Cervical spine (flexion and extension views)

Last revised by Andrew Murphy on 23 Mar 2023

The cervical spine flexion and extension views demonstrate the seven vertebrae of the cervical spine when the patient is in a lateral position.

These views are specialized projections often requested to assess for spinal stability.

Note, such functional views should not be performed on trauma patients without the strict instructions of a qualified clinician.

  • the patient is erect, left side against the upright detector 
  • the detector is placed portrait, parallel to the long axis of the cervical spine on the patients left side 
  • the patient will have the neck in the extended (chin up) or flexion (chin down) position depending on the projection
  • lateral projection
  • centering point
    • 2.5 cm above the jugular notch at the level of C4
  • collimation
    • superior to C1
    • inferior to T1
    • anterior to include soft tissue
    • posterior to the soft tissue
  • orientation  
    • portrait 
  • detector size
    • 24 cm x 30 cm
  • exposure
    • 50-75 kVp
    • 20-50 mAs
  • SID
    • 150-180 cm
  • grid
    • yes
  • there should be clear visualization of C7 to T1
  • the image is labeled as 'flexion' or 'extension'  
  • flexion images should demonstrate well separated spinous process 
  • extension images should demonstrate crowding of the spinous process
  • demonstrate to the patient what flexion and extension is before performing 
  • ensure the patient is aware when the examination is over as to avoid extended periods of time in that position 
  • patients who feel unstable on their feet can sit in a chair for this examination 
  • ensure this radiographic series is safe to perform, i.e. part of a secondary survey or under the guidance of an authorized physician 
  • >2.5-3.5 mm of intersegmental translation (a summation of the displacement observed between vertebra tracing the posterior line on both the flexion and extension view) is considered a marker of instability 3

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Cases and figures

  • Fig 1: flexion technique
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  • Fig 2: extension technique
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  • Case 1: normal flexion view
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  • Case 2: normal extension view
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