title: Influence of needle position on lumbar segmental nerve root block selectivity.
abstract: OBJECTIVE
  In patients with chronic low back pain radiating to the leg, segmental nerve root blocks (SNRBs) are performed to predict surgical outcome and identify the putative symptomatic spinal nerve. Epidural spread may lead to false interpretation, affecting clinical decision making. Systematic fluoroscopic analysis of epidural local anesthetic spread and its relationship to needle tip location has not been published to date. Study aims include assessment of epidural local anesthetic spread and its relationship to needle position during fluoroscopy-assisted blocks.
  
  
  METHODS
  Patients scheduled for L4, L5, and S1 blocks were included in this prospective observational study. Under fluoroscopy and electrostimulation, they received 0.5 mL of a mixture containing lidocaine 5 mg and iohexol 75 mg. X-rays with needle tip and contrast were scored for no epidural spread (grade 0), local spread epidurally (grade 1), or to adjacent nerve roots (grade 2).
  
  
  RESULTS
  Sixty-five patients were analyzed for epidural spread, 62 for needle position. Grade 1 epidural spread occurred in 47% of L4 and 28% of L5 blocks and grade 2 spread in 3 blocks (5%; L5 n = 1, S1 n = 2). For lumbar blocks, the needle was most frequently found in the lateral upper half of the intervertebral foramen. Epidural spread occurred more frequently with medial needle positions (P = .06).
  
  
  CONCLUSIONS
  The findings suggest (P = .06) that the risk of grade 1 and 2 lumbar epidural spread, which results in decreased SNRB selectivity, is greater with medial needle positions in the intervertebral foramen. The variability in anatomic position of the dorsal root ganglion necessitates electrostimulation to guide SNRB in addition to fluoroscopy.
authors.affiliation: Pain Centre, Department of Anesthesiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. a.wolff@anes.umcn.nl
authors.forename: André P
authors.initials: AP
authors.lastname: Wolff
authors.forename: Gerbrand J
authors.initials: GJ
authors.lastname: Groen
authors.forename: Oliver H
authors.initials: OH
authors.lastname: Wilder-Smith
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000767:Anesthesia, Epidural / Q000009:adverse effects / Q000379:methods*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D001340:Autonomic Nerve Block / Q000009:adverse effects / Q000379:methods*; D002908:Chronic Disease; D003287:Contrast Media / Q000008:administration & dosage; D004338:Drug Combinations; D004558:Electric Stimulation; D005260:Female; D005471:Fluoroscopy / Q000379:methods; D005727:Ganglia, Spinal / Q000033:anatomy & histology; D006801:Humans; D007268:Injections, Epidural / Q000009:adverse effects; D007472:Iohexol / Q000008:administration & dosage; D008012:Lidocaine / Q000008:administration & dosage*; D017116:Low Back Pain / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D008161:Lumbosacral Region; D008297:Male; D008875:Middle Aged; D009339:Needles; D011446:Prospective Studies; D015641:Radiography, Interventional
chemical_list: D000779:Anesthetics, Local; D003287:Contrast Media; D004338:Drug Combinations; D007472:Iohexol; D008012:Lidocaine