Objective:

To compare the predictive performance of the modified Frailty Index-5 (mFI-5) and the Risk Analysis Index (RAI) for postoperative outcomes in active smokers undergoing ALIF. 

Background:

Anterior lumbar interbody fusion (ALIF) accounts for a substantial proportion of spinal fusions in the United States. Frailty assessment may improve risk stratification, particularly in vulnerable populations such as active smokers, but comparative performance of different indices is uncertain. 

Design/Methods:

We analyzed ACS-NSQIP data (2015–2021) for patients aged ≥50 years who underwent elective ALIF and were active smokers. Frailty was assessed with mFI-5 and RAI. Multivariable logistic regression evaluated associations with outcomes. Model discrimination was assessed with AUROC and compared using the DeLong test, with bootstrap validation. 

Results:

Among 2,806 patients, 50.3% were frail by mFI-5 and 22.9% by RAI. Non-home discharge occurred in 10.2%. The RAI demonstrated superior discrimination compared to mFI-5 for non-home discharge (AUROC 0.732 vs 0.639, p<0.001), extended length of stay (0.633 vs 0.568, p<0.001), and minor complications (0.698 vs 0.520, p=0.013). Predictive performance was similar for mortality, readmission, and reoperation. 

Conclusions:

RAI outperformed mFI-5 in predicting non-home discharge and select complications following ALIF in active smokers. These findings support the RAI as a more effective tool for preoperative frailty assessment and perioperative planning in this high-risk population.