title: A biomechanical study of artificial cervical discs using computer simulation.
abstract: METHODS
  A virtual simulation model of the subaxial cervical spine was used to study the biomechanical effects of various disc prosthesis designs.
  
  
  OBJECTIVE
  To study the biomechanics of different design features of cervical disc arthroplasty devices.
  
  
  BACKGROUND
  Disc arthroplasty is an alternative approach to cervical fusion surgery for restoring and maintaining motion at a diseased spinal segment. Different types of cervical disc arthroplasty devices exist and vary based on their placement and degrees of motion offered.
  
  
  METHODS
  A virtual dynamic model of the subaxial cervical spine was used to study 3 different prosthetic disc designs (PDD): (1) PDD-I: The center of rotation of a spherical joint located at the mid C5-C6 disc, (2) PDD-II: The center of rotation of a spherical joint located 6.5 mm below the mid C5-C6 disc, and (3) PDD-III: The center of rotation of a spherical joint in a plane located at the C5-C6 disc level.
  
  
  RESULTS
  A constrained spherical joint placed at the disc level (PDD-I) significantly increased facet loads during extension. Lowering the rotational axis of the spherical joint towards the subjacent body (PDD-II) caused a marginal increase in facet loading during flexion, extension, and lateral bending. Lastly, unconstraining the spherical joint to move freely in a plane (PDD-III) minimized facet load build up during all loading modes.
  
  
  CONCLUSIONS
  The simulation model showed the impact simple design changes may have on cervical disc dynamics. The predicted facet loads calculated from computer model have to be validated in the experimental study.
authors.affiliation: Department of Orthopedic Surgery, Good Morning Hospital, Ulsan, South Korea.
authors.forename: Hyung Soo
authors.initials: HS
authors.lastname: Ahn
authors.forename: Denis J
authors.initials: DJ
authors.lastname: DiAngelo
mesh_terms: D019643:Arthroplasty, Replacement / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D001705:Bioprosthesis; D002574:Cervical Vertebrae / Q000503:physiopathology / Q000601:surgery*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000503:physiopathology / Q000601:surgery*; D008875:Middle Aged; D011474:Prosthesis Design; D012399:Rotation; D021801:Zygapophyseal Joint / Q000503:physiopathology / Q000601:surgery