title: Pedicle morphometry for thoracic screw fixation in ethnic koreans : radiological assessment using computed tomographic myelography.
abstract: OBJECTIVE
  In the thoracic spine, insertion of a pedicle screw is annoying due to small pedicle size and wide morphological variation between different levels of the spine and between individuals. The aim of our study was to analyze radiologic parameters of the pedicle morphometry from T1 to T8 using computed tomographic myelography (CTM) in Korean population.
  
  
  METHODS
  For evaluation of the thoracic pedicle morphometry, the authors prospectively analyzed a consecutive series of 26 patients with stable thoracic spines. With the consent of patients, thoracic CTM were performed, from T1 to T8. We calculated the transverse outer diameters and the transverse angles of the pedicle, distance from the cord to the inner cortical wall of the pedicle, and distance from the cord to the dura.
  
  
  RESULTS
  Transverse outer pedicle diameter was widest at T1 (7.66 +/- 2.14 mm) and narrowest at T4 (4.38 +/- 1.55 mm). Transverse pedicle angle was widest at T1 (30.2 +/- 12.0 degrees ) and it became less than 9.0 degrees below T6 level. Theoretical safety zone of the medial perforation of the pedicle screw, namely, distance from the cord to inner cortical wall of the pedicle was more than 4.5 mm.
  
  
  CONCLUSIONS
  Based on this study, we suggest that the current pedicle screw system is not always suitable for Korean patients. Computed tomography is required before performing a transpedicular screw fixation at the thoracic levels.
authors.affiliation: Department of Neurosurgery, Dankook University College of Medicine, Cheonan, Korea.
authors.forename: Yong Soo
authors.initials: YS
authors.lastname: Choi
authors.forename: Young Jin
authors.initials: YJ
authors.lastname: Kim
authors.forename: Hyeong-Joong
authors.initials: HJ
authors.lastname: Yi
authors.forename: Young-Joon
authors.initials: YJ
authors.lastname: Kim