title: Femoral Neurogram Before Transpsoas Spinal Access at L4-5 Intervertebral Disk Space: A Proposed Screening Tool.
abstract: METHODS
  Observational study.
  
  
  OBJECTIVE
  To illustrate the variability of the course of the femoral nerve across the L4-5 disk space, and to present a novel application of transforaminal epidural steroid injections (TFESI) in the visualization of femoral nerve roots.
  
  
  BACKGROUND
  A concern regarding the lateral retroperitoneal transpsoas approach is the proximity of the lumbar plexus. Current techniques of assessing the proximity of neural tissue to the L4-5 disk space have limited capabilities.
  
  
  METHODS
  A total of 100 patients were selected for L4-5 TFESI (L4 selective nerve root blocks) because of lumbar radiculopathy. L4 neurograms were obtained while performing L4-5 TFESI under flouroscopic guidance, using a retroneural technique. The course of the L4 root/femoral nerve was then evaluated under fluoroscopy in the anteroposterior and lateral planes. Images were then reviewed by a radiologist, physiatrist, and 2 orthopedic spine surgeons.
  
  
  RESULTS
  Fluoroscopic evaluation revealed that the pattern of location of the femoral nerve was highly variable. In males, it was located 4.7% in zone 2, 32.5% in zone 3, 53.5% in zone 4, and 9.3% in zone P. In female patients, it was located 7.0% in zone 2, 14% in zone 3, 54.4% in zone 4, and 24.6% in zone P.
  
  
  CONCLUSIONS
  An L4 neurogram will provide an accurate trajectory of L4 root/femoral nerve as it crosses the L4-5 intervertebral disk space. An accurate assessment is essential to help minimize the increasing frequency of thigh pain, paresthesias, and weakness associated with the lateral access to the L4-5 intervertebral disk space. Femoral nerves that fall within zones 2 and 3 will require more manipulation during retraction and may be better suited with a different surgical approach.
authors.affiliation: *Cedars Sinai Medical Center, The Spine Institute, Los Angeles †Kaiser Permanente Orthopedic Surgery Department, Spine Services, Downey, CA.
authors.forename: Timothy T
authors.initials: TT
authors.lastname: Davis
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Day
authors.forename: Hyun W
authors.initials: HW
authors.lastname: Bae
authors.forename: Alexandre
authors.initials: A
authors.lastname: Rasouli
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D005267:Femoral Nerve / Q000033:anatomy & histology*; D006801:Humans; D007268:Injections, Epidural / Q000379:methods; D007403:Intervertebral Disc / Q000033:anatomy & histology*; D008159:Lumbar Vertebrae / Q000601:surgery; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000209:etiology; D010292:Paresthesia / Q000209:etiology; D011843:Radiculopathy / Q000000981:diagnostic imaging / Q000473:pathology; D011859:Radiography; D012727:Sex Characteristics; D013123:Spinal Fusion / Q000379:methods; D013126:Spinal Nerve Roots / Q000033:anatomy & histology; D013131:Spine / Q000033:anatomy & histology*; D013256:Steroids / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D003287:Contrast Media; D013256:Steroids