Lumbar spine (oblique view)

The lumbar spine oblique view is used to visualise the articular facets and pars interarticularis of the lumbar spine. 

Indications

This view is used most commonly to assess for a pars interarticularis defect, although this has largely been superseded by CT and MRI. Additionally, it is a frequently used view for needle placement in fluoroscopic guided procedures ², such as transforaminal epidural steroid injections.  

Patient position

• the radiographs can be performed with the patient in the posteroanterior (PA) erect or supine position
  • PA erect
    •  two radiographs performed with patient at RAO 35-45°  and LAO 35-45°  
  • supine
    •  two radiographs performed with patient at RPO 35-45°  and LPO 35-45°  
• ensure arms are removed from the region of interest 
• using a 45° radiolucent sponge in the supine position will assist the patient in maintaining the correct position, whilst flexing the knees will also provide stability. 

Technical factors

• left and right oblique positions
• expiration (to minimise superimposition of the diaphragm over the upper lumbar spine) 
• centring point
  • PA erect
    • 2.5 cm above the iliac crests and 3 cm lateral from the spinous processes towards the upside. RAO and LAO will demonstrate the facet joints on the upside, for example, the LAO position will show the right facet joints
  • supine
    • 2.5 cm above the iliac crests and 5 cm medial from the ASIS on the upside. RPO and LPO will demonstrate the facet joints on the downside, for example, the RPO position will show the right facet joints 
• collimation
  • superiorly to include the T12/L1 junction 
  • inferior to include the L5/S1 junction 
  • anterior to include the anterior border of the lumbar vertebral bodies 
  • posterior to include all elements of the posterior column, particularly the spinous processes 
• orientation
  • portrait
• detector size
  • 35 cm x 43 cm 
• exposure
  • 70-80 kVp
  • 60-80 mAs 
• SID
  • 110 cm
• grid
  • yes (ensure the correct grid is selected if using focused grids)

Image technical evaluation

• the entire lumbar spine should be visible from T12/L1 - L5/S1
  • check department protocol before imaging, as focused imaging of the lower lumbar vertebrae may be required 
• a well-positioned oblique lumbar radiograph will demonstrate the scottie dog sign, showing the articular processes and facet joints  
• adequate image penetration and image contrast is evident by clear visualisation of lumbar vertebral bodies, with both trabecular and cortical bone demonstrated
• pedicles should be in the central of the vertebral bodies 

Practical points

• to correct poor positioning consider the location of the pedicles
  • if they are anterior on the vertebral body- rotate the patient more
  • if they are posterior on the vertebral body- rotate the patient less