The overall goal of work in this area is to enhance the understanding of neck injury mechanisms.  The studies will focus specifically on catastrophic neck injury, pediatric neck injuries, and whiplash injury.

Current efforts have shown that muscle forces can increase tensile tolerance for the adult cervical spine from 1800 N to over 4000 N in the face of full muscle activation (Van Ee et al., 2000).  These data are critical in that they provide rational estimates of human tolerance in tension, arguably for the first time.  They also have the potential to show how whole neck loads, which can be estimated from inverse dynamics of volunteers, relate to ligamentous spine loads that actually cause spinal column injury.  As the prototype Thor dummy has a muscular and a ligamentous cervical spine, understanding the load sharing of muscle and the ligamentous spine in injury in humans will be a key element for developing Thor dummy tolerances.  Therefore, first and foremost as an area of study is the field of cervical muscle dynamics. 

Dr. Myers has developed a computational model of the ligamentous spine and cervical muscles. These data include the physiological cross-sectional area of each muscle and the corresponding fiber length and pennation angle.  To this end, the musculoskeletal geometry of the model will be validated against measurements of muscle moment arms obtained from cadaver studies performed at Duke University and reported in the literature.  The mechanical behavior of each muscle will be taken into account by giving each muscle complex physiological properties involving a contractile element with realistic force-length-velocity properties, and series-and parallel-elastic elements with active and passive stiffness properties.

In whiplash injury, the goal will be to help complete the mechanical analysis that begins with contact of an automobile bumper and ends in the measurement of strain in human tissues and the assessment of the neurophysiologic basis of pain in those strained tissues.  Because many studies have examined how motor vehicles interact with bumpers, and how occupants interact with seats, we believe those elements of the whiplash event are relatively well described.

In the same context, there are many current and recent investigations of living human and human cadaver neck’s response to the rear-end collisions.  As such, cervical spine kinematics are also relatively well described.  We conclude, therefore, that the area of greatest weakness in whiplash is the lack of understanding of the site of injury.

This research domain’s work group identified that the criterion for head supported mass was an important and poorly characterized problem for aviators and for ground personnel.  Aviators suffer considerable lost time due to neck pain, and have increased incidence of cervical degenerative disease, as well as measurably diminished mission performance due to the inertial demands of such systems as night vision goggles and heads-up displays.  This problem is currently under investigation by the USAARL at Fort Rucker, Alabama.  Like the catastrophic injury problem, solving this problem relies heavily on understanding the loads generated in muscle during military exposures.  In response to this problem, the SCIB will submit a proposal to the USAARL addressing the question of head supported mass and computational modeling of the responses of the aviators to inertial loads with significant mass and mass moments of inertia on their head.

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