1530. Correlation of body mass index (BMI) and global sagittal alignment with anterior correction surgery in patients with flat back syndrome

Authors: Muhammad Burhan Ud Din Janjua, MD; Brendan McShane, BA; William Welch, MD; Vincent Arlet, MD; Ali Ozturk, MD (Dallas, TX)

Introduction: The influence of Body Mass Index (BMI) on global spinal alignment is scarcely known. Anterior surgery with the use of hyperlordotic cages (HCLs) helps in maximizing lumbar lordosis (LL) and correction of global sagittal parameters, such as sagittal vertical axis (SVA). No prior study investigated the effect of global correction on BMI. Therefore, authors hypothesized pre- to postoperative change in SVA correlates with the change in BMI in obese patients undergoing correction surgery with anterior approach. Methods: All patients operated for de novo or iatrogenic flat back syndrome with a pre-operative BMI of more than 25 were included in this study. Pre- and postoperative standing stereographs were used to calculate sagittal parameters including SVA and LL. Demographics including BMI preop- and postoperatively at last follow up were collected. Unpaired and paired t-tests, and a linear regression were used for statistical analysis. Results: Of total 74 patients with an average age of 59 years (SD ± 12), 48 patients with BMI of more than 25 and mean follow-up of 392 days (SD ± 441) were identified. Mean BMI was 31.1 (SD ± 4.5), mean pre-op SVA was 87.2mm (SD ± 60.3), and mean LL was 31.4° (SD ± 23.6°). Preoperative SVA was significantly correlated with preoperative BMI (R 2 =0.16, p=0.004). Post-surgery, mean change in SVA was 45.9mm (SD ± 64.1), and mean change in LL was 20.4° (SD ± 17.5°). Mean change in BMI was 0.1 (SD ± 3.2) with 27 (56%) patients having a significant decrease in BMI. Postoperative change in SVA was directly correlated with change in BMI (R 2 =0.083, p=0.047). Conclusion: Anterior surgery with HLCs is efficacious to overpower the overall LL thereby achieving global sagittal correction. High BMI is associated with global malalignment; however, postoperative reduction in SVA is strongly correlated with the decrease in BMI.