425 Comparison of Frailty and Comorbidity Indices for the Prediction of Adverse Postoperative Outcomes in Patients Aged 50 and Older Undergoing Robot-Assisted Primary Posterior Spinal Fusion

INTRODUCTION: Robotic-assisted posterior spinal fusion (PSF) increases the accuracy of pedicle screw insertion. Frailty and comorbidity indices assess a patient’s capacity to tolerate surgery, but the performance of these indices for patients undergoing robotic-assisted spine surgery has not been characterized. METHODS: A retrospective cohort of patients aged 50 and older undergoing robotic-assisted primary PSF at a single center between January 2022 and December 2023 was identified. Multivariable logistic regressions compared the ability of the mFI-5, CCI, and ASA indices to predict length of stay (LOS) exceeding the 75th percentile for the cohort and occurrence of a serious complication or unplanned readmission within 30 days of discharge. Covariates included sex, age, race, BMI, number of spinal levels, spinal region, and smoking status. RESULTS: We identified 267 patients (66.6 ± 8.8 (mean ± SD) years; 57.3% female; 70.8% mFI5 scores of 2-3; 96.6% ASA scores of 2-3; 75.7% CCI scores 0-2) who received 1,529 pedicle screws (62.85% lumbar). 21.4% of the cohort experienced an extended LOS, 25.1% were discharged non-routinely, 13.9% experienced a serious complication, and 6.7% were readmitted. Multivariable logistic regression identified mFI-5 as a predictor of extended LOS (OR: 1.60, 95%CI: 1.08-2.38, p=0.019). Predictors of a serious complication or unplanned readmission included mFI-5 (OR: 1.86, 95%CI: 1.24-2.79, p=0.003; OR 2.89, 95%CI: 1.55-5.38, p=0.001) and CCI (OR: 1.20, 95%CI: 1.03-1.40, p=0.020; OR: 1.33, 95%CI: 1.07-1.64, p=0.009). CONCLUSIONS: Although all three indices provide predictive information, mFI-5 was solely successful in forecasting all three postoperative outcomes evaluated in patients aged 50 or older who underwent robot-assisted primary PSF.