15-11-2012, 05:01 PM
Classification of flap
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When a deformity needs to be reconstructed, either grafts or flaps can be
employed to restore normal function and/or anatomy. For instance, when
wounds cannot be closed primarily or allowed to heal by secondary
intention, either grafts or flaps can be used to close an open wound.
Grafts — Grafts are harvested from a donor site and transferred to the
recipient site without carrying its own blood supply. It relies on new blood
vessels from the recipient site bed to be generated (angiogenesis).
I. SKIN GRAFTS
A. Thickness
1. Full thickness — Full thickness skin grafts (FTSGs) consist of the entire
epidermis and dermis
2. Split thickness — Split thickness skin grafts (STSGs) consist of the
epidermis and varying degrees of dermis. They can be described as thin,
intermediate,or thick
3. Harvested using a dermatome or freehand
B. Donor site
1. Full thickness — The full thickness skin graft leaves behind no epidermal
elements in the donor site from which resurfacing can take place. Thus, the
donor site of a FTSG must be closed. It must be taken from an area that
has skin redundancy. It is usually harvested with a knife between the
dermis and the subcutaneous fat.
2. Split thickness — The split thickness skin graft leaves behind adnexal
remnants such as hair follicles and sweat glands, foci from which epidermal
cells can repopulate and resurface the donor site. It is usually harvested
with either a special blade or dermatome that can be set to a desired
thickness.
C. Recipient site
1. Full thickness — Full thickness skin grafts are usually used to resurface
smaller defects because they are limited in size. It is commonly used to
resurfacedefects of the face. It provides a better colorconsistency, texture,
and undergoes less secondary contraction.
2. Split thickness — Split thickness grafts are usually used to resurface
larger defects. Depending on how much of the dermis is included, STSGs undergo secondary contraction as they heal
D. Survival
1. Full thickness and split thickness skin grafts surviveby the same
mechanisms
• Plasmatic imbibition — Initially, the skin grafts passively absorbs the
nutrients in the wound bed by diffusion
• Inosculation — By day 3, the cut ends of the vessels on the
underside of the dermis begin to form connections with those of the
wound bed
• Angiogenesis — By day 5, new blood vessels grow into the graft and
the graft becomes vascularized
2. Skin grafts fail by four main mechanisms
a. Poor wound bed — Because skin grafts rely on the underlying
vascularity of the bed, wounds that are poorly vascularized with bare
tendons or bone, or because of radiation, will not support a skin graft
b. Sheer — Sheer forces separate the graft from the bed and prevent the
contact necessary for revascularization and subsequent “take”
c. Hematoma/seroma — Hematomas and seromasprevent contact of the
graft to the bed and inhibit revascularization. They must be drained.
d. Infection — Bacteria have proteolytic enzymes that lyse the protein
bonds needed for revascularization. Bacterial levels greater than 105are
clinically significant.
E.Substitutes
1. Allograft/Alloderm — Cadaveric skin or dermis
2. Xenograft — Skin from a different species, ie pig skin
3. Synthetic — Biobrane, Integra