title: Magnetic Resonance Neurography of the Lumbar Plexus at the L4-L5 Disc: Development of a Preoperative Surgical Planning Tool for Lateral Lumbar Transpsoas Interbody Fusion (LLIF).
abstract: METHODS
  Observational study.
  
  
  OBJECTIVE
  To demonstrate use of magnetic resonance (MR) neurography to visualize the course of the lumbar plexus at the L4-L5 disc space.
  
  
  BACKGROUND
  Risk of injury to the lumbar plexus during lateral transpsoas approach for lumbar interbody fusion (LLIF) is significant. We describe a new technique for preoperative mapping using magnetic resonance neurography to directly visualize the course of the plexus relative to the L4-L5 disc space.
  
  
  METHODS
  Consecutive lumbar plexus MR neurograms (n=35 patients, 70 sides) were studied. Scans were obtained on a Siemens 3-Tesla Skyra magnetic resonance imaging scanner. T1- and T2-color-coded fusion maps were generated along with 3-dimensional models of the lumbosacral plexus with attention to the L4-L5 interspace. The position of the plexus and the shape of the psoas muscle at the L4-L5 interspace were evaluated and recorded.
  
  
  RESULTS
  Direct imaging of the lumbar plexus using MR neurography revealed a substantial variability in the position of the lumbar plexus relative to the L4-L5 disc space. The left-side plexus was identified in zone 2 (5.7%), zone 3 (54.3%), and zone 4 (40%) (P = 0.0014); on the right, zone 2 (8.6%), zone 3 (42.9%) or zone 4 (45.7%), and zone 5 (2.9%) (P = 0.01). Right-left symmetry was found in 18 of 35 subjects (51.4%) (P = 0.865). There was no association between the position of the plexus and the shape of the overlying psoas muscle identified. In patients with an elevated psoas (n = 12), the lumbar plexus was identified in zone 3 in 75% and 66% (left and right) compared with patients without psoas elevation (n = 23), 30.4% and 43.5% (left and right).
  
  
  CONCLUSIONS
  The course of the lumbosacral plexus traversing the L4-L5 disc space may be more variable than has been suggested by previous studies. Magnetic resonance neurography may provide a more reliable means of preoperatively identifying the plexus when compared with current methods.
  
  
  METHODS
  3.
authors: *Department of Orthopedics, Spine and Scoliosis Surgery, Hospital for Special Surgery, New York, NY; and †Department of Neuroradiology, Weill Cornell Medical Center New York-Presbyterian Hospital, New York, NY.
authors: John C
authors: JC
authors: Quinn
authors: Kristen
authors: K
authors: Fruauff
authors: Darren R
authors: DR
authors: Lebl
authors: Ashley
authors: A
authors: Giambrone
authors: Frank P
authors: FP
authors: Cammisa
authors: Ajay
authors: A
authors: Gupta
authors: J Levi
authors: JL
authors: Chazen
mesh_terms: D059925:Anatomic Landmarks; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007403:Intervertebral Disc / Q000294:innervation* / Q000473:pathology / Q000601:surgery; D008159:Lumbar Vertebrae / Q000294:innervation* / Q000473:pathology / Q000601:surgery; D008160:Lumbosacral Plexus / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging; D015588:Observer Variation; D059348:Peripheral Nerve Injuries / Q000517:prevention & control; D011237:Predictive Value of Tests; D016658:Psoas Muscles / Q000033:anatomy & histology* / Q000601:surgery; D015203:Reproducibility of Results; D013123:Spinal Fusion / Q000009:adverse effects / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000009:adverse effects