The glenoid labrum is a fibrocartilaginous structure that attaches as a rim to the articular cartilage of the glenoid fossa and serves to deepen and increase the surface area of the glenoid. In this capacity, it acts as a static stabilizer of the glenohumeral joint, resisting anterior and posterior movement, and preventing dislocation and subluxation at the extremes of the range of motion 4.
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Gross anatomy
The glenoid labrum is made of fibrocartilage, 3 mm thick and 4 mm wide although this is highly variable 4. On cross-section, the labrum can be triangular (more commonly) or round 4. Below the equatorial pole of the glenoid, the labrum becomes more rounded and smaller compared to superiorly where is more triangular in shape and larger.
Attachments
The glenoid labrum forms part of the periarticular fiber system that is continuous with the rotator interval as well as 4:
superiorly: tendon of the long head of biceps brachii
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anteriorly:
superior glenohumeral ligament
middle glenohumeral ligament (variably)
inferiorly: inferior glenohumeral ligament consisting of an anterior band, axillary pouch, and a posterior band
Blood supply
Arterial supply is from the ascending glenoid artery, branches of the suprascapular and circumflex scapular arteries, muscular branches of rotator cuff muscles, and anterior and posterior circumflex humeral arteries 5. Blood supply is also received from the underlying bony glenoid 5. The outer glenoid is vascular and the inner glenoid is avascular 4.
Radiographic features
The glenoid labrum can be described in two ways 4:
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clock face
12 o'clock: superior
3 o'clock: anterior
6 o'clock: inferior
9 o'clock: posterior
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segments
superior
anterosuperior
anteroinferior
inferior
posteroinferior
posterosuperior
Variant anatomy
variable cross-sectional shape: blunted, cleaved, notched or flat 4
medialised posterior labrum 4
variation in anterior capsulolabral insertion
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