title: Biomechanical study of the atlantoaxial joint after artificial atlanto-odontoid joint arthroplasty.
abstract: OBJECTIVE
  To investigate the stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint (AAOJ) arthroplasty by comparing with a conventional method.
  
  
  METHODS
  After anterior decompression, 24 human cadaveric spinal specimens of C0-C3 were randomly divided into two groups: Group A receiving artificial AAOJ arthroplasty; Group B experiencing anterior transarticular screw (ATAS) fixation. Two groups underwent flexibility test in intact and instrumented states. Rotational angle of the C0-C3 segments was measured to study the immediate stability and function of anterior decompression with AAOJ arthroplasty compared with the intact state and ATAS fixation.
  
  
  RESULTS
  Compared with the intact state, anterior decompression with AAOJ arthroplasty resulted in a significant decrease in the range of motion (ROM) and neutral zone (NZ) during flexion, extension and lateral bending (P less than 0.05); however, with regard to axial rotation, there was no significant difference in ROM and NZ (P larger than 0.05). Compared with anterior decompression with ATAS fixation, anterior decompression with AAOJ arthroplasty during flexion, extension and lateral bending, significant difference was found in ROM and NZ (P larger than 0.05); however, as for axial rotation, there was a significant increase in ROM and NZ (P less than 0.05).
  
  
  CONCLUSIONS
  The self-designed AAOJ has an excellent biomechanical performance, which can restore excellent instant stability and preserve the movement of the atlantoaxial joint.
authors.affiliation: Department of Spinal Surgery, Ningbo Sixth Hospital, Ningbo 315040, Zhejiang Province, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Hu
authors.forename: Yong-jie
authors.initials: YJ
authors.lastname: Gu
authors.forename: Zhen-shan
authors.initials: ZS
authors.lastname: Yuan
authors.forename: Xian-feng
authors.initials: XF
authors.lastname: He
authors.forename: Wei-xin
authors.initials: WX
authors.lastname: Dong
authors.forename: Wei-dong
authors.initials: WD
authors.lastname: Zhao
mesh_terms: D000328:Adult; D001178:Arthroplasty / Q000379:methods*; D001268:Atlanto-Axial Joint / Q000503:physiopathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D019299:Decompression, Surgical; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology