Permanent wound covering

Autograft is skin taken from the person burned, which is used to cover wounds permanently. Since the skin is a major organ in the body, a autograft is essentially an organ transplant. Autograft is surgically removed using a dermatome (a tool with a sharp razor blade). A dermatome sheers the donor skin off the body. Only the top layer of skin is used for donor skin. Donor skin is taken at such a depth where the site will heal on its own, very similar to a second degree burn. There are two types of autografts used for permanent wound coverage: sheet grafts and meshed grafts.

Sheet graft is piece of donor skin removed from an unburned area of the body, a process called "harvesting the donor." The size of the donor skin that is used to patch a burned area is about the same size as the burn wounds. The donor sheet is laid over the excised wound and stapled in place. The donor skin used in sheet grafts does not stretch; it takes a slightly larger size of donor skin to cover the same burn area because there is slight shrink after harvesting. When the body surface area of the burn is large, sheet grafts are saved for the face, neck and hands, making the most visible parts of the body appear less scarred. When a burn is small and there is plenty of donor skin available, a sheet graft is usually used to cover the entire burned area. The disadvantages of sheet grafts are that small areas of graft might be lost from build up of fluid (hemotoma) under the sheet right after surgery. Sheet grafts also create a larger donor site than meshed skin. A sheet graft is usually more durability and scars less.

Meshed skin grafts Very large areas of open wounds are difficult to cover because there might not be enough unburned donor skin available. In these large wounds it is necessary to enlarge donor skin to cover a larger body surface area. Meshing is a means to enlarge donor skin. Meshing involves running the donor skin through a machine that makes small slits, which allows expansion similar to that in fish netting. In a meshed skin graft, the skin from the donor site is stretched to allow it to cover an area larger than itself. The size of the mesh varies in ratios from 1:1 to 1:4. A 1:1 mesh has small slits that allow the donor skin to expand one times its original size. Likewise, a 2:1 mesh has slightly larger slits that allow the donor to be enlarged two times the size of the skin that has been harvested. Most donor skin is meshed at a 1:1 or 1:2 ratio because the larger the mesh the more fragile the graft. No matter what size meshing is used, healing occurs as the spaces between the mesh, called the intricities, fill in with new epithelial skin growth. The disadvantages of meshing are that it is a less durable graft than a sheet graft and that the larger the mesh, the greater the permanent scarring. Meshing serves two purposes: it allows blood and body fluids to drain from under the skin grafts, preventing graft loss; and it allows the donor skin to cover a greater burned area because it is expanded.

Allograft, cadaver skin or homograft is ordered from the local skin bank. Xenograft, or animal skin, is ordered from a medical supply company. Autograft is surgically removed from the patient using a dermatome.

Portions of this text courtesy: Severe Burns by Andrew M. Munster, M.D. and Burn Care and Rehabilitation Principles and Practice by Reginald L. Richard and Marlys J. Staley.