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Review
Skin Grafts
Jo Jo Leung, H.B.Mus, Faculty of Medicine (1T0), University of Toronto
Dr. Joel Fish, M.D., M.Sc, FRCSC, Chief Medical Officer, St. John's Rehab Hospital; Past Director, Ross Tilley Burn Unit, Sunnybrook
Health Sciences Centre; Associate Professor, Department of Surgery, University of Toronto; Attending Staff Surgeon, Sunnybrook
Health Sciences Centre
Abstract
Skin grafting is one of the most commonly used techniques of the plastic and reconstructive surgeon and
has progressed over the last century to the varied
methods and materials used today. Skin substitutes
range from wound dressings such as Biobrane,
Dermagraft, and cultured allogenic keratinocytes to
wound closure materials (including Integra,
Alloderm, and cultured autologous keratinocytes.)
The gold standard, however, remains the autologous
split thickness skin graft. In this paper, we review the
history of the skin graft, the physiology of graft take,
and current surgical indications, procedures, and
complications, as well as graft types and materials.
Introduction
S
kin grafting is one of the most commonly used techniques
of the plastic and reconstructive surgeon. The skin is the
body’s largest organ and serves many physiological functions. Damage to this organ can lead to high rates of morbidity
and mortality from infections and the inflammatory response. In
the last century, techniques of skin grafting have progressed
from relatively simple trial and error methods of skin transfer to
the varied surgical techniques, skin substitutes, and physiological understanding of wound healing used today.
History
The concept of skin transplantation through flaps and grafts
has long been in existence. The earliest use of skin grafting
reportedly took place 2500 years ago by the Hindus. In the 1500s,
Gaspare Tagliacozzi wrote a treatise describing a skin flap1 and in
1823, Buenger, a German physician, documented the first successful human skin graft, transferring skin from the buttock to the
nose.2 Around 1870, Reverdin, a surgical resident in Paris, and
George David Pollack, a British surgeon, separately reported
attempts at skin grafting.3 Pollock experimented with various
donor sources, including an unspecified human donor and then
himself. He went on to describe one of the earliest accounts of
transplant rejection. In 1872, Ollier experimented with split-thickness skin grafting (STSG) and in 1875, Wolfe first described fullthickness skin grafting.2
Plastic and reconstructive surgery saw an accelerated growth in
use at the beginning of the 20th century. Prior to WWI, only very
thin or full-thickness grafts were used.3 Blair and Brown documented successful split skin grafts and Padgett and Hood invent-
ed the dermatome, a device used even today to harvest large
grafts. In World War II, the injuries suffered by many soldiers,
especially those in the airforce, led to a boom in the range of plastic surgery techniques invented and refined; advances in burn
injury treatment were especially prominent. Skin grafting is also
notable as a model for describing the second set transplantation
rejection phenomenon, where the first graft sensitizes the recipient’s body to reject the second graft.
Graft Sources
Materials from skin grafts come from a variety of sources.
Biological grafts include: autografts, which are harvested from a
donor site on the patient, isografts from a genetically identical
donor (i.e. twins), allografts from another individual (e.g. cadaveric skin), and xenografts from an animal source. Prosthetic grafts
are manmade skin substitutes.4
Split Thickness versus Full Thickness
Skin grafts are either split thickness or full thickness. Split thickness skin grafts (STSG) contain the epidermis and varying thicknesses of dermis. Since blood and nutrients are initially supplied
to the graft by osmosis, the thinner the graft, the easier it is to
maintain (conversely, thicker skin grafts require a bigger blood
supply.) An important benefit of STSG is that once the epidermis
has regenerated (approximately 10 days), the donor site may be
re-harvested, a critical characteristic if a patient has a shortage of
healthy donor sites (e.g. post trauma.)2,3,4
STSG are indicated for large surface coverage, cavities, and
mucosal defects. They are commonly used for muscle flap coverage as well as skin flaps. Techniques of harvesting a STSG include
the knife or scalpel (e.g. Foulian, Weck or Blair) or dermatomes.
Figure 1. Graft using a dermatome.
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The knife is preferred for areas that are difficult to access or have
irregular borders. Dermatomes are used for large areas of consistent contour and thickness (e.g. thigh or back) and may be driven by air or electricity.2,3,4 (See Figure 1)
Physiology of Graft Take
Graft take occurs in four stages (see Table 1 below).
Table 1. Stages in Graft Take
Stage
Event
Imbibition
Day 0-3. The graft receives nutrients from the
plasma through direct contact
Revascularization
Day 3-7. Exact mechanism is unknown. Graft and
donor site regenerate or generate new blood
vessels, which anastomose and allow blood flow
to begin.
Regeneration
Dermal appendages and sweat glands regenerate.
Reinnervation begins and the graft takes on
recipient site sweating pattern.
Reinnervation
Graft takes on nerve pattern of recipient site.
Although STSG are reinnervated faster, FTSG
have a better final result.
the graft is kept moist and sterile.2 A stiff plastic backing may be
used to spread out the graft and to mesh if necessary.
Once the grafts have been obtained, the recipient site is prepared as needed – for example, temporary skin dressings are
removed and dead or unhealthy tissue debrided. Grafts are
applied on the tissue bed and may be attached using staples or
surgical glue.
Grafts may be meshed (See Figures 2 and 3). This maximizes
the area covered by a graft and minimizes the amount of donor
site needed. It allows the graft to better achieve the contour of the
recipient site, making for a better graft take and permitting fluid
drainage, thereby decreasing the risk of a hematoma or seroma.
However, the marks of meshing will remain, making it a technique
to be avoided on areas like the face and arms, where a more desirable cosmetic effect can be achieved by sheet graft. Another characteristic of meshing is that the graft is more likely to contract; this
effect may help shrink the wound, but is best avoided over joint
areas.4
Applications/Indications
Wounds that have skin loss close naturally by two main mechanisms: epithelial migration and wound contraction.
Contraction is a consequence of granulation tissue formation
and myofibroblasts, which allow the wound edges to tighten and
shrink together. This creates an area of tight skin called a contracture, which may be undesirable in areas that are highly visible or require mobility, such as the skin over joints. Further,
wounds closed through epithelial migration occur from the
wound edges, but lack the anchors, called rete pegs, that secure
epidermis and dermis so the tissue is easily avulsed.3 When these
natural processes are insufficient, the surgeon has the option of
a skin graft or flap.
Basic Surgical Procedure
Grafting takes place in several stages, often through multiple
operations. The exact plan of action depends on the sites chosen,
wound type, coverage needed, infection, patient’s medical condition, and other factors. Only when the plan is coordinated will
the operations begin. The following is an example of skin graft
harvest and placement, as performed by the authors while at the
Ross Tilley Burn Centre at Sunnybrook Hospital in Toronto,
Ontario. Many variations of this procedure exist.
To prepare the donor site, the surgeon chooses an area based
on availability of healthy skin, visibility of a scar, patient preference, etc. If the recipient site is above the clavicles, then the ideal
donor site is also from the “blush zones” above the clavicles. This
provides a closer colour and texture match for a better cosmetic
result.3,4
Operative sites are marked, prepared, and draped. The donor
site is injected with a tumescent solution containing saline to firm
and even out the skin and epinephrine to locally vasoconstrict and
decrease bleeding. If a dermatome is used, mineral oil is applied
and the dermatome is used to harvest the skin. Once obtained,
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Figure 2. Meshing device and graft.
Figure 3. Meshed graft.
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Skin Grafts
Complications and Failure
Grafts are susceptible to a variety of complications leading to
graft failure. Most commonly, these include hematoma, poor take
due to shearing forces, infections, and rejection.2,3,4
Hematomas can be prevented through use of meshing, as well
as proper and compressive dressings. Vacuum-assisted closure is
one method of achieving proper drainage and contact with the
wound bed. Elevation of the recipient site also aids in drainage.2,3,4
Infections are minimized through proper surgical and nursing
techniques and antibiotic prophylaxis, as indicated. Allografts and
other biological dressings are treated to maximize sterility and
decrease infection rates.3,4
One less encountered, but still common and easily avoidable
error is misplacing the graft dermis side up. Inspection will show
that the dermal side is shinier2 and the authors have found that an
easy way of distinguishing the correct side is to float the graft in
saline and observe the direction of curl; the dermal side will be
turned inwards.
Skin Substitutes
Figure 4. Hand with Biobrane.
The current ideal is to use an autologous skin graft, however,
depending on the patient’s condition, donor sites might not be
available. The patient will also have large areas of scarring. There
is a limited supply of allogenic grafts from cadavers and these will
always be rejected within weeks to months.1 Thus, prosthetic skin
substitutes are often used. There are two categories of skin substitutes – wound dressings and materials that are integrated as part
of wound closure (See Table 2).
Table 2. Skins Substitutes
Purpose
Wound Dressings
Wound Closure
Temporary cover; used
Integrated into the wound bed;
to protect the wound bed these materials also protect
and prepare it to receive
a permanent graft
and prepare the wound bed,
but some may function as the
permanent graft
Examples
Cadaveric grafts
Integra
Amniotic membranes
Alloderm
Biobrane
Autologous keratinocytes
Figure 5. Hand with Jelonet and graft.
Dermagraft
Allogenic keratinocytes
Wound Dressings
Wound dressings are designed for temporary coverage and are
used to protect and prepare the wound bed before the final skin
graft is placed. There are many types currently in use. Allogenic
cadaveric grafts are often used in Canada, but have limited availability and are subject to rejection.1 Amniotic membranes, taken
from the innermost layer of the amniotic sac, have been used
since 1910. Their effectiveness is similar to allografts, but they are
more fragile, are not integrated into the skin, and are suitable
mainly for shallow wounds.5
Biobrane is a bilaminate membrane of nylon mesh bonded to
a thin layer of silicone. The mesh contains porcine collagen peptides to aid in adherence and revascularization. As the wound
Figure 6. Hand healed.
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heals, Biobrane separates and is easily peeled off. It can be used
on the donor site to aid healing and is commonly used in
Canada.6 (See Figures 4, 5 and 6)
Dermagraft is a cryopreserved living dermal structure with
neonatal allogenic fibroblasts on an absorbable matrix of polyglycolic acid or polyglactin-910 (marketed as Vicryl or Dexon). The
fibroblasts secrete growth factors and dermal proteins, which stimulate ingrowth and epithelialisation.6 Dermagraft is not to be confused with Transcyte (formerly called Dermagraft TC, where TC
refers to temporary cover), consisting of fibroblasts on a nylon
mesh that is non-absorbable. Transcyte is not currently available
in Canada.5,6,7
Cultured allogenic keratinocytes secrete growth factors and
cytokines. After 7 days in culture, they no longer express MHC
class II and HLA class I antigens so there is no acute rejection.
However, these cells have a short life span, usually 1-6 weeks with
greater life spans related to a healthy dermis.6,7 These are not yet
available in Canada.
and costs decrease, we may someday see a shift in the preferred
materials for skin grafting.
Acknowledgements
The author wishes to thank the staff and patients of the Ross
Tilley Burn Centre for their wonderful teaching.
All photos courtesy of Dr. Joel Fish.
References
1.
2.
3.
4.
5.
6.
Wound Closure
Integra is one of the most widely used products for wound
closure and consists of two layers: a membrane of bovine
collagen and glycosaminoglycan and a silicone membrane. The
collagen is integrated to form a “neodermis”, which remains
while the silicon layer is removed and a STSG applied over the
neodermis.2,5,6,7 Integra is available in Canada.
Alloderm is treated human cadaveric skin from which “cellular and dermal components are removed” so that there is no
rejection. Its main function is to be a dermal regeneration template, similar to Dermagraft. Since it provides little barrier function, there is some debate over its classification as a skin substitute for closure or cover.6,7 It is used in Canada, albeit sparingly.
Cultured autologous keratinocytes are grown from the
patient’s own cells and grown in vitro to form sheets. Although
there is no rejection and only a small donor site is needed, such
a procedure is of limited use in trauma patients, since they take
several weeks to produce. The sheets are also very fragile and
may take weeks to months to develop firm anchors. Elastin production may take up to 4-5 years. These are available in
Canada.6,7
7.
Andreassi A, Bilenchi R, Biagioli, M, D’Aniello C. Classification and pathophysiology of skin grafts. Clinics in Dermatology. 2005 23:332-337.
MacFarlane DF. Current Techniques in Skin Grafting. Advances in Dermatology.
2006; 125-138.
Fisher JC, Dobke MK. Skin Grafting. In: Georgiade GS, Georgiade NG, Riefkohl R,
Barwick WJ, editors. Textbook of Plastic, Maxillofacial and Reconstructive Surgery.
2nd ed. Williams and Wilkins; 1992. p. 19-28
Chang EY. Grafts. In: Brown DL, Borschel GH, editors. Michigan Manual of Plastic
Surgery. Lippincott; 2004. p. 16-21.
Atiyeh BS, Hayek SN, Gunn SW. New technologies for burn wound closure and
healing - review of the literature. Burns 2005; 31:944-956.
Jones I, Currie L, Martin R. A guide to biological skin substitutes. British Journal of
Plastic Surgery 2002, 55:185-193.
Bar-Meir E, Mendes D, Winkler E. Skin Substitutes. Israel Medical Association
Journal. 2006; 8:188-191.
Future Direction
One of the main problems faced in biological skin substitutes is
the rejection phenomenon. There is work towards the development of cultured allogenic keratocyte sheets that are not rejected and become fully incorporated in the tissue. Research is also
ongoing in the area of molecular and genetic manipulation to
selectively maximize patients’ own beneficial growth factors
while suppressing unwanted inflammatory responses.5,6
Conclusion
Skin grafting is a well-established and fundamental technique in
the area of wound management and healing. Over the past century and a half, we have progressed from rudimentary trial and
error methods to the range of surgical techniques and skin substitutes used today. The gold standard, however, remains the
autologous split thickness skin graft. As technology progresses
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