1. Copyright © 2015 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited Supplemental PowerPoint Slides Prediction of curve correction using alternate level pedicle screw placement in Adolescent Idiopathic Scoliosis (AIS) Lenke 1 and 2 patients using Supine Side Bending (SB) and Fulcrum Bending (FB) radiograph: The influence of curve magnitude and Lenke AR curves Kwan Mun Keong, MS Orth*, Hassan E. Zeyada, MD**, Chris Chan Yin Wei, MS Orth * *Department of Orthopaedic Surgery, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, MALAYSIA. ** Faculty of Medicine, Alneelain University, Khartoum 11111, SUDAN

2. Background Data: Influence of curve magnitude and Lenke AR curve subtypes on the use of Supine Side Bending and Fulcrum Bending radiographs in prediction of post-operative curve correction has not been clearly investigated. Methods: This is a prospective study involving 100 AIS patients who underwent surgical correction with alternate level pedicle screw construct. Patients were divided to G1 for cobb angle between 41 and 60 degrees, G2 61 and 80 degrees, G3 for pre-operative cobb angle more than 80 degrees. The MT curves were also subclassified to Lenke AR type curves and the rest were considered left sided compensatory lumbar curves, ie L type curves as described by Miyanji et al 23. Objective: The objective of this study was to compare the use of Supine Side Bending (SB) and Fulcrum Bending (FB) radiographs in flexibility assessment of these patients and compare it with the post-operative correction. The strength of correlation between the Side Bending Flexibility (SBF) and Fulcrum Bending Flexibility (FBF) with the Correction Rate (CR) was also calculated.

3. Table: Pearson correlation values (r value) for SB Flexibility and FB Flexibility vs. Correction rate for G1, G2, G3 and the whole group. Figure: Correlation between correction rate and side bending flexibility and fulcrum flexibility for G1 (41-60 o ), G2 (61-80 o ) and G3 (>80 o ) G1 G2 G3

4. Key Points Correction rate for alternate level pedicle screw systems is about 70% for G1, G2 and G3. Side Bending Correction Index (SBCI) and Fulcrum Bending Correction Index (FBCI) increase significantly as cobb magnitude increases. However, correlation between Side Bending Flexibility and Fulcrum Bending Flexibility with Correction Rate remains strong for G1, G2 and very strong for G3 Lenke AR type curves shows better correctability with SB and FB films.