TO THE EDITOR
Re: Routine Use of Intraoperative Neuromonitoring During ACDFs for the Treatment of Spondylotic Myelopathy and Radiculopathy Is Questionable: A Review of 15,395 Cases. Spine (Phila Pa 1976) 2017 Jan 1;42(1):14–19.
We read with great interest the article recently published by Ajiboye et al,1 which questions the utility of intraoperative neuromonitoring (IONM) during ACDF surgery, and would like to draw attention to what we believe is a methodological error that invalidates many of the article's central conclusions.
In this retrospective study, the authors used the PearlDiver Database to identify cases of spondylotic myelopathy and/or radiculopathy that underwent ACDF from 2007 to 2014 with and without IONM. Major conclusions from this study include the following: (1) There was a significant decrease in the use of IONM for ACDFs from 2007 to 2014, (2) the IONM modalities used for these ACDFs were quite variable, and (3) utilization of IONM varies regionally.
Among the myriad critiques that one can make of this article, one major methodological error worth highlighting concerns their use of the PearlDiver database to analyze national trends in the utilization of IONM. A significant problem with using PearlDiver to draw conclusions about utilization of IONM is that this database is not designed to answer questions about utilization. Specifically, PearlDiver data are based on claims paid or adjusted (e.g., for IONM), but PearlDiver does not contain information about claims denied payment or claims not submitted for payment (personal communication confirmed with PearlDiver). In other words, data extracted from PearlDiver can only tell us how many times Humana agreed to pay for IONM during ACDF, and it cannot tell us how many ACDF cases were actually monitored.
The challenges that providers face in seeking reimbursement for IONM are significant; particularly with the erosion of concurrent monitoring which began in 2013.2 Additionally, the IONM profession's history of under-publishing results, despite the preponderance of data, has now introduced new obstacles as payors frequently change their medical coverage policies (MCP) to limit reimbursement for IONM. Neuromonitoring is reimbursed by diagnosis, not by procedure, and a critical factor that Ajiboye et al1 failed to consider is that Humana changed their MCP several times regarding reimbursement for IONM during the analysis period. Of particular relevance to this discussion is the fact that, in 2011, Humana added new language to their MCP for IONM, which states:
This new language clearly lays the foundation for decreasing IONM reimbursements for cervical discectomies. Thus, it is entirely possible that the reduction in reimbursements for ACDF that the authors observed in 2012 is directly related to the fact that Humana changed their MCP in the latter half of 2011.
Based on the evidence presented above, all of the authors’ conclusions and statements regarding increases or decreases in the use of IONM, regional variability in the use of IONM and patterns of usage for specific IONM test modalities (i.e., motor evoked potentials, somatosensory evoked potentials, electromyography) are all invalid because this database only describes privately insured Humana reimbursement for IONM, and not utilization.
In conclusion, we must exercise greater caution with the use of large datasets to make such conclusions about national trends without first verifying that the method of data collection does not undermine the research design. Given the gravity of the methodological errors highlighted above, we recommend as a course of action that the authors retract all statements related to the utilization of IONM, and examine more closely the myriad reasons why reimbursement for IONM is on the decline at a time when utilization is clearly on the rise.