How much foot rotation is required for the AP oblique medial rotation projection of the foot?

Citation, DOI & article data

Citation:

Murphy, A. Foot (medial oblique view). Reference article, Radiopaedia.org. (accessed on 08 Sep 2022) https://doi.org/10.53347/rID-44803

The medial oblique projection is part of the three view series examining the phalanges, metatarsals and tarsal bones that make up the foot. 

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This view demonstrates the location and extent of fractures in the foot and joint space abnormalities. It is also used in the determination of osteomyelitis and examination of foreign bodies.

• the patient may be supine or upright depending on comfort
• the affected leg must be flexed enough that the plantar aspect of the foot is resting on the image receptor
• the foot is medially rotated until the plantar surface sits at a 45° angle to the image receptor

• AP oblique projection
• centering point
  • x-ray beam centered to the base of the 3rd metatarsal
  • the beam will be perpendicular to the image receptor 
• collimation
  • lateral to the skin margins
  • anterior to the skin margins of the distal phalanges
  • posterior to the skin margins of the calcaneum
• orientation  
  • portrait
• detector size
  • 18 cm x 24 cm
• exposure
  • 50-55 kVp
  • 3-4 mAs
• SID
  • 100 cm
• grid
  • no

• superimposition is evident at the bases of the of 1st and 2nd metatarsals 
• there is no superimposition of the 3rd to 5th metatarsal
• base of the 5th metatarsal is free of superimposition from any structure 
• tarsal sinus is visible 
• joint spaces around the cuboid are open and equal
• cuboid is free of superimposition

The metatarsal and tarsal bones are the most reliable rotation indicator.

If the foot is over rotated the base of the 5th metatarsal will be superimposed by the tubercle of the 4th metatarsal.

If the foot is under rotated the bases of the 4th and 5th metatarsals will overlap; the image may have a closer resemblance to the DP projection.  

References

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