The pronator quadratus muscle in MSK ultrasound
This article, to be read in free full text in the URL provided below this post, provides the sonographer with information how to scan the pronator quadratus muscle, its standard reference values, anatomical variances, and the influence of sex and hand dominance, all visualized by MSK ultrasound.
The MSK ultrasound appearance of the pronator quadratus was evaluated. The patients hands were positioned in 90° supination with the wrist 5° to 10° extended and with the elbow flexed at 90°. The transducer was positioned perpendicularly against the volar surface of the examined distal forearm with minimal pressure. On the longitudinal image, the transducer was positioned along the flexor carpi radialis tendon (see image below). This image included the longitudinal section of the flexor carpi radialis, pronator quadratus, volar cortex of the radius, and, on the distal end of the image, the distal margin of the bony prominence attached to the pronator quadratus.
The pronator quadratus is a square shaped muscle on the distal forearm that acts to pronate the hand. As it is on the anterior side of the arm, it is innervated by a branch of the median nerve, the anterior interosseous nerve (roots C8 and T1 with T1 being primary). Arterial blood comes via the interosseous artery. Its fibres run perpendicular to the direction of the arm, running from the most distal quarter of the anterior ulna to the distal quarter of the radius. It is the only muscle that attaches only to the ulna at one end and the radius at the other end. When the pronator quadratus contracts, it pulls the lateral side of the radius towards the ulna, thus pronating the hand. Its deep fibers serve to keep the two bones in the forearm bound together.
Video: Pronator quadratus muscle
> From: Sato, J Ultrasound Med 33 (2016) 111-117. All rights reserved to American Institute of Ultrasound in Medicine. Click here for the Pubmed summary.