Thumb (lateral view)

The thumb lateral view is an orthogonal projection toof AP/PA view and helps helps in the localisation 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 in ulnar deviation and thumb abducted
• lateral aspect of thumb is brought ininto contact with the cassette by curling fingers (see Figure 1)

Technical factors 

• posteroanterior/anteroposterior projection
• Collimation:

  To include entire thumb and carpometacarpal joint, centring approximately over thepoint

  • first metacarpophalangeal joint space.
• collimation
  • laterally to the entire first digit is visualised, includingskin margins
  • distal to skin margin
  • proximal to the carpometacarpal (CMC) joint.

    Positioning

    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

1stThe first digit is positioned laterally, evidenced by open joint spaces and superimposition of the phalangeal and metacarpal heads. There

Practical points

This position is slight superimpositioneasily achieved with a gentle internal rotation of the basehand 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 2ndpatient 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 base ofthumb, you have raised the 1st metacarpal, which is not ideal.hand too much.