Biomedical Engineering Reference
In-Depth Information
elements, is best replaced with contralateral eyelid skin; whereas the skin of the
nose is thick and high in glandular elements, and it is better covered with thicker
skin of the nasolabial fold, supraclavicular, or anterior auricular area. Common
donor sites in hand surgery include the hypothenar, wrist crease and elbow crease
areas. Full-thickness grafting is preferable for most wounds in children, given that
the grafts will grow with the growing child and reduce the risk of scar contracture
(Baran and Horton, 1972). Defects on the face are frequently closed by local flaps
or full-thickness skin grafts. When skin grafts are used on the face, they should be
harvested from the 'blush' zone where color match is the best. The blush zone
comprises harvest sites above the shoulders, specifically the neck and supracla-
vicular area (Paletta
et al
., 2006; Valencia
et al
., 2000).
Autologous split-thickness skin grafting is the most commonly practiced form
of tissue transplantation in plastic surgery. Split-thickness skin grafts can be of
different thicknesses depending on the level of harvest through the dermis.
Advantages include a large area of available donor sites and better engraftment
rates, given that the metabolic activity of partial thickness grafts is less than their
full-thickness counterparts. However, split-thickness grafts are more likely to
result in wound contraction, hypertrophic scarring, pigment irregularities and are
more susceptible to trauma (Rudolph and Klein, 1973).
Split thickness skin grafts can be taken from any area of the body, including the
scalp (Fig. 5.2). In general, epithelial cells within epidermal appendages, such as
hair follicles and sweat glands, regenerate a split thickness skin graft donor site
within 7-21 days. Despite their ability to heal, donor sites frequently demonstrate
scarring and discoloration. Therefore, when possible, split graft harvest sites
should be hidden by current clothing styles, including most commonly, the thigh,
trunk and buttocks. In addition, the thickness of the donor skin is important in
choosing a harvest site. Skin is typically thin in infants and the elderly. Men
typically have thicker skin than women regardless of anatomic site. Skin is usually
thicker on the trunk and thighs and thinnest on the eyelids and postauricular areas.
Skin grafts can be applied as sheet (or unmeshed) grafts, or they can be meshed
at ratios ranging from 1:1 to 4:1. Meshing allows the egress of serum and blood
from wounds, thereby minimizing the risk that hematomas or seromas will form
that could compromise graft survival. In addition, meshed grafts can be expanded
or stretched to cover larger surface areas. When grafts are meshed at ratios of 3:1
or higher, allograft skin or another biologic dressing can be applied over them to
prevent the interstices from becoming desiccated before they close (Herndon and
Parks, 1986). Because of the lack of dermis in the interstices, widely expanded
meshed skin grafts always scar and contract, require longer healing times and
result in permanent unattractive mesh marks.
Sheet grafts should be used on the face, the neck, the hands and, whenever
possible, on the forearms and the legs. In these exposed areas, the superior
cosmetic and functional results obtainable with sheet grafts make such grafts more
desirable. Because sheet grafts have no interstices, they must be closely monitored
