Search Results

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.

Unlike other modes of loading, the tolerance of the human neck in tension depends heavily on the load bearing capabilities of the muscles of the neck. Because of limitations in animal models, human cadaver, and volunteer studies, computational modeling of the cervical spine is the best way to understand the influence of muscle on whole neck tolerance to tension. Muscle forces are a function of the muscle's geometry, constitutive properties, and state of activation. To generate biofidelic responses for muscle, we obtained accurate three-dimensional muscle geometry for 23 pairs of cervical muscles from a combination of human cadaver dissection and 50th percentile male human volunteer magnetic resonance imaging and incorporated those muscles into a computational model of the ligamentous spine that has been previously validated against human cadaver studies.

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.