Case 4 - Labral tear versus hyaline cartilage undercutting

Summary

Imaging description

To identify labral tears, morphologic criteria such as absence, fraying, detachment, displacement, or deformity, can be used. Fluid or contrast within the labral substance is also an indication of a labral tear (Figure 4.1). Labral tears occasionally present on MR imaging as focal or diffuse increase in signal intensity extending to the surface on all imaging sequences, but this is less reliable. In standard MR images, higher signal intensity is present between the labrum and the glenoid cartilage in short-TE sequences, occurring in the transition zone between two histologic structures. Areas of the transitional zone do not fill with contrast material in arthrographic images.

Importance

Pitfalls in standard MR imaging are related to the presence of transitional zones. The transitional zone is the area located between the fibrocartilage of the labrum and the hyaline cartilage of the glenoid.

Typical clinical scenario

Tears of the labrum are common in athletes with instability, especially those in sports that require forceful and repetitive adduction and overhead rotation of the humerus.

Differential diagnosis

Articular cartilage is frequently present between the labrum and the glenoid cortex, predominantly in the superior half of the joint. This interface can simulate a labral tear on axial MR images (Figure 4.2).

Teaching point

The most common variants and pitfalls are related to labral lesions in the anterior-superior aspect.