Internal morphology of human cervical pedicles

Study Design, The internal architecture of cervical spine pedicles was inve stigated by thin sectioning and digitization of radiographic images. Objectives. To provide quantitative information on the internal dimensions and cortical shell thicknesses of the middle and lower cervical pedicles. Summary of Background Data. Although there have been a number of studies pr esenting data on the external dimensions of the cervical pedicle, little is known regarding its internal architecture and cortical shell thickness alo ng the pedicle axis. Methods. Twenty-five human cervical vertebrae (C3-C7) were secured to a thi n-sectioning machine to produce three 0.7-mm-thick pedicle slices along its axis. Plain radiographs of the pedicle slices were scanned and digitized t o 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 thickne sses of the superior, inferior, lateral, and medial walls and the cancellou s core height and width) of cervical pedicles. Results. Superior and inferior wall cortical thicknesses of pedicle thin sl ices were similar, whereas the lateral wall cortical thickness was signific antly smaller than the medial wall thickness, The medial cortical shell (av erage 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 medi al and lateral cortical thicknesses were normalized for external dimensions , the combined cortical shell thickness was thinnest at C7 (average value r ange: 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 o f the cervical pedicle at different spinal levels must be noted before tran spedicular screw fixation.