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Glenoid Labrum

The glenoid labrum provides another static restraint to GH motion. The labrum is a fibrous ring attached to the glenoid articular surface through a fibrocartilagenous transition zone. The labrum functions as an anchor point for the GH ligaments and the biceps tendon; it also deepens the glenoid socket and enhances stability.

This wedge-shaped, fibrous structure consists of densely packed collagen bundles in a woven pattern within the hyaline cartilage. It is firmly attached to the glenoid rim below the equator, where it appears as a rounded, fibrous elevation. Above the glenoid equator, the glenoid is more mobile and meniscal-like, with a triangular shape. The superior labrum inserts directly into the biceps tendon distal to the insertion of the tendon at the supraglenoid tubercle. The biceps tendon anchor and the superior glenoid cover approximately 1.5 cm of the superior rim of the glenoid.

In addition to greatly increasing the depth of the glenoid socket, the labrum enhances the concavity–compression mechanism that is created as the humeral head is compressed in the glenoid during RTC contraction . Excision of the glenoid labrum decreases the depth of the socket by 50% and reduces the resistance to instability by 20% .

Branches of the suprascapular artery, the circumflex scapular branch of the subscapular artery, and the posterior circumflex artery supply the glenoid labrum as it is vascularized throughout its peripheral attachment to the joint capsule. The superior and anterosuperior portions of the labrum, however, are less vascular than the posterior and inferior parts. This decreased vascularity of the superior labrum may explain the vulnerability of this area to disruption.

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