Normal Anatomy:

The cervical spine contains 7 vertebrae.

The first  two of them are unique and have special names; the atlas and the axis Fig. 1

C3-C7 are mostly classic vertebrae with slight differences  Fig. 2

Cervical spine columns:

In general the vertebral column can be divided  into 3 distinct columns: anterior, middle, and posterior.

 The anterior column:

• The anterior longitudinal ligament (ALL) and the anterior two thirds of the vertebral bodies
• The annulus fibrosus
• The intervertebral discs. 

The middle column:

• The posterior longitudinal ligament (PLL) and the posterior one third of the vertebral bodies.
• The annulus fibrosus.
• The intervertebral discs.

The posterior column:

• Everything posterior to the (PLL).
• contains all of the bony elements formed by the pedicles, transverse processes, articulating facets, laminae, and spinous processes.

Cervical stability is compromised when 2 or more columns are disrupted, as the spine may move as two separate units. Yet, If only one column is disrupted, the other columns may provide sufficient stability to prevent spinal cord injury.  

Famous normal variants of the pediatric cervical spine:

Os odontoidium : Dens absent/ hypoplastic or incompletely fused to C2. Fig. 3

Congenital fusion: one level is usually involved. Not associated with any syndrome. Asymptomatic.

Bifid odontoid Fig. 4

Cleft in posterior neural arches

Spina bifida occulta

Cervical Spine Injuries

–      The most commonly injured vertebra is C2 and to a lesser extent C6 & C7.

–      The most common fracture mechanism in cervical injuries is flexion.

–      They can be classified according to their stability into:

Fig. 15: Classification of the cervical spine fractures according to their stability

UNSTABLE FRACTURES:

•    Jefferson fracture 

-  A burst fracture of the ring of C1 characterized by bilateral lateral displacement of the lateral masses. Fig. 5

-  The status of the transverse ligament is essential to be assessed to ensure C1/C2 stability (it can be suggested by separation distance of more than 7 mm).

•   Hangman's fracture:

            Traumatic spondylolisthesis of C2. Although it is mostly considered  an unstable fracture, it is rarely associated with spinal injury only when  associated with unilateral or bilateral facet dislocation at the level of C2. Fig. 6 Fig. 7

•  Unstable odontoid fractures:

Type II: the most common  

  Fracture of the base of the dens. 

  Always unstable

  Bad healing prognosis. Fig. 8

Type III:

  Fracture through the body of the axis
  Can be unstable,

  Better healing prognosis than type II.

•  Unstable wedge fracture :

     Anterior wedge fracture + interspinous ligamentous rupture ( Anterior and posterior column affection).

•  Bilateral interfacet dislocation :

- Anterior dislocation of the articular masses  associated with affection of the  posterior longitudinal ligament, the disc and the anterior longitudinal ligament. Fig. 9

- The upper vertebra is anteriorly displaced one-half of the lower vertebral body diameter. Fig. 10

•  Flexion teardrop fracture: 

- The teardrop bony fragment is the detached anteroinferior aspect of the vertebral body. Fig. 11
-The rest of the vertebral body is pushed into the spinal canal .

•  Extension teardrop fracture:

- The teardrop bony fragment is the avulsed anteroinferior aspect of the vertebral body. Fig. 12

- The cord injury is caused by ligamentum flava buckling during the accident

- This injury is stable in flexion but highly unstable in extension

STABLE FRACTURES:

•  Anterior subluxation also called hyperflexion sprain:

 Hyperflexion ligamentous rupture without bony fracture (the anterior and middle columns are intact).

•  Stable  odontoid fracture:

Type I: Avulsion of the tip of the dens where it is attached to C1.

•   Simple wedge fracture:

 Anterior wedging of 3mm or more suggesting fracture mostly involving the upper endplate. (The posterior ligaments are intact).

•  Unilateral interfacet dislocation

Sliding and locking of one superior facet over the inferior one with anterior subluxation of the vertebral body of the upper vertebrae about 25% of the lower one diameter . Fig. 13

•   Transverse process fracture

•   Clay Shoveler’s Fracture: 

Fracture of C7 cervical spine Fig. 14

Simple Systematic approach to cervical spine film reading :

1·  Check cervical spine alignment by following three imaginary lines :

• Anterior one passing through the anterior margin of all vertebrae
• Posterior one passing through the posterior aspect of all vertebrae
• Spinolaminar one passing  through the bases of the spinous processes

2·  Check each vertebra for obvious fracture lines.

3· Check predental space (normally <3 mm im adults and <5 mm in children).

4·  Check soft tissue changes in the prevertebral spaces.

•  At the level of C2 <7mm
•  At the level of C3 and C4 < 5 mm
•  At the level of C6 < 22 mmin adults or < 14 mm in children younger than 15 years.

5·  Check for widening of the space between the two spinous process tip.