Estimating Intraoperative Neurophysiological Monitoring Rates for Anterior Cervical Discectomy and Fusion: Are Diagnostic or Procedural Codes Accurate?

Background: The utility of intraoperative neurophysiological monitoring (IONM) is well established for some spine surgeries (eg, intramedullary tumor resection, scoliosis deformity correction), but its benefit for most degenerative spine surgery, including anterior cervical discectomy and fusion (ACDF), remains debated. National datasets provide "big data" approaches to study the impact of IONM on spine surgery outcomes; however, if administrative coding in these datasets misrepresents actual IONM usage, conclusions will be unreliable. The objective of this study was to compare estimated rates (administrative coding) to actual rates (chart review) of IONM for ACDF at our institution and extrapolate findings to estimated rates from 2 national datasets.

Methods: Patients were included from 3 administrative coding databases: the authors' single institution database, the Nationwide Inpatient Sample (NIS), and the National Surgical Quality Improvement Program (NSQIP). Estimated and actual institutional rates of IONM during ACDF were determined by administrative codes (International Classification of Diseases [ICD] or Current Procedural Terminology [CPT]) and chart review, respectively. National rates of IONM during ACDF were estimated using the NIS and NSQIP datasets.

Results: Estimated institutional rates of IONM for ACDF were much higher with CPT than ICD coding (73.2% vs 16.5% in 2019). CPT coding for IONM better approximated actual IONM usage at our institution (74.6% in 2019). Estimated IONM utilization rates for ACDF in national datasets varied widely: 0.76% in CPT-based NSQIP and 18.4% in ICD-based NIS.

Conclusions: ICD coding underestimated IONM usage during ACDF at our institution, whereas CPT coding was more accurate. Unfortunately, the CPT-based NSQIP is nearly devoid of IONM codes, as it has not been a collection focus of that surgical registry. ICD-based datasets, such as the NIS, likely fail to accurately capture IONM usage. Multicenter and/or national datasets with accurate IONM utilization data are needed to inform surgeons, insurers, and guideline authors on whether IONM has benefit for various spine surgery types.

Clinical Relevance: Currently available national databases based on administrative codes do not accurately reflect IONM usage.