title: The trajectory of iliac screw in the axial plane in 200 korean patients.
abstract: METHODS
  A retrospective radiographic analysis.
  
  
  OBJECTIVE
  To estimate the accurate trajectory in the axial plane for iliac screw insertion in 200 Korean patients using radiographic images.
  
  
  BACKGROUND
  Several complications have been encountered after fusion to the lumbosacral junction, including pseudarthrosis, S1 screw loosening, and sacral fractures. Iliac screw fixation is considered an efficient method for augmenting sacral screw fixation but there are few reports on the trajectory of iliac screw insertion. The trajectory in the sagittal plane can be visualized by intraoperative fluoroscopy. However, there is no method to check the accuracy of the trajectory in the axial plane during surgery.
  
  
  METHODS
  Between January 2007 and February 2009, 200 patients (107 men and 93 women) who underwent L-spine computed tomography were enrolled in this study. The mean age of the patients was 55.6 +/- 18.3 years (range, 13 to 92 years). The spino-iliac angle (SIA) was measured on the axial image at the S1 level, which was defined as the angle between a vertical line through the center of the spinous process and an oblique line that passed through the center of the outer and inner cortices of the ilium.
  
  
  RESULTS
  The group mean SIA was 30.1 degrees +/- 7.8 degrees ; 30.1 degrees +/- 7.7 degrees for men and 29.9 degrees +/- 81.1 degrees for women. There was no significant difference according to gender or age (p > 0.05).
  
  
  CONCLUSIONS
  The SIA for the axial trajectory of iliac screws is approximately 30 degrees in Korean patients.
authors.affiliation: Department of Orthopaedic Surgery, Hangang Sacred Heart Hospital, Hallym University College of Medicine, Seoul, Korea.
authors.forename: Jae-Hyuk
authors.initials: JH
authors.lastname: Shin
authors.forename: Young-Woo
authors.initials: YW
authors.lastname: Kim
authors.forename: Yong-Kuk
authors.initials: YK
authors.lastname: Kim
authors.forename: In-Sung
authors.initials: IS
authors.lastname: Kim
authors.forename: Soo-Bum
authors.initials: SB
authors.lastname: Kim
authors.forename: Ho-Guen
authors.initials: HG
authors.lastname: Chang