The Risk Analysis Index Frailty Assessment Tool Predicts Mortality and Non-Home Discharge Following Posterior Lumbar Interbody Fusion: A Nationwide Inpatient Sample Analysis of 429,380 Patients

Introduction: Frailty, or decreased baseline physiologic reserve, is an independent risk factor for adverse postoperative outcomes after spine surgery and helps identify, preoperatively, patients with the highest surgical risk. The ability of the Risk Analysis Index (RAI), an accumulation-of-deficit-based frailty model, to predict adverse outcomes following posterior lumbar interbody fusion (PLIF) has not been extensively studied in patients undergoing PLIF and may aid in preoperative risk stratification.

Methods: Patients undergoing PLIF were queried from the Nationwide Inpatient Sample (NIS) using diagnostic and procedural codes (2019-2020). The relationship between preoperative frailty, as measured by the RAI, and primary outcomes (in-hospital mortality, non-home discharge (NHD)) and secondary outcomes (extended length of stay (eLOS), complication rates) was assessed via multivariate analyses. The discriminatory accuracy of the RAI for primary outcomes was measured in area under the receiver operating characteristic (AUROC) curve analysis.

Results: A total of 429,380 PLIF patients (mean age = 61 years old) were identified, with frailty statuses stratified by RAI standard convention, with scores: 0–20 “robust” (R)(38.3%), 21–30 “normal” (N) (54.3%), 31–40 “frail” (F) (6.1%) and 41+ “very frail” (VF)(1.3%). Primary and secondary outcomes increased as frailty thresholds increased: mortality (R 0.1%, N 0.1%, F 0.4%, VF 1.3%; p< 0.001), NHD (R 6.5%, N 18.1%, F 36.9%, VF 42.0%; p< 0.001), eLOS (R 18.0%, N 21.9%, F 31.6%, VF 43.8%; p< 0.001) and complication rates (R 6.6%, N 8.8%, F 11.1%, VF 12.2%; p< 0.001). The RAI demonstrated good discrimination for NHD (C-statistic: 0.706) and in-hospital mortality (C-statistic: 0.676) in AUROC curve analysis.

Conclusion : Increasing patient frailty, as measured by the RAI, is significantly associated with increased NHD, eLOS, complication rates, and in-hospital mortality following PLIF. The RAI demonstrates strong discrimination for predicting NHD and in-hospital mortality. Preoperative frailty assessment of PLIF patients using the RAI may provide more precise risk assessment for surgeons and potentially improve surgical safety and outcomes.