When the amount of skin loss continues to be too great to allow adequate replacement with skin autografts, it might be necessary to use tissue-engineered skin substitutes. Skin substitutes are created to be left in place for long periods of time, and may be autologous, allogeneic, xenogeneic, or recombinant. They are able to either be used for wound coverage or wound closure.
Materials meant for wound coverage provide a barrier against infection, control water loss, and create an environment ideal for epidermal regeneration. Materials used for wound closure restore the epidermal barrier and become incorporated into the healing wound.
Skin substitutes used for wound coverage include Biobrane, TransCyte, cultured epidermal allogeneic keratinocytes, Dermagraft and Apligraf.
Biobrane is a bilaminar material made from nylon mesh bonded to a thin, semipermeable silicone membrane and used like a temporary skin replacement for superficial partial-thickness burns or skin graft donor sites. It eliminates the need for dressing changes and cuts down on the length of inpatient treatment.
TransCyte is Biobrane with the addition of neonatal fibroblasts seeded towards the collagen-coated nylon mesh. The advantages are similar to Biobrane, but TransCyte is considerably more expensive. Cultured allogeneic keratinocytes are obtained from neonatal foreskin or elective surgical specimens, and are used to cover burn wounds, chronic ulcers and skin graft donor sites.
While they don't achieve wound closure, they are able to survive up to 30 months and produce growth factors that facilitate host dermal and epidermal cell proliferation and differentiation, but they are thin, fragile and require meticulous wound care to outlive.
Apligraf and Dermagraft are multilaminar materials made to overcome the fragility of cultured allogeneic keratinocytes. Apligraf is a type I bovine collagen gel with living neonatal allogeneic fibroblasts overlaid by a cornified epidermal layer of neonatal allogeneic keratinocytes, which is accustomed to treat chronic ulcers, pediatric burns, epidermolysis bullosa and full-thickness wounds from Mohs' surgery pending definitive repair.
Dermagraft is really a cryopreserved dermal material comprised of neonatal allogeneic fibroblasts on a polymer scaffold, also it stimulates ingrowth of fibrovascular tissue in the wound bed and reepithelialization from the wound edges. It is accustomed to promote healing of chronic lesiongs and also to replace lost dermal tissue beneath meshed split-thickness skin grafts on full-thickness wounds.
Skin substitutes used for wound closure include Alloderm, Integra and cultured epithelial autografts.
Alloderm is acellular deepithelialized human cadaver dermis, which is used like a dermal graft in full-thickness or deep partial-thickness wounds. A STSG must be placed over Alloderm in a one- or two-stage procedure.
Integra is really a bilaminar skin substitute comprised of a cross-linked bovine collagen-glycosaminoglycan matrix coated with silicone elastomer barrier on one side. Integra is used in a two-stage procedure, in which a thin split-thickness skin graft is applied in the second stage following the silicone "epidermis" is taken away. It is very reliable, with good elasticity and cosmesis, and safe of infection, however it requires two operations and it is expensive.
Epicel, or cultured epithelial autografts were developed in the 1970s, and have been used for burns, chronic leg ulcers, giant pigmented nevi, epidermolysis bullosa and large regions of skin necrosis. A one square centimeter skin harvest is expected to develop to one square meter in 21 days. Cultured epithelial autografts must be applied on a wound bed with granulation tissue or muscle fascia for proper take.
Sheets are fragile, however, and frequently result in friable, unstable epithelium that spontaneously blisters, stops working, and contracts long afterwards application. Cultured epithelial autografts will also be very sensitive to infection and are only in a position to tolerate maximum bacterial counts of 100-1000/cm2, compared to 10,000-100,000/cm2 for standard split-thickness skin grafts. Finally, cultured epithelial autografts are extremely expensive.
Over time, the vacuum-assisted closure (VAC) device is gaining a reputation since the ultimate bolster dressing. The VAC bolster dressing consists of a sponge cut in the form of the graft, and then sealed and placed to 75-125 mmHg continuous suction. Usually, an intervening layer such as Conformant or Adaptik may be placed between your skin graft and VAC to prevent the graft from lifting from the bed once the dressing is removed. We now have found that the VAC promotes graft adherence towards the recipient bed and removes any accumulating serous fluid or blood. Once the VAC is used correctly, STSG take will approach 100%.
Our website is not responsible for the information contained by this article. Webworldarticles.com is a free articles resource thus practically any visitor can submit an article. However if you notice any copyrighted material, please contact us and we will remove the article(s) in discussion right away.
This article was sent to us by:
Linda Campbell at
02102011
1. What is lumpectomy and how is it performed
All articles in this directory are property of their respective authors. Additionally, read our Privacy Policy
© 2010 WebWorldarticles.com - All Rights Reserved. Partners: Gunblade Saga