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The midline posterior approach, which is the most commonly used surgical approach to the cervical spine, allows efficient and safe access to the posterior elements of the occipitocervical junction and the subaxial cervical spine. Although the posterior approach is one of the most elementary approaches in spine surgery, involving a simple midline incision, it is indicated for a variety of cervical spine procedures, including posterior fusion, enlargement of the spinal canal through laminectomy or laminoplasty, excision or debulking of tumors, open treatment of facet dislocations, open reduction of posterior element fractures, decompression of nerve roots, and removal of accessible herniated disks.
Preoperative Considerations
General Principles
A careful history and physical examination, as well as appropriate imaging studies, should be performed preoperatively in all patients. The surgical approach depends on the condition being treated, the specific signs and symptoms, and the patient’s expectations. Once surgery is planned for the patient and a posterior approach is chosen, the physical examination should be focused on ensuring that the appropriate landmarks and tactile cues, such as the external occipital protuberance and large C2 and C7 spinous processes, can be palpated. Other less common but important anatomic preoperative considerations include evaluating for unusual anatomy such as an aberrant vertebrobasilar artery, location and condition of preexisting scars in the setting of a revision procedure, and a Klippel-Feil segment or other congenital anomaly that could alter or complicate the surgical approach.
Imaging
An essential step in preoperative preparation is obtaining appropriate imaging studies. Anteroposterior, lateral, and open-mouth plain film radiographs of the cervical spine with full and clear views from C1 to T1 should be standard parts of the diagnostic evaluation. Preoperative computed tomography (CT) scans can help define the bony anatomy and facilitate the preoperative plan. Magnetic resonance imaging (MRI) is almost universally obtained before cervical spine surgery as well because these imaging sequences allow evaluation of the neural structures and disks and provide additional information on potential infections, tumors, or other pathologic processes. A thorough review of all available imaging should be completed when selecting the optimal surgical approach for the patients’ disorder.
Indications and Contraindications
A broad range of disorders may be addressed through a posterior approach to the cervical spine. It is easiest to consider the approach in two distinct anatomic regions: the occipitocervical junction (including the occiput to C2) and the subaxial cervical spine (C3 to C7). Although the approach to both regions is similar, the anatomy, function, and associated pathologic features of these two vertebral segments differ. Therefore, it is simpler to discuss these regions separately throughout this chapter. At the occipitocervical junction, both posterior decompressions and posterior fusions can be performed. Various types of decompressions, including that of the skull base, foramen magnum, spinal canal, and nerve roots, can be accomplished through this approach. A posterior approach is indicated for posterior occipitocervical and C1 to C2 fusions for atlantoaxial dissociations, C1 or C2 fractures, transverse cervical ligament disruptions, tumors, or infections. In the subaxial cervical spine, decompression of the canal and nerve roots, including laminectomy, laminoplasty, and keyhole laminoforaminotomy, can be performed through a posterior approach. Posterior fusion procedures for fractures, tumors, or infections can be undertaken through this approach. Additionally, treatment of facet joint dislocations and excision of some herniated disks can also be accomplished through a posterior approach.
If the posterior approach to the cervical spine is the most direct and least invasive access to the pathologic process being treated, this approach has essentially no contraindications. Having said that, many cervical spine disorders are better surgically managed through an anterior approach (see Chapter 3 ). Thus, it is important to consider the specific pathologic process and to determine the most appropriate and least invasive approach before the surgical procedure.
Surgical Technique
Positioning
Typically, prone positioning is used for the posterior approach to the cervical spine ( Fig. 4-1 ), although some surgeons prefer positioning the patient in a seated position. Preoperatively, the patient’s cervical spine should be carefully ranged in flexion and extension to determine a safe range of motion that does not produce symptoms. Additionally, movements of the cervical spine should be minimized as much as possible during intubation, especially for myelopathic patients.
The proper and safest operative head positioning is best achieved with the use of a halo head frame or Mayfield tongs for stabilization (see Fig. 4-1 ). Head and neck flexion separates the occiput and ring of C1 and also reduces overlap of the laminae and facet joints, thereby facilitating exposure of the occipitocervical region and allowing easier decompression of the subaxial spinal canal. The neck should be returned to a neutral position before any fusion or instrumentation procedures. The arms and shoulders should be placed at the patient’s side. Gentle taping of the shoulders to the distal end of the bed can facilitate intraoperative radiographic visualization. Excessive traction on the shoulders should be avoided to minimize the risk of intraoperative brachial plexus traction injury or skin blisters. The caudal scalp should be shaved of hair 1 to 2 cm cephalad of the external occipital protuberance to facilitate draping and palpation of landmarks.
Elevating the head of the operating table to 30 degrees of reverse Trendelenburg positioning can reduce venous epidural bleeding. Knee flexion prevents the patient from sliding inferiorly in this position. All bony prominences and peripheral nerves should be carefully padded to prevent intraoperative neurapraxia. Once satisfactory positioning has been obtained, fluoroscopy should be used for final assessment of cervical spine alignment and positioning before draping.
Hazards
Although the posterior approach to the cervical spine is relatively straightforward, the surgeon should be aware of certain significant hazards. Significant morbidity can result from improper positioning. Hyperextension or hyperflexion while the patient is under anesthesia can contribute to spinal cord injury. Excessive traction on the shoulders can result in brachial plexus injury. Improper padding of bony prominences or peripheral nerves can cause intraoperative decubitus ulcers or neurapraxia. Failure to allow the abdomen to hang free through the table can hamper venous return and also increase required inspiratory pressures.
Anatomic hazards are also present. Neural structures such as the spinal cord and cervical nerve roots, especially the greater occipital nerve (C2), must be properly handled during this approach. Vascular structures such as the vertebral artery (particularly at risk near the C1 ring), transverse sinus, and epidural veins must be properly identified and protected during the surgical approach.
Surgical Landmarks and Incisions
The external occipital protuberance and the spinous processes of C2 and C7 should be identified by palpation and fluoroscopy and marked because they assist in identifying the midline. When approaching the occipitocervical region, the surgeon should make a longitudinal midline incision beginning at the external occipital protuberance and extending distally to at least the level of C3 (approximately 6 to 7 cm) ( Fig. 4-2 ). When the subaxial cervical spine is approached, a similar longitudinal midline incision should be made, beginning at the C2 spinous process and extending distally to at least the C7 spinous process ( Fig. 4-3 ).
