Comparative Analysis of Lumbar Lordosis: Postoperative Upright versus Intraoperative Prone Imaging in Patients Undergoing Adult Spinal Deformity Surgery

Spinopelvic parameters [pelvic incidence (PI), lumbar lordosis (LL) sagittal vertical axis (SVA), and pelvic mismatch (PI-LL)] are vital for the assessment of sagittal spinal alignment. 1-3 Intraoperative prone radiographs may underestimate or overestimate postoperative lumbar lordosis and impact surgical planning and execution. 4 This study aims to determine the change in LL in prone intraoperative versus standing postoperative imaging. Data from patients undergoing adult spinal deformity (ASD) surgery at an academic center (2010–2013) were retrospectively recorded. Two spine surgeons measured spinopelvic parameters on Surgimap using full-length scoliosis radiographs. Differences between intraoperative, immediate postoperative and 3-month postoperative measurements of LL, PI, absolute change in (PI-LL) were assessed. A total of 138 patients were reviewed. Following surgical correction, the intraoperative prone LL measurement was 54.41° (SD 11.68°), the immediate standing postoperative LL was 50.31° (SD 10.76°) and the 3-month standing postoperative LL was 48.42° (SD 10.34°). ANOVA analysis of yielded a significant difference between the 3 cohorts f- ratio 10.81 (p < 0.05). A post-hoc Tukey HSD demonstrated significant differences between intraop LL and immediate postop LL (Q = 4.10 p < 0.05) and intraop LL and 3-month postop LL (Q = 5.99 p < 0.05) (Table 1). In patients undergoing ASD surgery, transitioning from prone to upright position results in a roughly 5° loss of lumbar lordosis. To estimate postoperative lumbar lordosis accurately, this study suggests using the calculation: postoperative LL = intraoperative LL - 5°. This information aids surgeons in optimizing intraoperative LL to align with the planned postoperative outcome.