MR arthrographic evaluation of posterior paraglenoid labral cysts: a retrospective study.

Background: Paraglenoid labral cysts (PLCs) around the shoulder are uncommon. Magnetic resonance imaging (MRI) is the primary imaging modality for the description of PLCs.

Purpose: The purpose of this study was to evaluate PLCs in the posterior part of the glenoid bone via MR arthrography as well as to describe associated labral abnormalities.

Material And Methods: This retrospective study included 14 patients, diagnosed with 15 posterior PLCs at MR arthrography between 2007 and 2012. Conventional MRI and MR arthrography were used for all patients.

Results: A total of 15 PLCs were detected in 14 patients with eight located on the right shoulder and six on the left shoulder. One case had two PLCs. While two cysts were multiloculated, the remaining 13 were seen as unilocated simple cysts. Moreover, 14 of 15 posterior PLCs (60%) were associated with labral tears at MR arthrography. The cysts in proximity to the glenoid labrum were posterosuperior in 33.3% (n = 5), mid-posterior in 36.7% (n = 7), and postero-inferior in 20% (n = 3). The majority of patients with posterosuperior and mid-posterior cysts had an associated superior labral tear from anterior to posterior (SLAP) lesions. Four of six patients with mid-posterior cysts had minimal denervation atrophy in the infraspinatus muscle.

Conclusion: Posterior PLCs are mostly associated with posterior labral defects. The majority of cysts localized in the posterosuperior and mid-posterior were also associated with SLAP lesions. Denervation atrophy in the infraspinatus muscle may frequently accompany mid-posterior PLCs.