Findings: MR arthrogram images demonstrate contrast material between the glenoid and the superior labrum consistent with an injury at this site. There is also increased signal extending into the biceps tendon at its insertion site on the superior labrum, indicating extension of the injury into this structure. Axial images also demonstrate extension of the injury along the anterior aspect of the labrum.

Diagnosis: Type IV SLAP lesion of the glenoid labrum.

Discussion: The SLAP (superior labral anterior and posterior) lesion of the glenoid labrum was first described by Snyder in 1990 as a specific pattern of injury seen at arthroscopy involving injury to the superior aspect of the labrum which begins posteriorly and extends anteriorly to the site of insertion of the long head of the biceps. Initially, these lesions were only diagnosed arthroscopically. Currently, imaging techniques including CT- and MR-arthrography allows for radiologic diagnosis. Recognition of these lesions is important in patients with nonspecific clinical findings because surgical intervention is often of significant benefit.

There are two purported mechanisms of injury which may produce SLAP lesions: (1) a fall on an outstretched hand which leads to compression of the superior aspect of the labrum by the humeral head and (2) sudden traction on the arm with resulting forceful biceps contraction (ex: catching a heavy weight or throwing a ball forcefully). Resulting clinical symptoms are usually nonspecific and include shoulder pain and clicking, especially with overhead activity.

Findings at MR imaging include abnormal increased signal on spin density and T2-weighted images within the superior aspect of the glenoid labrum extending in an anterior-posterior orientation, often seen best on serial coronal oblique images in a plane perpendicular to the glenoid surface. The abnormal signal may or may not extend into the biceps anchor at its site of insertion on the superior labrum. With CT- or MR-arthrography, contrast may penetrate the labrum and be seen between the labrum and the glenoid surface.

The Snyder classification of SLAP lesions is as follows:

• Type I - Superior labral fraying and degenerative change without detachment
  of the labrum from the glenoid and without biceps tendon involvement.

• Type II -A Type I lesion with stripping of the superior labrum with its attached
  biceps tendon from the superior rim of the glenoid.

• Type III - A bucket handle tear of the superior labrum with displacement of the
  inferior portion of the tear into the joint while the labrum and biceps tendon remain
  attached to the glenoid superiorly.

• Type IV - A bucket handle tear of the labrum with associated tear of the biceps tendon.
  The inferior displaced portion of the tear includes a portion of the injured biceps tendon
  and there is also a partial tear of the biceps tendon attached to the superior glenoid.

References:

1. Cartland JP, et al. "MR Imaging in the Evaluation of SLAP Injuries of the Shoulder:
   Findings in 10 Patients. AJR, 159:787-792, October 1992.

2. Hunter JC, et al. SLAP Lesions of the Glenoid Labrum: CT Arthrographic and Arthroscopic
   Correlation. Radiology, 184:513-518, August 1992.

3. Smith AM, et al. SLAP Lesions of the Glenoid Labrum Diagnosed with MR Imaging.
   Skeletal Radiology, 22:507-510, 1993.

4. Snyder SJ, et al. SLAP Lesions of the Shoulder. Arthroscopy: The Journal of Arthroscopic
   and Related Surgery, 6(4):274-279, 1990.