Thumb (lateral view)

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The thumb lateral view is an orthogonal projection of AP/PA view.

Indications

As with all thumb radiographs, this is a view requested for a number of reasons including trauma, suspected inflammatory process or foreign body (to name a few). This particular view helps in the localization of a foreign body in the thenar eminence, as well as providing valuable information of suspected dislocations.

Patient position

  • patient is seated alongside the table
  • the forearm is placed on table
  • the wrist is kept in ulnar deviation and thumb abducted
  • lateral aspect of thumb is brought into contact with the cassette by curling fingers (see Figure 1)

Technical factors 

  • posteroanterior/anteroposterior projection
  • centering point
    • first metacarpophalangeal joint space
  • collimation
    • laterally to the skin margins
    • distal to skin margin
    • proximal to the carpometacarpal joint 
  • orientation  
    • portrait
  • detector size
    • 18 cm x 24 cm
  • exposure
    • 50-60 kVp
    • 3-5 mAs
  • SID
    • 100 cm
  • grid
    • no

Image technical evaluation

The first digit is positioned laterally, evidenced by open joint spaces and superimposition of the phalangeal and metacarpal heads.

Practical points

This position is easily achieved with a gentle internal rotation of the hand until the thumbnail is running perpendicular to the detector. Doing it ulna deviation is the ideal method to attaining an image of high quality, yet previous injuries may prevent the patient from doing it. If the joint spaces are not open, and you have been conservative with raising the hand into the lateral position, you may need to place a small sponge under the patient's hand to maintain a lateral thumb without putting pressure on the hand. If the second metacarpal base is superimposed over the thumb, you have raised the hand too much.