Anatomical Variations in the Superior Thyroid Artery: A Systematic Review and Implications for Free Flap Surgery

Background: The superior thyroid artery (STA) exhibits significant anatomical variability, which is crucial for head and neck surgical procedures, particularly free flap reconstruction. This systematic review synthesizes the current knowledge on STA origin, branching patterns, perfusion territory, and its relationship with the superior laryngeal nerve (SLN), focusing on implications for flap selection and surgical planning. Methods: A comprehensive search of relevant databases was conducted to identify studies reporting on STA anatomy. Data extraction focused on the STA origin variations, relationships with anatomical landmarks, branching patterns, perfusion territory, and the STA-SLN relationship. Emphasis was placed on variations impacting STA's suitability as a recipient vessel for free flaps. Data were synthesized qualitatively. Results: The STA most commonly originates from the external carotid artery (ECA), with variations from the carotid bifurcation (CB) and common carotid artery (CCA). Sex-based and laterality differences were noted. Branching patterns varied considerably, influencing perfusion of the thyroid gland, larynx, and adjacent musculature. The STA's relationship with the external branch of the SLN (EBSLN), classified by Cernea's classification, highlighted the risk of iatrogenic injury. The STA provides perfusion to the thyroid gland, larynx, sternocleidomastoid muscle, and strap muscles, all of which can be raised as flaps. Conclusions: Understanding STA anatomical variations is essential for surgeons planning free flap reconstruction in the head and neck. This review underscores the importance of preoperative imaging to assess STA suitability as a recipient's vessel and minimize complications. Further research is needed to quantify the impact of STA variations on free flap outcomes.