MRI morphometric hip comparison analysis of anterior acetabular labral tears

Anterior (3 o'clock) acetabular labral tears (AALTs) have been reported to be associated with iliopsoas impingement (IPI). However, no study has examined the association between anatomical bony variables of the hip joint and AALTs. The purpose of this study was to evaluate the association between AALTs, femoroacetabular impingement (FAI) and other bony variables of the hip.

Seventy-six out of 274 hip MRI records met the inclusion criteria. Two independent blinded investigators evaluated the location of acetabular labral tears (ALTs), edema at the musculotendinous junction of the iliopsoas insertion, femoral neck anteversion angle, femoral neck shaft angle, acetabular anteversion angle, alpha angle, lateral central edge angle (LCEA), acetabular index, and acetabular depth. Comparison analyses between groups were performed.

Twenty-two patients had no ALTs (controls), 19 patients had AALTs, and 35 patients had ALTs not isolated at the 3 o'clock position (25 with cam-bony deformities [FAI-cam] and 10 with pincer-bony deformities [FAI-pincer]). The alpha angle mean was significantly higher (p < 0.001) in the FAI-cam group (62.7º, 95 % confidence interval [CI]: 56.2-69.2º) compared with the AALTs group (46.9º, 95 % CI: 40.1-53.7º). The LCEA mean was significantly higher (p < 0.001) in FAI-pincer group (41.9º, 95 % CI: 39.3º-44.5º) compared to AALTs group (29.4º, 95 % CI: 24.2º-34.6º). There was no statistically significant difference in any of the bony variables between the controls and the AALTs group.

Our study demonstrated that AALTs are pathologically distinct and not associated with FAI or other bony abnormalities. This supports the previous studies, which proposed that AALTs are associated with IPI.