Risk analysis index predicts mortality and non-home discharge following posterior lumbar interbody fusion: a nationwide inpatient sample analysis of 429,380 patients (2019–2020)

Frailty is an independent risk factor for adverse postoperative outcomes following spine surgery. The ability of the Risk Analysis Index (RAI) to predict adverse outcomes following posterior lumbar interbody fusion (PLIF) has not been studied extensively and may improve preoperative risk stratification.

Patients undergoing PLIF were queried from Nationwide Inpatient Sample (NIS) (2019–2020). The relationship between RAI-measured preoperative frailty and primary outcomes (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.

A total of 429,380 PLIF patients (mean age = 61y) were identified, with frailty cohorts stratified by standard RAI convention: 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%). The incidence of 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 acceptable discrimination for NHD (C-statistic: 0.706) and mortality (C-statistic: 0.676) in AUROC curve analysis.

Increasing RAI-measured frailty is significantly associated with increased NHD, eLOS, complication rates, and mortality following PLIF. The RAI demonstrates acceptable discrimination for predicting NHD and mortality, and may be used to improve frailty-based risk assessment for spine surgeons.