Biomedical Engineering Reference
In-Depth Information
Table 5.1
Properties of allogeneic skin which make it the present gold standard
for temporary wound coverage (from Burd and Chiu, 2005)
1. The intact stratum corneum provides a barrier function which:
a. limits desiccation of the wound
b. limits evaporative water loss
c. reduces bacterial contamination
d. protects underlying viable tissue
e. limits exudative tissue fluid loss.
2. The biomechanical properties of the dermal component allows:
a. effective draping of the wound
b. permits movements of joints
3. The biochemical properties of the skin cause:
a. in the partial-thickness burn
i. reduced pain
ii. enhanced healing
iii. decreased scar
b. in full-thickness excised wounds
i.
promotes angiogenesis on the wound bed which aids subsequent
autograft take.
The use of allograft skin is beneficial in the treatment of large burns with or
without concurrent autografts. Allograft skin is used as a temporary dressing while
awaiting the healing of autograft donor sites between sessions of harvesting
(Herndon and Parks, 1986). In addition, allograft skin can be employed as a
biologic dressing pending definitive surgical coverage of deep full-thickness
burns or spontaneous healing of partial-thickness skin loss. Early excision and
grafting with allograft skin avoids mortality and morbidity caused by disseminated
burn wound sepsis, by reconstituting the protective barrier of skin against micro-
organisms. Allograft skin also reduces the pain of an exposed wound, decreases
evaporative water loss, improves re-epithelialization and leads to improved cosmesis
(Seah, 1992). The technique of covering burn wounds with widely meshed
autograft and then allograft, known as the 'sandwich technique', may improve
healing (Burke
et al
., 1974; Burke
et al
., 1975; Burke
et al
., 1976; Alexander
et al
.,
1981). In addition, the immunocompromised state of critically ill burn patients
may delay rejection for several weeks. Some authors employ a variation of the
sandwich technique by using cultured keratinocyte spray as well as meshed
autograft with allograft applied over both. The allograft acts as a temporary
dressing without vascularization, by providing a moist protective environment for
re-epithelialization underneath (Burd and Chiu, 2005).
Cuono and colleagues demonstrated an important potential use of allograft
tissue and an insight into the immunogenicity of allogeneic skin transplants. In an
attempt to provide durable wound coverage, they employed cryopreserved, acel-
lular allograft dermis as a substrate for cultured autologous keratinocytes in two
patients with extensive burns (Cuono
et al
., 1987). In both patients, burn wounds
were excised and covered with allograft skin. Once keratinocyte grafts were ready
