Does the ACS NSQIP Surgical Risk Calculator Accurately Predict Complications Rates After Anterior Lumbar Interbody Fusion Procedures?

Ankur S. Narain, MD; Alexander Z. Kitto, MD; Benjamin Braun, MD; Matthew J. Poorman, MD; Patrick Curtin, MD; Justin Slavin, MD; Giles Whalen, MD; Christian P. DiPaola, MD; Patrick J. Connolly, MD; Michael P. Stauff, MD


Spine. 2021;46(12):E655-E662. 

In This Article


Patient Characteristics

Table 1 summarizes patient characteristics and demographics. Two hundred fifty-three (253) patients were included in this analysis. The average age in the study population was 51.6 ± 12.4 years. The patient population was 65.6% (166) female. The average body mass index was 29.4 ± 5.9 kg/m2. The most common preoperative comorbidity was "hypertension requiring medication" (43.5%, n = 110). The majority of patients were ASA class II (71.9%, n = 182).

Operative Characteristics

Table 2 details patient operative characteristics. More patients had a staged procedure (55.7%, n = 141) compared to stand-alone ALIF procedures (44.3%, n = 112). Most patients had one- to two-level procedures (87.8%, n = 222). For the patients that had staged procedures, the majority had supplemental posterior spinal instrumented fusion (PSIF, 93.3%, n = 140). ALIFs were performed as a revision procedure after a prior failed spinal fusion in 31.2% (n = 79) of cases. The average length of stay was 5.2 ± 3.3 days.

Complication Rates

Figure 3 compares the observed complications versus the number of complications predicted by the ACS NSQIP Risk Calculator. For any complication, the observed incidence was 22.9% (58) versus a predicted incidence of 6.7% (17). For serious complications, the observed incidence was 21.7% (55) versus a predicted incidence of 5.9% (15). The observed rate of adverse discharge was 17.8% (45) versus a predicted rate of 11.1% (28).

Figure 3.

Comparison of observed complications and predicted number of complications from the ACS NSQIP surgical risk calculator.

Quality of Prediction Analysis

Figure 4 presents ROC curves for the predictive ability of the ACS NSQIP Surgical Risk Calculator. The ACS NSQIP Surgical Risk calculator performed best in predicting acute renal injury/progressive renal insufficiency with AUC = 0.81. The ACS NSQIP Surgical Risk Calculator also had fair predictive ability for adverse discharge (AUC 0.71) and surgical site infections (AUC 0.70). Otherwise, the ACS NSQIP Surgical Risk Calculator had poor predictive capability for complications including any complication (AUC 0.61), serious complications (AUC 0.60), pneumonia (AUC 0.61), urinary tract infection (AUC 0.57), venous thromboembolism (AUC 0.66), length of stay (AUC 0.63), readmissions (0.58), and reoperations (AUC 0.53). For length of stay analysis, 112 cases of stand-alone ALIF were analyzed. The ACS NSQIP Surgical Risk Calculator was a poor predictor of length of stay with AUC = 0.63.

Figure 4.

Receiver-operating curve analysis of the predictive ability of the ACS NSQIP surgical risk calculator for each complication type.