Wound Grafts

Excerpt

Skin grafting is a procedure that is essential to reconstructive surgery for patients who have suffered burns, traumas, and non-healing or large wounds. This skill is necessary to provide improved quality of life for patients with significant wounds and extensive burns. Even more important than cosmesis is reestablishing the continuity of the skin to provide protection for the body.

Xenografts are harvested from different species, the most common of these are porcine, and they are used as temporary bandages on wounds. They will not revascularize. The next type of graft is an allograft. These are cadaveric skin grafts taken from organ donors. They are ideal biologic dressings for patients who need resuscitation and continued debridements of the wound bed to ensure that it will accept an autograft. Allografts will undergo revascularization in the initial period. The body’s host defenses will eventually reject both of these types of grafts. Autografts are skin grafts that are taken from the patient. In this case, antigenic compatibility is not an issue and will allow for permanent skin healing. This is often the final stage of wound healing after extensive debridement to ensure that the wound bed is healthy.

In addition to the different types of skin grafts available, there are also skin substitutes. One of the major limitations of skin substitutes is the associated cost. A majority of the available products provide either epidermis or dermis. The lack of dermis and subcutaneous tissue in epidermis substitutes results in a lack of elasticity and strength. Dermal layer products do not have epidermal coverage and depend on a long period of epidermal in-growth to effectively cover the wound.

Currently, the most commonly used skin substitute is a cultured epidermal autograft (CEA). A full-thickness skin biopsy from the patient is obtained, and the keratinocytes are then used to develop a graft by expanding the cells into a neoepidermis. These grafts are even more delicate than autografts, they are extremely susceptible to shear injuries, and after they are incorporated, they remain fragile and require longer periods of immobility to ensure they are not damaged.

Dermal substitutes are composed of a matrix of glycosaminoglycans and collagen. Alloderm is a popular dermal substitute that is obtained from cadaveric allografts. It has had good cosmetic outcomes in several studies with small populations, but extensive costs have limited widespread use and studies.

A newer therapy product requires a biopsy from the dermal-epidermal junction to produce autologous cells (keratinocytes, fibroblasts, melanocytes) that are delivered in a suspension. This suspension is then applied to the wound by spraying it on the wound. Integra is a bilayer product composed of bovine collagen and glycosaminoglycans with a silicone sheet that acts as an epidermis for 2 to 3 weeks while the allograft degradation matrix occurs. As neovascularization occurs, the matrix degrades and is replaced by a collagen matrix produced by the patient's body. The silicone is then removed and replaced with a split-thickness skin graft (STSG). This product is used to reduce the amount of skin surface area needed for the eventual STSG. Several other options are currently being developed and are under investigation. These products are accompanied by a high cost, and more research is necessary to confirm good cosmetic outcomes and long-term wound coverage.