title: Projection of the lumbar pedicle and its morphometric analysis.
abstract: METHODS
  This study defined the projection point of the lumbar pedicle on its posterior aspect and its relation to a reliable landmark and reported pedicle dimensions based on 50 lumbar spines.
  
  
  OBJECTIVE
  To establish the best starting point for a pedicle screw for passing the screw down the center (axis) of the pedicle; to describe quantitatively the relations of the pedicle projection point to a reliable landmark; and to evaluate the linear and angular dimensions of the lumbar pedicle.
  
  
  BACKGROUND
  Posterior transpedicular screw fixation has been most widely used for management of the unstable lumbar spine. Several studies of pedicular anatomy exist, but little quantitative data regarding the location of the lumbar pedicle axis for each level have been reported.
  
  
  METHODS
  Fifty dry lumbar specimens (250 lumbar vertebrae) were obtained for study of the lumbar pedicle. Anatomic evaluation focused on determination of the projection point of the lumbar pedicle axis on the junction of the superior facet and the transverse process and measured the distance from the projection point to the midline of the transverse process for each level of the lumbar vertebrae. Pedicle dimensions, including linear and angular, also were measured.
  
  
  RESULTS
  Differences in dimensions between men and women were not found to be statistically significant. The average distance from the projection point to the midline of the transverse process consistently changed from L1 to L5. Above L4, the projection point for men and women averaged 3.9 mm for L1, 2.8 mm for L2, and 1.4 mm for L3 superior to the midline of the transverse process, respectively. At L4, the projection point was close to the midline of the transverse process (0.5 mm inferior). At L5, the projection point was an average of 1.5 mm inferior to the midline of the transverse process.
  
  
  CONCLUSIONS
  The average distance from the projection point of the lumbar pedicle axis to the midline of the transverse process consistently varied at different levels. This information may prove helpful in the placement of screws into the lumbar pedicle.
authors.affiliation: Department of Orthopaedic Surgery, Medical College of Ohio, Toledo, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Ebraheim
authors.forename: J R
authors.initials: JR
authors.lastname: Rollins
authors.forename: R
authors.initials: R
authors.lastname: Xu
authors.forename: R A
authors.initials: RA
authors.lastname: Yeasting
mesh_terms: D000328:Adult; D000368:Aged; D002102:Cadaver; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000033:anatomy & histology*; D008297:Male; D008488:Medical Illustration; D008875:Middle Aged; D012727:Sex Characteristics