[Medial luxation of the long head of the brachial biceps. Magnetic resonance imaging].

The medial intraarticular dislocation of the biceps tendon of the shoulder is a rare pathologic condition and its diagnosis before surgery is very important to properly repair the tears of rotator cuff tendons, the rotator cuff being nearly always involved. We report our experience in 8 patients (1.8%) with biceps tendon dislocation observed in a series of 432 patients submitted to MR studies to address several diagnostic issues. The MR patterns of biceps tendon dislocation and the related physiopathologic mechanisms are discussed. The MR images were retrospectively reviewed by two of the authors and dislocations were diagnosed in a subgroup of 34 patients (7.8%), associated with full-thickness tears of the tendon of supraspinatus muscle; all patients also presented a full-thickness tear of the subscapularis tendon. A dislocated biceps tendon can follow a variety of courses depending on the pattern of subscapularis tendon tear. We always found a complete dislocation of the biceps tendon; other dislocation patterns reported in the literature, and particularly oblique and superficial dislocations, were never observed in our series. Dislocation is visible on axial images, where the tendon appears completely displaced from the bicipital groove, but also sagittal and coronal images can depict the more medial position of the tendon. In our patients this abnormality was correctly identified in 4 patients during the first observation and in the extant patients during the retrospective review. The dislocation of the biceps tendon of the shoulder was frequently associated with a complete tear of the supraspinatus tendon (23.5%). All patients exhibited severe joint effusion and in two patients the dislodged tendon was also inflamed.