title: Whiplash produces an S-shaped curvature of the neck with hyperextension at lower levels.
abstract: METHODS
  A bench-top trauma sled was used to apply four intensities of whiplash trauma to human cadaveric cervical spine specimens and to measure resulting intervertebral rotations using high-speed cinematography.
  
  
  OBJECTIVE
  To determine the cervical spine levels most prone to injury from whiplash trauma and to hypothesize a mechanism for such injury.
  
  
  BACKGROUND
  Whiplash injuries traditionally have been ascribed to hyperextension of the head, but other mechanisms such as hypertranslation also have been suggested.
  
  
  METHODS
  Six occiput to T1 (or C7) fresh cadaveric human spines were studied. Physiologic flexion and extension motions were recorded with an Optotrak motion analysis system by loading up to 1.0 Nm. Specimens then were secured in a trauma sled, and a surrogate head was attached. Flags fixed to the head and individual vertebrae were monitored with high-speed cinematography (500 frames/sec). Data were collected for 12 traumas in four classes defined by the maximum sled acceleration. The trauma classes were 2.5 g, 4.5 g, 6.5 g, and 8.5 g. Significance was defined at P < 0.01.
  
  
  RESULTS
  In the whiplash traumas, the peak intervertebral rotations of C6-C7 and C7-T1 significantly exceeded the maximum physiologic extension for all trauma classes studied. The maximum extension of these lower levels occurred significantly before full neck extension. In fact, the upper cervical levels were consistently in flexion at the time of maximum lower level extension.
  
  
  CONCLUSIONS
  In whiplash, the neck forms an S-shaped curvature, with lower level hyperextension and upper level flexion. This was identified as the injury stage for the lower cervical levels. A subsequent C-shaped curvature with extension of the entire cervical spine produced less lower level extension.
authors.affiliation: Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticut, USA.
authors.forename: J N
authors.initials: JN
authors.lastname: Grauer
authors.forename: M M
authors.initials: MM
authors.lastname: Panjabi
authors.forename: J
authors.initials: J
authors.lastname: Cholewicki
authors.forename: K
authors.initials: K
authors.lastname: Nibu
authors.forename: J
authors.initials: J
authors.lastname: Dvorak
mesh_terms: D001696:Biomechanical Phenomena; D002102:Cadaver; D002574:Cervical Vertebrae / Q000293:injuries / Q000503:physiopathology*; D006801:Humans; D009040:Motion Pictures; D012399:Rotation / Q000009:adverse effects; D014911:Whiplash Injuries / Q000209:etiology / Q000503:physiopathology*