OBJECTIVETo explore the relationship between the ratio of length to width of slender narrow pedicle and random flap survival area, and to provide a theoretical basis for the clinical application of slender narrow pedicle flaps.

METHODS25 pigs were randomly divided into 5 groups, 5 pigs in each group. The ratio of length to width of slender narrow pedicle in 5 groups respectively was: 0:2, 1:2, 2:2, 3:2, 4:2. Every ratio' s slender narrow pedicle was carrying five different size of random flaps, which were 2 cm x 2 cm(A), 3 cm x 3 cm(B),4 cm x 4 cm(C), 5 cm x 5 cm(D), 6 cm x 6 cm(E), respectively. Flap A was control flap. In each group, flap A, B, C, D and E were created in each pigs' bilateral back. The order in both sides back is contrary. The flaps were evaluated with the general observation, fluorescence examination, blood flow ECT test, pathological expression and computerized analysis of survival area.

RESULTS(1) The living process and pathologic process of traditional flap and slender narrow pedicle flap were consistent. It could not postpone the flap living process when the flap pedicle became long and narrow. (2) When the ratio of the length to width of the slender narrow pedicle was constant, along with the flap area increased, the flap survival area also increased, but when the flap reached a certain area , the distal flap would necrosis,the flap survival area would not reduce. (3) When the flap size remained unchanged, along with the ratio of the length to width of the slender narrow pedicle increased, the flap survival area was not affected, but when the ratio of the length to width of the slender narrow pedicle increased to a certain limit, distal flap would necrosis, the flap survival area would reduce.

CONCLUSIONS(1) Pedicle width of random flap can be much smaller than flap width. The ratio of pedicle width to flap length is far less than traditional ratio. (2) The pedicle of random flap can be designed as slender shape, so that the whole flap looks like "pingpang bat", which makes the narrow pedicle flap rotate easily. (3) A certain ratio of the length to width of a slender narrow pedicle has a maximum flap survival area, and increasing the flap size or ratio of the length to width of a slender narrow pedicle in a certain extent will not lead to flap necrosis.