Wednesday, December 21, 2011

  • If patient has possible wrist trauma, do not attempt this position before routine wrist series has been completed and evaluated to rules out possible truama of distal forearm and/or wrist

Pathology Demonstrated:
  • Fracture of the scaphoid are demonstrated. Non-displaced fractures may require additional projections on a CT scan of the wrist.

Technical Factors:
  • IR size - 18 x 24 cm (8 x 10 inches)
  • Division in half crosswise
  • Detail screen tabletop
  • Digital IR - use lead masking
  • 60 or add up to 6kV range

  • Place lead shield over patient's lap to shield gonads.

Patient Position:
  • Seat patient at end of table, with wrist and hand on cassette, palm down, and shoulder, elbow, and wrist on same horizontal plane.

Part Position:
  • Position wrist as for PA projection - palm down and hand and wrist aligned with center of long axis of portion of IR being exposed, with scaphoid centered to CR.
  • Without moving forearm, gently evert hand (move toward ulnar side) as far as patient can tolerate without lifting or rotating distal forearm.

See terminology, Chapter 1, for explanation of ulnardeviation versus radial deviation.
  • Angle CR 10 to 15degrees proximally, along long axis of forearm and toward elbow. (CR angle should be perpendicular to long axis of scaphoid.)
  • Center CR to scaphoid. (Locate scaphoid at a point 2 cm [3/4 inch] distal and  medial to radial styloid process.)
  • Minumum SID is 40 inches (100cm)

  • Collimate on four sides to carpal region.

  • Obscure fracture of scaphoid may require several projections taken with different CR angles. Rafert and long (1991)* describe a four projection series with the CR angled proximally 0degree, 10degrees, 20degrees, and 30degrees.

Radiographic Criteria:

Structure Shown:
  • Distal radius and ulna, carpals, and proximal metacarpals are visible.
  • Scaphoid should be demonstrated clearly without foreshortening, with adjacent carpal interspaces open (evidence of CR angle).

  • Long axis of risk and forearm should be aligned with side boarder of IR
  • Ulnar deviation should be evident by the angle of the long axis of the metacarpals to that of the radius and ulna.
  • No rotation of the wrist is evidenced by appearance of distal radius and ulna, with minimal superimposition of distal radioulnar joint.

Collimation and CR:
  • Collimation should be visible on four sides to area of affected wrist.
  • CR and center of collimation field should be to the scaphoid.

Exposure Criteria:
  • Optimal density and contrast with no motion visualize the scaphoid borders and clear, sharp bony trabecular markings.

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