Imaging description

With medical imaging, labral tears of the hip are best diagnosed using MR arthrography. Tears are diagnosed usually when there is intralabral or sublabral interposition of contrast (Figure 47.1). Regardless of the contour or shape of sublabral contrast interposition, any contrast material interposition occurring in the upper one-half of the anterior labrum should be considered a tear. However, sublabral contrast material interposition that occurs in the anteroinferior aspect of the labrum (typically the 8 o’clock position), has a linear shape, is partial thickness, and is not associated with perilabral pathology/cysts should be considered a normal recess (Figure 47.2).

Importance

Initial reports of the sensitivity of MR arthrography for labral tears were around 92%. However, a few more recent studies have reported sensitivity as low as approximately 66%. One of the potential reasons for this discrepancy is misdiagnosing a labral tear as a sublabral recess. It is important for radiologists to be aware of morphologic variants located in the anterior labrum because most labral tears occur in this area as well. It is important to recognize that sublabral contrast material interposition that is partial-thickness, linear, has no associated perilabral pathology, and is located near the 8 o’clock position should be considered a normal variant (sublabral recess). Incorrectly diagnosing a sublabral recess as a labral tear may lead to unnecessary surgery and its associated morbidity.