title: Utility of the analysis of intracranial venous sinuses using preoperative computed tomography venography for safe occipital screw insertion.
abstract: METHODS
  Prospective descriptive study.
  
  
  OBJECTIVE
  To verify the feasibility and utility of evaluating venous sinuses (VSs) using computed tomography venography (CTV) concomitant with preoperative CT angiography (CTA) for safe occipital screw fixation.
  
  
  BACKGROUND
  Preoperative evaluation of the vertebral artery by CTA is indispensable in occipitocervical spinal instrumentation surgery. Despite accumulating evidence showing the potential of CTV, no studies have reported the usefulness of concomitant use of CTV and CTA before placement of occipital plate-screw constructs.
  
  
  METHODS
  We analyzed 30 consecutive patients who underwent CTV simultaneously with CTA. First, we investigated VS anatomy in individual cases and classified the continuity patterns of relevant VSs. Subsequently, we evaluated the probable risk zones for VS injury, from the viewpoint of occipital screw insertion.
  
  
  RESULTS
  VSs can be clearly visualized using CTV simultaneously with CTA examination without significant increase of radiation exposure or extra workload for radiographical technicians. VS continuity was classified into 4 categories: the confluence type (n = 9), bifurcation type (n = 8), transverse type (n = 11), and others (n = 2). The confluence of sinuses and their relevant VSs were greatly variable between individuals, and occasionally, some cases with high-risk morphology for VS injury in occipital screw placement were observed.
  
  
  CONCLUSIONS
  Our findings indicate that there is no universal position for safe insertion of occipital screws that is applicable to all individuals. It is risky to determine optimal screw placement, only on the basis of traditional cadaveric information such as occipital bone thickness and several external bony landmarks. Spine surgeons must recognize that VS injury may occasionally lead to life-threatening complications. The detailed information on VSs obtained by preoperative CTV examination combined with CTA in individual cases can be useful in preoperative planning and can contribute greatly to the improvement of surgical safety.
  
  
  METHODS
  2.
authors.affiliation: Department of Orthopaedic Surgery, Kyoto University, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Izeki
authors.forename: Masashi
authors.initials: M
authors.lastname: Neo
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Fujibayashi
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Takemoto
authors.forename: Bungo
authors.initials: B
authors.lastname: Otsuki
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Watanabe
authors.forename: Koji
authors.initials: K
authors.lastname: Koizumi
authors.forename: Akira
authors.initials: A
authors.lastname: Matsuda
authors.forename: Koutatsu
authors.initials: K
authors.lastname: Nagai
authors.forename: Shuichi
authors.initials: S
authors.lastname: Matsuda
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001863:Bone Screws / Q000009:adverse effects*; D003392:Cranial Sinuses / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000000981:diagnostic imaging* / Q000601:surgery*; D010690:Phlebography / Q000706:statistics & numerical data; D011300:Preoperative Care / Q000379:methods*; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*; D055815:Young Adult