arcade of frohse arcade of frohse arcade of frohse, sometimes called the supinator arch, is the most superior part of the superficial layer of the supinator muscle, and is a fibrous arch over the posterior interosseous nerve. arcade of frohseposterior view of the supinator. (deep branch of radial nerve labeled at upper right and lower right. posterior interosseous is this nerve after passing the supinator, at lower right.)anatomical terms of muscle the arcade of frohse is a site of interosseous posterior nerve entrapment, and is believed to play a role in causing progressive paralysis of the posterior interosseous nerve, both with and without injury. the arcade of frohse was named after german anatomist, fritz frohse (1871-1916).