Thumb (oblique view)

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The thumb oblique view is a part of the thumb series and is particularly useful in cases with traumatic indications.

Indications

This projection will demonstrate the thumb in its natural 'AP' position, it is the thumb radiograph you would observe on an AP hand radiograph. It is a great projection to assess the thumb for the base of thumb fractures.

Patient position

  • patient is seated alongside the table
  • forearm is placed on table
  • the wrist is kept in ulnar deviation and thumb abducted
  • fingers are kept in contact with the image receptor allowing the thumb to sit in a 45 degree obliqued position (see Figure 1)

Technical factors 

  • posteroanterior projection
  • centering point
    • 1st metacarpophalangeal joint space.
  • collimation
    • laterally to the skin margins
    • distal to the midway up the metacarpals
    • proximal to the include one-quarter of the distal radius and ulna
  • orientation  
    • portrait
  • detector size
    • 18 cm x 24 cm
  • exposure
    • 50-60 kVp
    • 3-5 mAs
  • SID
    • 100 cm
  • grid
    • no

Image technical evaluation

1st digit is positioned obliquely. Ideally the long axis of the thumb should run parallel to the image receptor.  There should be no foreshortening of the phalanges, the joint spaces should bot be completely open.

Practical points

It is best not to overthink this projection, think of it as PA hand with some slight ulnar deviation and a tight collimation over the thumb. It's best to do dedicated thumb views when there is thumb pathology suspected, centering at the hand cause problems with beam divergence.