Fig. 9

Sonoanatomy of the deep radial (posterior interosseus) nerve. Short-axis views of the deep radial branch from its origin from the radial nerve to its exit from the supinator tunnel. A The origin of the deep radial nerve from the radial nerve trunk at the anterior lateral elbow appearing as a hypoechoic monofascicular structure. B The nerve distal to the elbow running under the Arcade of Froshe before it enters the supinator muscle. The arcade appears as a thin hyperechoic line over the nerve. C The deep radial (posterior interosseus nerve) running between the superficial and deep heads of the supinator muscle. D The posterior interosseus nerve as it exits the supinator muscle appearing as a train of fascicles