title: [Biomechanical study of atlantoaxial fixation for transverse ligament injury leading to atlantoaxial instability].
abstract: OBJECTIVE
  To explore the three-dimensional movement of atlantoaxial joint, complete transverse ligament and cracked transverse ligament after posterior atlantoaxial fixation.
  
  
  METHODS
  The fresh upper cervical cadaveric specimens were collected from 6 males dead from active craniocerebral injury. The average age was 39.7 years old (range: 26 - 57). The specimens were divided into 3 groups of intact (Group I), transverse ligament cracked (Group D) and posterior atlantoaxial fixation (Group F). They were tested consecutively.
  
  
  RESULTS
  The range of sagittal movement increased when the transverse ligament became cracked. And it had significant difference compared with the Group I (P < 0.05). But the ranges of lateral flexion and rotation showed no significant difference. When posterior atlantoaxial fixation was performed, all three-dimensional movements decreased. And significant differences existed as compared with Group I (P < 0.05).
  
  
  CONCLUSIONS
  Under normal conditions, the main movement of atlantoaxial joint is rotation with lesser sagittal movement and lest lateral flexion. The range of sagittal movement increases significantly when transverse ligament is cracked (P < 0.05), especially so for anteflexion movement. The increase of lateral flexion and rotation has no significant difference compared with Group I. When posterior atlantoaxial Fixation is performed, all three-dimensional movements decrease significantly as compared with Group I (P < 0.05), especially loss of rotation function.
authors.affiliation: Department of Orthopedic Surgery, First Affiliated Hospital, Shanghai Jiaotong University, Shanghai 200080, China. tjw609@163.com
authors.forename: Ji-wei
authors.initials: JW
authors.lastname: Tian
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wang
authors.forename: Qing-hua
authors.initials: QH
authors.lastname: Zhao
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Shuang-hai
authors.initials: SH
authors.lastname: Dong
authors.forename: Tian
authors.initials: T
authors.lastname: Xia
authors.forename: Cheng-yi
authors.initials: CY
authors.lastname: Liu
mesh_terms: D000328:Adult; D001268:Atlanto-Axial Joint / Q000503:physiopathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000601:surgery*; D008022:Ligaments / Q000293:injuries; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular