Ulnohumeral dislocation despite intact radiocapitellar joint: a rare Monteggia variant.

We treated one patient with a mid-diaphyseal radius fracture and concomitant anteromedial facet fracture of the coronoid. The ulnohumeral joint was severely unstable by complete ligament detachment and interosseous membrane rupture. Despite this gross instability, the radiocapitellar was congruent and stable. The possible mechanism of radiocapitellar stability is discussed and the concept of concavity-compression stability across the radiocapitellar joint is emphasized.