Pediatric elbow (horizontal beam AP view)

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The horizontal beam anteroposterior elbow view for pediatrics is an alternative projection to the anteroposterior view in the elbow series, examining the distal humerus, proximal radius and ulna.

Indications

This view is ideal for patients who are unable to move their arm as per the standard elbow positioning technique but require assessment of the elbow joint in its natural anatomical position. It demonstrates any suspected dislocations or fractures in the elbow joint.

Patient position

  • sitting (see Figure 1)
    • patient is seated next to the table
    • the medial border of the extended arm and forearm are kept in contact with the tabletop
    • detector is posterior to the elbow joint
  • standing erect (see Figure 2)
    • patient stands with back touching the upright bucky
    • the posterior aspect of the supinated and extended arm and forearm are kept in contact with the upright bucky

Technical factors

  • anteroposterior projection
  • centering point
    • midpoint between the humeral epicondyles 
  • collimation
    • superior to the distal third of the humerus
    • inferior to include one-third of the proximal radius and ulna
    • lateral to include the skin margin 
    • medial to include medial skin margin 
  • orientation  
    • portrait
  • detector size
    • 18 cm x 24 cm
  • exposure
    • 50-57 kVp
    • 1.6-2 mAs
  • SID
    • 110 cm
  • grid
    • no 

Image technical evaluation

  • the elbow is in an AP position, with slight internal rotation.
  • patient's arm should be rotated externally to ensure that the trochlea and capitellum are seen in profile. 

Practical points

Preparing the room beforehand (setting up the detector, exposure and preparing lead gowns) is extremely beneficial for elbow imaging as young children may begin to cry the moment their affected arm is brought away from their body.

If the patient is seated, it may be ideal to elevate the patient's arm by having a flat radiolucent sponge placed medially (see Figure 1). This ensures the medial soft tissue margin of the elbow is included, especially when the detector is positioned on the same tabletop as the patient's arm.

As with trauma imaging, preparing the room for a horizontal beam image may not always be the first line of action. Having clear positioning instructions prepared and all immobilization devices (i.e. radiolucent sponges) within reach may be useful in obtaining the image efficiently.

Immobilization techniques

To prevent malrotation/motion artifact in the radiograph, parental holding at the proximal half of the child’s arm and distal half of the forearm may be required.

  • if the parent is accompanying the child, whilst the parent puts on a lead gown, it is the radiographer's responsibility to ensure the child does not fall off the chair
  • other alternative methods such as distraction techniques may be ideal to avoid scattered radiation to parents and staff