A skin graft is a medical procedure where healthy skin is taken from one area of the body and transplanted to cover a wound that is too large or too deep to heal naturally. This intervention becomes necessary when the skin damage, typically from a severe burn, has destroyed the body’s ability to regenerate its own surface layer. The goal of grafting is to provide a permanent protective barrier, reducing the risk of infection, minimizing fluid loss, and improving the long-term function and appearance of the healed area.
Understanding Burn Depth and Natural Healing
Burns are classified based on how deeply they penetrate the skin layers, determining the potential for natural healing. A superficial burn, similar to a mild sunburn, affects only the outermost layer, the epidermis, and typically heals rapidly within a few days without scarring because the underlying regenerative cells remain intact.
Partial-thickness burns extend into the dermis and are further categorized as superficial or deep. Superficial partial-thickness burns are characterized by blistering, but they retain enough dermal cells, such as those lining hair follicles and sweat glands, to re-epithelialize and heal within two to three weeks, usually with minimal scarring. Deep partial-thickness burns damage the deeper portion of the dermis, leaving fewer regenerative cells, which makes healing much slower and results in significant scarring.
Full-thickness burns, also known as third-degree burns, destroy all layers of the skin, including the epidermis and the entire dermis, often extending into the underlying fat. These wounds have no remaining skin cells capable of regeneration, resulting in a dry, often leathery appearance, and the area may have no sensation because the nerve endings are destroyed. A full-thickness burn will not heal on its own and will lead to severe contracture and scarring without surgical intervention. Fourth-degree burns are even more severe, extending into muscle, tendon, or bone, and require specialized surgical treatment.
Criteria Determining the Need for a Skin Graft
The decision to perform a skin graft is made by burn specialists based on several factors, with the primary consideration being the depth of the injury. Any full-thickness burn requires a graft because the destruction of the entire dermal layer means the wound lacks the cellular components necessary to close itself.
For deep partial-thickness burns, the size of the injury, measured as the Total Body Surface Area (TBSA) affected, plays a major role. For adults, burns exceeding a threshold of 20% TBSA necessitate grafting, and for children or older adults, this threshold is lower, typically around 10% TBSA. Grafting these large, deep wounds prevents excessive fluid loss, minimizes the risk of severe infection, and accelerates healing.
The location of the burn is also a significant factor. Burns that cross functional areas are often grafted to prevent severe scarring and contractures that would limit movement. These areas include:
- Hands
- Feet
- Face
- Perineum
- Major joints
A partial-thickness burn over a finger joint may be grafted to ensure the skin heals with enough flexibility to allow full range of motion.
Failure of a wound to heal within an expected timeframe is another criterion. If a deep partial-thickness burn does not heal after approximately two to three weeks, surgeons may elect to excise the damaged tissue and apply a graft. This reduces the risk of hypertrophic (raised) scarring and long-term functional impairment that occurs with prolonged open wounds.
Types of Skin Grafts and the Grafting Procedure
The most common method for permanent coverage is a Split-Thickness Skin Graft (STSG), which involves harvesting the epidermis and only a partial layer of the dermis. This technique is preferred because the donor site, frequently the thigh or buttocks, retains enough dermis to heal on its own, similar to a superficial abrasion, usually within two weeks.
The harvested STSG can be passed through a meshing machine to create a pattern of slits, allowing the graft to be expanded to cover a much larger area. Meshing results in a less cosmetic, web-like appearance and is more prone to contraction during healing. Once the burn wound bed is prepared by removing all non-viable tissue, the graft is applied, placed dermis-side down, and secured with staples, sutures, or specialized adhesives, followed by a dressing to ensure proper blood supply integration.
For smaller, cosmetically or functionally sensitive areas like the face or hands, a Full-Thickness Skin Graft (FTSG) may be used, which includes the entire epidermis and dermis. FTSGs provide superior color match, texture, and flexibility, and they contract much less than STSG during the healing process. However, the donor site for an FTSG leaves a full-thickness defect that cannot heal naturally and must be surgically closed with sutures, limiting the size of the graft that can be taken. Successful integration, or “take,” of any graft depends entirely on the recipient wound bed being well-vascularized, as the graft has no blood supply of its own and must receive nutrients from the underlying tissue.