Response of Random Skin Flaps to Rapid Expansion
We studied the physiologic accommodation of tissues to 5-day expansion in a porcine random flap model to assess the time taken to expand skin to provide early coverage of traumatic defects. Three 6 × 20 cm random flaps were outlined but not elevated on the backs of 12 small (20-kg) pigs. One flap was not manipulated (control). A 450-ml expander was inserted at the base of the second flap and left in place (sham). At the base of the third flap a 450-ml expander was inserted and sequentially filled to the limits of skin viability each day for 5 days (expanded). Skin tension produced by the pressure of expansion and tissue oxygen (TpO2) in each flap were measured before and after each manipulation. Flaps were raised on day 8, and survival determined on day 15.
Creation of the pocket reduced TpO2 to 55% of control values, expansion to 17.5% of control. Within 24 hours both sham and expanded had recovered to 80% of control values. After the second expansion, recovery from hypoxia was again almost complete after 24 hours. Recovery after subsequent expansions was less complete, but 3 days after the final expansion there was no statistical difference between TpO2 values in expanded, sham, and control groups. High pressures generated in the flap by expansion also returned to near normal within 24 hours. Flaps utilizing expanded skin survived to greater length (14.2 cm) than did sham (11.6 cm) or control (7.2 cm) flaps (p < 0.05).
We conclude that porcine skin can be rapidly expanded on 5 consecutive days without jeopardizing viability, and be ready for use in 8 days. Flaps using this expanded skin survive to greater length than similar nonexpanded flaps. This experiment in a porcine model may find application in humans who require early coverage of soft-tissue loss, but this remains to be tested.