[Temporary skin replacement with lyophilized swine skin and foam substances--comparative experimental studies]

Using the skin replacement materials Corethium 2, Coldex, Epigard and SYSpur-derm, both fresh wound and wounds up to 6 days old were covered in rats. The histological work-up 1-7 days later showed material-dependent differences in the wound reaction. Under Corethium 2, a heavy layer of wound exudate formed on the first day both on fresh and granulating wound surfaces. Beneath this layer granulation tissue formed that was of regular thickness and well vascularized, filling the defect. Reepithelialization of the wound surface was not hindered by the material. In contrast, a strong connection was established between the wound base and the covering material when using the three foam substances Coldex, Epigard and SYSpur-derm, through the formation of granulation tissue. This process was dependent on the age of the wound. Thickening of the granulation tissue under the covering material was suppressed by the foam substances. Reepithelialization of the surface of the wound was disturbed by the growth of granulation tissue. The netlike structure of Epigard and the properties of the cover layer (fluid-resistant and protective against bacteria) make it possible for the granulation tissue to infiltrate evenly in the whole area of the wound covering and permit growth within the material right up to the surface. In addition to granulation tissue, epithelium also grows into the foam and spreads evenly. Epigard is suitable for long-term covering of large wounds. SYSpur-derm has a different fine structure than Epigard, which hinders the growth of granulation tissue, so that there are only cone-shaped connections between the wound base and the covering material. Rapid desiccation of the wound exudate cannot be prevented. Leukocytes and granulation tissue cannot spread in the foam. With SYSpur-derm an intermediate layer of wound exudate was observed more frequently than with Epigard. SYSpur-derm should be changed regularly in order to remove the detritus and exsudate from the wound. In comparison with polyurethane foam material the polyvinyl-alcohol foam (Coldex) was more complicated to handle, did not adapt as well to the wound, and dried up within a few hours. Between the base of the wound and Coldex, an intermediate layer often formed and, because of the rapid drying-out process, there was appreciably less infiltration with leukocytes and granulation tissue than with SYSpur-derm. With Coldex, as a rule the granulation tissue was more generously vascularized than in the other three materials.