Slip of the lip--tears of the superior glenoid labrum-anterior to posterior (SLAP) syndrome. A report of four cases.

The shoulder's unique wide range of motion is largely restrained by the articular capsule and the external ligaments of the glenohumeral joint. Internally, the long head of the biceps tendon passes within the capsule and inserts on the superior lip of the glenoid labrum. Trauma distracting this tendon can tear the superior glenoid labrum, producing the superior labrum anterior to posterior (SLAP) syndrome. Four patients, two of whom were female, presented with complaints of acute shoulder pain associated with weakness in abduction and forward flexion. Routine shoulder roentgenograms were normal. Magnetic resonance imaging (MRI) studies revealed a superior glenoid labral tear consistent with a SLAP syndrome. The superior labrum, unlike the firmly bound inferior portion, is loosely attached to the glenoid fossa. This inherent mobility predisposes it to disruption. To routine ultrasonography and arthrogram, the superior labrum may be obscured by superimposed structures. Shoulder arthroscopy, computed tomography, arthrography, and MRI have relatively equal sensitivity in visualizing these labral tears. The SLAP lesion accompanies 16% of all rotator cuff tears, occurring more often than heretofore recognized. When clinically suspected, they can be readily visualized by a noninvasive MRI examination.