Factors affecting curve flexibility in skeletally immature and mature idiopathic scoliosis

Background The determination of factors affecting curve flexibility is important in idiopathic scoliosis patients with regard to the Risser sign. The objective of this retrospective study was to identify factors affecting curve flexibility in patients with skeletally immature and mature idiopathic scoliosis. Methods The records of all patients with idiopathic scoliosis who received surgical treatment from July 2001 to August 2008 at our hospital were screened. The Risser sign was used to separate the patients into a skeletally mature group (Risser grade = 5) and skeletally immature group (Risser grade < 5). Data recorded and compared were flexibility (%), bending angle (degrees), apical vertebral rotation (degrees), Cobb angle (degrees), curve location, prior use of brace treatment, and number of vertebrae in the curve. Results The study cohort consisted of 217 patients (34 males, 183 females) in the Risser grade < 5 group and 124 (21 males, 103 females) in the Risser grade = 5 group. Multiple linear regression analysis revealed that the Cobb angle and the curve location significantly affected curve flexibility in the Risser grade < 5 group, whereas in the Risser grade = 5 group, Cobb angle and age significantly affected flexibility. Conclusions Cobb angle and curve location influence main curve flexibility in skeletally immature adolescent idiopathic scoliosis, and Cobb angle and age influence curve flexibility in skeletally mature adult scoliosis. Measurement of these values may aid in the evaluation of treatment options and preoperative planning.