Final answer:
The best management for a 5-year-old with 20% third-degree burns to the torso is debridement and a split thickness skin graft, as the burn cannot heal without medical intervention.
Step-by-step explanation:
A 5-year-old with 20% burns to the torso exhibiting fixed pigmentation and a white, dry appearance is likely suffering from a third-degree burn, which requires medical attention as it extends through the epidermis and dermis, destroying tissue.
The best management plan would include debridement to remove the necrotic tissue, followed by a split thickness skin graft, where skin is taken from an unaffected part of the body to cover the excised area. This approach promotes healing, as full-thickness burns cannot repair themselves due to the destruction of local tissues necessary for repair.