title: [Influence of the included angle between anterior aspects of S2 and S1 vertebral bodies on pelvic inlet imaging in mid-line sagittal plane].
abstract: OBJECTIVE
  To analyze the influence of included angle between the anterior aspects of S2 and S vertebral bodies on pelvic inlet imaging in the pelvic midline sagittal plane.
  
  
  METHODS
  Totally 58 axial pelvic CT scans were chosen as study objects including 43 males and 15 females,with an average age of 40.7 years old (ranged,18 to 68 years old). The angles between the anterior aspects of S2 and S1, vertebral bodies and the horizontal plane on midline sagittal CT reconstruction were measured to simulate the optimal S2 and S1 inlet angles. The included angle between the anterior aspects of S2 and S1 vertebral bodies was calculated by subtrocting the S1,inlet angle from the S2 inlet angle defined as a base number. Then, the impact of the calculated included angles on the pelvic inlet imaging was analyzed. Results:The S2 inlet angles averaged (30.5±6.5) degrees; the S inlet angles averaged (25.7±5.9) degrees. The difference between them was significant (t=3.35, P=0.001). Ten patients had zero angle between the anterior aspects of S2 and S1 vertebral bodies; 14 patients had negative angle, averaged-(8.9±8.1) degrees; 34 patients had positive angle,averaged (11.8+6.4) degrees.
  
  
  CONCLUSIONS
  The difference of included angle between the anterior aspects of S2 and S1 vertebral bodies leads to the difference between S1 inlet view and S2 inlet view in most cases, complicating the pelvic inlet imaging,and affecting the reliability of the application of pelvic inlet view. Utilizing the angles measured on the preoperative midlihe sagittal CT reconstruction to obatin the patient-customized S1 and S2 inlet views could accurately guide the S1 and S2 iliosacral screw insertion.
authors.forename: Hong-ming
authors.initials: HM
authors.lastname: Cai
authors.forename: Shu-tu
authors.initials: ST
authors.lastname: Gao
authors.forename: Chuan-de
authors.initials: CD
authors.lastname: Cheng
authors.forename: Xue-jian
authors.initials: XJ
authors.lastname: Wu
authors.forename: Wu-chao
authors.initials: WC
authors.lastname: Wang
authors.forename: Jin-cheng
authors.initials: JC
authors.lastname: Tang
authors.forename: Shou-ya
authors.initials: SY
authors.lastname: Chang
authors.forename: Wei-feng
authors.initials: WF
authors.lastname: Duan
authors.forename: Chuan
authors.initials: C
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001863:Bone Screws; D005260:Female; D005593:Fracture Fixation, Internal / Q000379:methods; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D010388:Pelvis / Q000033:anatomy & histology* / Q000293:injuries; D013131:Spine / Q000033:anatomy & histology*; D014057:Tomography, X-Ray Computed; D055815:Young Adult