Arcade of Frohse: the radial nerve at supinator

The deep branch of the radial nerve, or posterior interosseous nerve, enters the supinator muscle beneath its proximal border, the arcade of Frohse. It is the classic site of posterior interosseous nerve syndrome and radial tunnel syndrome. This page locates it in 3D and on ultrasound.

Anatomy of the passage

Entry to supinator · arcade of Frohse — Plate derived from Z-Anatomy / BodyParts3D · CC BY-SA 4.0

The deep branch of the radial nerve enters supinator beneath its proximal edge, called the arcade of Frohse when it is tendinous. It is a described site of compression. Radial tunnel pain should be distinguished from the motor deficit of posterior interosseous nerve syndrome.

Nerve: Radial nerve: arcade of Frohse and superficial branch
Frequency: Described site, less commonly seen.
Type of evidence: Anatomical and clinical review

References

Choi SJ, Ahn JH, Ryu DS, Kang CH, Jung SM, Park MS, Shin DR. Ultrasonography for nerve compression syndromes of the upper extremity. Ultrasonography 2015. PubMed 25682987 · DOI

Ultrasound landmarks

At the anterolateral elbow, the radial nerve divides into superficial and deep branches; the deep branch enters supinator beneath its proximal edge (arcade of Frohse), between brachioradialis and the radial extensors of the carpus.