Pronator quadratus sign
Updates to Article Attributes
The pronator quadratus sign, also known as MacEwan 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 as seen on a lateral wrist radiograph.
Pathology
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 high specificity but wide-ranging sensitivity for fracture ranging from 26 to 98%; thus a negative pronator quadratus sign does not exclude fracture 1,2,4.
Radiographic features
Plain radiograph
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. One study 4, has suggested a cut-off of <8 mm (female) and 9 mm (male) on lateral x-rays as a cut-off for normal.
History and etymology
It was first described by Douglas W MacEwan (fl. 20202021)6, a Canadian radiologist, in 1964 3,5.
Differential diagnosis
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, cellulitis
- septic arthritis of the wrist
-<p>The <strong>pronator quadratus sign</strong>, also known as <strong>MacEwan sign</strong>, can be an indirect sign of distal forearm trauma. It relies on displacement of the fat pad that lies superficial to the <a href="/articles/pronator-quadratus-muscle">pronator quadratus muscle</a> as seen on a <a title="Wrist radiograph" href="/articles/wrist-radiograph-1">lateral wrist radiograph</a>.</p><h4>Pathology</h4><p>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 high specificity but wide-ranging sensitivity for fracture ranging from 26 to 98%; thus a negative pronator quadratus sign does not exclude fracture <sup>1,2,4</sup>.</p><h4>Radiographic features</h4><h5>Plain radiograph</h5><p>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 <sup>1,2</sup>. It is observed ~90% of the time <sup>1</sup>. One study <sup>4</sup>, has suggested a cut-off of <8 mm (female) and 9 mm (male) on lateral x-rays as a cut-off for normal.</p><h4>History and etymology</h4><p>It was first described by <strong>Douglas W</strong> <strong>MacEwan</strong> (<a title="Fl. (term)" href="/articles/biographical-article-structure">fl.</a> 2020), a Canadian radiologist, in 1964 <sup>3,5</sup>.</p><h4>Differential diagnosis</h4><p>In the absence of trauma, there are other causes for a positive pronator quadratus sign:</p><ul>- +<p>The <strong>pronator quadratus sign</strong>, also known as <strong>MacEwan sign</strong>, can be an indirect sign of distal forearm trauma. It relies on displacement of the fat pad that lies superficial to the <a href="/articles/pronator-quadratus-muscle">pronator quadratus muscle</a> as seen on a <a href="/articles/wrist-radiograph-1">lateral wrist radiograph</a>.</p><h4>Pathology</h4><p>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 high specificity but wide-ranging sensitivity for fracture ranging from 26 to 98%; thus a negative pronator quadratus sign does not exclude fracture <sup>1,2,4</sup>.</p><h4>Radiographic features</h4><h5>Plain radiograph</h5><p>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 <sup>1,2</sup>. It is observed ~90% of the time <sup>1</sup>. One study <sup>4</sup>, has suggested a cut-off of <8 mm (female) and 9 mm (male) on lateral x-rays as a cut-off for normal.</p><h4>History and etymology</h4><p>It was first described by <strong>Douglas W</strong> <strong>MacEwan</strong> (<a href="/articles/biographical-article-structure">fl.</a> 2021) <sup>6</sup>, a Canadian radiologist, in 1964 <sup>3,5</sup>.</p><h4>Differential diagnosis</h4><p>In the absence of trauma, there are other causes for a positive pronator quadratus sign:</p><ul>
References changed:
- 6. Manitoba opera (@ManitobaOpera). 2021.11.21. Happy 97th Birthday to Dr. Douglas MacEwan, WWII veteran and Manitoba Arts hero. One year ago today, Dr. MacEwan completed <a href="https://twitter.com/ManitobaOpera/status/1458894871125798921">https://twitter.com/ManitobaOpera/status/1458894871125798921</a> [Accessed 09 January 2022].
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