title: Craniovertebral junction fixation with transarticular screws: biomechanical analysis of a novel technique.
abstract: OBJECTIVE
  The authors compared the biomechanical stability resulting from the use of a new technique for occipitoatlantal motion segment fixation with an established method and assessed the additional stability provided by combining the two techniques.
  
  
  METHODS
  Specimens were loaded using nonconstraining pure moments while recording the three-dimensional angular movement at occiput (Oc)-C1 and C1-2. Specimens were tested intact and after destabilization and fixation as follows: 1) Oc-C1 transarticular screws plus C1-2 transarticular screws; 2) occipitocervical transarticular (OCTA) plate in which C1-2 transarticular screws attach to a loop from Oc to C-2; and (3) OCTA plate plus Oc-C1 transarticular screws. Occipitoatlantal transarticular screws reduced motion to well within the normal range. The OCTA loop and transarticular screws allowed a very small neutral zone, elastic zone, and range of motion during lateral bending and axial rotation. The transarticular screws, however, were less effective than the OCTA loop in resisting flexion and extension.
  
  
  CONCLUSIONS
  Biomechanically, Oc-C1 transarticular screws performed well enough to be considered as an alternative for Oc-C1 fixation, especially when instability at C1-2 is minimal. Techniques for augmenting these screws posteriorly by using a wired bone graft buttress, as is currently undertaken with C1-2 transarticular screws, may be needed for optimal performance.
authors.forename: L Fernando
authors.initials: LF
authors.lastname: Gonzalez
authors.forename: Neil R
authors.initials: NR
authors.lastname: Crawford
authors.forename: Robert H
authors.initials: RH
authors.lastname: Chamberlain
authors.forename: Luis E
authors.initials: LE
authors.lastname: Perez Garza
authors.forename: Mark C
authors.initials: MC
authors.lastname: Preul
authors.forename: Volker K H
authors.initials: VK
authors.lastname: Sonntag
authors.forename: Curtis A
authors.initials: CA
authors.lastname: Dickman
mesh_terms: D000328:Adult; D001269:Atlanto-Occipital Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D004867:Equipment Design; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009984:Orthopedic Fixation Devices; D013718:Tensile Strength; D014057:Tomography, X-Ray Computed