title: Internal morphology of human cervical pedicles.
abstract: METHODS
  The internal architecture of cervical spine pedicles was investigated by thin sectioning and digitization of radiographic images.
  
  
  OBJECTIVE
  To provide quantitative information on the internal dimensions and cortical shell thicknesses of the middle and lower cervical pedicles.
  
  
  BACKGROUND
  Although there have been a number of studies presenting data on the external dimensions of the cervical pedicle, little is known regarding its internal architecture and cortical shell thickness along the pedicle axis.
  
  
  METHODS
  Twenty-five human cervical vertebrae (C3-C7) were secured to a thin-sectioning machine to produce three 0.7-mm-thick pedicle slices along its axis. Plain radiographs of the pedicle slices were scanned and digitized to facilitate measurement of the internal dimensions. Computer software was specifically developed to determine the external dimensions (i.e., pedicle height and width) and the internal dimensions (i.e., cortical shell thicknesses of the superior, inferior, lateral, and medial walls and the cancellous core height and width) of cervical pedicles.
  
  
  RESULTS
  Superior and inferior wall cortical thicknesses of pedicle thin slices were similar, whereas the lateral wall cortical thickness was significantly smaller than the medial wall thickness. The medial cortical shell (average value range: 1.2-2.0 mm) was measured to be 1.4 to 3.6 times as thick as the lateral cortical shell (average value range: 0.4-1.1 mm). When medial and lateral cortical thicknesses were normalized for external dimensions, the combined cortical shell thickness was thinnest at C7 (average value range: 18. 6-25.6% of the external width), and this result was statistically significant when compared with other vertebral levels.
  
  
  CONCLUSIONS
  The cervical pedicle is a complex, three-dimensional structure exhibiting extensive variability in internal morphology. Characteristics of the cervical pedicle at different spinal levels must be noted before transpedicular screw fixation.
authors.affiliation: Biomechanics Research Laboratory, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, CT 06520-8071, USA. manohar.panjabi@yale.edu
authors.forename: M M
authors.initials: MM
authors.lastname: Panjabi
authors.forename: E K
authors.initials: EK
authors.lastname: Shin
authors.forename: N C
authors.initials: NC
authors.lastname: Chen
authors.forename: J L
authors.initials: JL
authors.lastname: Wang
mesh_terms: D001863:Bone Screws; D002574:Cervical Vertebrae / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D007593:Joint Instability / Q000601:surgery; D008867:Microtomy; D011859:Radiography; D012015:Reference Standards; D013123:Spinal Fusion