Split thickness skin grafts
Also known as thiersch graft,split-thickness grafts consist of epidermis and a variable thickness of dermis. Thinner grafts (<0.016 in.) have a higher rate of engraftment, whereas thicker grafts, with a greater amount of dermis, are more durable and aesthetically acceptable. Common donor sites are the thigh, buttock, and scalp.
Full thickness skin grafts
Also known as Wolfe graft ,full-thickness grafts include epidermis and a full layer of dermis. Common donor sites include groin and postauricular and supraclavicular sites, but the hypothenar eminence and instep of the foot can also be used. The donor site is usually closed primarily. These grafts are generally used in areas for which a high priority is placed on the aesthetic result (e.g., face and hand).
Thinner grafts have greater secondary contraction and do not grow commensurate with the individual. They have fewer adnexal cells and therefore have variable pigment, less hair, and less sebum, with a proclivity toward dryness and contractures. Full-thickness grafts, with more dermis and the requisite adnexal structures, exhibit less contraction and better cosmesis.
Grafts can be meshed in expansion ratios from 1.5:1 to 6:1. Meshing a graft allows coverage for a wider area using the same-size donor site and decreases the risk of serous fluid accumulating under the graft without a method of egress. The interstices are covered within 1 week by advancing keratinocytes. However, because the entire area is not covered by dermis, meshed grafts are less durable, and the meshing pattern remains after healing, making them inappropriate for aesthetically important areas, such as the face.
Factors affecting graft take
Initial metabolism is supported by imbibition or diffusion of nutrients from the wound bed. Revascularization occurs between days 3 and 5 by ingrowth of recipient vessels into the graft (inosculation).
Therefore, for a graft to take, the bed must be well vascularized and free of infection, and the site must be immobilized for a minimum of 3 to 5 days. Prevention of shear forces is particularly important during this period of inosculation.
Although bare bone and tendon do not engraft, periosteum and peritenon can support skin grafts, especially if they are first left to form a layer of granulation tissue. Graft failures are most often the result of hematoma, seroma, or shear force prohibiting diffusion and vascular ingrowth.