Labrum

The glenoid labrum is a rim of fibrous tissue that deepens the glenoid and allows attachment of the biceps tendon, capsule and the glenohumeral ligaments to the glenoid. [1,18]

The labrum has two attachments to the glenoid: “…one directly to the glenoid rim via a fibrocartilaginous transition zone, and the other to the periosteum of the scapular neck and the fibrous capsule”. [10]

In a number of cadaveric studies, Detrisac and Johnson [19] reported two variations in the attachment of the labrum to the underlying glenoid: in one variant, the inner free edge of the labrum is detached superiorly, whilst being firmly attached at its anterior, inferior and posterior margins. In the other variant, “…the entire labrum is attached directly to the articular margin”. [19]

In an anatomical study, Cooper et al [20] reported loose attachment of the superior and antero-superior portions of the labrum to the underlying glenoid, whereas the “…inferior portion [is] firmly attached to the glenoid rim and appears as a fibrous, immobile extension of the articular cartilage.

The appearance, size, shape and thickness of the glenoid labrum are variable [Table 3]. [1-2,18,21] The shape of the labrum dynamically changes with different arm positions, being flat in external rotation of the arm and folded up in internal rotation. [18] In cross-section, the labrum appears a triangular shape. [9] Fraying of the glenoid labrum is the most common variant encountered when viewed through an arthroscope. [5]

Table 3 – Variation in the size of glenoid labrum