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

Abstract

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. 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°, main thoracic (MT) curve was 60.5°, and thoracolumbar/lumbar (TL/L) curve was 48.0°. 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). 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).

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.

Level of evidence: III.

Keywords: Adolescent idiopathic scoliosis; Bending radiographs; Lenke classification; Traction radiographs.