title: Biomechanical analysis of a disc prosthesis distal to a scoliosis model.
abstract: METHODS
  Biomechanical study of bovine spines.
  
  
  OBJECTIVE
  The purpose of this study was to perform a biomechanical test to analyze intervertebral deflections following placement of both 1 and 2 semiconstrained TDRs in the subjacent segments of a long fusion.
  
  
  BACKGROUND
  Long-term sequela of long lumbar fusion for scoliosis include adjacent segment disease and flatback syndrome. Total disc replacement (TDR) is a viable option for the treatment of these conditions. Little data has been published regarding the placement of a TDR distal to a scoliosis fusion.
  
  
  METHODS
  Six thoracolumbar bovine spines (T12-S1) were instrumented from T12 to L5, with bilateral pedicle screw fixation at each level. L5-L6 and L6-S1 served as the test levels. One TDR (FlexiCore, Stryker Spine, Allendale, NJ) was initially performed adjacent to the fusion, followed by a subsequent TDR insertion at the last spinal segment. The applied load, total specimen deflection, and local transducer deflections were recorded before and after a TDR at both levels. The results were expressed as a percentage of the intact specimen. Flexion, extension, lateral bending, and torsional deflections were recorded.
  
  
  RESULTS
  There were no significant differences (P > 0.05) in sensor deflection observed at the L5-L6 and L6-S1 levels in the anterior and lateral transducers when compared to intact spines specimens. A similar effect was observed at the L5-L6 and L6-S1 levels in the anterior and lateral transducers when compared to intact or prior L5-L6 and intact L6-S1 constructs.
  
  
  CONCLUSIONS
  This study has shown that using the FlexiCore system at 1 and/or 2 intervertebral disc spaces caudal to a scoliosis fusion model did not significantly change the sensor deflection at the 2 segments adjacent to a scoliosis fusion construct. Future research will continue to define the clinical setting and patients best suited for management by TDR systems.
authors.affiliation: NYU Hospital for Joint Diseases, New York, NY 10016, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Quirno
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Kamerlink
authors.forename: Antonio
authors.initials: A
authors.lastname: Valdevit
authors.forename: Matthew
authors.initials: M
authors.lastname: Kang
authors.forename: Burt
authors.initials: B
authors.lastname: Yaszay
authors.forename: Naphysah
authors.initials: N
authors.lastname: Duncan
authors.forename: Oheneba
authors.initials: O
authors.lastname: Boachie-Adjei
authors.forename: Baron S
authors.initials: BS
authors.lastname: Lonner
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Errico
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D004195:Disease Models, Animal; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery; D019919:Prosthesis Implantation; D012600:Scoliosis / Q000503:physiopathology / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D013904:Thoracic Vertebrae / Q000601:surgery