title: Analysis of pedicle and translaminar facet fixation in a multisegment interbody fusion model.
abstract: METHODS
  This is a biomechanical study. We compared pedicle screws and translaminar screws in the setting of multisegment interbody fusions.
  
  
  OBJECTIVE
  We investigated the significance of the middle segment pedicle screws in a 2-level interbody fusion model and examined translaminar screw fixation as an alternative to pedicle screw fixation in this 2-level model.
  
  
  BACKGROUND
  Surgical treatment of disc disease focuses on restoration of normal disc height and restriction of abnormal motion. Interbody fusion significantly reduces motion and restores disc space height. Combined anterior and posterior fusion improves fusion rates.
  
  
  METHODS
  Human cadavers were tested for range of motion (ROM) and stiffness. Each specimen underwent a 2-level interbody fusion and posterior fixation. There were 3 types of posterior fixation: pedicle screws at 3 levels, pedicle screws at 2 levels, and translaminar facet screws. Biomechanical testing was repeated for each group.
  
  
  RESULTS
  The overall ROM decreased after the interbody fusion (P < 0.05). There were no significant differences in construct stiffness for torsion, but there were significant differences when comparing intact to the 3 groups for both flexion and extension (P < 0.05). ROM at L2 and L4 was significantly less for all groups in comparison to the intact condition (P < 0.05).
  
  
  CONCLUSIONS
  This study supports the omission of the middle segment screws in a 2-level interbody fusion. In addition, translaminar screws are similar to pedicle fixation in a 2-level interbody lumbar fusion.
authors.affiliation: SUNY Syracuse Medical University, USA. eskanm01@ummhc.org
authors.forename: Mark
authors.initials: M
authors.lastname: Eskander
authors.forename: Dahari
authors.initials: D
authors.lastname: Brooks
authors.forename: Nat
authors.initials: N
authors.lastname: Ordway
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Dale
authors.forename: Patrick
authors.initials: P
authors.lastname: Connolly
mesh_terms: D000465:Algorithms; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D006801:Humans; D016268:Internal Fixators; D007403:Intervertebral Disc / Q000601:surgery*; D007796:Laminectomy; D017116:Low Back Pain / Q000601:surgery; D008159:Lumbar Vertebrae / Q000601:surgery*; D008954:Models, Biological; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods