title: Multidirectional instabilities of experimental burst fractures of the atlas.
abstract: For the purpose of understanding the acute instability of a burst (Jefferson) fracture of the atlas, the authors produced the fractures experimentally and measured multidirectional flexibilities in seven cadaveric C0-C3 specimens. The flexibilities were measured by the authors' standardized method: they applied six types of physiologically pure moments (up to 1.5 Nm) and recorded the ensuing C0-C2 motions by stereophotogrammetry. The flexibility tests were performed before and after the production of the fracture. The greatest increase in flexibility due to the injury was in flexion-extension (+22.0 degrees, 41.7%). In lateral bending, the increase was 7.7 degrees, or 23.9%. The flexibility was mostly maintained in axial rotation (+4.8 degrees, 5.4%). The increase in motion was due to an increase in neutral zone in flexion-extension, and an increase in the elastic zone in lateral bending. These flexibility results of experimentally produced fractures reflect quite well the acute instabilities seen clinically.
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Medical School, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Oda
authors.forename: M M
authors.initials: MM
authors.lastname: Panjabi
authors.forename: J J
authors.initials: JJ
authors.lastname: Crisco
authors.forename: T R
authors.initials: TR
authors.lastname: Oxland
mesh_terms: D001270:Cervical Atlas / Q000000981:diagnostic imaging / Q000293:injuries* / Q000503:physiopathology; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008875:Middle Aged; D011859:Radiography; D016059:Range of Motion, Articular; D016103:Spinal Fractures / Q000000981:diagnostic imaging / Q000503:physiopathology*