Association of Head and Neck Anatomic Zones with Microvascular Reconstruction Outcomes.

Background: Head and neck free flap survival relies on adequate tissue perfusion from the external carotid artery (ECA), and vessel length is inversely proportional to blood flow rate. Objective: Investigate whether distance from the ECA (as a proxy for pedicle vessel length) predicts flap survival or complications. Methods: Retrospective review of free flaps performed at three academic centers from 9/2006 to 8/2021. Flaps were categorized by distance from the ECA: orbit and above (zone 1), maxilla to parotid (zone 2), and mandible and below (zone 3). Secondary analysis assessed flap outcomes stratified by average historical pedicle length. Results: A total of 2,369 flaps were identified in zones 1 ( n  = 109), 2 ( n  = 1878), and 3 ( n  = 382). Rates of flap failure (4.9%) and perioperative complications (36.3%) did not differ by zone or pedicle length. Zone 3 flaps, most commonly located in the larynx and hypopharynx, had significantly higher rates of fistula and infection. Conversely, 30-day readmission rates were significantly lower in patients with zone 2 flaps ( p  < 0.001). Rates of all other complications did not differ significantly between zones. Conclusions: Proximity to mucosal anatomic sites was a more powerful predictor of free flap viability than pedicle length or ECA proximity.