Comparison of Native Porcine Skin and a Dermal Substitute Using Tensiometry and Digital Image Speckle Correlation

Dermal substitutes are currently used in plastic surgery to cover various soft tissue defects caused by trauma, burns, or ablative cancer surgery. Little information is available on the biomechanical properties of these dermal substitutes after adequate incorporation as compared to normal skin. Determining parameters such as tensile strength in these skin substitutes will help us further understand their wound healing properties and potential in developing artificial tissue constructs. We hypothesize that a dermal substitute has a lower stress-strain curve and altered stress-induced deformation quantified with tensiometry and digital image speckle correlation (DISC) analysis. Two separate 5 x 10-cm full-thickness wounds were created on the dorsum of 3 female swine. Fibrin glue was applied before either a full-thickness skin graft (FTSG) or application of artificial dermal matrix. On day 42, cultured autologous keratinocytes were applied as a cell sheet to the wound covered with Integra. On day 56, the wounds were fully excised and fresh tissue specimens, including normal skin, were stored in a physiological solution and prepared for analysis. Rectangular samples were excised from the center of each specimen measuring 4 x 4 x 30 mm. Using a tensiometer and DISC analysis, we evaluated the tensile strength of 3 different groups of skin, namely, normal, FTSG, and Integra. There is a significant difference between the Integra specimen when compared to normal skin and FTSG. We found a minimal difference in the stress-strain curves of the latter two. Integra alone shows plastic deformation with continued stretching before ultimate midline fracture. There is significant change between the Young's moduli of the normal skin and the Integra, whereas there is little difference between the FTSG and the normal skin; DISC confirms this analysis. The normal skin and FTSG show a convergence of vectors to a linear plane, whereas Integra shows very little organization. Using 2 different methods of analysis, we have shown a dermal substitute does not display similar biomechanical properties after adequate incorporation. These major tensile strength differences are shown between normal, grafted, and Integra constructs under physiological conditions. These properties will lead to further understanding of artificial tissue and engineered constructs in laboratory and clinical applications.