Can the American College of Surgeons Risk Calculator Predict 30-Day Complications After Spine Surgery?

Michael H. McCarthy, MD, MPH; Partik Singh, BA; Rusheel Nayak, BA; Joseph P. Maslak, MD; Tyler J. Jenkins, MD; Alpesh A. Patel, MD; Wellington K. Hsu, MD


Spine. 2020;45(9):621-628. 

In This Article

Abstract and Introduction


Study Design: Retrospective cohort study.

Objective: The aim of this study was to assess the American College of Surgeons National Surgery Quality Improvement Program (ACS NSQIP) Risk Calculator's ability to predict 30-day complications after spine surgery.

Summary of Background Data: Surgical risk calculators may identify patients at increased risk for complications, improve outcomes, enhance the informed consent process, and help modify risk factors. The ACS NSQIP Risk Calculator was developed from a cohort of >1.4 million patients, using 2805 unique CPT codes. It uses 21 patient predictors and the planned procedure to predict the risk of 12 different outcomes within 30 days following surgery.

Methods: A retrospective chart review was performed on patients who underwent primary lumbar and cervical fusions with at least 30-day postoperative follow-up between 2009 and 2015 at a single-institution. Descriptive statistics were calculated for the overall sample, anterior versus posterior fusion (cervical only), and single versus multilevel fusion. Logistic regression models were fit with actual complication occurrence as the dependent variable in each model and ACS estimated risk as the independent variable. The c-statistic was used as the measure of concordance for each model. Receiver-operating charateristic curves depicted the predictive ability of the estimated risks. Acceptable concordance was set at c >0.80.

Results: A total of 237 lumbar and 404 cervical patients were included in the study. The Risk Calculator risk estimates significantly predicted (P < 0.001) "any complication" and "discharge to skilled nursing facility" among the cervical cohort and demonstrated no significant outcome prediction the lumbar cohort.

Conclusion: The ACS Risk-Calculator accurately predicted complications in the categories of "any complication" and "discharge to skilled nursing facility" for our cervical cohort and failed to demonstrate benefit for our lumbar cohort. Although the ACS Risk-Calculator may be useful in general surgery, our findings demonstrate that it does not necessarily provide accurate information for patients undergoing spinal surgery.

Level of Evidence: 3


The increasing number of spine surgeries in the United States has significantly increased over the past two decades.[1] Clinical studies, such as the SPORT trials, have provided evidence to support success rates to establish surgical indications for these pathologies.[2] Interestingly, the significant rise of spine surgery in the United States has occurred despite the similar prevalence and incidence rates in other countries that have not experienced similar observations.[3] In spite of the expanding role of evidence-based spine surgery, a significant proportion of morbidity and mortality has been associated with these surgical interventions.[4–6]

The assessment of risk and reduction of complications is increasingly under scrutiny in our current cost-conscious health care system. National health care improvement efforts are utilizing quality-reporting metrics to identify adverse events within surgery. Most notably, the enactment of the Patient Protection and Affordable Care Act authorizes the occurrence of certain adverse outcomes following surgery to be publicly reported, factoring into quality-related reimbursement schemes.[7] The intention of risk stratification models is to facilitate valid comparison of risk-adjusted profiles providing patients preoperatively with an understanding of potential surgical complications. The Charlson Comorbidity Index and the American College of Surgeons National Surgery Quality Improvement Program Surgical Risk Calculator are commonly used by providers to assess complication rates in patients undergoing surgery.

The ACS NSQIP database tracks data from >500 hospitals and is accessible via an online, publicly available platform. The program offers an ACS NSQIP Surgical Risk Calculator which is a validated, prospective multi-institutional database of surgical data across all surgical specialties.[8] This specifically focuses on 21 preoperative factors to predict an individual's perioperative risk profile. Patient demographics and presurgical comorbidities are entered into the Risk Calculator which calculates probability for each of the 11 complication categories. The National Quality Forum (NQF), a nonprofit, nonpartisan organization that works to catalyze improvements in healthcare, sited the Risk Calculator as a foundational element within the Measure 358- Patient-Centered Surgical Risk Assessment and Communication.[9] The NQF advocates it as a viable tool to assess individual risk for numerous surgical intervention in addition to spine surgery. Recently, the validity and accuracy of the Risk Calculator for patients undergoing orthopedic procedures have been studied demonstrating its limited ability to accurately predict outcomes.[10,11] However, to date there is only one such study regarding the Risk Calculator's ability to assess outcomes in spine patients. Veeravagu et al[12] found the Risk Calculator to consistently underestimate complication occurrence and offer an alternative risk assessment tool within their study. Due to the limited assessment of the Risk Calculator within spine surgery, we aim to assess the ability of this tool to predict 30-day complication after elective spine surgery.