Pediatric thumb (oblique view)

The oblique thumb view in pediatrics is an additional projection for thumb imaging. Typically, this view is not performed unless specified by the referring doctor or radiologist. 

Indications

For pediatrics, this oblique view is only indicated when specifically requested. This view may help to demonstrate the location of a foreign body or to demonstrate the location of any fractures. This view best demonstrates base of thumb fractures. 

Patient position

• patient is seated alongside the table or supine with arm outstretched
• fingers are kept in contact with the image receptor allowing the thumb to sit in a 45 degree obliqued position

Technical factors

• posteroanterior oblique projection
• centering point
  • first metacarpophalangeal joint space
• collimation
  • laterally to the skin margins
  • proximal to the carpometacarpal joint
• orientation
  • portrait
• detector size
  • 18 cm x 24 cm
• exposure ¹
  • 40-46 kVp
  • 0.8-2 mAs
• SID
  • 100cm
• grid
  • no

Image technical evaluation

Thumb is visualized with a concave appearance on the anterior side of the phalanges ². Interphalangeal and metacarpophalangeal joint spaces may not be completely open. The correct thumb must be correctly labeled and identified. 

Practical points

Preparing the room beforehand (setting up the detector, exposure and preparing lead gowns) is important as pediatric patients may not remain still when their affected thumb is moved onto the detector. 

Immobilization techniques

For this oblique view, it is particularly important to avoid superimposition of the other fingers; hence the child's parent or radiographer may need to assist in keeping other fingers still. 

It is also important for the radiograph to be free from motion artifact and rotation to avoid repeated x-rays.

• it may be necessary for the parent or radiographer to hold the patient in position
• ideally the parent should be in the child's direct line of sight
• techniques will vary based on the department
• distraction techniques can be utilized to avoid scattered radiation to parents and staff ³