Skin grafts - Biomaterials for Treating Skin Loss - page 73

but dessication and avascular necrosis inevitably occurs. Similarly, no immuno-
logic response develops to the xenograft tissue and no antidonor antibodies
develop in the recipient after usage (Bromberg et al ., 1965; Sokolic et al ., 1960;
Rappaport et al ., 1970; Miller et al ., 1961). The porcine skin is sloughed rather than
rejected, by the growth of complete epithelium beneath it (Chiu and Burd, 2005).
Similar to allograft skin, porcine skin can be either used fresh and is potentially
viable (refrigerated up to 30 days) (Rappaport et al ., 1970), or treated but rendered
non-viable, by lyophilization (freeze-drying) or chemical dehydration with glyc-
erol.
There are multiple uses of porcine skin. Given that porcine skin does not
incorporate into wound beds it can be used as a temporary biologic dressing over
wounds expected to heal without skin autografts, including partial thickness burns
(Still et al ., 1996), split thickness skin graft donor sites (Chang et al ., 1973;
Aronoff et al ., 1976), or exfoliative conditions (such as toxic epidermal necrolysis)
(Heimbach et al ., 1987; Honari et al ., 2001; Imahara et al ., 2006). When used over
open wounds, the porcine skin must be inspected daily to assure adherence. Similar
to allograft 'sandwich technique', porcine xenograft can be placed over widely
meshed autograft in the treatment of extensive burns, thereby reducing dessication
over the wound interstices and subsequent scarring (Burd and Chiu, 2005).
There are multiple reports in the literature attesting to the benefits of porcine
skin in the treatment of extensive wounds, including a decrease in healing rates for
partial thickness burns and granulating wounds (Chang et al ., 1973; Pruitt, 1997),
a reduction in pain when placed over burns (Pruitt and Levine, 1984, Aronoff et al .,
1976; Lee, 1972; Rappaport et al ., 1970) and a decline in heat, fluid, protein and
electrolyte loss (Elliott and Hoehn, 1973; Pruitt and Levine, 1984). Furthermore,
porcine skin provides a physical protective layer for a re-epithelializing wound
(Zawacki, 1974; Pruitt and Levine, 1984) and it decreases bacterial overgrowth
(Sokolic et al ., 1960; Burd and Chiu, 2005; Pruitt and Levine, 1984). As mentioned
before, data from our own institution demonstrates the effective use of porcine
xenograft as a temporary biologic dressing in the treatment of toxic epidermal
necrolysis, when employed to protect the dermis until re-epithelialization occurs
(Imahara et al ., 2006). The major disadvantages affecting the widespread use of
porcine skin are bacterial infection, cost and the theoretical risk of zonoses such as
meningitis, brucellosis, hydatidosis, cysticercosis and influenza (Pirnay et al .,
1997). However, these risks may be abated if the pigs are raised in a clean
laboratory environment.
5.6 Future trends
The continual demand for techniques and products to aid in the rapid and durable
closure of extensive burns and wounds, while re-establishing normal skin archi-
tecture remains a challenge. Important barriers to advances in this area of plastic
surgery remain an evolving understanding of the allogeneic transplant immunology,