title: A zero-profile anchored spacer in multilevel cervical anterior interbody fusion: biomechanical comparison to established fixation techniques.
abstract: METHODS
  In vitro biomechanical analysis of different multilevel cervical fixation techniques.
  
  
  OBJECTIVE
  To compare the multilevel stability of a cervical anchored spacer (AS) with established fixation techniques.
  
  
  BACKGROUND
  To avoid plate-related complications, for example, dysphagia zero-profile AS has been developed. The use of these new zero-profile implants for treatment of cervical degenerative disc disease is widely accepted after encouraging biomechanical results for single-level instrumentation. However, there is only little knowledge about the biomechanical stability of these zero-profile devices in multilevel instrumentations.
  
  
  METHODS
  Eight fresh-frozen human cadaveric cervical spines (C3-C7) were nondestructively tested in a biomechanical 3-dimensional spine test setup. Segmental range of motion (ROM) under torsional load of 1.5 N·m was measured optoelectronically. Intact spine baseline measurement specimens were tested with 2- and 3-level instrumentation including (1) stand-alone PEEK-cage; (2) PEEK-cage plus locking plate; and (3) AS. Repeated-measures analyses of variance were used for statistical analysis.
  
  
  RESULTS
  Comparison of baseline ROM and stand-alone PEEK-cage instrumentation showed a significant lower segmental ROM only for 2-level instrumentations. Cage plus plate and AS were able to reduce segmental ROM significantly (P < 0.05) in 2- and 3-level instrumentations. Comparing cage plus plate and AS, a significant lower ROM was detected for flexion/extension in 2- and 3-level instrumentation and for lateral bending in 2-level instrumentation using cage plus plate.
  
  
  CONCLUSIONS
  Segmental stability decreases with the number of instrumented segments regardless of the used implant. Comparing the different fixation techniques biomechanically, the locking plate and cage construct was stiffer in all test modes than the anchored devices in multilevel constructs. However, it remains unclear what the clinical significance may be.
  
  
  METHODS
  N/A.
authors.affiliation: *Center for Spinal Surgery and Neurotraumatology, BG-Hospital Frankfurt/Main, Germany; and †Schön Clinic Harthausen, Bad Aibling, Germany.
authors.forename: Matti
authors.initials: M
authors.lastname: Scholz
authors.forename: Philipp
authors.initials: P
authors.lastname: Schleicher
authors.forename: Simone
authors.initials: S
authors.lastname: Pabst
authors.forename: Frank
authors.initials: F
authors.lastname: Kandziora
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000379:methods; D006801:Humans; D066298:In Vitro Techniques; D016268:Internal Fixators; D055959:Intervertebral Disc Degeneration / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods*; D014057:Tomography, X-Ray Computed