This is called the arcade of Frohse. The radial nerve can be entrapped within the arcade of Froshe as it enters the supinator muscle. The compression occurs as the radial nerve dives through the supinator to become the posterior interosseus nerve. Compression can affect innervation of the supinator and the muscles supplied by the posterior interosseus N. Remember the deep radial becomes the posterior interosseus after it exits the supinator. Compression can cause weakness and pain in the extensor carpi ulnaris, extensor digitorum, extensor digiti minimi, extensor indicis, abductor pollicis longus, extensor pollicis brevis and extensor pollocis longus.
Patients have difficulty making a fist due to the lack of use of the portion of the flexor dig.
Wrist adduction is decreased, when wrist flexion is attempted the hand becomes radially deviated. The cutaneous innervation over the 5th and medial half of the 4th digits is lost.