Normative Values of Femoral Inclination Angle and Medial Proximal Femoral Angle: An MRI-Based Study

BACKGROUND This study aimed to establish normative values for the femoral inclination angle (FIA) and medial proximal femoral angle (MPFA) using magnetic resonance imaging (MRI), which minimizes projectional and rotational errors, in a large cohort. Sex-based and side-to-side comparisons, as well as correlations with age, were also investigated for these proximal femoral angle measurements. MATERIAL AND METHODS After exclusion of patients with trauma, infection, prior surgery, advanced osteoarthritis, femoroacetabular impingement, avascular necrosis, coxa vara, coxa valga, and low-quality magnetic resonance images, 631 pairs of proximal femurs were retrospectively evaluated for FIA and MPFA measurements. All measurements were performed by consensus between 2 radiologists, then analyzed regarding sex and side differences and correlations with age. RESULTS The mean FIA was 128.53±4.62°, whereas the mean MPFA was 86.62±3.40°. No significant differences were observed between men and women (FIA: P=0.057, MPFA: P=0.050) or between right and left sides (FIA: P=0.178, MPFA: P=0.853). Age was not significantly correlated with either proximal femoral angle measurement. No significant association was found between age and FIA (right: P=0.554, left: P=0.321) or MPFA (right: P=0.954, left: P=0.935). CONCLUSIONS This large MRI-based study provides normative reference values for FIA and MPFA. Neither angle was significantly influenced by sex, side, or age, suggesting that these parameters remain relatively stable across adult populations. These findings may serve as useful reference values for assessment of proximal femoral morphology and preoperative orthopedic planning.