Assessing child restraint misuse by parental survey.

Objective: To determine the extent to which child restraint system (CRS) misuse can be evaluated by parental survey.

Methods: A cross sectional survey was conducted at eight CRS clinics from May to October, 1998. Before CRS inspection, parents were administered a structured interview to identify distinct characteristics of restraint use and misuse.

Computer crash simulations in the development of child occupant safety policies.

Objective: To address the predictability of injury from air bag activation by use of crash simulation software.

Methods: Using current, validated crash simulation software, the effect of air bag activation on injury risk was assessed for the 6-year-old child, both restrained and unrestrained. Results were compared with those for adult occupants in similar crash scenarios.

The effect of one injection of Depo-Provera on the human vaginal epithelium and cervical ectopy.

Two studies in rhesus monkeys have shown that progesterone implants, Depo-Provera and Norplant, were associated with vaginal thinning. Progesterone implants have also been associated with an increased risk of simian immunodeficiency virus (SIV) acquisition. This study in 16 women was done to assess vaginal epithelial thickness and number of cell layers from biopsies taken in the untreated follicular and luteal phases, and at 1 month and 3 months after administration of Depo-Provera.

A fiber-reinforced composite model of the viscoelastic behavior of the brainstem in shear.

Brainstem trauma occurs frequently in severe head injury, often resulting in fatal lesions due to importance of brainstem in crucial neural functions. Structurally, the brainstem is composed of bundles of axonal fibers distinctly oriented in a longitudinal direction surrounded by an extracellular matrix. We hypothesize that the oriented structure and architecture of the brainstem dictates this mechanical response and results in its selective vulnerability in rotational loading.

Material characterization of the brainstem from oscillatory shear tests.

Traumatic damage to the brainstem occurs frequently when the brain skull complex experiences injurious loading especially during those traumatic situations that produce diffuse axonal injury (DAI). DAI has been shown to be dependent on load direction and correlated with regional tissue deformation in response to rotational inertial loads. Possible mechanisms for the selective vulnerability of the brainstem are (1) the geometry of the central nervous system is responsible for producing high tissue strains in these regions, (2) regional differences in overall material stiffness result in larger deformations at these sites, and (3) the anisotropic mechanical properties of these regions lead to a sensitivity to the rotational load direction and magnitude.

A high-frequency shear device for testing soft biological tissues.

Accurate mechanical property data obtained at large shear deformations and high frequencies are a fundamental component of realistic numerical simulations of soft tissue injury. Although many commercial systems exist for testing shear properties of viscoelastic materials with properties similar to soft biological tissue, none are capable of determining properties at high loading rates necessary for modeling soft tissue injury. Previous custom shear testing systems, though capable of high-frequency loading, indirectly measure tissue properties by using analytical corrections for inertial effects.

Improved assessment of lumbar vertebral body strength using supine lateral dual-energy x-ray absorptiometry.

Clinical and biomechanical investigations indicate that assessment of vertebral body bone mineral density (BMD) by anteroposterior dual-energy x-ray absorptiometry (DXA) is a useful index of vertebral body strength and fracture risk in osteoporosis. However, inclusion of non-force-bearing and small-force-bearing mineralized structures, such as the posterior elements and aortic calcifications, in the measurement of anterior BMD obscures the assessment of vertebral body mass by this technique. Indeed, such interference is particularly severe in the presence of posterior element degeneration or previous spinal surgery.