title: Comparison of contemporary occipitocervical instrumentation techniques with and without C1 lateral mass screws.
abstract: OBJECTIVE
  This study was designed to test the kinematic properties of three occiput-C2 instrumentation constructs with and without supplemental rigid C1 fixation. The results are compared with intact specimens and with constructs incorporating contemporary cabling techniques.
  
  
  METHODS
  Five unembalmed human cadaver specimens underwent range of motion (ROM) testing in the intact condition, followed by destabilization with odontoid osteotomy. Destabilized specimens then underwent ROM testing with each of seven occipitocervical instrumentation constructs, all incorporating occipital screws: C1 and C2 sublaminar cables with cable connectors, C2 pars screws +/- C1 lateral mass screws, C2 lamina screws +/- C1 lateral mass screws, and C1-C2 transarticular screws +/- C1 lateral mass screws.
  
  
  RESULTS
  All seven constructs demonstrated significantly lower ROM in all loading modes than intact specimens (P < 0.05). With a single exception, the addition of C1 lateral mass screws to the screw-based constructs produced no significant change in ROM in any of the loading modes. Compared with intact specimens, constructs anchored by C1-C2 transarticular screws demonstrated the greatest decrease in ROM, and those anchored by sublaminar cables demonstrated the least decrease in ROM.
  
  
  CONCLUSIONS
  Any of the tested screw-based constructs are likely to provide adequate support for the patient with an unstable craniocervical junction. Therefore, the choice of construct should be based on anatomic considerations. The routine incorporation of C1 lateral mass screws into occipitocervical instrumentation constructs does not seem necessary.
authors: Department of Neurosurgery, The Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA. cwolfla@mcw.edu
authors: Christopher E
authors: CE
authors: Wolfla
authors: Simon A
authors: SA
authors: Salerno
authors: Narayan
authors: N
authors: Yoganandan
authors: Frank A
authors: FA
authors: Pintar
mesh_terms: D001268:Atlanto-Axial Joint / Q000503:physiopathology / Q000601:surgery*; D001269:Atlanto-Occipital Joint / Q000503:physiopathology / Q000601:surgery*; D001863:Bone Screws; D002102:Cadaver; D006801:Humans; D016268:Internal Fixators; D007593:Joint Instability / Q000503:physiopathology* / Q000601:surgery*; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods*; D013673:Technology Assessment, Biomedical