title: Cervical spine injuries and flexibilities following axial impact with lateral eccentricity.
abstract: OBJECTIVE
  Determine the effects of dynamic injurious axial compression applied at various lateral eccentricities (lateral distance to the centre of the spine) on mechanical flexibilities and structural injury patterns of the cervical spine.
  
  
  METHODS
  13 three-vertebra human cadaver cervical spine specimens (6 C3-5, 3 C4-6, 2 C5-7, 2 C6-T1) were subjected to pure moment flexibility tests (±1.5 Nm) before and after impact trauma was applied in two groups: low and high lateral eccentricity (1 and 150 % of the lateral diameter of the vertebral body, respectively). Relative range of motion (ROM) and relative neutral zone (NZ) were calculated as the ratio of post and pre-trauma values. Injuries were diagnosed by a spine surgeon and scored. Classification functions were developed using discriminant analysis.
  
  
  RESULTS
  Low and high eccentric loading resulted in primarily bony fractures and soft tissue injuries, respectively. Axial impacts with high lateral eccentricities resulted in greater spinal motion in lateral bending [median relative ROM 3.5 (interquartile range, IQR 2.3) vs. 1.4 (IQR 0.5) and median relative NZ 4.7 (IQR 3.7) vs. 2.3 (IQR 1.1)] and in axial rotation [median relative ROM 5.3 (IQR 13.7) vs. 1.3 (IQR 0.5), p < 0.05 for all comparisons] than those that resulted from low eccentricity impacts. The developed classification functions had 92 % classification accuracy.
  
  
  CONCLUSIONS
  Dynamic axial compression loading of the cervical spine with high lateral eccentricities produced primarily soft tissue injuries resulting in more post-injury spinal flexibility in lateral bending and axial rotation than that associated with the bony fractures resulting from low eccentricity impacts.
authors.affiliation: Orthopaedic and Injury Biomechanics Group, Departments of Mechanical Engineering and Orthopaedics, University of British Columbia, 6250 Applied Science Lane, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Van Toen
authors.forename: J
authors.initials: J
authors.lastname: Street
authors.forename: T R
authors.initials: TR
authors.lastname: Oxland
authors.forename: Peter A
authors.initials: PA
authors.lastname: Cripton
mesh_terms: D000368:Aged; D002102:Cadaver; D002574:Cervical Vertebrae / Q000293:injuries* / Q000503:physiopathology*; D016002:Discriminant Analysis; D006801:Humans; D016059:Range of Motion, Articular / Q000502:physiology; D017695:Soft Tissue Injuries / Q000503:physiopathology; D016103:Spinal Fractures / Q000503:physiopathology; D016474:Weight-Bearing / Q000502:physiology