Deformity angular distance ratio independently predicts intraoperative neuromonitoring alerts in spinal deformity correction.

Background: Intraoperative neuromonitoring (IONM) alerts are critical concerns for surgeons performing spinal deformity corrective surgeries, as they indicate a heighteded risk of postoperative neurological deficits. Previous studies have demonstrated that patients with large Cobb angle or elevated deformity angular ratio (DAR) are at an increased risk of IONM alerts. However, spinal curves with similar Cobb angles and DARs may exhibit significantly different risks of IONM alerts during surgery. Current methods for evaluating spinal deformity fail to comprehensively and accurately reflect its severity. The purpose of this study was to investigate whether the deformity angular distance ratio (DADR) serves as an independent predictor of IONM alerts during corrective surgery for spinal deformity.

Methods: This study analyzed a consecutive series of 404 patients undergoing corrective surgery at a single academic center. Preoperative radiographs were used to calculate the DAR and DADR. Twelve clinically relevant candidate variables were selected for univariable analysis. Multivariable logistic regression analysis was then conducted to identify independent predictors of IONM alerts.

Results: The incidence of IONM alerts in this cohort was 25.2%. Univariable analysis identified several factors potentially associated with IONM alerts, including older age, type-III spinal cord morphology, location of apex, etiological diagnosis, preoperative sagittal Cobb angle, sagittal DAR, sagittal DADR, coronal DADR, total DAR, total DADR, three-column osteotomy, and preoperative neurological deficits. Multivariable analysis revealed that an apex location at C7-T4, preoperative neurological deficits, sagittal DADR, and total DADR were independent predictors of IONM alerts.

Conclusions: Among patients undergoing corrective surgeries for spinal deformities, the DADR is a robust measure of spinal deformity severity and is strongly correlated with the risk of IONM alerts. Compared to other deformity parameters, DADR is an independent predictor of IONM alerts. Additional independent predictors include the location of the apex and the presence of preoperative neurological deficits.