Influencing factors of the curve flexibility in adolescent idiopathic scoliosis and prediction method of Cobb's angle measured on supine lateral-bending roentgenograph
Objective To analysis the influencing factors of the curve flexibility in idiopathic scoliosis and find out the prediction method of Cobb's angle measured on supine lateral-bending roentgenographs. Methods Standing position spinal full-length posteroanterior-roentgenographs and supine lateral-bending roentgenographs of 150 patients suffered idiopathic scoliosis with 216 curvatures (included thoracic,thoracolumbar,lumbar) were analyzed retrospectively. Correction rate on supine lateral-bending roentgenographs as flexibility index was analyzed with age,gender,standing-position coronal-plane Cobb's angle,Risser sign,whether main curve or not,position of scoliosis by Pearson or Spearman correlation to select the related factors for multiple linear regression analysis. Cobb's angle measured on supine lateral-bending roentgenograph was analyzed with the 6 factors as the same way. Results Statistic significant linear relationships were demonstrated between standing-position coronal-plane Cobb's angle and flexibility index (P0.01),it was also demonstrated between position of scoliosis and flexibility index (P0.01). Statistic significant linear relationships also existed in standing-position coronal-plane Cobb's angle (P0.01),position of scoliosis (P0.01),whether main curve or not (P0.01) with Cobb's angle measured on supine lateral-bending roentgenograph. Every 10°increase in standing-position coronal-plane Cobb's angle resulted in a 8% decrease in flexibility,and thoracic curves had approximately 10% less flexibility than thoracolumbar or lumbar curves. For the minor thoracic curve with standing-position coronal-plane Cobb's angle 45° could be considered structural minor curves,but for thoracolumbar or lumbar curves,the situation was the minor curves with standing-position coronal-plane Cobb's angle 50°. Conclusion The standing-position coronal-plane Cobb's angle and curvature location are predictors of flexibility of adolescent idiopathic scoliosis. These are methods to predict the supine bending Cobb's angle,which can help with clinical work.