title: Stereotactic navigation with the O-arm for placement of S-2 alar iliac screws in pelvic lumbar fixation.
abstract: OBJECTIVE
  Pelvic fixation is a crucial adjunct to many lumbar fusions to avoid L5-S1 pseudarthrosis. It is useful for treatment of kyphoscoliosis, high-grade spondylolisthesis, L5-S1 pseudarthrosis, sacral tumors, lumbosacral dislocations, and osteomyelitis. The most popular method, iliac fixation, has drawbacks including hardware prominence, extensive muscle dissection, and the need for connection devices. S-2 alar iliac fixation provides a useful primary or salvage alternative. The authors describe their techniques for using stereotactic navigation for screw placement.
  
  
  METHODS
  The O-arm Surgical Imaging System allowed for CT-quality multiplanar reconstructions of the pelvis, and registration to a StealthStation Treon provided intraoperative guidance. The authors describe their technique for performing computer-assisted S-2 alar iliac fixation for various indications in 18 patients during an 18-month period.
  
  
  RESULTS
  All patients underwent successful bilateral placement of screws 80-100 mm in length. All placements were confirmed with a second multiplanar reconstruction. One screw was moved because of apparent anterior breach of the ilium. There were no immediate neurological or vascular complications due to screw placement. The screw length required additional instruments including a longer pedicle finder and tap.
  
  
  CONCLUSIONS
  Stereotactic guidance to navigate the placement of distal pelvic fixation with bilateral S-2 alar iliac fixation can be safely performed in patients with a variety of pathological conditions. Crossing the sacroiliac joint, choosing trajectory, and ensuring adequate screw length can all be enhanced with 3D image guidance. Long-term outcome studies are underway, specifically evaluating the sacroiliac joint.
authors.affiliation: Department of Neurosurgery, Clinical Neurosciences Center, University of Utah, 175 North Medical Drive East, Salt Lake City, Utah 84132, USA.
authors.forename: Wilson Z
authors.initials: WZ
authors.lastname: Ray
authors.forename: Vijay M
authors.initials: VM
authors.lastname: Ravindra
authors.forename: Meic H
authors.initials: MH
authors.lastname: Schmidt
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Dailey
mesh_terms: D000328:Adult; D000368:Aged; D001863:Bone Screws / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D010388:Pelvis / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D013904:Thoracic Vertebrae / Q000601:surgery*; D014057:Tomography, X-Ray Computed