MR Arthrography of the Labral-Capsular-Ligamentous Complex: Normal Anatomy, Anatomic Variations, and Pitfalls - Preliminary Study

ABSTRACT

PURPOSE: To evaluate anatomic variations and pitfalls of the labral-capsular-ligamentous complex in the shoulder joint for the proper interpretation of magnetic reasonance arthrographic images. MATERIALS AND METHODS:To determine the presence of sublabral sulci, undercutting of the base of the glenoid labrum by the articular cartilage, and the proximity of the middle glenohumeral ligament to the anterior glenoid labrum, 56 MR arthrograms of 41 asymptomatic volunteers were prospectively evalvated for labral shape and capsular insertion. We also evaluated the axillary fold, which was often confused with a loose body. RESULTS: The anterior and posterior parts of the labra, varied but their shape showed several dominant features; triangular(72%, 36%, respectively), rounded(13%, 35%), cleaved(8%, 1%), notched(2%, 0%), flat(5%, 24%), and absent(0%, 4%). Anterior capsular insertion was type 1 in 82% of cases, type 2 in 13% and type 3 in 5%, whereas posterior insertion was type 1 in 62%, type 2 in 36% and type 3 in 2%. We could also detect many pitfalls, such as undercutting of the base of theglenoid labrum by the articular cartilage(29%), sublabral sulci(25%), a prominent axillary fold(38%), and the middle glenohumeral ligament in proximity to the anterior labrum(5%). CONCLUSION: Our study revealed wide variability in the MR arthrographic appearance of the labral-capsular-ligamentous complex in asymptomatic shoulders. A good understanding of normal variation and pitfalls of the normal shoulder may be helpful pathologic condition in case of glenouhumeral instability.