Bony Morphological Features of the Proximal Femur in Patients With Developmental Dysplasia of the Hip

Purpose Developmental dysplasia of the hip (DDH) is a precursor of secondary osteoarthritis, with borderline DDH (BDDH) often overlooked. This study explores three-dimensional (3D) proximal femoral morphology in DDH and BDDH and examines their distinctions from normal hips (NH), emphasizing new correlations between femoral parameters and hip instability. Methods We retrospectively analyzed 130 hips from 120 patients categorized as DDH (lateral center-edge angle (LCEA) < 20°), BDDH (20°-25°), or NH (>25°). Detailed 3D analyses using advanced CT imaging measured unique femoral parameters such as femoral neck anteversion (FAV), lesser trochanter version (LTV), and femoral head morphology. Statistical methods assessed differences among groups and identified novel correlations. Results The study confirmed that DDH is associated with increased FAV and decreased LTV, alongside reduced femoral head-lesser trochanter distance (FH-LT) and an elliptical femoral head. BDDH displayed intermediate morphological changes, highlighting its biomechanical significance. Correlations revealed new insights into the relationship between hip morphology and clinical symptoms. Discussion External rotational abnormalities, such as increased FAV and decreased LTV, may predispose DDH patients to ischiofemoral impingement, psoas bursitis, and joint degeneration. The shortened FH-LT and elliptical femoral head further contribute to instability and early osteoarthritis. These findings underscore the role of 3D proximal femoral morphology in DDH biomechanics and clinical symptoms. Conclusion This study extends previous research by identifying previously unreported associations between proximal femoral abnormalities and hip biomechanics in DDH and BDDH. These findings inform diagnostic and therapeutic strategies for early intervention.