title: Biomechanical evaluation of a low-profile, anchored cervical interbody spacer device at the index level or adjacent to plated fusion.
abstract: METHODS
  In vitro biomechanical study.
  
  
  OBJECTIVE
  To test the hypotheses: (1) an anchored spacer device would decrease motion similarly to a plate-spacer construct, and (2) the anchored spacer would achieve a similar reduction in motion when placed adjacent to a previously fused segment.
  
  
  BACKGROUND
  An anchored spacer device has been shown to perform similar to the plate-spacer construct in previous biomechanical evaluation. The prevalence of adjacent segment disease after fusion is well established in the literature.There is currently no evidence supporting the use of an anchored interbody spacer device adjacent to a previous fusion.
  
  
  METHODS
  Eight human cervical spines (age: 45.1 ± 13.1 yr) were tested in moment control (±1.5 Nm) in flexion-extension, lateral bending, and axial rotation without preload. Flexion-extension was then retested under 150-N preload. Spines were tested intact and after anterior cervical discectomy and fusion (ACDF) at C4-C5 and C6-C7 with either a plate-spacer or anchored spacer construct (randomized). The specimens were tested finally with an ACDF at the floating C5-C6 segment using the anchored spacer device adjacent to the previous fusions.
  
  
  RESULTS
  Both the plate-spacer and anchored spacer significantly reduced motion from the intact spine in flexion-extension, lateral bending, and axial rotation (P < 0.005). There was no statistically significant difference between the 2 fusion constructs in their abilities to reduce motions (P = 1.0). ACDF using the anchored spacer at the floating C5-C6 level (in between the plate-spacer and anchored spacer constructs) resulted in significant motion reductions in all modes of testing (P < 0.05). These motion reductions did not significantly differ from those of a single-level anchored-spacer construct or a single-level plated ACDF.
  
  
  CONCLUSIONS
  The anchored spacer provided significant motion reductions, similar to a plated ACDF, when used as a single-level fusion construct or placed adjacent to a previously plated segment.
  
  
  METHODS
  N/A.
authors.affiliation: *Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, Maywood, IL †Musculoskeletal Biomechanics Laboratory, Department of Veterans Affairs, Edward Hines Jr. VA Hospital, Hines, IL; and ‡Synthes Spine, West Chester, PA.
authors.forename: Ajay K
authors.initials: AK
authors.lastname: Balaram
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Ghanayem
authors.forename: Patrick T
authors.initials: PT
authors.lastname: OʼLeary
authors.forename: Leonard I
authors.initials: LI
authors.lastname: Voronov
authors.forename: Robert M
authors.initials: RM
authors.lastname: Havey
authors.forename: Gerard
authors.initials: G
authors.lastname: Carandang
authors.forename: Celeste
authors.initials: C
authors.lastname: Abjornson
authors.forename: Avinash G
authors.initials: AG
authors.lastname: Patwardhan
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D002102:Cadaver; D002574:Cervical Vertebrae / Q000502:physiology* / Q000601:surgery; D017586:Diskectomy / Q000379:methods*; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000502:physiology* / Q000601:surgery; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology; D013123:Spinal Fusion / Q000379:methods*; D013904:Thoracic Vertebrae / Q000502:physiology / Q000601:surgery; D059145:Total Disc Replacement / Q000379:methods*; D016474:Weight-Bearing / Q000502:physiology