Medial dislocation of the biceps brachii tendon: appearance at MR imaging.

Abnormalities of the long tendon of the biceps brachii muscle commonly accompany other lesions about the shoulder, especially rotator cuff rupture, and are a frequent cause of a painful shoulder. The spectrum of abnormalities associated with medial displacement of the biceps tendon seen at magnetic resonance (MR) imaging was reviewed in six patients. MR imaging was performed on a 1.5-T system with use of a dedicated surface coil. The findings at MR imaging were correlated with those at surgery. Two types of medial displacement of the biceps tendon were identified. More frequently observed was a defect in the subscapularis apparatus that allowed intraarticular entrapment of the biceps tendon. Less commonly observed was incomplete dislocation, with the biceps tendon lying between a partially disrupted subscapularis tendon. MR imaging enabled accurate identification of medial dislocation of the biceps tendon and entrapment of the tendon within the glenohumeral joint. MR imaging also demonstrated the associated disruption of the subscapularis tendon that must be present to allow the biceps tendon access to the joint space.