Traction versus supine side-bending radiographs in determining flexibility: What factors influence these techniques?

STUDY DESIGN. Prospective clinical, radiologic study of adolescent idiopathic scoliosis (AIS). OBJECTIVE. We evaluated a Cobb angle in standing position, patient age, the level of the apex, and the number of involved vertebrae in patients with AIS to determine whether the corrective ability of traction or side-bending radiographs was superior. SUMMARY OF BACKGROUND DATA. Side-bending and traction radiographs are used to evaluate curve flexibility during corrective surgery for AIS despite notable differences in the flexibilities of identical curves. Thus, interpretation for the differences among these techniques should be investigated. METHODS. A total of 229 consecutive patients with AIS who were surgically treated were evaluated. Standing, supine side-bending, and traction radiographs were obtained before surgery. Curves were divided into main thoracic (MT) or thoracolumbar/lumbar (TL/L) curves, and proximal thoracic (PT) curves. We evaluated the Cobb angle in standing position, the level of the apex, the number of involved vertebrae, kyphosis angle of main thoracic curve, and patient age in patients with AIS to determine whether the corrective ability of traction or side-bending radiographs was superior. RESULTS. A total of 219 curves were observed in MT lesions. The traction flexibility rate (FR) was higher than the side-bending FR at angle of ≥60° (P = 0.02), in patients younger than 15 years (P = 0.02), in curves whose apex was located at T4-T8/T9(P = 0.01), in curves whose involved vertebrae were 6 or 7 (P = 0.02), and at kyphosis angle between 10° and 39° (P = 0.02). In 96 TL/L curves, side-bending FR was higher at angle of <60° (P < 0.01). In 163 PT curves, traction FR was higher at angles of ≥40° (P = 0.02). CONCLUSION. In addition to a Cobb angle, patient age, the level of the apex, and the number of involved vertebrae also influence the conditions under which the corrective ability of traction radiographs is superior to that of side-bending radiographs.