Utility of Risk Analysis Index for Assessing Morbidity in Patients Undergoing Posterior Spinal Fusion for Adult Spinal Deformity

Abstract

This study investigates the predictive values of the Risk Analysis Index (RAI), the modified 5-item Frailty Index (mFI-5), and advanced age for predicting 30-day extended length of stay (LOS), 30-day complications and readmissions in patients undergoing posterior spinal fusion (PSF) for adult spinal deformity (ASD). A retrospective cohort study was performed using the 2012-2021 ACS NSQIP database. Adults undergoing posterior spinal fusion for ASD were identified using CPT and ICD codes. Using receiver operating characteristic (ROC) and multivariable analyses, we compared the discriminative thresholds and independent associations of RAI, mFI-5, and greater patient age for extended LOS, 30-day complications and readmissions. In this cohort of 3,814 patients, RAI identified 90.7% as Robust, 6.0% as Normal, and 3.3% as Frail/Very Frail, while mFI-5 classified 47.1% as Robust, 37.5% as Normal, and 15.3% as Frail/Very Frail. Multivariate analysis revealed both RAI and mFI-5 as significant predictors of extended LOS for Normal (RAI: p<0.001; mFI-5: p=0.012) and Frail/Very Frail patients (RAI: p<0.001; mFI-5: p=0.002). Additionally, RAI was a significant predictor of 30-day complication risk for Normal patients (p=0.005). Furthermore, mFI-5 was a significant predictor of 30-day readmission among Frail/Very Frail patients (p=0.002). This study highlights the utility of RAI and mFI-5 in predicting extended LOS patients undergoing PSF for ASD. RAI was found to be superior to mFI-5 for predicting 30-day readmissions, while mF-5 was greater for 30-day complications. These findings highlight the importance of incorporating frailty assessments into preoperative surgical planning.