Posterior Approach to Cervical Spine

Fig. 11.1

The standard midline posterior approach to the cervical spine is carried through the two symmetrical extensor muscle compartments down to the dorsal surface of the neural arches

Thus, ligamentum nuchae, the septum between the two continuous muscular compartments, is a true internervous plane, and no particular structure is at risk if dissection is carefully conducted through it. Moreover, this minimizes blood loss and maintains a stout tissue layer for closure of the wound.

The posterior midline approach allows surgical exposure of the posterior arches of the vertebrae up to the occiput.

After positioning of the patient (Fig. 11.2), prior to any incision, an accurate trichotomy of the nuchal area might be necessary depending on the segments to be exposed.

Fig. 11.2

Prior to incision, identification of the superficial landmarks is crucial. Shoulders are retracted in order to allow intraoperative fluoroscopic control at the cervicothoracic junction

The main superficial landmarks are as follows:

External occipital prominence of the occiput (inion)
First palpable spinous process → C2 (axis)
Prominent spinous process of the cervicothoracic junction → C7 (vertebra prominens)
Mastoid processes

11.1 Upper Cervical Spine (C1-C2)

The width of the spinal canal at the craniocervical junction (CVJ) is wider than that in the lower segments of the cervical spine. Thus, instability is a more frequent indication than cord compression to assess the CVJ from posterior.

After midline skin incision, the tip of the spinous process of C2 can be palpated under the inferior aspect of the occipital bone. Immediately above, on the midline and 1–2 cm anteriorly, lies the posterior tubercle of C1 under the thick layer of suboccipital muscles (rectus capitis posterior – major and minor; oblique – superior and inferior, Fig. 11.3).

Fig. 11.3

Muscles of the occipitocervical region (rectus capitis posterior – major and minor; oblique – superior and inferior)

The bony topography between the lamina and the lateral mass of C2 (axis) is indistinct. Thus, dissection of these muscles must be carried gently and special care must be taken beyond the first 12–15 mm in order not to damage the following neurovascular structures:

Vertebral artery
First cervical nerve
Second cervical nerve (Arnold nerve)
Suboccipital venous plexus (behind C1-C2 interspace)

11.1.1 Anatomical Key Points

1.

Posterior tubercle of C1
2.

Transverse processes of C1
3.

Spinous process of C2 (bifidus)

11.1.2 Focus On: Vertebral Artery

Surgical anatomy of the vertebral artery (VA) can be subdivided in four segments (Fig. 11.4):

V1, from its origin from the subclavian artery (anterior to the C7 transverse process) to the entry point of C6 foramen transversarium
V2, within C6-C1 transverse foramina
V3, from the superior aspect of the arch of the atlas to the foramen magnum (C0)
V4, intradural course from the foramen magnum to unite with the contralateral VA to form the basilar artery

Fig. 11.4

Course of the vertebral artery (VA)

The highest risk for injury during posterior approaches is in the V3 tract while dissecting the occipitocervical junction (4.2–8.1%). Ebraheim et al. suggest that dissection on the posterior aspect of the posterior ring should remain within 12 mm lateral to the midline, and dissection on the superior aspect of the posterior ring should remain within 8 mm of the midline.

However, depending on the procedures to be performed, different tracts of the VA can be at risk (Fig. 11.5).

Fig. 11.5

Case report. A 19-year-old female, C4 right lateral mass osteoblastoma (OBL, WBB 8–10/A-D) complaining of neck pain with occasional numbness to the right arm (a). Right dominant VA symptomatic at occlusion test prior to embolization. Double-approach procedure, A: pre-SCM approach, VA release (b) and intralesional excision (c); P: posterior approach, stabilization with lateral mass screws and complete excision (d). Unlike most posterior procedures, VA is at risk at V2 crossing the deep surgical field (e). Postoperative CT scan shows complete excision (f)

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