title: Flexion-rotation manoeuvre increases dimension of the acoustic target window for paramedian thoracic epidural access.
abstract: BACKGROUND
  The posterior longitudinal ligament (PLL) has been found to be a reliable measure of the acoustic target window for lumbar spinal anaesthesia and a predictive tool for difficult spinals. Currently, there is limited information on the PLL in the thoracic spine and its potential use for optimizing the acoustic target window during thoracic epidural placement. This study examined the effects of changes in body position on the length of the PLL as a measure of the acoustic target window for paramedian thoracic epidural access.
  
  
  METHODS
  We performed thoracic ultrasonography on 30 adult volunteers to measure the length of the PLL at the T9/10 interspace, in five different positions: P1, neutral; P2, thoracic and lumbar flexion; P3, as in position 2 with dorsal table tilt to 10°; P4, as in position 2 with 45° rightward shoulder rotation; and P5, as in position 2 with 45° leftward shoulder rotation.
  
  
  RESULTS
  The mean (sd) PLL length increased significantly from 9.9 (3.9) mm in P1 to 11.7 (3.4) mm in P2, 12.9 (3.1) mm in P3, and 13.8 (4.0) mm in P4 (P<0.01, <0.01, and <0.01, respectively). The mean PLL length in P3 and P4 was also significantly longer compared with P2 (P<0.01 and 0.01, respectively).
  
  
  CONCLUSIONS
  In volunteers, flexion with 10° dorsal table tilt and flexion with right rotation significantly increased the length of the ipsilateral PLL, compared with the standard flexed sitting position, as visualized by paramedian ultrasonography at the level of T9/10.
authors.affiliation: Department of Anesthesiology, Vancouver General Hospital, Vancouver Coastal Health, 855 West 12th Avenue, Vancouver, BC, Canada V5Z 1M9.
authors.forename: N
authors.initials: N
authors.lastname: Ramsay
authors.forename: J
authors.initials: J
authors.lastname: Walker
authors.forename: R
authors.initials: R
authors.lastname: Tang
authors.forename: H
authors.initials: H
authors.lastname: Vaghadia
authors.forename: A
authors.initials: A
authors.lastname: Sawka
mesh_terms: D000328:Adult; D004824:Epidural Space / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D017846:Longitudinal Ligaments / Q000000981:diagnostic imaging*; D008161:Lumbosacral Region; D008297:Male; D056888:Patient Positioning; D016059:Range of Motion, Articular; D012399:Rotation; D018401:Sample Size; D013909:Thorax / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014159:Transducers; D018084:Ultrasonography, Interventional / Q000379:methods*
keywords: anaesthetic techniques, epidural; monitoring, ultrasound