Wednesday, September 19, 2012

Pathology Demonstrated:

  • Pathologies, including possible fractures involving the distal tibiofibular joint, the distal fibula and lateral malleolus, and the base of the fifth metatasals, are demonstrated.

Technical Factors:

  • IR size - 24 x 30 cm (10 x 12 inches)
  • Divide in half, crosswise
  • Detail screen
  • Digital IR - use lead masking
  • 60 +- 5 kV range
  • mAs 6


  • Place lead shield over pelvic area to shield gonads.

Patient Position:

  • Take radiograph with patient in the supine position; place pillow under head; legs should be fully extended (small sandbag or other knee increases comfort of patient).

Part Position:

AP oblique Medial Rotation
  • Center and align ankle joint to CR and to long axis of potion of IR being exposed.
  • If patient's condition allows, dorsiflex the foot id needed so that the plantar surface is at least 80 to 85 degree from the IR (10 to 15 degrees from vertical). see note below
  • Rotate leg and foot internally 45 degrees.

Central Ray:

  • CR perpendicular to IR, directed to a point midway between malleoli.
  • Minimum SID of 40 inches (100 cm)


  • Collimate to lateral skin margins; include distal tibiafibula and proximal matatasals (see note below)

CR and DR:

  • Close collimation and lead masking are important over unused portion of image plate.

Notes: If the foot is extended of plantar flexed more than  10 to 15 degrees from vertical, the calcaneus will be superimposed over the lateral malleolus on this 45 degree oblique, thus obscuring an important area of interest.

  • The base of the fifth metatasal (a common fracture site) will be demonstrated in this projection and should be included in the collimation field (see AP mostise projection.)

Radiographic Criteria:

Structure Shown:

AP Oblique medial rotation
  • The distal one-third of the lower leg, the malleoli, the talus, and the proximal half of the metatarsals should be seen.


  • A 45degree medial oblique will demonstrate the distal tibiofibular joint open, with no or minimal overlap on the average person.
  • The lateral malleolus and talus joint should show no or only slight superimposition, but the medial malleolus and talus will be pertially superimposed.

Collimation and CR:

  • The ankle joint should be in the center of the four-sided collimated field with the distal one-third of the lower leg to the proximal half of the metatasals and surrounding soft tissue included.

Exposure Criteria:

  • The bony cortical margins and trabecular patient should be sharply defined on the image if no motion is present.
  • The talus should be sufficiently penetrated to demonstrate the trabeculae, and soft tissue structure also must be evident. 

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