Magnetic resonance imaging assessment of the discoid glenoid labrum

The glenoid labrum varies in size and shape, sometimes resembling the knee's meniscus with a free inner edge projecting into the joint. This incomplete discoid-shaped or meniscoid glenoid labrum is a seldom recognized rare variant.

To determine the prevalence and magnetic resonance imaging [MRI] characteristics of discoid glenoid labrum.

Retrospective review of the MRI shoulder joints of 201 patients. The MR images were evaluated for the presence of a discoid labrum, and various characteristics were assessed using predefined criteria.

Among the 201 patients, a discoid glenoid labrum was identified in 27 cases; incidence rate of 13.4 %. The mean age of these patients was 41.85 years [range 15-73 years, SD ± 16.9]. The most common position was anterior or antero-inferior [n = 25; 92.6 %], with the apices of almost all discoid folds found between 3-6o'clock position. Twenty-one [77.8 %] of the discoid folds were small, and 6 [22.2 %] were large. Tears or degeneration were observed in 9 [33.3 %]. A statistically significant difference between genders was found in age [p = 0.026] and width [p = 0.044], with discoid labrum appearing in younger men and covering a larger part of the glenoid fossa. The labra were widest at the 3o'clock position [p = 0.008]. Additionally, we discovered a novel radiological finding termed the 'reversed Oreo cookie sign' in discoid glenoid labra.

The discoid glenoid labrum is a shoulder variant that is often overlooked. Recognizing this condition is crucial to avoid misdiagnosing labral pathology and to understand its potential susceptibility to labral tears, degeneration, and shoulder pain.