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The lateral, anterior and posterior passive bending responses of the human cervical spine were investigated using unembalmed cervical spinal elements obtained from cadavers. Bending stiffness was measured in six modes ranging from tension-extension through compression-flexion. Viscoelastic responses studied included relaxation, cyclic conditioning and constant velocity deformation. A five-axis load cell was used to measure the applied forces. Results include moment-angle curves, relaxation moduli and the effect of cyclic conditioning on bending stiffness. The Hybrid III ATD neckform was also tested and its responses are compared with the human. It was observed that the Hybrid III neckform was more rate sensitive than the human, that mechanical conditioning changed the stiffness of the human specimens significantly, and that changing the end condition from pinned-pinned to fixed-pinned increased the stiffness by a large factor.

The passive torsional responses of the human cervical spine were investigated using unembalmed cervical spines in a dynamic test environment. Kinematic constraints were designed to simulate in vivo conditions. A physiologic axis of twist was determined based on a minimum energy hypothesis. Six-axis load cells completely described the resultant forces. Results include viscoelastic responses, moment-angle curves, and piece-wise linear stiffness. The Hybrid III ATD neckform was also tested, and its responses compared with the human. The Hybrid III neckform was stiffer than the human, was more rate sensitive than the human, and unlike the human, was relatively insensitive to the axis of twist. A rotational element to improve the biofidelity of the Hybrid III neckform in rotation was developed, and the results presented.

Child head trauma in the United States is responsible for 30% of all childhood injury deaths with costs estimated at $10 billion per year. The common tools for studying this problem are the child anthropomorphic test devices (ATDs). The headform sizes and structural properties of child ATDs are based on various anthropometric studies and scaled Hybrid III mass and center of gravity (CG) properties. The goals of this study were to produce pediatric head and skull contours, provide estimates of pediatric head mass, mass moment of inertia and CG locations, and compare the head contours with the current child ATD head designs. To that end, computer tomography (CT) scans from one hundred eighty-five children in twelve age groups were analyzed to develop three-dimensional head and skull contours. The contours were averaged to estimate head and skull contours for children aged 1 month to 10 years. Inertial properties were estimated from a small sample of post-mortem human subjects (PMHSs).

The adult head has been studied extensively and computationally modeled for impact, however there have been few studies that attempt to quantify the mechanical properties of the pediatric skull. Likewise, little documentation of pediatric anthropometry exists. We hypothesize that the properties of the human pediatric skull differ from the human adult skull and exhibit viscoelastic structural properties. Quasi-static and dynamic compression tests were performed using the whole head of three human neonate specimens (ages 1 to 11 days old). Whole head compression tests were performed in a MTS servo-hydraulic actuator. Testing was conducted using nondestructive quasi-static, and constant velocity protocols in the anterior-posterior and right-left directions. In addition, the pediatric head specimens were dropped from 15cm and 30cm and impact force-time histories were measured for five different locations: vertex, occiput, forehead, right and left parietal region.

This study evaluated the biofidelity of both the Hybrid III and the THOR-NT anthropomorphic test device (ATD) necks in quasistatic tension-bending and pure-bending by comparing the responses of both the ATDs with results from validated computational models of the living human neck. This model was developed using post-mortem human surrogate (PMHS) osteoligamentous response corridors with effective musculature added (Chancey, 2005). Each ATD was tested using a variety of end-conditions to create the tension-bending loads. The results were compared using absolute difference, RMS difference, and normalized difference metrics. The THOR-NT was tested both with and without muscle cables. The THOR-NT was also tested with and without the central safety cable to test the effect of the cable on the behavior of the ATD. The Hybrid III was stiffer than the model for all tension-bending end conditions.