Investigating the utility of intraoperative neurophysiological monitoring for anterior cervical discectomy and fusion: analysis of over 140,000 cases from the National (Nationwide) Inpatient Sample data set

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OBJECTIVE

Intraoperative neurophysiological monitoring (IONM) is a useful adjunct in spine surgery, with proven benefit in scoliosis-correction surgery. However, its utility for anterior cervical discectomy and fusion (ACDF) is unclear, as there are few head-to-head comparisons of ACDF outcomes with and without the use of IONM. The authors sought to evaluate the impact of IONM on the safety and cost of ACDF.

METHODS

This was a retrospective analysis of data from the National (Nationwide) Inpatient Sample of the Healthcare Cost and Utilization Project from 2009 to 2013. Patients with a primary procedure code for ACDF were identified, and diagnosis codes were searched to identify cases with postoperative neurological complications. The authors performed univariate and multivariate logistic regression for postoperative neurological complications with use of IONM as the independent variable; additional covariates included age, sex, surgical indication, multilevel fusion, Charlson Comorbidity Index (CCI) score, and admission type. They also conducted propensity score matching in a 1:1 ratio (nearest neighbor) with the use of IONM as the treatment indicator and the aforementioned variables as covariates. In the propensity score–matched cohort, they compared neurological complications, length of stay (LOS), and hospital charges (in US dollars).

RESULTS

A total of 141,007 ACDF operations were identified. IONM was used in 9540 cases (6.8%). No significant association was found between neurological complications and use of IONM on univariate analysis (OR 0.80, p = 0.39) or multivariate regression (OR 0.82, p = 0.45). By contrast, age ≥ 65 years, multilevel fusion, CCI score > 0, and a nonelective admission were associated with greater incidence of neurological complication. The propensity score–matched cohort consisted of 18,760 patients who underwent ACDF with (n = 9380) or without (n = 9380) IONM. Rates of neurological complication were comparable between IONM and non-IONM (0.17% vs 0.22%, p = 0.41) groups. IONM and non-IONM groups had a comparable proportion of patients with LOS ≥ 2 days (19% vs 18%, p = 0.15). The use of IONM was associated with an additional $6843 (p < 0.01) in hospital charges.

CONCLUSIONS

The use of IONM was not associated with a reduced rate of neurological complications following ACDF. Limitations of the data source precluded a specific assessment of the effectiveness of IONM in preventing neurological complications in patients with more complex pathology (i.e., ossification of the posterior longitudinal ligament or cervical deformity).

ABBREVIATIONS ACDF = anterior cervical discectomy and fusion; CCI = Charlson Comorbidity Index; HCUP = Healthcare Cost and Utilization Project; IONM = intraoperative neurophysiological monitoring; LOS = length of stay; NIS = National (Nationwide) Inpatient Sample; OPLL = ossification of the posterior longitudinal ligament; SSEP = somatosensory evoked potential; tceMEP = transcranial electrical motor evoked potential.
Article Information

Contributor Notes

Correspondence Jefferson R. Wilson: University of Toronto, St. Michael’s Hospital, Toronto, ON, Canada. wilsonjeff@smh.ca.INCLUDE WHEN CITING Published online March 29, 2019; DOI: 10.3171/2019.1.SPINE181110.Disclosures Dr. Wilson reports being a consultant for Stryker Canada.
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