MR imaging of the acetabular labrum: variations in 200 asymptomatic hips.

OBJECTIVE: The purpose of this study was to describe the MR appearance of the acetabular labrum in asymptomatic subjects and correlate the MR appearance with age and sex. MATERIALS AND METHODS: We evaluated high-resolution T1-weighted spin-echo coronal MR images of one hip in each of 200 asymptomatic individuals (84 men, 116 women; mean age, 44 years old; range, 15-82 years old). The labral shapes (triangular, round, flat, or absent), the intralabral signal intensity changes, and the possible extension of the intralabral signal intensity changes to the labral surface were assessed on two sections for each subject and correlated with age and sex. RESULTS: Triangle was the dominant shape seen on MR imaging (66%). However, its frequency decreased significantly with age. Absence of labrum was the second most frequent pattern (14%) and increased significantly with age. Round and flat labra were found in 11% and 9% of subjects, respectively, with no significant age correlation. The frequency of homogeneous labra with low signal intensity decreased with age. Intralabral areas of high signal intensity communicating with the free surface increased with age. CONCLUSION: The large variability of the MR appearance of the labrum in asymptomatic hips must be considered when interpreting MR examinations of patients in whom labral lesions are suspected.