Anterior Surgical Approach to the Cervical Spine

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Chapter Synopsis	The approach to the anterior cervical spine is one of the most common approaches performed in cervical spine surgery. Because of the vital anatomy near the surgical dissection, potential complications from this approach are severe. Therefore, a thorough understanding of the anatomy is crucial to performing this elegant approach safely and expeditiously. This chapter describes and illustrates the approach and provides insight into prevention of complications.
Important Points	A thorough understanding of the anatomy allows for a safe anterior exposure of the cervical spine. The surgeon should recognize all potential complications to avoid and prevent them.
Clinical and Surgical Pearls	All patients undergoing cervical revision procedures should be referred to otolaryngology for either direct or indirect laryngoscopy and vocal cord evaluation. Preintubation, postintubation, and postpositioning neuromonitoring should be considered when the spinal cord is at risk. Below the deep cervical fascia, blunt dissection is the rule.
Clinical and Surgical Pitfalls	Retractors should be kept below the longus colli muscle, and the esophagus and carotid sheath should be protected. The crossing vessels should be identified when the surgeon is working in the upper or lower cervical spine, to protect them. The surgeon should ensure adequate hemostasis at closure and consider ligation of crossing vessels if needed to sacrifice.

The approach to the anterior cervical spine was first described by Robinson and Smith in 1955 and was then modified by Southwick and Robinson in 1957. Since then, the approach has remained very similar, with slight modifications based on increased experience with the procedure. Because of the predictable and successful results, the anterior cervical diskectomy and fusion operation has become one of the most common procedures performed in the United States and around the world. Therefore, most surgeons have experience with the procedure. The purposes of this chapter are to outline the procedure for those who may not be familiar with it and to provide technical tips for those who are seeking to improve their surgical skills.

Preoperative Considerations

History

Although the surgical indications for anterior cervical procedures are discussed in later chapters, the history that is pertinent to the approach is any previous history of anterior neck surgery. Included are previous carotid artery surgery and thyroid surgery because both have also been reported to damage the innervation of the vocal cords. If patients present with any history of anterior surgery or have any concern about vocal cord paralysis, preoperative direct or indirect laryngoscopy should be performed by an otolaryngologist. Because of adjacent segment degeneration in the cervical spine, vocal cord paralysis is unfortunately not an uncommon occurrence, and preoperative planning is a must. Additional history that is relevant to the approach includes the diagnosis of a carotid bruit or carotid artery stenosis. It is reasonable to approach a side away from the carotid artery stenosis or bruit, out of concern for causing a stroke.

Physical Examination

When a patient is evaluated for anterior cervical surgery, the most important aspect of the physical examination is the presence or absence of neck extension with or without pain. This feature guides the options for intubation and intraoperative neck extension. Additional findings that should be considered are previous incisions and their anatomic locations near the planned surgical procedure.

Imaging

Preoperative imaging is important for obtaining the correct diagnosis, but it is also relevant to the approach. The course of the vertebral artery should be thoroughly evaluated on preoperative magnetic resonance imaging, to ensure that this vessel does not have an aberrant course. The vertebral artery can course through the vertebral body or disk or anterior to it instead of maintaining its normal location through the foramen transversarium. If the vertebral artery traverses the anterior aspect of the vertebral body or disk, it is at risk with the approach, and therefore, surgical dissection must proceed with caution. Additionally, if this artery courses through the vertebral body or disk, corpectomy and diskectomy may be contraindicated.

Indications and Contraindications

The relative contraindications to anterior cervical approaches are a previous history of cervical radiation, radical neck dissection or excision, and esophageal surgery. An anterior cervical approach has no absolute contraindications, but any history of the foregoing procedures makes the approach more challenging and higher risk.

Left-Sided Versus Right-Sided Approach

Currently, no conclusive evidence demonstrates improved outcomes or reduced complication rates with either a left-sided or a right-sided cervical approach. Proponents of the left-sided approach argue that the recurrent laryngeal nerve has a more predictable course within the tracheoesophageal groove and is at less risk, although the evidence in the literature to support this view is limited. Proponents of the right-sided approach state that it is more comfortable for the right-handed surgeon, avoids the thoracic duct, and has less risk to the esophagus (which is slightly more to the left).

Ultimately, no difference exists, and the approach side is surgeon specific unless the patient has any previous history of neck surgery. If a patient had previous neck surgery and the vocal cords are functioning normally (as confirmed by indirect laryngoscopy), then the approach should be from the contralateral side. Conversely, if the vocal cords are not functioning normally on the side of a previous approach, then the approach should be from the same side as before, to avoid damage to the one remaining normal vocal cord.

Surgical Technique

Anesthesia and Positioning

Communication with anesthesia providers and neuromonitoring personnel is the key to avoiding complications with positioning for anterior cervical surgery. If a patient cannot safely extend the neck without pain or neurologic symptoms preoperatively, then indirect laryngoscopy (i.e., GlideScope or fiberoptic intubation) should be considered. Additionally, if the patient has a history of myelopathy, or if concern about the spinal cord exists, mean arterial pressure requirements (>85 mm Hg) may be indicated. Furthermore, if any concern with neck extension exists, preintubation neuromonitoring baselines values should be obtained. Once total intravenous anesthesia is induced, bite blocks should be placed, and baseline motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SSEPs) should be obtained before intubation. Communication with the anesthesia team to avoid muscle relaxants if possible during intubation allows postintubation monitoring. Only by constant communication with the anesthesia team can this be done expeditiously.

If intubation did not require muscle relaxants, then positioning can be adequately monitored with MEPs and SSEPs. First, the authors place the bed in approximately 20 degrees of reverse Trendelenburg positioning, which allows for venous drainage ( Fig. 3-1 ). If the patient can tolerate neck extension, a small roll can be placed between the scapulae. In the authors’ practice, an inflatable pressure bag covered by a gel pad placed behind the scapula allows for more controlled neck extension. Obviously, if the patient’s head is lifted from the table with neck extension, too much neck extension has been attempted. Additionally, in patients with significant motion, neck extension may tether the trachea or esophagus to the anterior spine, thus making mobilization of these structures difficult. Therefore, a simple manual check of tracheal mobility can be performed following neck extension.