Second and third-degree burn injuries and full-thickness burns require skin graft surgery to replace scarred tissue and help the skin heal.   Second-degree burns affect the outermost layer of the skin, the epidermis, while third-degree burns can also damage muscles, tendons, nerve endings and bones. In these cases, skin grafts can be transplanted into the injured areas over the surgically-cleaned wound to help it heal.   A first-degree or superficial burn may heal naturally, but that depends on the patient’s overall medical condition.