Wound Grafts

Nonhealing wounds affect millions of people annually in the United States and approximately 1% of the global population, significantly impacting the quality of life and healthcare resources. With an aging population, the prevalence of chronic wounds is expected to rise worldwide. Loss of skin integrity due to infection, burns, or trauma leads to substantial morbidity and mortality, with burns alone causing around 180,000 deaths globally each year. Wound coverage is crucial to minimize fluid loss, prevent infection, and alleviate pain. Skin grafting is vital in restoring tissue continuity for patients with burns, trauma, or chronic wounds. Key outcomes include graft survival, mechanical function, sensory restoration, cosmetic appearance, and overall patient satisfaction. Skin grafting has evolved to treat surgical defects and chronic wounds, including venous and diabetic ulcers that fail to heal over several months. By covering wounds, grafting reduces infection risk and creates a moist, vascularized environment conducive to healing. Key principles in skin grafting include thorough debridement of nonviable tissue and adequate coverage of exposed areas. Various graft types and techniques are available, primarily autografts, allografts, and xenografts. Autografts are harvested from the patient, allografts come from cadaveric donors, and xenografts are derived from animal tissue. Porcine xenografts are commonly used for temporary wound coverage, though they do not revascularize. Allografts, obtained from cadaveric skin, serve as temporary biological dressings, particularly for patients requiring resuscitation and debridement before autografting. These grafts stabilize patients without additional donor sites but pose disease transmission, rejection, and limited availability risks. Recently, allografts have been explored as permanent grafting options due to their ability to undergo revascularization. Autografts, taken from the patient's skin, eliminate antigenic compatibility concerns and preserve native skin elements. These grafts are typically placed after extensive wound debridement to ensure an optimal wound bed. Because they are completely separated from their donor site, autografts rely on capillary ingrowth for survival. Full-thickness autografts include both the epidermis and dermis, whereas split-thickness grafts contain only a portion of the dermis. Split-thickness grafts are ideal for poorly perfused areas, such as joints and nerves, due to their lower vascular requirements, while full-thickness grafts need a robust blood supply. Split-thickness grafts can also cover larger areas and allow for repeated harvesting from the donor site. For patients with extensive skin loss, autograft harvesting may not be feasible due to insufficient donor tissue. In such cases, alternative grafts are necessary. Composite grafts incorporate additional tissues like cartilage, providing deeper coverage for complex wounds. Bioengineered skin substitutes function as synthetic skin equivalents and are available in multiple formats, including split-thickness, full-thickness, autologous engineered material, and acellular dermal grafts. Options such as acellular dermal allografts and allografts treated with antibiotic ointments expand treatment possibilities. However, most bioengineered skin substitutes provide dermal or epidermal coverage but lack the elasticity and strength of native skin. Dermal substitutes rely on epidermal ingrowth to complete wound closure. One of the most commonly used skin substitutes is the cultured epidermal autograft. This process involves taking a full-thickness skin biopsy from the patient, isolating keratinocytes, and expanding them into a neoepidermis. However, these grafts remain fragile, are prone to shear injuries, and require extended periods of immobility for successful integration. Dermal substitutes comprise a matrix of glycosaminoglycans and collagen and provide good cosmetic outcomes, but their high-cost limits widespread use. Recent innovations in skin grafting include techniques that use dermal-epidermal junction biopsies to generate keratinocytes, fibroblasts, and melanocytes, which are then sprayed onto the wound. Another emerging product is a bilayer structure made from bovine collagen and glycosaminoglycans supported by a silicone sheet. This temporary epidermal substitute degrades as neovascularization occurs, allowing an autologous collagen matrix to replace it. Once the wound bed contracts, the silicone layer is removed, and a split-thickness graft is applied. While promising, many advanced products are costly and require further research to optimize their efficacy and accessibility.