title: Biomechanical stability of a posterior-alone fixation technique after craniovertebral junction realignment.
abstract: OBJECTIVE
  The aim of the current study was to investigate the biomechanical stability and fixation strength provided by a posterior approach reconstruction technique to realign the craniovertebral junction.
  
  
  METHODS
  We tested seven human cadaver occipito-cervical spines (occiput-C4) by applying pure moments of ± 1.5 Nm on a spine tester. Each specimen was tested in the following modes: 1) intact; 2) injured; 3) spacers alone at C1-C2 articulation (S); 4) spacers plus C1-C2 Posterior Instrumentation (S+PI); and 5) spacers plus C1-C2 posterior instrumentation plus midline wiring (S+PI+MLW). C1-C2 range of motion for each construct was obtained in flexion-extension, lateral bending, and axial rotation.
  
  
  RESULTS
  In all the loading modes, S, S+PI, and S+PI+MLW constructs significantly reduced range of motion compared with the intact and injured condition (P < 0.05). There was no statistical difference between any of the three instrumentation constructs (P > 0.05).
  
  
  CONCLUSIONS
  This study investigated the biomechanics of the posterior approach technique for realignment of the craniovertebral junction and also made comparisons with additional posterior fixations. The stand-alone spacers were stable in all three loading modes. Posterior instrumentation increased the stability as compared to stand-alone spacers. The third point of fixation, carried out by using midline wiring, increased the stability further. However, there was not much difference in the stability imparted with the midline wiring versus without. The present study highlights the biomechanics of this novel concept and reaffirms the view that distraction of the C1-C2 articular facets and direct articular joint atlantoaxial fixation would be an ideal method of management of basilar invagination.
authors: Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
authors: Roy Thomas
authors: RT
authors: Daniel
authors: Aditya
authors: A
authors: Muzumdar
authors: Aditya
authors: A
authors: Ingalhalikar
authors: Mark
authors: M
authors: Moldavsky
authors: Saif
authors: S
authors: Khalil
mesh_terms: D001268:Atlanto-Axial Joint / Q000473:pathology / Q000601:surgery*; D001269:Atlanto-Occipital Joint / Q000473:pathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D005592:Fracture Fixation / Q000379:methods*; D006801:Humans; D016268:Internal Fixators; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods*; D016059:Range of Motion, Articular; D014057:Tomography, X-Ray Computed