title: Feasible and accurate occipitoatlantal transarticular fixation: an anatomic study.
abstract: BACKGROUND
  Defining the anatomic zones for the placement of occiput-C1 transarticular screws is essential for patient safety.
  
  
  OBJECTIVE
  The feasibility and accuracy of occiput-C1 transarticular screw placement were evaluated in this anatomical study of normal cadaveric specimens.
  
  
  METHODS
  Sixteen measurements were determined for screw entry points, trajectories, and lengths for placement of transarticular screws, as applied in the technique described by Grob, on the craniovertebral junction segments (occiput-C2) of 16 fresh human cadaveric cervical spines and 41 computed tomographic reconstructions of the craniovertebral junction. Acceptable angles for screw positioning were measured on digital x-rays.
  
  
  RESULTS
  All 32 screws were placed accurately. As determined by dissection of the specimens, none of the screws penetrated the spinal canal. Screw insertion caused no fractures, and the integrity of the hypoglossal canal was maintained in all the disarticulated specimens.
  
  
  CONCLUSIONS
  Viable transarticular occiput-C1 screw placement is possible, despite variability of the anatomy of the occipital condyle.
authors.affiliation: Department of Neurosurgery, School of Medicine, Kahramanmaras Sutcu Imam University, Kahramanmaras, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Senoglu
authors.forename: Sam
authors.initials: S
authors.lastname: Safavi-Abbasi
authors.forename: Nicholas
authors.initials: N
authors.lastname: Theodore
authors.forename: Neil R
authors.initials: NR
authors.lastname: Crawford
authors.forename: Volker K H
authors.initials: VK
authors.lastname: Sonntag
mesh_terms: D000328:Adult; D000368:Aged; D001269:Atlanto-Occipital Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D001863:Bone Screws; D002102:Cadaver; D001270:Cervical Atlas / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D004210:Dissection / Q000379:methods; D005260:Female; D005539:Foramen Magnum / Q000033:anatomy & histology / Q000502:physiology / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D016268:Internal Fixators; D007431:Intraoperative Complications / Q000209:etiology / Q000517:prevention & control; D007593:Joint Instability / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D009777:Occipital Bone / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D011183:Postoperative Complications / Q000209:etiology / Q000517:prevention & control; D011300:Preoperative Care / Q000379:methods; D013122:Spinal Diseases / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed