Lumbar spine (AP/PA view)

The lumbar spine AP view images the lumbar spine which consists of five vertebrae. It is utilised in many imaging contexts including trauma, postoperatively, and for chronic conditions. 

  • the patient is erect or supine, depending on clinical history
    • ideally, spinal imaging should be taken erect in the setting of non-trauma to give a functional overview of the lumbar spine
    • all imaging of patients with suspected spinal injury must occur in the supine position without moving the patient
  • in the supine projection hands are placed by the patient's side
  • if performing erect, position the patient in the PA position; this has numerous advantages including reduced dose to the gonadal region and utilisation of beam divergence; arms can be placed by the side, or the handlebars of the erect bucky can be held for patient stability
  • anteroposterior projection
  • suspended expiration (for a uniform density) 
  • centring point
    • the level of the iliac crests at the MSP 
    • the central ray is perpendicular to the image receptor 
  • collimation
    • superiorly to include the T12/L1 junction
    • inferior to include the sacral region 
    • lateral to include the transverse processes and sacroiliac joints
  • orientation  
    • portrait
  • detector size
    • 35 cm x 43 cm 
  • exposure
    • 70-80 kVp
    • 40-60 mAs 
  • SID
    • 110 cm
  • grid
    • yes (ensure the correct grid is selected if using focused grids)
  • the entire lumbar spine should be visible, with demonstration of T11/T12 superiorly and the sacrum inferiorly. 
  • no patient rotation as evident by central spinous processes and the symmetrical appearance of the sacroiliac joints and iliac wings
  • intervertebral joints are visualised 
  • adequate image penetration and image contrast is evident by clear visualisation of lumbar vertebral bodies, pedicles, and facet joints, with both trabecular and cortical bone demonstrated
  • the three column concept of thoracolumbar spinal fractures is of particular importance when assessing this image for pathology
  • take particular care when imaging patient on a trauma trolley that the image receptor is aligned to the central ray to prevent anatomy exclusion and grid cut-off
  • ideally, the transverse processes should be visible, although demonstration is often obscured by overlying bowel gas; radiographers should ensure over exposure is not a factor contributing to the poor visualisation which could mask a transverse process fracture 
  • when imaging in a supine position, a triangular cushion can be placed under flexed knees to reduce lumbar lordosis, and thus aiding to open the intervertebral joints
Radiographic views
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Article information

rID: 49355
Section: Radiography
Synonyms or Alternate Spellings:

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Cases and figures

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    Case 1: normal lumbar spine radiographs
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    Case 2: normal lumbar spine radiograph - infant
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    Case 3: acute L1 burst compression fracture
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