• David J Kennedy, Ryan Mattie, Alan Scott Hamilton, Bryan Conrad, and Matthew Smuck.
• *Department of Orthopaedic Surgery, Stanford University, Redwood City, California djkenned@stanford.edu.
• Pain Med. 2016 Jun 1; 17 (6): 1031-1036.

Background ContextMedial branch blocks may have unrecognized vascular uptake potentially resulting in false- negative results.PurposeTo determine the rate of unintended vascular injection of contrast medium during medial branch blocks (MBB) with digital subtraction (DS) technology in the context of negative vascular uptake as determined by live fluoroscopy.Study Design/SettingProspective Study in an academic medical center.Patient Sample344 consecutive MBBs in 80 subjects.Outcome MeasuresThe presence of vascular flow as determined by live fluoroscopy and DS technology.MethodsUnintended vascular injection of contrast medium was determined on 344 consecutive MBBs in 84 subjects, first using live fluoroscopy followed by DS. If live fluoroscopy initially detected vascular uptake, the needle was repositioned until no vascular flow was detected. Once no vascular uptake was confirmed by live fluoroscopy, a contrast medium was then injected while being visualized with DS to again assess the presence or absence of vascular flow undetected by live fluoroscopy.ResultsLive fluoroscopy revealed inadvertent vascular uptake in 38 of the 344 blocks [11% (95% CI 8.0-15%)]. DS uncovered an additional 27 of the 344 blocks [7.8% (95% CI 5.3-11.4%)] with evidence of vascular uptake that were not detected with conventional live fluoroscopy.ConclusionDS enhances the ability to detect inadvertent vascular flow during medial branch blocks. This study demonstrates that standard live fluoroscopy can miss a small percentage of cases with unintentional vascular uptake during MBB when compared with DS and may contribute to occasional false-negative responses.© 2016 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

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