Effect of distal venous drainage on the survival of four-territory flaps with no pedicle vein: Results from a rat model

Background: Venous super-drainage can improve flap survival not only because it prevents congestion, but also because it affects the dominant circulation in multi-territory thin skin flaps. We aimed to evaluate the survival of various flap areas and detect vascular changes in artery-based, four-territory skin flaps after different distal venous drainage procedures. Methods: 4 x 12 cm sized flaps were elevated based only on the deep circumflex iliac artery. Fifty rats were divided into five groups, as follows: group 1, flaps drained with the deep circumflex iliac vein; group 2, flaps drained with the ipsilateral superficial inferior epigastric vein; group 3, flaps drained with the contralateral superficial inferior epigastric vein; group 4, flaps drained with the contralateral deep circumflex iliac vein; and group 5, flaps super-drained with the contralateral deep circumflex iliac vein. On the fourth postoperative day, the survival of the flaps was assessed by measuring the necrotic and surviving areas, and vascular changes were evaluated angiographically. Results: Compared to flaps with only arterial-based pedicles, most flaps with distant drainage showed significantly greater survival. The flap survival area percentages were 37.82 ± 5.01%, 49.23 ± 10.47%, 68.22 ± 9.24%, 83.90 ± 12.03%, and 89.17 ± 10.42% for groups 1, 2, 3, 4, and 5, respectively. Furthermore, distal vein drainage above the ventral midline resulted in significantly better flap survival. Super-drainage and drainage via the most distal vein resulted in similar flap survival. Conclusions: Distal vein drainage is effective for increasing survival in artery-based flaps.