Prevalence of Asymptomatic Acetabular Labrum Abnormalities in the Active Pediatric Population.

Background: The prevalence of labral tears in asymptomatic active adults has been reported, but the prevalence of labral tears and other incidental hip lesions in the asymptomatic active pediatric population remains unclear. The purpose of this study was to determine the prevalence of hip abnormalities detected on 3T MRI in an active pediatric population with no hip symptoms and to compare with hip abnormalities found in children and adolescents who underwent an MRI for a hip-related condition.

Methods: After IRB approval, pediatric patients self-reporting as athletes and presenting with isolated, acute-onset knee pain requiring knee MRI were prospectively recruited to undergo 3T MRI of their asymptomatic contralateral hip (ASx). A comparison group of pediatric subjects who underwent an MRI for hip pain was enrolled retrospectively (Sx). All MRI scans were anonymized and randomized. Fifty subjects were enrolled for each cohort. Two fellowship-trained musculoskeletal radiologists independently evaluated MRIs for abnormal hip lesions, including labral tears. Inter-reader reliability was evaluated using Cohen Kappa. χ 2 or Fisher exact test was used to compare the prevalence of hip lesions between the 2 cohorts.

Results: The average patient age was 14.9 years for both cohorts (range 9 to 18 y) and 48% were male. In the ASx group, incidental labral tears were found in 18%, labral/paralabral cysts 6%, cartilage lesion 0%, subchondral cyst 0%, ligamentum teres tear 0%, femoral fibrocystic change 0%, cam lesion 30%, acetabular bone edema 0%, acetabular rim fracture 0%. The prevalence of labral tears (30%, P -value 0.16) and cam lesion (36%, P -value 0.52) in the Sx group was not significantly different from the ASx cohort. No significant correlation was found between the presence of femoral neck osseous bump and labral tear, labral cyst, or paralabral cyst in either cohort.

Conclusions: Labral tears were present on 3T MRIs of active pediatric patients with and without hip pain. Although MRI is essential to confirm the surgeon's suspicion and to detect unexpected pathology, clinical examination and history are crucial in pinpointing clinically relevant abnormal imaging findings.

Level of evidence: Level III.