Comparison of the Risk Analysis Index and the Modified 5-Item Frailty Index in Predicting 30-Day Morbidity and Mortality After Occipitocervical Fusion

Study Design Retrospective Cohort Study. Objectives To evaluate the predictive performance of the Risk Analysis Index (RAI) and Modified 5-Item Frailty Index (mFI-5) in identifying risk for adverse postoperative outcomes in patients undergoing occipitocervical fusion (OCF). Methods The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database was queried for patients who underwent OCF from 2015 to 2020. Frailty was measured using both the RAI and mFI-5. The primary outcome was 30-day mortality. Secondary outcomes included major complications, minor complications, unplanned readmission, extended length of stay (eLOS), and non-home discharge (NHD). Multivariable logistic regression was used to assess associations, while receiver operating characteristic (ROC) curve analysis evaluated model discrimination. Results A total of 1637 patients were included (median age 68 years; 51.4% male). Higher frailty scores on both RAI and mFI-5 were associated with increased odds of mortality, major complications, and NHD. However, the RAI demonstrated superior discrimination for predicting mortality (C-statistic: 0.79 [95% CI: 0.75-0.83]) compared to mFI-5 (0.57 [95% CI: 0.53-0.61], P < .001), as well as for major complications (RAI: 0.64 vs mFI-5: 0.57, P = .01) and NHD (RAI: 0.73 vs mFI-5: 0.65, P < .001). Conclusions The RAI outperformed the mFI-5 in predicting key adverse outcomes following OCF. Incorporating RAI into preoperative evaluation may improve frailty-based risk stratification and guide surgical decision-making in vulnerable patients.