scalene hiatus

sca·lene hi·a·tus

triangular gap bounded by the scalenus anterior and scalenus medius muscles and the first rib to which the muscles attach; the hiatus provides passage for the subclavian artery and the roots of the brachial plexus. Compression of the structures passing through the hiatus by any means is manifest as "thoracic outlet syndrome." Synonym(s): interscalene triangle