Comparative strengths and structural properties of the upper and lower cervical spine in flexion and extension

J Biomech. 2002 Jun;35(6):725-32. doi: 10.1016/s0021-9290(02)00037-4.


The purpose of this study is to test the hypothesis that the upper cervical spine is weaker than the lower cervical spine in pure flexion and extension bending, which may explain the propensity for upper cervical spine injuries in airbag deployments. An additional objective is to evaluate the relative strength and flexibility of the upper and lower cervical spine in an effort to better understand injury mechanisms, and to provide quantitative data on bending responses and failure modes. Pure moment flexibility and failure testing was conducted on 52 female spinal segments in a pure-moment test frame. The average moment at failure for the O-C2 segments was 23.7+/-3.4Nm for flexion and 43.3+/-9.3Nm for extension. The ligamentous upper cervical spine was significantly stronger in extension than in flexion (p=0.001). The upper cervical spine was significantly stronger than the lower cervical spine in extension. The relatively high strength of the upper cervical spine in tension and in extension is paradoxical given the large number of upper cervical spine injuries in out-of-position airbag deployments. This discrepancy is most likely due to load sharing by the active musculature.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Aged
  • Air Bags / adverse effects
  • Air Bags / standards
  • Cadaver
  • Cervical Vertebrae / injuries*
  • Cervical Vertebrae / physiopathology*
  • Compressive Strength
  • Female
  • Humans
  • In Vitro Techniques
  • Joint Dislocations / etiology
  • Joint Dislocations / physiopathology
  • Joint Dislocations / prevention & control
  • Middle Aged
  • Models, Biological
  • Range of Motion, Articular
  • Reproducibility of Results
  • Rotation
  • Sensitivity and Specificity
  • Spinal Injuries / etiology
  • Spinal Injuries / physiopathology*
  • Spinal Injuries / prevention & control*
  • Statistics as Topic
  • Stress, Mechanical
  • Tensile Strength
  • Torque
  • Weight-Bearing