Hip Rotation Arc

Sepand  Heidari; Mohammad Hossein  Nabian; Mohammad Mahdi  Ebrahim Nasab

doi:10.18502/jost.v12i1.21117

Sepand Heidari Resident, Department of Orthopedic Surgery, Joint Reconstruction Research Center, Tehran University of Medical Sciences, Tehran, Iran
Mohammad Hossein Nabian Assistant Professor, Center of Orthopedic Trans-Disciplinary Applied Research (COTAR), Tehran University of Medical Sciences, Tehran, Iran
Mohammad Mahdi Ebrahim Nasab Assistant Professor, Department of Orthopedic Surgery, Joint Reconstruction Research Center, Tehran University of Medical Sciences, Tehran, Iran

DOI: https://doi.org/10.18502/jost.v12i1.21117

Keywords: Tibial Torsion; Three-Dimensional Image; Computed Tomography; Bone Anteversion

Abstract

Background: Rotational deformities of the lower extremity, such as altered femoral neck anteversion (FNA) and tibial torsion (TT), are common pediatric orthopedic conditions associated with intoeing gait. Accurate diagnosis is essential for effective treatment, yet the correlation between clinical examination and three-dimensional (3D) computed tomography (CT) measurements remains unclear. This study evaluates the agreement between clinical assessments and 3D CT in children with rotational deformities.

Methods: In a cross-sectional study at Imam Khomeini Hospital, Tehran City, Iran, 21 children (42 limbs) aged ≥10 years (girls) or ≥11 years (boys) with intoeing gait were assessed. Clinical measurements included hip internal rotation (HIR), hip external rotation (HER), and thigh-foot angle (TFA). Low-dose 3D CT (0.8-1.3 mSv) measured FNA and TT. Pearson correlation coefficients evaluated relationships between clinical and CT findings, with sliding threshold analysis to assess the impact of total hip rotation arc (HIR + HER) on correlations.

Results: Mean clinical measurements were: HIR = 63.54° ± 9.30°, HER = 42.11° ± 6.80°, and TFA = 9.60° ± 8.50°. CT measurements showed FNA 27.71° ± 6.60° and TT 16.11° ± 9.90°. Correlations were moderate (HIR vs. FNA: r = 0.41; HER vs. FNA: r = 0.57; TFA vs. TT: r = 0.483). At a total arc threshold of 98.5°, HIR-FNA correlation increased to r = 0.74 for arcs > 98.5°.

Conclusion: Clinical and 3D CT measurements show moderate correlation, suggesting complementary roles. Greater hip rotation arc enhances clinical reliability, supporting refined examination protocols to reduce imaging reliance in pediatric rotational deformity assessment.