Preoperative supine traction radiographs often result in higher Lenke classifications than supine bending radiographs in adolescent idiopathic scoliosis

Study design Retrospective chart and radiographic review. Objective The purpose of this study is to determine if both traction and side-bending radiographs yield the same Lenke classification. Summary of background date 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. Methods Retrospective chart and radiographic review were performed on AIS patients that underwent a posterior spinal fusion from 2008 to 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 degrees vs 18.9 degrees, p < 0.001), MT (38.9 degrees vs 37.9 degrees, p = 0.015), and TL/L (25.9 degrees vs. 18.0 degrees, p < 0.001). 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 degrees vs. 22.1 degrees, p = 0.011), MT (45.3 degrees vs. 37.5 degrees, p < 0.001), and TL/L (29.3 degrees vs 25.1 degrees, p = 0.019). 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. A single supine traction film is not an adequate substitute to side-bending radiographs when determining Lenke classification in patients with Adolescent Idiopathic Scoliosis.