Introduction

Owens described the sternocleidomastoid (SCM) flap in 1955 utilizing the entire length of skin overlying the muscle.¹ Later, the flap design was modified by Ariyan to include only the lower third of the skin.² Since its description, the flap has had a diminished role in the reconstruction of head and neck defects. Although numerous authors have published variations of the use of the SCM flap and espouse the advantages of the flap, it has always retained the role of a seldom-used flap for head and neck reconstruction.^3,4 The diminished role of the SCM in reconstruction of head and neck defects stems from two main reasons. The first is that its use as a myocutaneous flap continues to be viewed as unreliable due to the common loss of the skin component of the flap. Second is the fact that the most common head and neck defects are a result of ablation of malignancies and therefore there is often an accompanying neck dissection, which may result in the compromise of the flap. In cases where a neck dissection has already been done, the blood supply to the SCM is often compromised. The site where this may occur is the blood supply entering the muscle as either the superior or middle third. The occipital vessels are often ligated in the dissection of level IIb nodes. As most head and neck defects are located in the upper third of the neck or within the oral cavity, using the SCM as a superiorly based flap is no longer a possibility.

The SCM receives its blood supply from several blood vessels and is commonly divided into thirds, the superior, middle, and inferior third. This segmental blood supply enables the flap to be used in three possible ways: superiorly based, inferiorly based, or as a perforator based on the middle third.⁵ The limitations of the SCM flap are similar to any other pedicled flap, i.e., the arc of rotation and the ability to reach the location of the defect. The use of the flap as a superiorly based flap allows for the reconstruction of various defects in the head and neck as well as the oral cavity. The inferiorly based flap can be used to repair defects around the inferior aspect of the mandible, and the upper, central, and lower neck region. The SCM may be of particular use in reconstructing pharyngeal fistulas.

Anatomy

The sternocleidomastoid is a paired muscle in the anterior neck, enclosed by the superficial cervical fascia, directly beneath the platysma. The external jugular vein and the great auricular nerve cross the surface of the muscle vertically. The muscle has a medial sternal head that originates from the upper part of the anterior surface of the manubrium sterni and a clavicular head that arises from the superior and anterior surface of the medial third of the clavicle. As the muscle ascends obliquely beyond the supraclavicular fossa, the two heads fuse together and insert into the lateral surface of the mastoid process and the superior nuchal line of the occipital bone. It is classified as a type II pattern of vascular circulation.⁶ The dominant blood supply to the muscle is from branches of the occipital artery. These branches form a rich anastomosis within the muscle that can supply its entire length with the exception of the inferior 3–5 cm.⁷ The middle third of the muscle receives its blood supply from branches of the superior thyroid artery and external carotid artery.⁸ The vascular supply from the upper and middle third of the muscle can maintain viability of the entire muscle and overlying skin. The lower third of the muscle has shown the most variability in its vascular supply with branches arising from the thyrocervical trunk, suprascapular artery, and the transverse cervical artery. The venous drainage is through the accompanying occipital vein, posterior auricular vein, external jugular vein, and branches from the internal jugular vein. The motor innervation to the muscle is via a branch of the spinal accessory nerve as it courses to the trapezius.

Flap harvest

• The flap is raised with the patient in a supine position with the donor side exposed and the head rotated to the contralateral side.
• A shoulder roll should be placed to help elevate the base of the neck and therefore provide better exposure for harvest.
• The SCM should be easily visualized and or palpated; this is easier in thin patients and those with long necks.
• The markings for the flap should be made by outlining the muscle from the mastoid region as it travels in a diagonal path to the insertion in the clavicle and sternum.
• If the flap is to be raised as myocutaneous flap, the skin paddle should be outlined with care to center it over the belly of the muscle.
• Regardless of whether the flap is to be raised as an inferiorly based or superiorly based flap, the surgeon should determine the arc of rotation and confer the reach of the flap, particularly if it is a myocutaneous flap. This will ensure that the skin component will reach the defect in a safe manner without tension.
• Once the skin paddle is designed, the next step is to incorporate the rest of the incision with that of the skin paddle.

Superiorly based flap

• The incision for the harvest of the flap is often done in conjunction with that of the neck dissection, this is often a low apron incision which begins behind the sternocleidomastoid area, extends inferiorly along a neck crease, and transverses the neck to the contralateral side.
• Using either electrocautery with a Colorado tip or a 15 blade, the skin is incised down to and through the platysma.
• A subplatysma flap is then raised to the inferior border of the mandible. This should allow for visualization of the SCM along the neck from its origin to the superior aspect of the skin paddle.
• The area inferior to the skin flap is equally raised in the subplatysmal plane as was done superiorly.
• The skin paddle is sutured to the overlying fascia of the sternocleidomastoid muscle. This maneuver minimizes sharing of the skin flap and potential compromise of the skin paddle.
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