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.

The effect of occlusion on the survival of an isolated dorsal skin flap in the rat.

Previous studies have documented that maintenance of a moist environment can increase flap survival in the rat model. However, the distal aspect of the dorsal rat flap can survive as a graft, a fact that masks the behavior of this tissue as a flap, thereby making previous studies difficult to interpret. Using a dorsal rat flap model designed to control for the skin graft variable, the effect of occlusive dressings on flap survival was determined. In two groups of rats (n = 10), treatment with a semipermeable occlusive dressing was compared with no treatment. In both groups, 2 x 7-cm flaps based caudally were raised on the dorsum of each rat and the wound closed beneath the flap to prevent take of the flap as a graft. No significant difference in surviving flap surface area was noted (p greater than 0.2). We conclude that, although a moist environment may enhance wound healing, it will not improve the survival of an ischemic flap.