Reference values and variation of acetabular angles measured by computed tomography in 170 asymptomatic hips

Background We have little knowledge of reference values for acetabular angles.

Purpose The purpose of this study was to report values and variation for the center-edge (CE), the acetabular-index (AI), the anterior-sector (AASA), the posterior-sector (PASA), and the acetabular-anteversion angle (AcAV) and to investigate gender differences.

Material and Methods Retrospectively, we recruited 96 individuals, 52 women (mean age = 63 ± 12 years) who had undergone computed tomography (CT) as part of examination for lymphomas in 2013 at Aarhus University Hospital. After CT, the participants completed the Oxford Hip Score. Eight individuals indicated hip problems and three had missing data; those 11 were excluded from the material. The acetabular angles for both hips were measured on CT images by an experienced radiologist. The acetabular angles are reported for right and left hip as mean ± SD degrees and compared women and men with a two-sample t-test.

Results The CE angle [right;left] averaged [34±6;35±5]. The AI angle averaged [3±6;1±5]. The AASA averaged [58±7;60±9]. The PASA averaged [94±7;95±7]. The AcAV averaged [18±5;18±5]. The AASA was lower whereas the PASA and the ACAV were higher for women compared to men.

Conclusion We found considerable variation in the values for acetabular angles. There were gender differences in the sector angles and for the AcAV. Knowledge of reference values is important when we attempt to diagnose the pathological hip conditions.