The dorsal skin-flap model in the rat: factors influencing survival.

Several authors have postulated that the standard McFarlane-type dorsal rat flap model can survive as a graft. Therefore, in an effort to better understand the metabolic support governing the survival of this flap, five flap designs on the dorsal surface of the rat were studied. Each was manipulated to control progressively for the metabolic support to the flap by means of skin-graft and/or skin-flap physiology. The flap designs included (1) a standard McFarlane flap (n = 10), (2) a full-thickness "flap" graft (n = 10), (3) a McFarlane flap separated from the bed with plastic sheeting (n = 9), (4) a McFarlane flap separated from the bed by closing the wound beneath the flap (n = 29), and (5) flaps raised as in group 4 after a 2-week delay procedure (n = 9). Based on direct comparisons of both the pattern of necrosis and the surviving surface area in each group, we conclude that (1) the distal aspect of the dorsal rat flap can survive as a graft when in contact with the underlying bed, (2) the "take" of the flap as a graft is variable, and (3) to serve as a reasonable indicator of human flap behavior, the skin-graft effect must be controlled for by separating the flap from the underlying bed.