MRI NEWSLETTER: Posterior Labral Tears and Glenoid Dysplasia

Posted March 22, 2017

Glenoid dysplasia is a developmental anomaly of the scapula that results in bony deficiency of the posteroinferior glenoid. The normal glenoid labrum is shaped like a wine glass, with the bony margin extending to both edges. In glenoid dysplasia (also called glenoid hypoplasia or posterior glenoid rim deficiency) there is hypoplasia of the posterior bony glenoid. Since the bone is deficient posteriorly, there is hypertrophy of the labrum to fill-in the space of the deficient bone. However, this hypertrophied posterior labrum is very fragile and susceptible tears.

In mild glenoid dysplasia, there is rounding to the posterior inferior glenoid rim with mild thickening of the labrum. In moderate glenoid dysplasia there is more marked rounding of the glenoid and associated labral thickening. With severe glenoid dysplasia, there is marked rounding and sloping of the posterior glenoid with associated markedly thickened labrum replacing the deficient areas of the posterior glenoid rim.

In the past, it was thought that glenoid dysplasia was unusual. However recent studies have shown that glenoid dysplasia is relatively common. Recent studies reveal that 14% of the population have moderate or severe glenoid dysplasia. The incidence of posterior labral tears in people with moderate to severe glenoid deficiency is about 64%. In some studies, 93% of patients with posterior labral tears had some component of glenoid dysplasia. Glenoid dysplasia is a developmental anomaly and when present is bilateral in 60% of patients.

Posterior dislocation in young people primarily involves weightlifters and contact sport players. During lifting of heavy weights such as in the bench-press, mild subluxation of the humeral head posteriorly frequently occurs. This leads to posterior labral tears. Traumatic posterior dislocation seen in contact sports also leads to posterior labral tear, usually associated with reverse Hill-Sachs lesions with bony impaction fracture of the high medial anterior humeral head (the opposite of the standard Hill-Sachs lesion that creates a high posterior lateral humeral head impaction injury).

Read the full article here Posterior Labral Tears and Glenoid Dysplasia

By Dr. William Renner