Trauma X-ray - Axial skeleton Cervical spine - Normal anatomy
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 - Pre-vertebral
Edge of image
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.
Lateral view
The lateral view is often the most informative image. Assessment requires a systematic approach.
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
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
Pre-vertebral soft tissue - Some fractures cause widening of the pre-vertebral soft tissue due to pre-vertebral haematoma
- Normal pre-vertebral 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 pre-vertebral haematoma - lack of pre-vertebral soft tissue thickening should NOT be taken as reassuring
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.
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 itself 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.
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.
