P0863 - Which Radiographic Technique Better Predicts Post-Operative Correction in Idiopathic Scoliosis?

Introduction:
Preoperative radiographic assessment of curve flexibility in patients with idiopathic scoliosis (IS) is important to determine Lenke classification, operative levels, and post-operative correction. No consensus exists as to the best technique. We compared measurements from supine side bending (SB) and intra-operative traction radiographs under general anesthesia (UGA) with actual post-operative correction.

Methods:
We reviewed our prospective Pediatric Orthopaedic Spine database and identified patients with IS and posterior spinal fusion with segmental spinal instrumentation between 2010 and 2018. Pre-operative radiographs included standing posterior-anterior (PA) and lateral radiographs, supine SB radiographs, and intra-operative traction radiographs UGA. Post-operatively, standing PA and lateral radiographs were obtained at one month, 5 months and one year.

Major curves were categorized into proximal thoracic (PT), major thoracic/thoracolumbar (MT), and distal thoracolumbar/lumbar (TL/L) curves. Flexibility was calculated from the SB radiographs and traction UGA radiographs and correction rates were calculated from the one month and 12 month radiographs. Univariate analysis and multivariate linear regression models were utilized for statistical analysis. Bending radiographs that correlated significantly with post-operative correction with p<0.10 were eligible for inclusion. Preoperative demographics, etiology, deformity details, and surgical details were included in the multivariate models.

Results:
Patient and curve characteristics are shown in Table 1. On univariate analysis, traction radiographs correlated with post-operative correction at one month and one year on the major curves [(r=0.214, p=0.001), (r=0.209, p=0.001)] and distal curves [(r=0.280, p<0.001), (r=0.181, p=0.006)]. Supine SB radiographs did not correlate with post-operative correction on either major or distal curves. Neither supine bending or traction correction radiographs of proximal curves correlated with post-operative correction at one month or one year.

On multivariate analysis, major curve traction correction radiographs were independently associated with post-operative major curve correction at one month (beta: 0.158, 95% confidence interval [CI]: 0.035-0.280, p=0.012) and one year (beta: 0.195, 95% CI: 0.049-0.340, p=0.009). Major curve SB radiographs were not associated with post-operative major curve correction at one month (p=0.088). Distal curve traction correction radiographs were independently associated with post-operative distal curve correction at one month (beta: 0.251, 95% CI: 0.144-0.357, p<0.001) and at one year (beta: 0.280, 95% CI: 0.149-0.412, p<0.001). Distal curve supine SB radiographs were associated with post-operative distal curve correction at one year (beta: 0.092, 95% CI: 0.014-0.169, p=0.021) (Table 2).

Conclusions:
Intra-operative traction UGA radiographs independently correlated with post-operative major and distal curve correction at one month and one year post-operatively. Supine SB radiographs independently correlated only with distal curve correction at one year post-operatively. However, the correlation was not as strong as traction UGA correction (beta of 0.280 vs beta of 0.092). Traction UGA radiographs appear superior to supine SB radiographs in predicting curve correction after surgery.