Pronator quadratus sign

Dr Derek Grady and Dr Henry Knipe et al.

The pronator quadratus sign can be an indirect sign of distal forearm trauma. It relies on displacement of the fat pad that lies superficial to the pronator quadratus muscle.

On lateral wrist radiographs, the pronator fat pad normally appears as a thin radiolucent triangle, with its base attached to the palmar surface of the distal radius 1,2. It is observed ~90% of the time 1.

Displacement, anterior bowing, or obliteration of the fat plane in the setting of trauma may indicate a distal radius or ulna fracture. Various studies have described a wide ranging sensitivity for fracture ranging from 26 to 98%; thus a negative pronator quadratus sign does not exclude fracture 1-2.

In the absence of trauma, there are other causes for a positive pronator quadratus sign:

  • muscle strain or haematoma
  • inflammatory conditions
  • infectious conditions, e.g. osteomyelitis or cellulitis
  • septic arthritis of the wrist

It was first described by MacEwan in 1964 3.

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Article information

rID: 26112
Section: Signs
Synonyms or Alternate Spellings:
  • Pronator quadratus fat pad sign
  • Obliteration of pronator quadratus fat plane

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Cases and figures

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    Case 1: normal
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    Case 1: annotated
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    AP and lateral views
    Case 2: anterior bowing
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    Case 3: displacement
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    Case 4
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    Case 5
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