title: An anatomic study of the S2 iliac technique for lumbopelvic screw placement.
abstract: METHODS
  An anatomic study conducted on cadaveric specimens.
  
  
  OBJECTIVE
  The objectives of the study were (1) to determine course of S2 lumbopelvic screws with reference to the articular cartilage of the sacroiliac joint, (2) to determine the length and trajectory of screws placed using anatomic placement techniques, and (3) to determine vital structures at risk using this technique.
  
  
  BACKGROUND
  Multiple techniques exist for fixation distal to S1 including alar screws, iliac post bolts, and transiliac rods. Distal fixation is crucial in adult deformity surgery when fusion to the sacrum is indicated.
  
  
  METHODS
  Five female and 5 male cadaveric specimens were instrumented with S1 promontory screws and S2 iliac lumbopelvic screws. The specimens then underwent computed tomography scanning to determine structures at risk, cortical violations, and characteristics of screws placed. The sacroiliac joints were opened to examine articular cartilage penetration.
  
  
  RESULTS
  Articular violation occurred in 60% of screws placed. Average length was 84 mm. No vital structures were at risk from screw placement. No intrapelvic cortical violations occurred.
  
  
  CONCLUSIONS
  S2 iliac technique is a potential option for distal fixation in spine surgery. Biomechanical and clinical data are required to fully evaluate the potential of this technique.
authors.affiliation: Department of Orthopaedic Surgery, George Washington University, Washington, DC 20037, USA. jobrien@mfa.gwu.edu
authors.forename: Joseph R
authors.initials: JR
authors.lastname: O'Brien
authors.forename: Warren D
authors.initials: WD
authors.lastname: Yu
authors.forename: Rishi
authors.initials: R
authors.lastname: Bhatnagar
authors.forename: Paul
authors.initials: P
authors.lastname: Sponseller
authors.forename: Khaled M
authors.initials: KM
authors.lastname: Kebaish
mesh_terms: D001863:Bone Screws / Q000009:adverse effects / Q000592:standards*; D002102:Cadaver; D002358:Cartilage, Articular / Q000033:anatomy & histology / Q000601:surgery; D005260:Female; D005471:Fluoroscopy / Q000379:methods; D006801:Humans; D007085:Ilium / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D016268:Internal Fixators / Q000009:adverse effects / Q000592:standards; D007431:Intraoperative Complications / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D016343:Monitoring, Intraoperative / Q000379:methods; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D011542:Pseudarthrosis / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D012446:Sacroiliac Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D012447:Sacrum / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D013121:Spinal Curvatures / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D014057:Tomography, X-Ray Computed