Current understanding of the biomechanics of cervical spine injuries in head-first impact is based on decades of epidemiology, mathematical models, and in vitro experimental studies. Recent mathematical modeling suggests that muscle activation and muscle forces influence injury risk and mechanics in head-first impact. It is also known that muscle forces are central to the overall physiologic stability of the cervical spine. Despite this knowledge, the vast majority of in vitro head-first impact models do not incorporate musculature. We hypothesize that the simulation of the stabilizing mechanisms of musculature during head-first osteoligamentous cervical spine experiments will influence the resulting kinematics and injury mechanisms. Therefore, the objective of this study was to document differences in the kinematics, kinetics, and injuries of ex vivo osteoligamentous human cervical spine and surrogate head complexes that were instrumented with simulated musculature relative to specimens that were not instrumented with musculature. We simulated a head-first impact (3 m/s impact speed) using cervical spines and surrogate head specimens (n = 12). Six spines were instrumented with a follower load to simulate in vivo compressive muscle forces, while six were not. The principal finding was that the axial coupling of the cervical column between the head and the base of the cervical spine (T1) was increased in specimens with follower load. Increased axial coupling was indicated by a significantly reduced time between head impact and peak neck reaction force (p = 0.004) (and time to injury (p = 0.009)) in complexes with follower load relative to complexes without follower load. Kinematic reconstruction of vertebral motions indicated that all specimens experienced hyperextension and the spectrum of injuries in all specimens were consistent with a primary hyperextension injury mechanism. These preliminary results suggest that simulating follower load that may be similar to in vivo muscle forces results in significantly different impact kinetics than in similar biomechanical tests where musculature is not simulated.
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November 2013
Research-Article
Compressive Follower Load Influences Cervical Spine Kinematics and Kinetics During Simulated Head-First Impact in an in Vitro Model
Peter A. Cripton,
Peter A. Cripton
1
e-mail: cripton@mech.ubc.ca
Orthopaedic and Injury Biomechanics Group,
Department of Orthopaedics,
Orthopaedic and Injury Biomechanics Group,
Department of Orthopaedics,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
Department of Mechanical Engineering,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
International Collaboration on
Repair Discoveries,
Repair Discoveries,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
1Corresponding author.
Search for other works by this author on:
Eyal Itshayek
Eyal Itshayek
Orthopaedic and Injury Biomechanics Group,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
Department of Orthopaedics,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
International Collaboration on
Repair Discoveries,
Repair Discoveries,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
Department of Neurosurgery,
Hadassah—Hebrew University Hospital
,Jerusalem 91120
, Israel
Search for other works by this author on:
Peter A. Cripton
e-mail: cripton@mech.ubc.ca
Orthopaedic and Injury Biomechanics Group,
Department of Orthopaedics,
Orthopaedic and Injury Biomechanics Group,
Department of Orthopaedics,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
Department of Mechanical Engineering,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
International Collaboration on
Repair Discoveries,
Repair Discoveries,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
Eyal Itshayek
Orthopaedic and Injury Biomechanics Group,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
Department of Orthopaedics,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
International Collaboration on
Repair Discoveries,
Repair Discoveries,
University of British Columbia
,Vancouver, BC V5S 2X9
, Canada
Department of Neurosurgery,
Hadassah—Hebrew University Hospital
,Jerusalem 91120
, Israel
1Corresponding author.
Contributed by the Bioengineering Division of ASME for publication in the JOURNAL OF BIOMECHANICAL ENGINEERING. Manuscript received September 4, 2012; final manuscript received May 27, 2013; accepted manuscript posted June 17, 2013; published online September 24, 2013. Assoc. Editor: Brian D. Stemper.
J Biomech Eng. Nov 2013, 135(11): 111003 (11 pages)
Published Online: September 24, 2013
Article history
Received:
September 4, 2012
Revision Received:
May 27, 2013
Accepted:
June 17, 2013
Citation
Saari, A., Dennison, C. R., Zhu, Q., Nelson, T. S., Morley, P., Oxland, T. R., Cripton, P. A., and Itshayek, E. (September 24, 2013). "Compressive Follower Load Influences Cervical Spine Kinematics and Kinetics During Simulated Head-First Impact in an in Vitro Model." ASME. J Biomech Eng. November 2013; 135(11): 111003. https://doi.org/10.1115/1.4024822
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