Neck Reconstruction

Cutaneous Anatomy

The anterior aspect of the neck is bound superiorly by the mandible of the jaw and inferiorly by the clavicle. The posterior aspect of the neck is bound superiorly by the hairline or base of the skull and inferiorly by the upper portion of the scapula.

Triangles

The sternocleidomastoid muscle divides the neck into the anterior and posterior triangles ( Fig. 17.2 ). The anterior triangle is defined by the anterior border of the sternocleidomastoid, the inferior margin of the mandible, and the midline of the neck. This triangle contains the platysma muscle, which constitutes a major component of the superficial musculoaponeurotic system (SMAS) layer, and is continuous with the SMAS of the face. This muscle overlays the investing cervical fascia and is approximately 0.6 mm thick, but becomes slightly thicker in the submental area. The platysma is considered a muscle of facial expression, as contraction of the platysma muscle pulls down the lower lip and results in grimacing.

The posterior triangle is defined by the posterior border of the sternocleidomastoid muscle, the anterior border of the trapezius muscle, and the superior aspect of the clavicle. This triangle contains the spinal accessory nerve (cranial nerve XI) at its most superficial point, known as Erb's point. Erb's point describes the area where the spinal accessory nerve emerges from approximately one-third down the posterior border of the sternocleidomastoid muscle and courses through the posterior triangle inferiorly and diagonally along the levator scapulae muscle to penetrate a point two-thirds down the anterior edge of the trapezius muscle before it runs deep under the muscle.

Erb's point can be easily located by finding the half-way point between the mastoid process and the angle of the jaw and drawing a perpendicular line 6.0 cm vertically down the neck to the point where it intersects the posterior aspect of the sternocleidomastoid muscle ( Fig. 17.3 ). Another way to identify Erb's point is by drawing a horizontal line from the thyroid notch to the posterior triangle on the neck. The area approximately 2 cm above and below where this line crosses the posterior border of the sternocleidomastoid is the where the nerve traverses the posterior triangle and is most prone to injury.

This point is particularly important for dermatologic surgeons given the superficial nature of the spinal accessory nerve lying just below the skin and subcutaneous tissue. Fig. 17.4A shows a basal cell carcinoma located over the posterior triangle of the neck, and the spinal accessory nerve is visible after removal of the tumor (see Fig. 17.4B ). Damage to the spinal accessory nerve can cause significant morbidity including shoulder drop and the inability to abduct the shoulder past 80 degrees. Paresthesias and pain may also accompany damage to this nerve. Given the superficial nature of this nerve, great care should be taken when operating in this area.