Lumbar spine (lateral view)

The lumbar spine lateral view images the lumbar spine which generally consists of five vertebrae (see: lumbosacral transitional vertebra).

Indications

This projection shows an orthogonal view of the AP/PA view and is utilized in many imaging contexts including trauma, postoperatively, and for chronic conditions. This view is also ideal in characterizing spinal alignment. 

Note: Ideally, spinal imaging should be taken erect in the non-trauma setting to give a functional overview of the lumbar spine. Otherwise, patients with a suspected spinal injury must remain in the supine position without any movement.

Patient position

• the patient is positioned erect, supine or lateral recumbent, depending on clinical history
• in the lateral decubitus position, position the patient so that the humeri are extended 90 degrees to the thorax, with the elbows flexed so that the forearms are parallel to the thorax. Spinal curvature in the AP projection will determine if a right lateral or a left lateral is performed. 
• when implementing horizontal beam technique, ensure the distal upper limbs are not overlying the region of interest. Ask the patient to cross their arms over their upper thorax, or to extend them in a similar position to that achieved in the lateral decubitus position

Technical factors

• lateral projection
• expiration (to minimize superimposition of the diaphragm over the upper lumbar spine) 
• centering point
  • the level of the iliac crest 
  • coronal centering point is directly over the lumbar vertebra, which corresponds to the posterior third of the abdomen 
  • the central ray is perpendicular to the image receptor 
• collimation
  • superiorly to include the T12/L1 
  • inferior to include the sacrum 
  • 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 
• superimposition of the greater sciatic notches, the superior articulating facets and the superior and inferior endplates. This indicates a true lateral has been achieved 
• adequate image penetration and image contrast is evident by clear visualization of lumbar vertebral bodies, with both trabecular and cortical bone demonstrated

Practical points

• the three-column concept of thoracolumbar spinal fractures is of particular importance when assessing this image for pathology
• utilize an erect bucky when performing horizontal beam laterals to utilize oscillating grids, automatic expose control, and CR/IR alignment  
• if the patient demonstrates spinal scoliosis, ensure that the side with the convexity is closest to the IR. This will utilize the diverging beam and aid in achieving superimposition of the upper and lower endplates
• for particular patients, it is advisable to place a small radiolucent triangle sponge under the side in contact with the table at waist height to reduce spine convexity
• a spot radiograph may be required to show a clearer visualization of the L4/L5/S1 articulation 
• try to remove as many possible image artefacts (i.e. ECG leads, urinary catheters), especially when performing horizontal beam technique in a trauma context 
• a breathing technique is a radiographical technique employed in some departments if imaging equipment permits. 
• if using a CR system, a smaller cassette 30x35 can be used when the sacral region does not need to be demonstrated. When centering, place the height of the CR 2.5cms above the iliac crests