SKIN SUBSTITUTES IN BURN
MANAGEMENT (HISTORICAL PERSPECTIVE)
A) Overview
It has been recognized for centuries
(but not widely practiced) that wound care using a dressing with "skin
like" properties increases healing.
In order to better understand the
principles used in the development of the "optimum skin substitutes" ;
it is best to review the history of skin substitutes from antiquity to the
present.
The skin substitute restores the optimal
biological environment to a clean wound surface and protects the wound from
conversion. Thus, its use is relegated to the wound free of non viable tissue
and infection. The impetus for the use of temporary skin substitutes evolved
centuries ago for the acute partial thickness wound described as: redness
and blistering of the skin or withering without charring" Fabricius
Hildanus in his book on burns, DeCombustionbus 1607.
The use of skin substitutes for the
burn with "eschar formation and charring" (DeCombustionbus 1607) awaited
the recent advances in burn excision in which massive burn injuries commonly
survive.
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Evolution
of Skin Substitutes
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- temporary
skin substitutes
-help heal the partial thickness burn or wound
-close the excised wound till skin is available
- permanent
skin substitute
-to replace lost skin, epidermis alone or with dermis
-provide a higher quality of skin than a thin skin graft
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Ideal Properties
- firm
adherence to wound
- maintains
surface fluid layer
- avoids
desiccation
- barrier to
bacteria
- barrier to
evaporative water loss
- barrier to
heat loss
- decreases
pain
- durable,
flexible, non-toxic
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The evolution and current technology of
these temporary and permanent skin substitutes are very different and the new
technology will be discussed separately.
B) Xenograft
Use/Historical Perspective
The importance of wound closure in healing is
well documented beginning in Ancient Greece where burn wounds were occluded with
dressings rather than left open. The concept of occlusion is the first step
toward the concept of wound closure. As there were no synthetic materials
with the properties of skin, animal or reptile skin (Xenograft) was used to
mimic human skin.
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A Xenograft
is defined as a tissue graft transferred from one species to another.
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The use of animal and reptile skin as a
"skin substitute" dates back several hundred years. Frog and lizard
skin use was reported in the 16th and 17th century and
frog skin is used today in Brazil. The skin of a variety of animal species were
used beginning in the early 1900’s. Pig skin became popularized in the
1960’s and is currently the most common Xenograft used. The objective remains
to close the burn wound using a bi layer tissue like found with
skin. The inner (dermal layer) having surface collagen, can bind to the wound
surface if there is no non-viable tissue.
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Xenograft
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- initial use on partial and
full thickness burns
- current use only on
partial thickness wounds and burns and clean wound bed
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XENOGRAFTS:
(PAST AND PRESENT)
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Xenograft
Tissue Use in Burns
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| Frog |
1500
BC to present |
| Lizard |
1692
to present |
| Rabbit |
1906
to present |
| Dog |
1966
report |
| Pig |
1965
to present |
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Xenograft
= Non human
tissue
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Xenografts:
|
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Advantages:
- availability
compared to allograft
- bioactive
(collagen) inner surface
Disadvantages:
- cannot
obtain blood supply from wound and will slough
- potential
disease transmission
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CURRENT USE OF
PIGSKIN
Pigskin consists of a
thin dermal layer (epidermis removed) which is stored frozen to maintain
adhesive properties. The dermis is meshed to allow drainage to seep through
The pigskin dermis
adheres to a cleaned partial thickness burn - a dry gauze dressing follows
Click the Image to Enlarge
Pigskin covering a
larger partial thickness burn on the back. The thin dermal layer allows
visualization of the wound. Xenograft remains adherent while patient is turned.
A gauze dressing is added.
Click the Image to Enlarge
Meshed pigskin on clean
debrided wound at one week is beginning to dissolves no blood supply is provided
by the wound in contact with autograft or allograft
B) ALLOGRAFT TISSUE USE
Human tissue use as a skin substitute was
reported in the mid- 19th century but really became popularized
beginning about 1950. Cadaver skin and human amnion have and
continue to be used.
Allograft skin is used primarily to cover
excised full thickness wound as opposed to just partial thickness injuries.
Human amnion has been more commonly used on
partial thickness wounds or excised wounds.
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Allograft
Skin
Advantages
- bilayer
skin
- re-vascularizes
maintaining viability
- dermis
incorporates
Disadvantages
- epidermis
will reject
- difficult
to obtain and store
- risk of
disease transfer
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Beneficial
properties of viable cutaneous allograft
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- Prevents desiccation of
wound surface
- Promotes development of
granulation tissue
- Decreases evaporative
water loss
- Decreases heat loss
- Limits bacterial
proliferation
- Prevents exudative protein
and red cell loss
- Decreases wound pain
- Facilitates movement of
involved joints
- Protects exposed tendons,
vessels, and nerves
- Enhance healing of partial
thickness burns
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Allograft
(Amniotic Membrane)
Human amnion has fibronectin, a collagen,
lattice as well as an epithelial cell layer which can act as a barrier similar
to the epidermis while also adhering, although weak; to the burn. Amnion was
introduced in 1910 as a biologic dressing and was popular as a burn-wound
dressing until the 1960’s when alternatives like pigskin became more
available.
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Human
Amnionic Membrane
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Advantages
- acts like biologic barrier
- easy to apply, remove
- transparent
Disadvantages
- difficult to obtain,
prepare and store
- need to change every 2
days
- disintegrate easily
- risk of disease transfer
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Allograft
covering debrided burn
Note: Excellent adhesive
C)
CURRENT STATE OF SKIN SUBSTITUTE
