Sonographic studies of a patient with a proximal radial nerve lesion.

<p>(A, B) Transversal study of the posterior interosseous nerve (PIN; arrow) within the supinator muscle (asterisk) on the healthy side (A) in comparison to the affected side (B) with a significant swelling of the PIN within the muscle. (C) Longitudinal study of the PIN with a swelling before entering the Arcade of Frohse (thin arrows) and within the supinator muscle (asterisk). (D) Longitudinal study of the radial nerve in the distal upper arm with impression of the nerve (arrow) by a screw (thin arrow). p—proximal, d—distal