title: Anatomic relations between the lumbar pedicle and the adjacent neural structures.
abstract: METHODS
  The authors analyzed anatomic parameters between the lumbar pedicles and the dural sac as well as the spinal nerve roots.
  
  
  OBJECTIVE
  To determine quantitatively the anatomic relations between the lumbar pedicle and adjacent dural sac and nerve roots.
  
  
  BACKGROUND
  Posterior transpedicular screw fixation is the most commonly used method of instrumentation for stabilization of the unstable lumbar spine. A thorough knowledge of the unique anatomy of the lumbar pedicle and adjacent neural structures may avoid or minimize neurologic complications with pedicular screw placement.
  
  
  METHODS
  Fifteen adult cadavers were obtained to evaluate quantitatively the anatomic relations of the lumbar pedicle to the adjacent neural structures. After removal of the laminas and facets, the lumbar pedicles, dural sac, and nerve roots were exposed. Direct measurements were taken from the pedicle to the dural sac medially, to the nerve roots superiorly and inferiorly, and between the pedicles. Also, the superoinferior diameter of the nerve root and the frontal angle of the nerve root were measured. Symmetric structures were measured bilaterally.
  
  
  RESULTS
  No consistent changes from L1 to L5 were found in all parameters. The mean distances from the lumbar pedicle to the dural sac medially and to the adjacent nerve roots superiorly and inferiorly for all levels were 1.5 mm, 5.3 mm, and 1.5 mm, respectively. The mean interpedicular distance ranged from 23.2 to 24.4 mm. The mean superoinferior diameter of the nerve root ranged from 3.8 to 4.6 mm. The mean nerve root angle ranged from 33.7 degrees to 39.2 degrees.
  
  
  CONCLUSIONS
  On the basis of this study, improper placement of the pedicle screw medially or caudally in the lumbar spine should be avoided.
authors.affiliation: Department of Orthopaedic Surgery, Medical College of Ohio, Toledo, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Ebraheim
authors.forename: R
authors.initials: R
authors.lastname: Xu
authors.forename: M
authors.initials: M
authors.lastname: Darwich
authors.forename: R A
authors.initials: RA
authors.lastname: Yeasting
mesh_terms: D000328:Adult; D000368:Aged; D001863:Bone Screws; D002102:Cadaver; D004388:Dura Mater / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000294:innervation* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D013126:Spinal Nerve Roots / Q000033:anatomy & histology*