 80/30–75%, and 90/20–100% (P=0.05). Wound areas at 28 days by injury conditions were 70/20–8.1 cm ², 70/30–7.8 cm ², 80/20–6.6 cm ², 80/30–4.9 cm ², and 90/20–4.8 cm ² (P=0.007). Depth of injury judged by depth of endothelial damage for the 80/20 and 80/30 burns at 1 hr was 36% and 60% of the dermal thickness respectively. The depth of injury to the endothelial cells 1 hour after injury was inversely correlated with the degree of scar area (Pearson’s correlation r=−0.71, P<0.001).

Conclusions

Exposure of porcine skin to an aluminum bar preheated to 80°C for 20 or 30 seconds results initially in a partial thickness burn that when treated with an occlusive dressing progresses to a full thickness injury and heals with significant scarring and wound contracture.