Each segment from C3 to C7 is made up of a centrum (body) and two posterior arches that form from mesenchymal tissue migrating around each side of the neural tub.

The facet joints initially are relatively horizontal and, during growth, gradually become more vertical, which enhances stability in flexion and extension. The vertebral bodies initially have an oval or wedge shape but gradually become fully ossified in a more rectangular configuration.⁴ The spinal nerve exits the canal through the interpedicular foramen. The ventral ramus travels anterolaterally on the transverse process. The spinal nerve sits anteromedial to the anterior aspect of the superior facet. The dorsal ramus runs posteriorly against the anterolateral corner of the base of the superior articular process. When the lateral mass is divided into quadrants, the superolateral quadrant is away from the spinal nerve.

The vertebral artery enters the transverse foramen of the sixth cervical vertebra and courses cephalad through the foramina. The vertebral artery is anterior to the lateral mass but is also anterior to the spinal nerve (FIG 2).

A study by Al-Shamy et al¹ of computed tomography (CT) scans of the pediatric cervical spine found that in children age 4 years and older, the size of the lateral mass would allow for lateral mass screw fixation from C3 to C7.

Trauma

Tumor: Aneurysmal bone cyst, osteoblastoma, and osteochondroma involving posterior elements are the tumors most likely to be encountered in the first and second decades of life.

Iatrogenic: posterior instability after tumor decompression or postlaminectomy

Congenital/syndromic: Anomalous cervical spine anatomy can be seen with VACTERL (vertebral, anal atresia, cardiac, tracheoesophageal fistula, renal anomalies, and limb defects) and Klippel-Feil syndrome.

Cervical kyphosis

Instability of the subaxial spine can present with or develop myelopathy.

There is risk of progressive neurologic symptoms and/or progressive deformity of the cervical spine.

Paralysis or death are rare but may occur.

A thorough history for traumatic injury, conditions that are associated with cervical instability, or history of posterior cervical surgery

Patients may present with complaints of neck pain or decreased range of motion. Patients may have neurologic symptoms on presentation, which may be radicular in nature from cervical nerve root compression or myelopathic from spinal cord compression.

Examination should include a thorough neurologic evaluation including motor and sensory examinations and assessment for myelopathy (hyperreflexia, clonus, pathologic reflexes).

Assess for possible associated abnormalities including a cardiac examination (for congenital/syndromic etiologies).

Standard radiographs including anteroposterior (AP) and lateral views in neutral, flexion, and extension. An open mouth view should also be taken to ensure that concomitant O/C1/C2 instability is not present.

Lateral views allow for assessment of true instability from pseudosubluxation, which occurs most commonly between the second and third cervical vertebrae and between the third and fourth cervical vertebrae.

The spinolaminar line of Swischuk is helpful to differentiate between pseudosubluxation and true subluxation. This line is drawn along the posterior arch from the first cervical vertebra to the third. It should pass within 1.5 mm of the anterior cortex of the posterior arch of the second cervical vertebra during forward flexion. As long as Swischuk line is maintained, as much as 4 mm of vertebral body subluxation can be accepted.

Fine-cut CT scan of the cervical spine to assess for anomalies of the cervical anatomy including location of the vertebral artery and for preoperative planning of screw lengths and trajectories

Magnetic resonance imaging (MRI) to evaluate for spinal cord or nerve root involvement

Stable cervical spine deformity with no neurologic involvement can be treated with observation and serial imaging.

Unstable cervical spine, neurologic involvement, or progressive deformity would be indications for surgical management.

Many techniques of posterior cervical fusion including wiring, plate and screw, and rod and screw constructs have been described.

Lateral mass screw fixation provides benefits compared to nonrigid fixation including fixation of patients with posterior laminar element deficiency, providing immediate stability, and allowing for greater deformity correction.