Pronator quadratus sign

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.

Plain radiograph

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

Displacement, anterior bowing or obliteration of the fat plane in 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% and thus a negative pronator quadratus sign does not exclude fracture 1-2.

Asides from trauma there can be 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
  • Obliterarion 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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    Distal radius and...
    Case 3: displacement
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    Case 4
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    Case 5
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