Overview
Although intense discussions persist in regard to which approach should prevail in treating pathology of the cervical spine, anterior approaches have become vastly more common and accepted over the last few decades. The anterior approach affords the surgeon the most direct route to ventral compressive pathology, and it is achieved through a small incision, without excessive blood loss, while providing ready access from C2–C3 to T1. Surgical techniques have been variable since the initial reports from Cloward and Smith and Robinson. Regardless of individual preferences, anterior fusions have become an indispensable tool in the armamentarium of spine surgeons for dealing with a wide range of pathologies.
Anatomy Review
Surface anatomy may help localize levels of vertebrae. The most superior bony prominence below the mandible is the hyoid bone, and it commonly demarcates C3; the hyoid bone can be palpated at the angle of the mandible. The thyroid cartilage is typically over C4–C5, and the cricoid cartilage marks C5–C6. With heightened attention to avoiding wrong-level surgery, the use of anatomic landmarks alone is discouraged. The authors use fluoroscopy with an endotracheal tube stylet as a radiopaque marker to localize the targeted levels and plan a skin incision. Transverse and longitudinal incisions and both left- and right-sided approaches have been described. The variable course of the recurrent laryngeal nerve on the right and its vulnerability to injury gives reason for some to advocate a left-sided approach; however, the thoracic duct is on the left side, and chylothorax is a serious complication that can be avoided with the right-sided approach.
No side of approach to the anterior cervical spine is undisputed, and surgeon handedness plays an important role in deciding which side to access. We have found success even for multiple levels of decompression with a short transverse incision that just crosses the midline and spares more lateral exposure. We have successfully reached C2 to T2 with transverse incisions and mobilization above and below the platysma, and we seldom perform an incision along the sternocleidomastoid (SCM) unless a high anterior retropharyngeal approach is required to reach C1 ( Figs. 18-1 and 18-2 ).
Equipment
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Radiolucent operating table (helpful but not mandatory)
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Fluoroscopy
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Optical loupes
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Monopolar and bipolar cautery
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Cloward retractors
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Kittner dissector
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Black Belt self-retaining retractor
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1- to 3-mm Kerrison punches
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High-speed drill (we prefer a 13-mm M-32 cutting burr)
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Up-angled curette
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Pointed nerve microhook
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Operating microscope
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Bone graft
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Cage
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Anterior plate and screws
Operative Technique
Positioning
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Adequate exposure is essential to optimal instrumentation and is contingent on sound positioning.
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A roll is placed between the shoulder blades to create gentle extension, provided this is not neurologically detrimental.
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Keep the neck straight, although some have advocated slight rotation away from the proposed incision.
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A donut is generally placed under the occiput, sometimes on top of towels, to avoid hyperextension and in conjunction with rolls above to obtain lordosis. The primary goal is to prevent rotation of the head after draping of the patient.
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The patient’s arms are tucked, and the body is wrapped with care to pad bony prominences, particularly the elbows and wrists, to prevent a peripheral nerve injury. Gentle caudal retraction of the shoulders can facilitate lateral radiographic images.
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A lateral fluoroscopic image is acquired to assess degree of preoperative lordosis.
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A C-arm is draped in the field at the head of the bed. Although cranial tongs have in the past been advocated, we do not routinely use them.
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A Foley catheter is placed to avoid bladder distension and excess pressure on the inferior vena cava, reducing venous oozing from the bone and epidural plexus.
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Thromboembolic deterrent hose and sequential compression boots for deep vein thrombosis prophylaxis.
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Consider nasotracheal intubation for levels at or above C2–C3 (and C3–C4 disk space, depending on anatomy).
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Other helpful devices used by some surgeons include a chin strap and Caspar head rest, which help extend the neck and provide close juxtaposition to the patient, respectively. Some advocate the lounge position, with knees and back slightly flexed, to avoid stretch injury and pressure points and to offer a more direct view of the disk space.
Incision
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A fluoroscopic image is acquired with a radiopaque marker in the surgical field.
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When rostral-caudal self-retaining retractors are used in lieu of distraction pins, the exposure tends to shift caudally once the retractors are inserted. Planning for a slightly more rostral incision obviates this difficulty.
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The incision starts 2 to 5 mm to the left of the midline and is carried to the right approximately 4 to 6 cm in the lines of Langer.
Technique for Approaching the Cervical Spine
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After skin incision, a self-containing retractor is placed, and the platysma is transected with monopolar cautery transversely. However, some authors prefer an anatomic splitting of the platysma, particularly for a single-level surgery. Medial approaches with release and lateral reflection of the platysma have also been used.
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The platysma is then undermined rostrally and caudally, with the extent of each direction based on whether more exposure is needed inferiorly or superiorly.
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Superficial fascia investing the SCM is released, and the omohyoid is palpated. Although blunt dissection and retraction are often enough to release and obtain adequate exposure, this occasionally requires transection at the middle.
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The middle layer of the deep cervical fascia contains the omohyoid, trachea, and esophagus. The trachea and esophagus are retracted medially. The carotid artery may be palpated laterally, and the spine may be palpated medially and deep to the exposure.
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A handheld retractor is used with the nondominant hand to expose the spine, and the retractor can be given to the assistant when firmly on the spine and retracting midline structures away.
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A Kittner dissector is used to bluntly develop the plane of the prevertebral fascia, and bipolar cautery or a sheathed Bovie can be used to free the medial edges of the longus colli muscles, the center of which can be used to identify the midline.
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With the carotid sheath swept laterally, a Black Belt retractor system is placed using all four blades, although some choose only the lateral blades or defer placement until the appropriate level is confirmed.
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An 18-gauge spinal needle is bent twice to create a right angle at the distal end to prevent inadvertent advancement toward the spinal cord. Intraoperative fluoroscopy is used to place the needle in the intervertebral disk space.
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Once any levels of interest have been confirmed, the disk space is marked with either a skin marker or the Bovie, and the longus collus muscle is reflected further laterally if needed. Initial exposure is made with attention to avoiding disruption of the annulus of any disk that is not intended to be treated.
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The superior half of the most caudal vertebral segment to be included in the fusion is cleared of soft tissue as is the inferior half of the most rostral body.
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Care is taken not to disrupt the disk space of the level above or the level below the fusion construct.
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The dissection is carried out laterally to the uncovertebral joints.
Technique for Approaching the Upper Cervical Spine
An anterior approach to the basiocciput and upper cervical spine is complicated by the internal carotid artery, vagus, and hypoglossal nerves, all of which may be injured if retracted significantly. The approaches include dislocation of the temporomandibular joint, osteotomy of the mandible, transoral approach, and anterior retropharyngeal approaches.
One effective extraoral approach, described by DeAndrade and MacNab, is via an oblique incision parallel to the anterior border of the SCM, which grants access to the retropharyngeal space anterior to the SCM and carotid sheath. Unfortunately, this approach requires retraction or division of the laryngeal or pharyngeal nerves, which creates a minor but lasting hoarseness. In any case, this anteromedial retropharyngeal approach is an extension of the Smith-Robinson approach to the lower spine, in which the neck is hyperextended, and the chin is turned to the opposite side.
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Care is taken not to hyperextend the neck, because this may result in spinal canal diameter restriction because of buckling of the ligamentum flavum. The incision is made along the anterior aspect of the SCM and is curved toward the mastoid process.
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The platysma and superficial layer of the deep cervical fascia are divided along the incision to expose the anterior border of the SCM.
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The muscle is retracted anteriorly, and the carotid is retracted laterally.
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While the superior thyroid artery and lingual vessels are ligated, the facial artery must be identified at the rostral portion of the incision as a landmark for the hypoglossal nerve, which is adjacent to the digastric muscle. This nerve must be retracted carefully to avoid injury, as must the superior laryngeal nerve, which is in close proximity to the superior thyroid artery.
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Another retropharyngeal anterior exposure described by McAfee involves a right-sided submandibular transverse incision and division of the platysma, leading to the SCM and deep cervical fascia.
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Nerves can be identified with a nerve stimulator, and the retromandibular vein is ligated during the initial exposure.
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The anterior border of the SCM is mobilized, and the submandibular salivary gland and digastric lymph nodes are resected with care to suture the duct in the gland to prevent a salivary fistula.
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The digastric tendon is split and tagged for future repair, and the hypoglossal nerve is identified and mobilized.
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To move the carotid contents laterally, the carotid sheath is opened, and arterial and venous branches are ligated.
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A stimulator is also used to identify the superior laryngeal nerve.
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Prevertebral fasciae are dissected longitudinally to expose and dissect the longus colli.
Yet another anterolateral retropharyngeal approach described by Whitesides and Kelley provides exposure to the upper cervical spine but not to the basiocciput. This approach uses an incision made from the mastoid along the anterior aspect of the SCM with dissection anterior to the SCM and posterior to the carotid sheath.
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Effort is made to spare the greater auricular nerve, and the jugular vein is ligated.
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The splenius capitis and SCM are dissected off the mastoid, and cranial nerve (CN) XI must be recognized and protected.
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After the carotid is retracted anteriorly and the SCM is retracted posteriorly, blunt dissection leads to the transverse processes and anterior aspect of C1–C3. Caveats to this approach include possible injuries to CN XI, the verterbral artery, and sympathetic ganglion.
An alternate means of approaching the basiocciput is a transpharyngeal approach with division of the soft and hard palates. Although this approach involves some difficulty, a small working space, and contamination by pharyngeal organisms, it may be appropriate when instrumentation is not required and durotomy is not anticipated.
Diskectomy
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An annulotomy is made with a #11 blade, and disk material is removed with a pituitary rongeur.
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The anterior inferior osteophyte lip is removed from the vertebral segment above using the Kerrison rongeur to better visualize the disk space. Proud ventral osteophytes are also removed with rongeurs, allowing the eventual plate to sit flush with the ventral surface of the vertebral bodies. This bone is saved for use in the interbody cage.
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The end plates are then scraped with an up-angled curette to delineate the superior and inferior margins of the disk space.
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Next, the high-speed drill is used to drill the end plates, taking care to stay parallel to them. The removal of bone is carried out laterally to the uncovertebral joints.
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The posterior longitudinal ligament is opened using a pointed nerve hook and fine Kerrison punches ( Fig. 18-3 ).
Related posts:
Craniovertebral Junction Instabilities and Surgical Fixation Techniques
Surgical Approaches to the Craniovertebral Junction in Rheumatoid Arthritis
Thoracic Microdiskectomy: Lateral and Posterolateral Approaches
Lumbar Facet Screw Fixation Techniques
Surgical Management of Scheuermann Kyphosis
Primary Malignant and Benign Tumors of the Spine
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