Applied Anatomy for Percutaneous Approaches to the Cervical Spine

39 Applied Anatomy for Percutaneous Approaches to the Cervical Spine

Gun Choi, Alfonso García, Akarawit Asawasaksakul, and Ketan Deshpande

39.1 Introduction

To understand the surgical technique of percutaneous endoscopic cervical diskectomy (PECD) and to produce successful outcomes, it is imperative to have a thorough knowledge of the regional anatomy of the neck. The approach to the cervical disk in PECD is always anterior; hence this chapter focuses on the anterior triangle of the neck in describing the surgical anatomy.1,2,3,4

39.2 Surface Anatomy

Orientation to surface anatomy helps to locate the surgical level and proper needle trajectory to the disk space (Fig. 39.1). The sternocleidomastoid (SCM) muscle separates the anterior and posterior triangles of the neck. The landmarks are described below from the midline and beginning with the top of the neck and moving downward.

Fig. 39.1 Surface anatomy of the cervical region.

39.2.1 Hyoid Bone

• About 1.5 cm above the thyroid cartilage

• Corresponds with level of C3 vertebra

39.2.2 Thyroid Cartilage

• Most prominent midline structure, especially in postpubertal males

• Corresponds with C4–C5 level

• Also corresponds with the carotid artery bifurcation into external and internal carotids

39.2.3 Cricoid Cartilage

• Located just below the thyroid cartilage

• Corresponds to the C6 vertebral level

• A horizontal plane approximately at the junction of C6–C7 has the following associations:

• Pharyngoesophageal junction

• Laryngotracheal junction

• Inferior thyroid artery, carotid sheath, and omohyoid muscle

• Entrance of the inferior laryngeal nerve (recurrent nerve) into the larynx

• Entrance of the vertebral artery into the transverse foramen of C6

• The thyroid isthmus and the greatest height of the thoracic duct are located at the C7 level.

39.3 Topographic Anatomy of the Cervical Spine

The neck is divided into anterior and posterior triangles. The following description presents the surgical anatomy of the anterior triangle of the neck (Fig. 39.2, Fig. 39.3).

39.4 Boundaries of the Anterior Triangle

• Lateral: SCM muscle

• Superior: inferior border of the mandible

• Medial: anterior midline of the neck

The anterior triangle is further subdivided into the following sections:

• Submandibular

• Submental

• Carotid

• Muscular

39.4.1 Submandibular Triangle

Boundaries

• Superior: inferior border of the mandible

• Inferior: anterior and posterior bellies of the digastric muscle

Content

The submandibular gland is the largest structure of the triangle. The roof is formed by skin, superficial fascia composing platysma, and the underlying mandibular and cervical branches of the facial nerves. Below the roof, from superficial to deep, lie the retromandibular vein, part of the facial artery, the submental branch of fascia (deep cervical fascia), the lymph nodes, the deep layer of the deep cervical fascia, and the hypoglossal nerve. Below this lie the mylohyoid muscle with its nerve, the hypoglossus muscle, and the middle constrictor muscle of the pharynx. Farther down lie the deep portion of the submandibular gland, the submandibular duct, the lingual nerve, the sublingual vein, the sublingual gland, the hypoglossal nerve, and the submandibular ganglion.

Fig. 39.2 The surgical anatomy of the anterior triangle of the neck.

39.4.2 Submental Triangle

Boundaries

• Lateral: anterior belly of digastric

• Inferior: hyoid bone

• Medial: midline

Floor: mylohyoid muscle

Roof: skin and superficial fascia, platysma, cutaneous nerves

Contents: lymph nodes

39.4.3 Muscular Triangle

The inferior carotid triangle (muscular triangle) is bounded superolaterally by the anterior belly of the omohyoid, inferolaterally by the SCM, and medially by the midline of the neck from the hyoid bone to the sternum. The roof is formed by the superficial fascia, platysma, deep fascia, and branches of the supraclavicular nerves. Beneath these superficial structures are the sternohyoid and sternothyroid muscles, which, along with the medial (anterior) border of the SCM, protect the lower part of the common carotid artery. This vessel is enclosed within the carotid sheath with the internal jugular vein and vagus nerve. The veins lie lateral to the artery on the right side but overlap below on the left side. The nerve lies between the artery and vein in a plane posterior to both. In front of the sheath are a few descending filaments of ansa hypoglossus; behind the sheath are the inferior thyroid artery and recurrent laryngeal nerve and the sympathetic trunk; and on its medial side lie the esophagus, trachea, thyroid/parathyroid glands, and lower part of the larynx. Most of the anterior cervical approach is done in this triangle.