Objectives Most biomechanical research on brain injury focuses on direct blows to the head. There are a few older studies that indicate craniocervical stretch could be a factor in concussion by causing strain in the upper spinal cord and brainstem. The objectives of this study are to assess the biomechanical response and estimate the strain in the upper cervical spine and brainstem from primary impact to the chest in American football.
Methods Impact testing was conducted to the chest of a stationary unhelmeted and helmeted anthropomorphic test device (ATD) as well as the laboratory reconstruction of two NFL game collisions resulting in concussion. A finite element (FE) study was also conducted to estimate the elongation of the cervical spine under tensile and flexion loading conditions.
Results The helmeted ATD had a 40% (t=9.84, p<0.001) increase in neck tensile force and an 8% (t=7.267, p<0.001) increase in neck flexion angle when compared with an unhelmeted ATD. The case studies indicated that the neck tension in the injured players exceeded tolerable levels from volunteer studies. The neck tension was combined with flexion of the head relative to the torso. The FE analysis, combined with a spinal cord coupling ratio, estimated that the strain along the axis of the upper cervical spinal cord and brainstem was 10%–20% for the combined flexion and tension loading in the two cases presented.
Conclusion Strain in the upper spinal cord and brainstem from neck tension is a factor in concussion.
- upper neck forces
- Hybrid III dummy
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Contributors RJ, DCV and JRM designed the test matrix for this research. RJ generated documentation for Wayne State University Institutional Review Board, conducted the laboratory impact testing, analysed and summarised the data and conducted finite element simulations. RJ, DCV and AIK reviewed the data and conducted the analysis. All authors contributed to this manuscript, its review, and approved the final version.
Funding Funding for this research has been received from McCarthy Engineering and from the Institute for Injury Research.
Competing interests None declared.
Patient consent Not required.
Ethics approval This study has been reviewed by the Wayne State University Institutional Review Board and it was determined that an IRB review was not required (HPR determination number 2017-51).
Provenance and peer review Not commissioned; externally peer reviewed.
Data statement No additional data are available.
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