What is the optimal postoperative sagittal alignment in ankylosing spondylitis patients with thoracolumbar kyphosis following one-level pedicle subtraction osteotomy?

Abstract Background Context Radiographic realignment objectives for the surgical correction of adult spinal deformity (ASD) has been well-described. However, the optimal sagittal spinopelvic alignment after corrective osteotomy for thoracolumbar kyphosis secondary to ankylosing spondylitis (AS) is still unknown so far. Purpose To comprehensively investigate the relationship between radiographic parameters and clinical outcomes measured by Oswestry Disability Index (ODI) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) in thoracolumbar kyphosis patients caused by AS following one-level pedicle subtraction osteotomy (PSO) and to determine the optimal sagittal alignment at a minimum of two-year follow-up. Study Design A retrospective review of consecutive AS patients from one institution (2006-2016). Patient Sample One hundred AS-related thoracolumbar kyphosis patients who underwent one-level PSO with a minimum of 2-year follow-up (range, 2-10 years). Outcome Measures Spinopelvic parameters at final follow-up (≥2 years) included thoracic kyphosis (TK), lumbar lordosis (LL), osteotomized vertebra angle (OVA), pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), sagittal vertical axis (SVA), spinosacral angle (SSA), T1 pelvic angle (TPA), spinopelvic angle (SPA), and global kyphosis (GK). Clinical outcomes at final follow-up (≥2 years) was evaluated by ODI and BASDAI, and ODI Methods Pre- and postoperative radiographic and clinical outcomes were compared by paired samples t-test. The correlation between the postoperative radiographic parameters and clinical outcomes was investigated by Pearson correlation analysis. Linear regression analysis was performed to construct predictive models of the clinically relevant radiographic parameters based on ODI scores and to determine the realignment goals. Multiple stepwise regression analysis was applied to figure out the major radiographic contributors of ODI score at the final follow-up. Results In total, one hundred AS patients (92 males and 8 females) with a mean age of 34.7±9.5 years (range, 17-63 years) were followed up for 38.6±17.5 months (range, 24-120 months). At the final follow-up, PT and TPA were positively correlated with both ODI and BASDAI score (P Conclusions Based on the regression models, the optimal sagittal alignment of AS patients satisfying good clinical outcome (ODI 108°, TPA 152°. Realizing the aforementioned realignment goals may contribute to satisfied clinical outcome for AS patients with thoracolumbar kyphosis undergoing one-level PSO.