Article Text

Download PDFPDF

Magnetic Positioning System and Ultrasound Guidance for Lumbar Zygapophysial Radiofrequency Neurotomy: A Cadaver Study
  1. Michael Gofeld, MD*,
  2. Michael N. Brown, DO,
  3. Laurent Bollag, MD,
  4. John G. Hanlon, MD* and
  5. Brian R. Theodore, PhD
  1. *Department of Anesthesia, St. Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada
  2. Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA
  1. Address correspondence to: Michael Gofeld, MD, Department of Anesthesia, St Michael’s Hospital, 30 Bond Street, Toronto, ON, Canada M5B1W8 (e-mail: michael.gofeld{at}


Background and Objectives Chronic low back pain related to degenerative spondylosis is commonly managed by the radiofrequency ablation of sensory nerves. Fluoroscopic guidance has been considered mandatory to ensure placement of the active tip of the cannula parallel to the nerve to provide adequate neurolysis. Conversely, analgesic (or diagnostic) blockade is usually accomplished by placing the needle perpendicular to the nerve using either fluoroscopy or ultrasound (US) guidance. The recently introduced disposable equipment of internally cooled radiofrequency allows the denervation procedure to be performed similarly to the routine diagnostic block. Consequently, US may now potentially be used for image-guided radiofrequency neurotomy. We sought to compare the accuracy using a novel US-based technique with the traditional fluoroscopy-guided placement.

Methods The proof of concept study was performed using a magnetic positioning US-guided system. The precision of needle placements was compared with the standard fluoroscopic guidance. The primary outcome of this study was defined as the procedural accuracy. Procedural and radiation exposure time was also recorded. In addition, projected operational expenses were calculated.

Results Ultrasound-guided procedural accuracy reached 97%. Both the imaging and procedure times were similar between the 2 forms of imaging guidance. Of significant importance, the US-guided approach (no radiation exposure) was quantitatively advantageous over fluoroscopy-guidance, which required an average of 170 seconds of radiation per procedure. Thus, the US method seems to be cost effective.

Conclusions A magnetic positioning system allows accurate and quick US-guided placement of radiofrequency cannula to the desired anatomical targets, sparing patients and personnel from exposure to ionized radiation.

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Dr Gofeld was previously a consultant for the Kimberly-Clark Corporation.

    The other authors declare no conflict of interest.

    This study received funding from the Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA, and a GE Healthcare Research Grant (FA78344).

    Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (