Several studies have reported an association between adolescent idiopathic scoliosis (AIS) and hip decentration (HD). However, these previous studies evaluated the hip center-edge (CE) angle at only a single time point. This study aimed to evaluate the longitudinal change in CE angle and to assess the influence of AIS on the hip joint development in patients with AIS. Patients with AIS treated conservatively were retrospectively reviewed. The hip CE angle and Cobb angle were measured using standing whole-spine radiographs at the first visit and two-year follow-up. HD was defined as a CE angle < 20°. The patients were further stratified based on the presence of HD, bone maturity (Risser classification) and age (patients < 12 years old vs. those ≥ 12 years old) at the first presentation. A total of 132 patients with a mean age of 12.9 ± 2.1 years old (boys/girls, 16/116) were finally included in this study. The prevalence of HD at the first visit and at 2-year follow-up were 24.2% (32/132) and 22.0% (29/132), respectively. The mean CE angle significantly decreased over time (left hip, 25.0 ± 4.9 to 24.6 ± 4.7, p = 0.04; right hip, 23.7 ± 4.5 to 23.1 ± 4.4, p = 0.002), while the mean Cobb angle significantly increased over time (25.2 ± 8.2 to 26.3 ± 9.4, p = 0.001). In patients without HD, the mean CE angle significantly decreased over time (left hip, 26.7° to 26.1°, p = 0.0004; right hip, 25.4° to 24.5°, p = 0.0001), while no significant change was observed in patients with HD. When the patients were divided based on bone maturity, neither the immature nor the mature group showed an increase in the CE angle (immature group, left hip, 24.2° to 24.1°, p = 0.47; right hip, 23.0° to 22.4°, p = 0.01; mature group, left hip, 26.3° to 25.6°, p = 0.005; right hip, 24.8° to 24.2°, p = 0.06 ). In patients < 12 years old at the first presentation, no significant differences were detected in the bilateral CE angles between the two timepoints. A total of 24.2% of Japanese AIS patients exhibited radiographic findings of HD. Contrary to normal hip development, the hip CE angle did not increase with age in patients with AIS. The study findings suggest that AIS affects hip joint development.
Matsumoto et al. (Mon,) studied this question.