Catherine Ford Corrigan

Electromyographic activity and posturing of the human neck during rollover tests

Lateral head motions, torso motions, lateral neck bending angles, and electromyographic (EMG) activity patterns of five human volunteer passengers are compared to lateral motions of a Hybrid III ATD during right-left and left-right fishhook steering maneuvers leading to vehicular tip-up. While the ATD maintained relatively fixed lateral neck angles, live subjects leaned their heads slightly inward and actively utilized their neck musculature to stiffen their necks against the lateral inertial loads. Except for differences in neck lateral bending, the Hybrid III ATD reasonably reflects occupant kinematics during the pre-trip phase of on-road rollovers.

Evaluation of Human Surrogate Models for Rollover

Anthropomorphic test dummies (ATDs) have been validated for the analysis of various types of automobile collisions through pendulum, impact, and sled testing. However, analysis of the fidelity of ATDs in rollover collisions has focused primarily on the behavior of the ATD head and neck in axial compression. Only limited work has been performed to evaluate the behavior of different surrogate models for the analysis of occupant motion during rollover. Recently, Moffatt et al. examined head excursions for near- and far-side occupants using a laboratory-based rollover fixture, which rotated the vehicle about a fixed, longitudinal axis. The responses of both Hybrid III ATD and human volunteers were measured. These experimental datasets were used in the present study to evaluate MADYMO ATD and human facet computational models of occupant motion during the airborne phase of rollover. Occupant motion predicted by the Hybrid III ATD computation models provided a good match to the temporal movement patterns and corridors of torso and head excursion measured in the volunteers. Differences in torso and head-neck posture were attributed to active muscle contractions in the volunteers. Simulations performed using the TNO human facet model, in the absence of muscle tone, predicted large head excursions and lateral neck and torso bending. These findings were attributed to the stiffer Hybrid III ATD neck and torso as compared to the spinal model incorporated in the human facet model. Although it is possible to model active muscle forces using the TNO human facet model, the appropriate control schemes for coordinating muscle activity in the rollover environment have not been established. Without the implementation of appropriate muscular controls, the TNO human model appears to be best suited to high-force environments or low-force environments where the occupant is unconscious or incapacitated. Our results indicate that among the currently available human computational surrogate models, the Hybrid III ATD provides the best prediction of occupant motion when compared to the available human volunteer data. These results have provided us the impetus to study future human models that incorporate active muscle control.

Development of a computational method to predict occupant motions and neck loads during rollovers

The mechanics of on-road, friction-induced rollovers were studied with the aid of a three-dimensional computer code specifically derived for this purpose. Motions of the wheels, vehicle body, occupant torso, and head were computed. Kanes method was utilized to develop the dynamic equations of motion in closed form. On-road rollover kinematics were compared to a dolly-type rollover at lesser initial speed, but generating a similar roll rotation rate. The simulated on-road rollover created a roof impact on the leading (drivers) side, while the dolly rollover simulation created a trailing-side roof impact. No head-to-roof contacts were predicted in either simulation. The first roof contact during the dolly-type roll generated greater neck loads in lateral bending than the on-road rollover. This work is considered to be the first step in developing a combined vehicle and occupant computational model for studying injury potential during rollovers.

Inertial Neck Injuries in Children Involved in Frontal Collisions

There is a paucity of data regarding the potential for pediatric cervical spine injury as a result of acceleration of the head with no direct impact during automotive crashes. Sled tests were conducted using a 3-year-old anthropomorphic test device (ATD) to investigate the effect of restraint type and crash severity on the risk of pediatric inertial neck injury. At higher crash severities, the ATD restrained by only the vehicle three-point restraints sustained higher peak neck tension, peak neck extension and flexion moments, neck injury criterion (Nij) values, peak head accelerations, and HIC values compared to using a forward-facing child restraint system (CRS). The injury assessment reference values (IARVs) for peak tension and Nij were exceeded in all 48 and 64 kph delta-V tests using any restraint type. The test at a delta-V of 64 kph using only the vehicle belts as restraints resulted in peak upper neck tension, peak upper neck extension moment, and Nij values two times greater than the corresponding IARV. Only small differences were found in the injury metrics between a CRS installed with and without webbing tension except that head excursion was greater in the installation without webbing tension. These data show that the potential for neck injury exists for children involved in severe frontal crashes and restrained in either a forwardfacing CRS or by vehicle belts–only, even in the absence of head contact.

Inertial Neck Injuries in Children Involved in Frontal Collisions: Sled Testing Using the 6-Year-Old ATD

Sled tests were conducted using a 6-year-old anthropomorphic test device (ATD) to investigate the effect of restraint type and crash severity on the risk of pediatric inertial neck injury. Tests were conducted at three severities, using three restraint configurations: properly restrained, misused restraint, and an age-inappropriate restraint. ATD injury measurements increased with increased crash severity. Head accelerations, head injury criteria, and neck loads, with the exception of neck flexion, were relatively independent of restraint configuration at a given crash severity. The data show that children are at risk of inertial neck injuries at high frontal crash severities.Copyright

Letter to the Editor regarding Bajaj D, et al., The resistance of cortical bone tissue to failure under cyclic loading is reduced with alendronate, Bone 2014;64:57–64

• Experimental data were excluded from analyses of effects of alendronate treatment on fatigue life of bone specimens from canine ribs.