Article Text

Download PDFPDF
Morphologic Study of Nerve Root and Types of Needle Used in Transforaminal Injections
  1. José M. Hernández-García, MD*,
  2. Miguel A. Reina, MD, PhD*,
  3. Alberto Prats-Galino, MD, PhD and
  4. José A. De Andrés, MD, PhD
  1. From the *Department of Anaesthesiology and Pain Management, Hospital Universitario Madrid-Montepríncipe, and Department of Clinical Sciences and Applied Molecular Medicine Institute, CEU San Pablo University School of Medicine, Madrid;
  2. Human Anatomy and Embryology Unit, Faculty of Medicine, Universidad de Barcelona, Barcelona; and
  3. Department of Anesthesia, Critical Care and Pain Management, Hospital General Universitario, Valencia, Spain.
  1. Address correspondence to: José M. Hernández-García, MD, Hospital Universitario Montepríncipe, Av Montepríncipe 25, Boadilla del Monte, Madrid, Spain (e-mail: jmhernandez{at}


Background: The bevel type and location of the distal orifice of the needle may have relevance for potential complications occurring during transforaminal epidural injection.

Methods: We examined by scanning electron microscopy the structural aspects of spinal nerve root cuffs of 3 human cadavers, and 3 needle types used in transforaminal injections: 22-gauge Quincke spinal needles, 22-gauge blunt nerve block needles, and 20-gauge radiofrequency blunt needles. We made punctures in vitro in the spinal nerve root cuffs, and we studied the structures affected.

Results: There is fat tissue within the nerve root with irregular distribution. In needles with a round tip, the distal orifice maintained an extraneural location after puncture of the nerve root cuff. The length of the needle required to introduce the distal orifice completely inside the nerve root cuff was variable, depending on the type: shortest for a Quincke needle (1.8 mm), 4.1 mm for the Epimed, and longest for radiofrequency needles (5.7 mm).

Conclusions: The layer of fat around nerve roots may prevent the contact of the needle tip with axons. The sharp needle tip entered the nerve root cuff more easily than the blunt tip in the cadaveric nerve root samples, measured in a qualitative manner. There is a need for clinical studies to ascertain if blunt needles may be safer than sharp needles for transforaminal injections.

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.


  • The authors have no conflict of interest to report.