To compare the predictive performance of mFI-5 versus RAI for postoperative outcomes following ALIF in Black patients.

Anterior lumbar interbody fusion (ALIF) represents a substantial share of the over 350,000 interbody fusions performed annually in the United States. Frailty, defined as decreased physiologic reserve, is an established predictor of adverse outcomes. The modified Frailty Index-5 (mFI-5) and the Risk Analysis Index (RAI) are validated frailty measures, but their comparative predictive performance in ALIF, particularly among Black patients, remains unclear.

We conducted a retrospective cohort analysis using ACS-NSQIP data (2015–2021) of Black or African American patients aged ≥50 years undergoing elective ALIF. Frailty was assessed using mFI-5 (functional dependence, diabetes, COPD, CHF, hypertension) and RAI (age, sex, comorbidities, weight loss, renal failure, dyspnea, functional status). Outcomes included non-home discharge (primary) and extended length of stay (secondary). Model discrimination was evaluated using AUROC with DeLong tests and bootstrap validation.

Among 1,024 patients, 76.9% were classified as frail by mFI-5 compared to 39.4% by RAI. RAI demonstrated superior discrimination for non-home discharge (AUROC 0.711 vs 0.585, p<0.001) and for extended length of stay (0.612 vs 0.551, p=0.018).

RAI outperformed mFI-5 in predicting non-home discharge and extended length of stay following ALIF in Black patients. These findings highlight the potential of RAI as a more effective frailty measure for preoperative risk stratification in this population, supporting more individualized surgical planning and postoperative care.