P0848 - Preoperative Supine Traction Radiographs Often Result in Higher Lenke Classifications than Supine Bending Radiographs in Adolescent Idiopathic Scoliosis

Background/Purpose: Supine side-bending radiographs are used to evaluate curve flexibility and assign Lenke classification in Adolescent Idiopathic Scoliosis (AIS). Supine traction radiographs are another tool used by treating surgeons to gauge flexibility and appropriate levels for spinal fusion in AIS. The purpose of this study is to determine if both traction and side-bending radiographs yield the same Lenke classification.

Methods: Retrospective chart and radiograph review was performed on AIS patients that underwent a posterior spinal fusion from 2008– 2017. Cobb angles and Lenke classifications were determined on all upright posterioanterior (PA) spine radiographs, supine traction radiographs, and four supine bending radiographs. Statistical analysis using independent t-tests and chi-square tests as appropriate were compared between patients with or without discordant Lenke classifications with p-value set at <0.05 for statistical significance.

Results: 184 patients met inclusion criteria, 36 males and 148 females. The average Cobb angle for the proximal thoracic (PT) curve was 27.2 degrees, main thoracic (MT) curve was 60.5 degrees, and thoracolumbar/lumbar (TL/L) curve was 48.0 degrees. Significantly less curve correction was found with supine traction radiographs compared with bending radiographs: PT (23.1 vs 18.9, p<0.001), MT (38.9 vs 37.9, p=0.015), and TL/L (25.9 vs. 18.0, p<0.001) (Table 1). Lenke Classification was found concordant in 151/184 (82.1%). Traction views in the discordant Lenke classification group demonstrated less curve correction than those in the concordant group: PT (27.4 vs. 22.1, p=0.011), MT (45.3 vs. 37.5, p<0.001), and TL/L (29.3 vs 25.1, p=0.019) (Table 2). Of the 33 discordant Lenke classifications, the supine traction film assigned structurality by Lenke for the TL/L curves in 22 patients, and in 17 patients for the PT curve.

Conclusion: Supine traction and supine bending radiographs provided a concordant Lenke classification 82.1% of the time. However, supine traction radiographs demonstrate less curve correction, a higher Lenke classification, and underestimated the TL/L curve correction to a greater degree. Supine side-bending radiographs are superior in determining curve flexibility and assigning curve structurality per Lenke than a single supine traction film in patients with Adolescent Idiopathic Scoliosis.