Published cadaveric injection studies have identified the external carotid and subclavian arteries as the main sources of blood supply to the anterior neck with a proposed watershed area between these territories running horizontally in the lower neck (2). The same studies have also suggested that there is little or no vascular communication across the midline. As a result of these findings, it has been suggested that anterior neck skin flaps should not be raised across the midline and should not incorporate the watershed area between the two parent vascular territories. This approach has limited the usefulness, size, and reach of anterior neck flaps. However, a recent description by Behan et al. (2010) of the cervicosubmental island flap brought into question the validity of these previous studies (3), with the skin of the anterior neck used with reliability.

In our anatomical studies, we have found a dominant thyroid artery perforator greater than 0.5 mm in diameter in every case (90/90 cases) on computed tomographic angiography (CTA) with a diameter range of 0.5 to 1.3 mm with a mean of 0.9 mm (Fig. 217.1). At least one such perforator was consistently shown to arise from its source vessel deep to the investing layer of deep cervical fascia, and to emerge from this layer at the anterior border of the sternocleidomastoid (SCM) muscle, at its caudocranial midpoint (within 2 cm of this point in all 90 cases). Other smaller thyroid artery perforators were shown to perforate the SCM. The dominant perforators arose from the superior thyroid artery (STA) in 89 of 90 cases and from the inferior thyroid artery (ITA) in 1 case. The dominant perforator consistently emerged between the investing layers of fascia forming the epimysium of the SCM, and traversed a variable subplatysmal course, before consistently perforating the platysma within the ipsilateral neck. After perforating the platysma, the STA perforator traversed an axial (transverse) subcutaneous course up to the midline, adjoining the axial
course of the STA perforator of the contralateral side of the neck. A long flap between the medial borders of each SCM could thus be planned as an axial pattern flap. These imaging findings have been confirmed operatively (Fig. 217.2).