Advances of Wound Coverage - Dermal Template Transplantation

Abstract

The function and appearance of grafted skin over the recipient wound is depended upon the thickness of the donor skin. In extensive burn injury, the donor skin is not always available in the acute stage and usually patient needs a temporary skin substitute to cover the wound, the better long enough until the surgeon has chances to reharvest the same donor site. To use very thin skin for grafting can ensure successful skin graft take and permit faster donor site healing but leave recipient wound contraction. The harvest thick skin for grafting will produce deep wound over donor site and induce infection, scarring, blistering, and pigmentation. During the wound coverage, if we can support additional dermal template other than the autologous dermis may promote prompt and perfect quality healing for recipient wound. In 1995 Alloderm (Life Cell Inc., the Woodland, Texas) was successfully applied to cover full-thickness burn wound with applied a piece of meshed thin split-thickness skin autograft. Since then, the Alloderm had been utilized as a substitute to cover full-thickness burn wound, release scar, repair the nasal septum and for lip agumentation. Our personal experiences also confirm with same result except the meshed skin mark is always unacceptable by most of the patients. Since 1980, Yannas and Burke began to design a bilayer artificial skin, finally named as ‘Integra’, composed of a temporary silastic epidermis and a porous collagen-chondroitin 6-sulfate fibrillar dermis and applied it to cover extensive burn wound. The neodermis was then covered by a piece of ultra thin split-thickness skin after the silastic epidermis was removed. In 1988, Heimbach had reported a multi-center clinical trial by using Integra to cover extensive burn wound and showed that the Integra could provide a vascularized dermal template to take ultra thin split-thickness autologous skin graft. Their long term follow up study also showed that the grafted wound demonstrated minimal scar contraction with rare complications. In 1998, Pandya had provided that Integra can provide a stable environment to support cultured epidermal keratinocytes growth for 1 year firmly (18). Decontaminated pig skin had been used as a biological dressing for burn wound coverage since 1966. In 1984, the porcine dermis had been utilized as a dura substitute, urinary bladder sling, to repair orbit defects and inguinal hernias with acceptable biocompatibility. In 1995, Livesey investigated the potential use of acellular porcine dermis as an allograft combine with a meshed split-thickness autograft can successfully to cover a full-thickness skin wounds in pig model. In 1995 we used meshed porcine dermis combined with a widely expanded mesh autologous thin split-thickness skin (ASTS) graft for a rat wound. Wounds were studied by clinical inspection for texture and contraction, and by histological and immuno-fluorescent techniques. The results showed that the integrity of this complex skin graft was maintained for 4 months with acceptable wound contraction. The cultured epidermal autograft (CEA) was first described in 1984 for cover extensive bum wounds. Unfortunately the CEA showed poor adhesion to recipient wound due to inadequate formation of rete ridges between neoepidermis and wound bed. Evidences had indicated that the formation of rete ridge from CEA needs a recipient wound with dermal-like matrix, such as collagen-glycosaminoglycan (C-GAG), allodermis, autodermis or, must apply fibrin glue to create tight interface integration. In the recent 20 years, because of shortage of the allogenic skin substitute, we had produced 4 generations of pig skin to help for high quality wound healing, they are: 1. Regular porcine skin, 12-15/1000 inches, epidermis / dermis, for temporary wound coverage. It is usually be removed or sloughed by 7-10 days after tansplantation.2. Acellular porcine dermis, 20/1000 inches, when transplantation, it usually combined with a sheet of autologous thin skin overlay. It is a permanent graft.3. Silicon-Acellular Porcine Dermis (SAPD), need 2-stage procedures a. Thin SAPD - temporary / 4-6 weeksb. Thick SAPD - permanent, need autologous STSG / CEA for wound coverage in the second procedure at day 10-14. The safety of using the porcine products had been discussed in the past. In 1993, there is an occasion to developed lymphocytic meningitis with culture negative y using of a porcine dermis implant to repair an operative dura defect, which was considered a hypersensitivity reaction to the porcine dermal implant. The existence of the porcine endogenous retorovirus (PERV) DNA during transplantation of porcine products had been always be raised, and will be discussed.