Thoracic and Spinal Status in Mild to Moderate Idiopathic Scoliosis Patients Prior to Initiating PSSEs and Bracing: Implications for Scoliogenesis

Introduction – aim: There is a lack of studies focusing on the thoracic and spinal condition in mild to moderate idiopathic scoliosis (IS) patients prior to the initiation treatment. This report aims to address the above issue in children who are about to begin nonoperative treatment, whether through Physiotheraputic Scoliosis Specific Exercises PSSE, bracing, or a combination of both. The outcomes may also enhance our understanding of scoliogenesis. Method and Materials. N = 252 scoliotic children in total were studied. Two groups were formed, a) Group 1 with curves of 10 -25 Cobb angle, n= 34 males (24%) and 110 females (76%) and b) Group 2 with curves of 26 – 40 Cobb angle, n= 18 males (17%) and 90 females (83%). The assessment included age, sex, body height, scoliometry, Cobb angle, apical vertebra, apical vertebra rotation (AVR), and segmental Rib Index (SRI) in the lateral spinal radiographs. Moreover, the Rib index (RI) was assessed at the level of the maximum Double Rib Contour Sign (DRCS) distance, the average SRI value across T1-T12, the average difference between these two variables and RI at the apical vertebra of the primary curvature, (rib apical vertebra - RIAV). It is considered that in RI equal or more than 1,45-1,50 express a significant thoracic deformity in the transverse plane. In statistical analysis the following tools were included to examine distributional properties, predictive relationships, and subgroup differences relevant to the study’s objectives. These were histograms, Q–Q plots, Kolmogorov–Smirnov and Shapiro–Wilk, descriptive statistics, including measures of central tendency and dispersion, linear regression analysis, model adequacy using coefficient of determination (R²), standardized beta coefficients and residual diagnostics, a multifactorial General Linear Model (GLM) , including all two-way and three-way interactions on Cobb angle and vertebra rotation (VR), a correlation analysis applying Pearson’s correlation coefficient, one-way analysis of variance (ANOVA) and Bonferroni correction. Statistical significance was determined at the conventional threshold of p < 0.05. Results yielding p-values between 0.05 and 0.10 were interpreted as borderline significant, warranting cautious consideration in the context of effect size and theoretical relevance. All analyses were performed using IBM SPSS Statistics for Windows, Version 30.0 (IBM Corp., released 2023, Armonk, NY, USA). Results. For all groups rib asymmetry, as measured by SRI showed level- and severity-dependent associations with VR and Cobb angle. In mild scoliosis (Cobb 10°–25°), significant effects of SRI were mainly observed at lower thoracic levels (T10–T12) for VR, while associations with Cobb angle were weak and largely non-significant. In moderate scoliosis (Cobb 26°–40°), SRI effects were stronger, particularly at T10–T12, with VR and Cobb angle showing significant associations. Age contributed modestly to VR in mild scoliosis, whereas gender effects were mostly weak, occasionally reaching borderline significance. Curve type significantly influenced VR in moderate scoliosis, highlighting structural differences in thoracic anatomy. Adjusted R² values indicate that RI alone accounts for a moderate proportion of variance in VR (up to ~24%) and a smaller proportion in Cobb angle (up to ~8–10%), consistent with scoliosis being a multifactorial condition. Rib asymmetry is a better predictor of VR than Cobb angle, particularly in moderate scoliosis. Significant effects are concentrated in the mid- and lower thoracic spine (T7–T12), suggesting regional vulnerability. SRI measures may provide additional clinical insight into three-dimensional deformity beyond standard Cobb assessment. Discussion. The findings of this research highlight the important role of thoracic deformity in cases of mild and moderate IS. The observed correlation in mild IS between the SRI and mainly rotation not to the Cobb angle suggests that asymmetric rib growth, exerting unequal pressure/force on the vertebrae, may initiate spinal rotation. Within the context of the pathoremodeling sequence in IS, these results align with earlier studies which proposed that spinal deformity in the frontal plane originates at the level of the intervertebral discs than the vertebral bodies (Grivas et al., 2006; Will et al., 2009). Furthermore, this study supports the view that scoliotic deformity likely come first in the thoracic cage and then the spine. The diurnal "accordion-like" phenomenon observed in the intervertebral discs may then contribute to vertebral deformation and subsequent progression of IS. In conclusion, this study demonstrates that the use of RI and SRI methods provides valuable insight into scoliogeny of mild and moderate IS and emphasizes the critical role of the thoracic cage in its development.