Rectangular flaps on the rat or mouse dorsum are frequently used for flap survival elongation research. However, since rectangular flaps are purely random, the survival rate varies among individuals. A reliable animal flap model with low individual variation is desirable for flap survival research, especially in the angiogenic field. We investigated the survival rate of paired flaps in the rat dorsum containing 3 vascular territories in each flap, and determined their usefulness for flap elongation research. Two symmetrical adjoining rectangular flaps (11×3 cm each) were drawn on the rat dorsum. Two days after material injection, flaps were elevated with only the deep circumflex iliac vessels as the vascular pedicle. Flaps were immediately sutured back and the flap survival area was measured 7 days after the operation. The control group (n = 9) had saline solution injected in both flaps. The bone marrow group (n = 8) had bone marrow injected in the right flap, and saline solution injected in the left flap. In the control group, the survival rate of the paired flaps was not statistically different (right flap, 89.0±5.6%; left flap, 89.3±4.5%). In the bone marrow group, the survival rate between the bone marrow injected flap (89.9±3.7%), and the saline flap (84.8±4.3%) was statistically different. The rat dorsal paired island skin flap model shows low difference in flap survival rate and uses an internal control. This is a suitable model for flap survival elongation research.
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