title: Lumbar plexus block surface landmarks as assessed by computed axial tomography in adult patients with scoliosis: a case series.
abstract: OBJECTIVE
  Lumbar plexus (LP) block is a common and useful regional anesthesia technique. Surface landmarks used to identify the LP in patients with healthy spines have been previously described, with the distance from the spinous process (SP) to the skin overlying the LP being approximately two-thirds the distance from the SP to the posterior superior iliac spine (PSIS) (SP-LP:SP-PSIS ratio). In scoliotic patients, rotation of the central neuraxis may make these surface landmarks unreliable, possibly leading to an increased block failure rate and an increased incidence of complications. The objective of the present study was to describe these surface landmarks of the LP in patients with scoliosis.
  
  
  METHODS
  We selected 47 patients with known thoracolumbar scoliotic disease from our institution's radiology archives. We measured bony landmark geometry, Cobb angle, and the LP location and depth. Additionally, we calculated the SP-LP:SP-PSIS ratio for both the concave and convex sides.
  
  
  RESULTS
  In scoliotic patients (31 females and 16 males), the median (range) Cobb angle was 23 (8-54) degrees. The LP depth was 7.5 (5.7-10.7) cm on the concave side of the scoliotic spine and 7.6 (5.4-10.8) cm on the convex side, while the distance from the SP-LP was 3.4 (1.9-4.7) cm on the concave side and 3.7 (2.4-5.1) cm on the convex side. The SP-LP:SP-PSIS ratio was 0.61 (0.20-0.97) and 0.65 (0.45-0.98) on the concave and convex sides, respectively. None of these distances were significantly different between sides.
  
  
  CONCLUSIONS
  In patients with scoliotic disease of the spine, there is wide variability in the bony surface landmarks. The location of the LP is generally more medial than expected when compared with both modified and traditional landmarks. A review of the imaging studies and the pre-procedural ultrasound assessment of the anatomy should be considered prior to needle puncture.
authors.affiliation: Department of Anesthesiology, Mayo Clinic Florida, 4500 San Pablo Road, Jacksonville, FL, 32224, USA, robards.christopher@mayo.edu.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Robards
authors.forename: Kevin
authors.initials: K
authors.lastname: Riutort
authors.forename: Colleen S
authors.initials: CS
authors.lastname: Thomas
authors.forename: Steven B
authors.initials: SB
authors.lastname: Porter
authors.forename: R Doris
authors.initials: RD
authors.lastname: Wang
authors.forename: Steven R
authors.initials: SR
authors.lastname: Clendenen
authors.forename: Brandon R
authors.initials: BR
authors.lastname: Runyan
authors.forename: Roy A
authors.initials: RA
authors.lastname: Greengrass
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008160:Lumbosacral Plexus; D008297:Male; D009407:Nerve Block / Q000379:methods*; D012189:Retrospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000473:pathology*; D014057:Tomography, X-Ray Computed / Q000379:methods*