A comprehensive review of the infrahyoid flap

The infrahyoid myocutaneous flap (IHMCF) consists of the sternohyoid, sternothyroid and superior belly of the omohyoid muscles with an overlying skin paddle, all nourished by a neurovascular pedicle. The IHMCF can be used for head and neck reconstruction following neoplasm resection. Precise anatomical knowledge is crucial for surgeons to ensure the neurovascular supply is maintained. This paper aimed primarily to define the anatomy of the IHMCF for surgical reference, with particular focus on the arterial and nerve supply to the infrahyoid muscles, whilst secondly examining the role of the IHMCF in modern-day surgery. A comprehensive literature search assessed online databases. Forty-two studies were analysed and five cadaveric studies met the inclusion criteria. Three studies identified that two arterial pedicles- superior and inferior- were most commonly associated with the sternohyoid muscle, representing 56.0%–91.7% of cases. The superior pedicle originated from the superior thyroid (ST) artery in 100.0% of these cases, while the origin of the inferior pedicle varied with both the inferior thyroid (IT) and ST arteries reported. Two studies identified that a single arterial pedicle was associated with the sternothyroid muscle, representing 78.5%–100.0% of cadavers. The origin of this pedicle varied: one study reported the IT artery in 100.0% of cases whereas the ST artery was identified in 78.5% of cases by the second study. Three studies identified that a single arterial pedicle was associated with the superior belly of the omohyoid muscle, representing 56.0%–100.0% of cases. The arterial origin of this pedicle was from the ST artery in 100.0% of cases. These results highlighted an anastomotic network between the ST and IT arteries, enabling the flap to be elevated on a single pedicle. Two studies considered innervation and agreed that the sternohyoid muscle was innervated by the ansa cervicalis (AC). The AC supplied the sternothyroid muscle in 100.0% of cases and the superior belly of the omohyoid muscle in 85.7%–100.0% of cases. Clinically, the popularity of the IHMCF has diminished due to alternative techniques. This paper, however, recognised that with enhanced anatomical knowledge, relevant surgical adaptations and specific patient cohorts, the IHMCF can remain an important reconstructive technique.