The 5-Item Modified Frailty Index Independently Predicts Morbidity in Patients Undergoing Instrumented Fusion following Extradural Tumor Removal

INTRODUCTION: The management of spinal neoplasia consists of surgical, radiation, and systemic options. Little data exist to guide management based on overall health status, which is particularly challenging when patients who could benefit from surgery may be too frail for it. This study's objective was to evaluate the 5-Item Modified Frailty Index (mFI-5) as a predictor of 30-day morbidity in patients undergoing instrumented resection for metastatic extradural spinal tumors. METHODS: Adults undergoing extradural tumor resection from the 2011 to 2019 National Surgical Quality Improvement Program datasets were identified by Current Procedural Terminology codes 63275-63278 with an adjunct instrumentation code (22840-22843). Patients were classified into frailty levels 0, 1, or 2+ based on mFI-5 scores of 0, 1, or 2-5, respectively. The primary outcome was morbidity. Secondary outcomes were readmission and reoperation. Multivariate modeling was utilized to analyze mFI-5 as a predictor of outcomes. The Akaike information criterion (AIC) was used to compare relative-model-fit based on frailty versus individual comorbidity variables to determine the optimal model. Chi-squared and Fisher's exact tests were used to establish significance between individual complications and frailty. RESULTS: There were 874 patients. Readmission, reoperation, and morbidity rates were 19.5%, 5.0%, 52.3%, respectively. In multivariate analyses, mFI-5=1 (OR: 1.45, SE: 0.31, p=0.036), mFI-5=2+ (OR: 1.41, SE: 0.40, p=0.036), operative time (OR: 1.18, SE: 0.03, p≤0.001), and chronic steroid use (OR: 1.56, SE: 0.42, p=0.037) independently predicted morbidity. Elective surgery (OR: 0.61) was protective. Frailty did not predict readmission or reoperation. Frailty was found to be significantly associated with respiratory complications, urinary tract infections, cardiac events, and sepsis/septic shock specifically. CONCLUSIONS: mFI-5=1 independently predicted 45% increased odds of morbidity. mFI-5=2+ independently predicted 41% increased odds of morbidity. Further, every 30 additional minutes of operative time predicted 18% increased odds of morbidity, suggesting an increased risk of site-related complication events. Taken together, the mFI-5 serves as a valid predictor of morbidity in patients with extradural tumor undergoing instrumented excision.