Pronator Quadratus

Anterior Interosseus Nerve, Median Nerve, Lateral and Medial cords. Anterior Divisions, Middle and Lower Trunks, C7, C8, Tl. 

Lower fourth of lateral border and volar surface of shaft of radius. 

Three fingerbreadths proximal to midpoint of a line connecting the radial (RAD.ST.) and ulnar styloids (UL.ST) insert needle electrode 

If the needle electrode is inserted too deeply, it will be in the flexor digitorum sublimis. 

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During supination, the interosseous membrane between the radius and ulna becomes taut. Supination is produced by contraction of the supinator and biceps muscles pronation involves the pronator quadratus and pronator teres. The pronators are less powerful than the supinators. 

The first anatomic level to be examined is over the pronator quadratus muscle. This muscle can be easily detected with US as a hypoechoic muscular belly lying over the volar aspect of the distal metaphyses of... 

On gray-scale US images, the ulnar and radial arteries are readily visible because of their pulsatil-ity. The main landmark for the radial artery is the lateral aspect of the flexor carpi radialis while the ulnar artery passes medial to the flexor carpi ulnaris (Fig. 10.23). More distally, the radial artery moves in a lateral position within the subcutaneous tissue, between the skin and the superficial aspect of the pronator quadratus (Fig. 10.24a). As it approaches the distal radius, this artery deepens to pass on the dorsal aspect of the wrist, within the anatomic snuff-box. Its palmar branch can be imaged in the subcutaneous tissue as a small hypoechoic pulsatile structure. Variations in size of the palmar branch are common and this vessel may also appear as large as the radial artery. The ulnar artery can be found in... 

The volar surface of the body of the radius from the bicipital tuberosity to the attachment of the pronator quadratus and interosseus membrane. 

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