ANTERIOR APPROACH TO THE CERVICAL SPINE

USES

This approach is used to access the anterior vertebral bodies of C3 through T1, including the disk spaces in between. Its main utility is for anterior cervical decompression and fusion (ACDF), which ranges from a single-level diskectomy to a multilevel corpectomy with bone grafting and plating. This approach may be used for resection of tumors and debridement of infection located in the anterior and middle columns of the cervical spine.

ADVANTAGES

This approach is relatively easy to perform. The supine positioning is less time consuming and, in theory, safer for the patient compared to the prone position. Furthermore, as the skin incision follows skin creases, a more cosmetic scar usually results.

DISADVANTAGES

Numerous vital structures are placed at risk in this approach (see below). Hence, a clear understanding of the anatomy is important to minimize complications. Also, significant postoperative soft tissue swelling around the trachea may occur, causing transient airway compromise.

STRUCTURES AT RISK

Many important structures are at risk with this approach. The right and left recurrent laryngeal nerves, which supply the larynx, are branches of the vagus nerve. The left recurrent laryngeal nerve, after circumventing the aortic arch, ascends in the tracheoesophageal groove. The right recurrent laryngeal nerve, on the other hand, takes off from the parent vagus nerve and curves around the right subclavian artery at a more cephalad level, crossing from lateral to medial in the lower part of the cervical spine, then ascending the neck directly adjacent to the trachea. Also, anatomic variability in the takeoff level of the right recurrent laryngeal nerve has been described. This renders the nerve more vulnerable in the right-sided approach, as the level where it crosses the operative field is less predictable.

The carotid sheath and its contents (common carotid artery, internal jugular vein, and vagus nerve) are also at risk in the lateral margin of the dissection. The sheath should be carefully identified and protected after the deep cervical fascia on the medial aspect of the sternocleidomastoid muscle is divided. Midline structures, such as the trachea and esophagus, must be identified and protected. Overzealous, continuous, or sharp retraction of these structures should be avoided, as this may cause damage. Blunt handheld retractors are preferred.

Deeper in the dissection, the vertebral artery is at risk. It ascends the spine within the lateral aspect of the transverse processes, within the costotransverse foramen. It is not normally visualized in this approach. Dissection lateral to the uncinate process of the vertebral body increases the likelihood of arterial injury. Also in the deep dissection, the cervical sympathetic trunk may be at risk as it lies directly anterior to the prevertebral fascia, which envelopes the prevertebral muscles. After incising the fascia in the midline, careful subperiosteal dissection of the vertebral body protects this structure.

Finally, as with any approach to the spine, the dura must be meticulously dissected to prevent cerebrospinal fluid leak.

TECHNIQUE

The patient is placed in the supine position with a roll placed transversely between the scapulae in order to extend the neck. The head is turned away from the side of the approach. Following palpation of landmarks, a 5-cm skin incision is made along a skin crease at the level of interest. Alternatively, a longer oblique or longitudinal incision can be made if an extensive decompression is planned (i.e., >3-level corpectomy). Injection of lidocaine with epinephrine into the skin prior to incising may help diminish superficial bleeding.

Incise the superficial fascia overlying the platysma along the skin incision. The fibers of the platysma muscle are then either incised longitudinally along the directions of its fibers or split transversely. The deep cervical fascia underneath is then identified. Next, palpate the medial border of the sternocleidomastoid (SCM) muscle and carefully split the fascia longitudinally, which facilitates retracting the SCM laterally. The laryngeal strap muscles (sternohyoid, sternothyroid) as well as the midline structures immediately deep to them (trachea and esophagus) are then retracted medially. Deep to the SCM muscle, identify the carotid sheath as well as the pretracheal fascia overlying it. Carefully incise the fascia medial to the sheath while protecting the midline structures. The carotid sheath can now also be retracted laterally.