The Lateral Cervical Spine X-Ray
The normal cross-table lateral cervical
spine X-ray must visualise the entire cervical spine, from the skull
base to the cervico-thoracic junction. A film that does not show the
upper border of T1 is inadequate and should be repeated or supplemented
with a swimmer's view (flying angel). Caudad traction on the arms
will improve the view obtained - someone else should stabilise the
patient's head and pelvis during the X-Ray.
Next, examine the alignment of the columns of the cervical spine.
The anterior vertebral line, posterior vertebral line and spinolaminar
line should have a smooth curve with no steps or discontinuities.
Note that malalignment of the posterior vertebral bodies is more
significant than that anteriorly, which may be due to rotation.
A translation of > 3.5mm is significant anywhere. Spinal canal diameter
(between posterior cortex of vertebral bodies and spinolaminar line)
should be 18mm or greater. Narowing of the canal is definitely present
if this is reduced to 14mm or less.
Anterior subluxation of one vertebra on another indicates facet
dislocation. Less than 50% of the width of a vertebral body and
this is a unifacet dislocation. More than 50% is a bilateral facet
dislocation. This is usually accompanied by widening of the interspinous
and interlaminar spaces.
Examination of the vertebral bodies and the intervertebral disc
space will reveal compression and burst type injuries. Bodies should
be regular cuboids similar in size and shape to the vertebrae immediately
above and below (not C1/C2). Compression fractures may present as
anterior wedging of the vertebral body or teardrop fractures of
the antero-inferior portion of the body (compression in flexion).
The presence of a compression type injury as shown, with malalignment
of the anterior or posterior cortices or anterior compression of
greater than 40% of normal body height indicates a burst fracture,
with retropulsion of fragments of the vertebral body into the spinal
Loss of height of an intervertebral disc space, when compared
to adjacent spaces may indicate disc herniation - usually posteriorly
into the canal. Analysis of the prevertebral soft tissues may allow
the diagnosis of cervical injuries from very subtle changes on the
lateral film. The soft tissue shadow is created by the pharyngeal
and prevertebral tissues, with the posterior larynx and oesophagus
thickening the shadow below C4. Above C4 the width of the shadow
should be less than 50% of the width of a vertebral body, while
below C4 the limit is one full vertebral body width.
Atlanto-occipital disassocation can be very difficult to diagnose
and is easily missed. The distance from the occiput to the atlas
should not exceed 5mm anywhere on the film.
The odontoid peg must also be specifically examined for fractures.
Soft tissue swelling anterior to the arch of C1 will suggest the
presence of a fracture at this level. The Atlanto-Dens Interval
(ADI) in adults should be < 3mm (in flexion). Shift of more than
3.5mm implies injury to the transverse ligament, and more than 5mm
indicates complete rupture and instability. The C1-C2 interspinous
space should not be more than 10mm wide.