title: Ultrasound-guided lumbar facet nerve block: accuracy of a new technique confirmed by computed tomography.
abstract: BACKGROUND
  Lumbar facet nerve (medial branch) blocks are often used to diagnose facet joint-mediated pain. The authors recently described a new ultrasound-guided methodology. The current study determines its accuracy using computed tomography scan controls.
  
  
  METHODS
  Fifty bilateral ultrasound-guided approaches to the lumbar facet nerves were performed in five embalmed cadavers. The target point was the groove at the cephalad margin of the transverse (or costal) process L1-L5 (medial branch T12-L4) adjacent to the superior articular process. Axial transverse computed tomography scans, with and without 1 ml contrast dye, followed to evaluate needle positions and spread of contrast medium.
  
  
  RESULTS
  Forty-five of 50 needle tips were located at the exact target point. The remaining 5 were within 5 mm of the target. In 47 of 50 cases, the applied contrast dye reached the groove where the nerve is located, corresponding to a simulated block success rate of 94% (95% confidence interval, 84-98%). Seven of 50 cases showed paraforaminal spread, 5 of 50 showed epidural spread, and 2 of 50 showed intravascular spread. Despite the aberrant distribution, all of these approaches were successful, as indicated by contrast dye at the target point. Abnormal contrast spread was equally distributed among all lumbar levels. Contrast traces along the needle channels were frequently observed.
  
  
  CONCLUSIONS
  : The computed tomography scans confirm that our ultrasound technique for lumbar facet nerve block is highly accurate for the target at all five lumbar transverse processes (medial branches T12-L4). Aberrant contrast medium spread is comparable to that of the classic fluoroscopy-guided method.
authors.affiliation: Department of Anesthesiology and General Intensive Care (B), Medical University of Vienna, Austria. manfred.greher@univie.ac.at
authors.forename: Manfred
authors.initials: M
authors.lastname: Greher
authors.forename: Lukas
authors.initials: L
authors.lastname: Kirchmair
authors.forename: Birgit
authors.initials: B
authors.lastname: Enna
authors.forename: Peter
authors.initials: P
authors.lastname: Kovacs
authors.forename: Burkhard
authors.initials: B
authors.lastname: Gustorff
authors.forename: Stephan
authors.initials: S
authors.lastname: Kapral
authors.forename: Bernhard
authors.initials: B
authors.lastname: Moriggl
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D009407:Nerve Block / Q000379:methods*; D013131:Spine / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography; D021801:Zygapophyseal Joint / Q000000981:diagnostic imaging*