Background: The Gustilo classification serves as a proxy for injury severity, but recent data suggest rising complications with decreasing arterial runoff. This study aims to compare different microsurgical anastomosis options based on the number of patent vessels in the lower extremity. Methods: A single-center retrospective review of 806 lower extremity free flaps performed from 1976 to 2016 was performed. Patients with Gustilo type IIIB injuries were grouped based on the number of patent vessels in the leg (three, two, or one). Patients were compared based on the type of anastomosis performed, evaluating for perioperative complications and flap failures. Results: Perioperative complications occurred in 111 flaps (27 percent): 71 take-backs (17 percent), 45 partial losses (11 percent), and 37 complete losses (9 percent). Among patients with three-vessel runoff (61.8 percent), there was no difference in take-backs or flap loss between those with end-to-end versus end-to-side anastomoses. In 68 patients (18.7 percent) with two-vessel runoff, no difference between take-backs or flap loss was noted when comparing any anastomosis (i.e., end-to-end into an injured vessel, end-to-end into an uninjured vessel, or end-to-side into an uninjured vessel), although vein grafts were required more often in the end-to-side groups (p < 0.01). Finally, in 39 patients (10.7 percent) with single-vessel runoff, no difference was seen between end-to-end anastomosis into an injured vessel or end-to-side anastomosis into an uninjured vessel in terms of take-backs or flap loss. Conclusion: Higher rates of flap failure correlated with decreasing numbers of patent vessels in the leg, but neither type of microvascular anastomosis nor vessel selection demonstrated any impact on reconstructive outcomes. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.
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