title: Morphologic study of nerve root and types of needle used in transforaminal injections.
abstract: 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.
authors.affiliation: Department of Anaesthesiology and Pain Management, Hospital Universitario Madrid-Montepríncipe, Spain. jmhernandez@madridsindolor.com
authors.forename: José M
authors.initials: JM
authors.lastname: Hernández-García
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Reina
authors.forename: Alberto
authors.initials: A
authors.lastname: Prats-Galino
authors.forename: José A
authors.initials: JA
authors.lastname: De Andrés
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000648:ultrastructure; D005539:Foramen Magnum / Q000166:cytology / Q000648:ultrastructure; D006801:Humans; D007268:Injections, Epidural / Q000295:instrumentation* / Q000379:methods; D008159:Lumbar Vertebrae / Q000166:cytology / Q000648:ultrastructure; D009339:Needles; D013126:Spinal Nerve Roots / Q000166:cytology / Q000648:ultrastructure*; D013904:Thoracic Vertebrae / Q000166:cytology / Q000648:ultrastructure