Trauma X-ray - Axial skeleton

Cervical spine - Normal anatomy

Clinical considerations are particularly important in the context of Cervical spine (C-spine) injury. This is because normal C-spine X-rays cannot exclude significant injury, and because a missed C-spine fracture can lead to death, or life long neurological deficit.

Clinico-radiological assessment of spinal injuries should be managed by experienced clinicians in accordance with local and national clinical guidelines. Imaging should not delay resuscitation.

Further imaging with CT or MRI (not discussed) is often appropriate in the context of a high risk injury, neurological deficit, limited clinical examination, or where there are unclear X-ray findings.

Standard views

The 3 standard views are - Lateral view - Anterior-Posterior (AP) view - and the Odontoid Peg view (or Open Mouth view). In the context of trauma these images are all difficult to acquire because the patient may be in pain, confused, unconscious, or unable to cooperate due to the immobilisation devices.

Additional views

If the lateral view does not show the vertebrae down to T1 then a repeat view with the arms lowered or a 'Swimmer's view' may be required.

Key points

  • Normal C-spine X-rays do not exclude significant injury
  • Clinical considerations are of particular importance when assessing appearances of C-spine X-rays
  • Look at all views available in a systematic manner

C-spine - Systematic approach

  • Coverage - Adequate?
  • Alignment - Anterior/Posterior/Spinolaminar
  • Bones - Cortical outline/Vertebral body height
  • Spacing - Discs/Spinous processes
  • Soft tissues - Prevertebral
  • Edge of image

Lateral view

The lateral view is often the most informative image. Assessment requires a systematic approach.

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C-spine systematic approach - Normal Lateral 1

  • Coverage - All vertebrae are visible from the skull base to the top of T2 (T1 is considered adequate)
  • - If T1 is not visible then a repeat image with the patient's shoulders lowered or a 'swimmer's' view may be necessary

  • Alignment - Check the Anterior line (the line of the anterior longitudinal ligament), the Posterior line (the line of the posterior longitudinal ligament), and the Spinolaminar line (the line formed by the anterior edge of the spinous processes - extends from inner edge of skull).
  • - GREEN = Anterior line

    - ORANGE = Posterior line

    - RED = Spinolaminar line

  • Bone - Trace the cortical outline of all the bones to check for fractures
  • Note: The spinal cord (not visible) lies between the posterior and spinolaminar lines
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C-spine systematic approach - Normal Lateral 2

  • Disc spaces - The vertebral bodies are spaced apart by the intervertebral discs - not directly visible with X-rays. These spaces should be approximately equal in height
  • Prevertebral soft tissue - Some fractures cause widening of the prevertebral soft tissue due to prevertebral haematoma
  • - Normal prevertebral soft tissue (asterisks) - narrow down to C4 and wider below

    - Above C4 ≤ 1/3rd vertebral body width

    - Below C4 ≤ 100% vertebral body width

    Note: Not all C-spine fractures are accompanied by prevertebral haematoma - lack of prevertebral soft tissue thickening should NOT be taken as reassuring

  • Edge of image - Check other visible structures
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C-spine normal anatomy - Lateral (detail)

  • Bone - The cortical outline is not always well defined but forcing your eye around the edge of all the bones will help you identify fractures
  • C2 Bone Ring - At C2 (Axis) the lateral masses viewed side on form a ring of corticated bone (red ring )
  • This ring is not complete in all subjects and may appear as a double ring
  • A fracture is sometimes seen as a step in the ring outline

AP view

Although often less informative than the lateral view this view may nevertheless provide important corroborative information - a systematic approach is required.

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C-spine systematic approach - Normal AP

  • Coverage - The AP view should cover the whole C-spine and the upper thoracic spine
  • Alignment - The lateral edges of the C-spine are aligned (red lines )
  • Bone - Fractures are often less clearly visible on this view than on the lateral
  • Spacing - The spinous processes (orange) are in a straight line and spaced approximately evenly
  • Soft tissues - Check for surgical emphysema
  • Edges of image - Check for injury to the upper ribs and the lung apices for pneumothorax

Odontoid peg/Open mouth view

Although called the 'odontoid peg' view the odontoid peg is often obscured on this view by overlapping structures such as the teeth or occiput. Many refer to this view as the 'open mouth' view. Its primary purpose is to view lateral mass alignment.

Even if a fracture of the odontoid peg is present it is often not visible with this view. If a peg fracture is not visible, but is suspected clinically by a senior clinician, then further imaging with CT should be considered.

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C-spine normal anatomy - Open mouth view

  • This view is considered adequate if it shows the alignment of the lateral processes of C1 and C2 (red circles)
  • The distance between the peg and the lateral masses of C1 (asterisks) should be equal on each side
  • Note: In this image the odontoid peg is fully visible which is not often achievable in the context of trauma due to difficulty in patient positioning
Open mouth view - Rotated
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Open mouth view - Rotated

  • The distance between the peg and the lateral processes is not equal - compare A (right) with B (left)
  • This is because when the image was acquired the patient's head was rotated to one side
  • Alignment of the lateral processes can still be assessed and is seen to be normal

'Swimmer's' view

This is an oblique view which projects the humeral heads away from the C-spine. A swimmer's view may be useful in assessing alignment at the cervico-thoracic junction if C7/T1 has not been adequately viewed on the lateral image, or on a repeated lateral image with the shoulders lowered.

The view is difficult to achieve, and often difficult to interpret. If plain X-ray imaging of the cervico-thoracic junction is limited then CT may be required.

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C-spine normal anatomy - ' Swimmer's' view

  • Oblique image with the humeral heads projected away from the C-spine
  • The cervico-thoracic junction can be seen
  • Check alignment by carefully matching the corners of each adjacent vertebral body - anteriorly and posteriorly

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