Purpose <p>Spinal deformity surgery carries a high risk of intraoperative neuromonitoring (IONM) signal loss and neurological complications. The Cobb angle has traditionally been used to assess spinal deformity severity, but the Deformity Angular Ratio (DAR) has been proposed as a potentially more precise predictor of surgical risks. This systematic review and meta-analysis aimed to compare the preoperative DAR to the Cobb angle to predict the loss of IONM signal and the presence of postoperative neurological complications in spinal deformity correction.</p> Methods <p>A systematic literature search followed PRISMA guidelines across PubMed, Scopus, Embase, and Web of Science from their inception to August 2024. Studies were included if they reported Cobb angles, DAR values, IONM signal loss, and/or neurological complications in spinal deformity patients. The Newcastle-Ottawa Scale (NOS) was used for quality assessment. Random-effects meta-analysis was performed to assess the association between Cobb angles, DAR, IONM signal loss, and neurological complications, with Trim and Fill correction applied to adjust for publication bias.</p> Results <p>Seven high-quality retrospective cohort studies (1,074 patients) were included. Sagittal Cobb (S-Cobb), Coronal Cobb (C-Cobb), and Total Cobb (T-Cobb) angles were significantly associated with IONM signal loss. Sagittal DAR (S-DAR &gt; 12°) and Total DAR (T-DAR &gt; 22°) were strongly correlated with IONM signal loss, while Coronal DAR (C-DAR) showed no significant association after publication bias correction. T-DAR greater than 39° was the only parameter significantly associated with postoperative neurological complications.</p> Conclusions <p>DAR demonstrates greater predictive value than the Cobb angle for identifying patients at high risk for IONM signal loss, with T-DAR showing the strongest correlation. The greater impact of sagittal imbalance (S-DAR, S-Cobb) on IONM signal loss is likely due to spinal cord vascular and mechanical factors.</p>