Irreducible anterior and posterior dislocation of the shoulder due to incarceration of the biceps tendon

Mechanical obstacles may infrequently impede closed reduction of anterior shoulder dislocation. Imaging techniques such as arthrography, computed tomography (CT) and magnetic resonance imaging (MRI) complement conventional radiography by allowing identification of obstacles to reduction. We present a case of irreducible anterior glenohumeral dislocation resulting from an initial anterior dislocation, converted to a posterior dislocation with an attempt at reduction, then converted back to anterior dislocation with a second reduction attempt. Soft tissue obstacles to shoulder reduction should be suspected when plain films do not identify a bony fragment as the culprit. CT and MRI are useful for identifying the cause of irreducibility and for operative planning.