The interpretation of spinal xrays (esp the c-spine) is often done by the most inexperience staff in the hospital and can be one of the most daunting xrays to view and comment on. This tutorial is applicable to all levels of medical staff from student to consultant!

Incidence of injuries vs spinal level

The graph above illustrates the incidence of injuries at particular levels in the spinal column. From this it can be seen that after inspection of the xrays you go back and have another look at C1/C2; C5/C6 and T11 – L2

Other statistics about spinal injuries are:

• In children the relative incidence of dorsal fractures is higher
• If a fracture of the spinal column is present then in 20% of cases a second fracture will be present elsewhere
• Cord injuries occur in 10-14% of spinal column fractures
  • Cervical spine 40% of cases
  • Thoracic / lumbar spine 4% of cases
  • Thoracic spine 10% of cases
• If the posterior elements are involved or there is mal-alignment then there is a 60% risk of cord injury

Of those patients with cord injury

• ~ 85% are sustained at time of injury
• ~ 5-10% immediate post injury (mishandling)
• ~ 5-10% present as a late complication

10% of cases of traumatic cord injury have no radiological signs of injury

Spinal Columns

BIOMECHANICS

Spinal column is divided into three columns

1. Anterior - Anterior vert. body + anterior long ligament
2. Middle - Posterior vert. body + post long ligament
3. Posterior

Middle column: If middle column intact → STABLE
or if 2 or more columns affected → UNSTABLE

Injuries are produced by forces generated by movement of the head and trunk. It is very rarely the result of a direct injury.

FLEXION INJURIES

Spine arches anteriorly pivots middle column • Compression vertebral body • Tension on neural arch Anterior Wedging ? posterior ligamentous injury Head flexed on trunk maximum forces on C4-7 Trunk flexes on itself maximum forces on T12-L2

COMPRESSION INJURIES

All 3 columns compressed Especially anterior + middle columns (no fulcrum) Vertebrae + discs act as shock absorbers Pressure inside vertebrae increases → # endplates → sagittal comminuted # "Burst" fracture Often associated with retropulsed fragments with subsequent compromise of the canal.

EXTENSION INJURIES

Arched posteriorly Therefore anterior column in tension Posterior column in compression Spinal Injury cont. EXTENSION Cont. → Rupture of anterior longitudinal ligament +/- Avulsion fracture +/- Disruption of disc space ? Fractures of lamina and facets EXTENSION INJURIES RARELY SEEN OUTSIDE CERVICAL SPINE

ROTATION

High risk of ligamentous disruption with fractured posterior elements Spinal ligaments good at withstanding compressive and tensile forces BUT POOR AT ROTATIONAL FORCES • I.e. " To dispatch a chicken don't flex or extend the neck - wring it !"

SHEARING

High risk of ligamentous disruption Often combined with rotational forces Results in high risk of displacement injuries

IMAGING TECHNIQUES

Radiography - is always the place to start!
Is there an osseous or ligamentous injury?
Is it stable?

Stability is provided by

• Bony structures and ligaments
• Intravertebral discs
• Capsules of apophyseal joints

Instability depends on degree of disruption of stabilising structures. The states of the ligamentous structures are as important as bone in maintenance of stability. Ligamentous / soft tissues not seen by plain x-ray Therefore: VARIATION IN ALIGNMENT OF BONE → INJURY.
Also remember that the eventual position of the bones may not be the same as that at the time of the injury → Initial displacement may have been more severe. Remember as said above that if two or more columns are disrupted then assume instability.

Suggested Protocol for Imaging Cervical Spine

Plain Films

• Lateral
• AP
• Peg (open mouth)

If they are normal and the patient has no relevant symptoms then there is very little chance of injury. However, you MUST SEE C7/T1. If you can't C7/T1 then:

1. Pull arms down
2. Obliques
3. Swimmers
4. ? CT

Flexion/extension views (Following clinical guidelines)

CT

If the plain films show an injury then CT may be indicated to clarify or substantiate the lesion. CT is not the first line of investigation. CT rarely demonstrates unknown fractures. Therefore CT used to further elucidate a known injury.

CT can be difficult to interpret
• Transverse fractures easily missed UNLESS 1. Careful technique 2. Spiral - overlapping slices • Reconstruction • MIPS etc To demonstrate relationship to other vertebrae etc.
• CT used to demonstrate abnormality already detected
• C7/T1
• Poor screening method for Spinal trauma.
• Only 2% of fractures seen on CT are not seen on plain film (i.e. assumed normal)

MRI

• CSF (↑ T2 myelogram like effect)
• Good for looking at soft tissues such as cords, discs, and ligaments
• MPRs
• Possible to assess the whole of the spine
• Difficult to investigate acutely ill patients if ventilated etc.