title: New Posterior Atlantoaxial Restricted Non-Fusion Fixation for Atlantoaxial Instability: A Biomechanical Study.
abstract: BACKGROUND
  Loss of axial rotation and lateral bending after atlantoaxial fusion reduces a patient's quality of life. Therefore, effective, nonfusion fixation alternatives are needed for atlantoaxial instability.
  
  
  OBJECTIVE
  To evaluate the initial stability and function of posterior atlantoaxial restricted nonfusion fixation (PAARNF), a new protocol, using cadaveric cervical spines compared with the intact state, destabilization, and posterior C1-C2 rod fixation.
  
  
  METHODS
  Cervical areas C0 through C3 were used from 6 cadaveric spines to test flexion-extension, lateral bending, and axial rotation range of motion (ROM). With the use of a machine, 1.5-Nm torque at a rate of 0.1 Nm/s was used and held for 10 seconds. The specimens were loaded 3 times, and data were collected in the third cycle and tested in the following sequence: (1) intact, (2) destabilization (using a type II odontoid fracture model), (3) destabilization with PAARNF (PAARNF group), and (4) rod implantation (rod group). The order of tests for the PAARNF and rod groups was randomly assigned.
  
  
  RESULTS
  The average flexion-extension ROM in the PAARNF group was 7.44 ± 2.05°, which was significantly less than in the intact (P = .00) and destabilization (P = .00) groups but not significantly different from that of the rod group (P = .07). The average lateral bending ROM (10.59 ± 2.33°; P = .00) and axial rotation ROM (38.79 ± 13.41°; P = .00) of the PAARNF group were significantly greater than in the rod group. However, the values of the PAARNF group showed no significant differences compared with those of the intact group.
  
  
  CONCLUSIONS
  PAARNF restricted atlantoaxial flexion-extension but preserved axial rotation and lateral bending at the atlantoaxial joint in a type II odontoid fracture model. However, it should not be used clinically until further studies have been performed to test the long-term effects of this procedure.
authors.affiliation: ‡Department of Orthopedics, Fuzhou General Hospital, Nanjing Military Command, Fuzhou, P.R. China;§Department of Orthopedics, Changzheng Hospital, The Second Military Medical University, Shanghai, P.R. China;¶Department of Orthopedics, No. 451 Hospital of PLA, Xi'an, P.R. China.
authors.forename: Jinshui
authors.initials: J
authors.lastname: Chen
authors.forename: Fengjin
authors.initials: F
authors.lastname: Zhou
authors.forename: Bin
authors.initials: B
authors.lastname: Ni
authors.forename: Qunfeng
authors.initials: Q
authors.lastname: Guo
authors.forename: Huapeng
authors.initials: H
authors.lastname: Guan
authors.forename: Tianming
authors.initials: T
authors.lastname: Xu
authors.forename: Qi
authors.initials: Q
authors.lastname: Liu
mesh_terms: D000293:Adolescent; D000328:Adult; D001268:Atlanto-Axial Joint / Q000473:pathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D002102:Cadaver; D002574:Cervical Vertebrae / Q000473:pathology / Q000601:surgery; D002985:Clinical Protocols; D005260:Female; D005592:Fracture Fixation / Q000379:methods*; D006801:Humans; D016268:Internal Fixators; D007593:Joint Instability / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009809:Odontoid Process / Q000473:pathology / Q000601:surgery; D011788:Quality of Life; D016059:Range of Motion, Articular; D055815:Young Adult