Assessment of instability of the long head of the biceps tendon by MRI

Objective. To determine whether MRI can identify instability of the long he ad of the biceps tendon (LBT) in the rotator interval. Design and patients. A retrospective review was carried out of 19 patients, all arthroscopically examined, nine of whom had surgically confirmed insta bility of the LET. Results. A LET perched on the lesser tuberosity correctly indicated all nin e cases of instability with one false positive. In six of seven cases where the LET was oval in shape, no instability of the biceps tendon existed, wh ereas LET instability was present in eight of 12 patients with a flat long head of the biceps tendon. In seven of eight acutely angled intertubercular sulci there was no instability of the LET while eight of 11 obtusely angle d sulci were associated with LET instability. By consensus impression, inst ability of the LET could be determined with 67% sensitivity, 90% specificit y, 86% positive predictive value, and 75% negative predictive value. Conclusions. A flat LET perched on the lesser tuberosity with an obtusely a ngled intertubercular sulcus suggests the diagnosis of instability of the L ET in the correct clinical setting.