Spinal Imaging

OVERVIEW

• CT is the best way to image the spine for bony injuries (will miss 6% of discoligamentous injuries)
• if suspected soft tissue or spinal cord injury -> patient requires an MRI

CHECK LIST

Sagittal images

• space between anterior arch of C1 and peg (< 3mm in adults, < 5mm in children)
• posterior cortex of C1
• anterior cortex of peg
• spinolaminar line of C1-C3
• anterior and posterior spinolaminar lines
• bodies height and alignment
• facets aligned
• no subluxation or widening
• no prevertebral swelling
• discs intact
• no soft tissue swelling

Axial images

• space between arch and peg < 3mm
• no significant rotation (< 15 degrees OK)
• no soft tissue swelling
• integrity of ring

Coronal images

• symmetry of peg and lateral masses
• facets aligned
• height of vertebral bodies
• discs and facet joints aligned

DISORDERS

Bilateral facet joint dislocation

• AP: narrowed disc space
• lateral: anterior and posterior vertebral body lines and spinolaminar lines disrupted > 50%, angulation
• surgical emergency: requires urgent traction or immediate open reduction if patient is neurological normal or has a incomplete spinal injury.

Unilateral facet joint dislocation

• AP: spinous processes below the dislocation do not align with those above it, interspinous processes widened.
• lateral: facet joint dislocation, 25% forward shift
• oblique: facet join dislocation better seen
• traction can be used but if unsuccessful -> emergency surgery seldom required.

Odontoid fractures

• I: tip of odontoid
• II: junction of dens and body
• III: extending into body of C2

Atlanto-occipital subluxation

• can be potentially fatal -> injury of craniocervical junction or brain stem
• I: anterior subluxation
• II: vertical distraction of atlanto-occipital joint > 2mm
• III: posterior dislocation

Compressive flexion injury

• I: blunting of the anterior-superior vertebral margin
• II: beak-like appearance to the anterior vertebral body with loss of anterior vertebral height and an oblique contour.
• III: fracture extending from the anterior surface of the vertebral body into the disc space.
• IV: posterior displacement of the inferoposterior aspect of the vertebral body 3mm

Distraction extension injury

• I: abnormal widening of the disc space (disruption of the anterior longitudinal ligament and disc)
• II: posterior ligaments are disrupted and the cephalad vertebrae are displaced into the spinal canal.

Compressive extension injury

• damage to vertebral arch but the body of the affected vertebra remains intact.
• can be unilateral or bilateral
• can involve the pedicle, articular or lamina (or a combination of these)

Vertebral compression injury

• body fracture (loss of height)
• retropulsion into the vertebral canal
• I: central fracture of either the superior of inferior endplate with a ‘cupping deformity’
• II: both endplates are involved
• III: vertebral body fragmented with fragments displaced in multiple directions.

Diffuse idiopathic skeletal hyperostosis (DISH)

• anterior extensive ossification along vertebral bodies.
• if come with neck pain -> require an MRI as cord is very susceptible given small canal.

Chance fracture

• flexion-distraction injury
• widening of the interspinous interval
• fracture line through the body
• high incidence of a intra-abdominal injury

TRICKS AND TRAPS

Congenital anomalies

• look for fractures lines -> if lines smooth think congenital problem
• deficiency in posterior arch of C1
• C1 ring symmetry will be maintained
• odontoideum: dens separated from the body of C2
• deficiency of anterior arch of C1