In the SNPRM on advanced air bags, the National Highway Traffic Safety Administration (NHTSA) proposed a comprehensive set of injury criteria for evaluating the potential for injury to the head, neck, chest and lower extremities for the various dummy sizes, ranging from the 1-year-old child to the 50th percentile male. The comments received and the agency's responses are summarized in this paper and the various performance limits implemented in the final rule are shown in Table SES-1.In the SNPRM on advanced air bags, the National Highway Traffic Safety Administration (NHTSA) proposed a comprehensive set of injury criteria for evaluating the potential for injury to the head, neck, chest and lower extremities for the various dummy sizes, ranging from the 1-year-old child to the 50th percentile male. The comments received and the agency's responses are summarized in this paper and the various performance limits implemented in the final rule are shown in Table SES-1.

Supplement: development of improved injury criteria for the assessment of advanced automotive restraint systems - ii

The large strain mechanical properties of adult porcine gray and white matter brain tissues were measured in shear and confirmed in compression. Consistent with local neuroarchitecture, gray matter showed the least amount of anisotropy, and corpus callosum exhibited the greatest degree of anisotropy. Mean regional properties were significantly distinct, demonstrating that brain tissue is inhomogeneous. Fresh adult human brain tissue properties were slightly stiffer than adult porcine properties but considerably less stiff than the human autopsy data in the literature. Mixed porcine gray/white matter samples were obtained from animals at "infant" and "toddler" stages of neurological development, and shear properties compared to those in the adult. Only the infant properties were significantly different (stiffer) from the adult.

Regional, Directional, and Age-Dependent Properties of the Brain Undergoing Large Deformation

Acknowledgements Prologue 1. Dental anthropology and morphology 2. Description and classification of permanent crown and root traits 3. Biological considerations: ontogeny, asymmetry, sex dimorphism and intertrait association 4. Genetics of morphological trait expression 5. Geographic variation in toot crown and root morphology 6. Establishing method and theory for using tooth morphology in reconstructions of late Pleistocene and Holocene human population history 7. Tooth morphology and population history Epilogue Appendices References Index.

The Anthropology of Modern Human Teeth: Dental Morphology and its Variation in Recent Human Populations

Recent research has suggested a possible link between sports-related concussions and neurodegenerative processes, highlighting the importance of developing methods to accurately quantify head impact tolerance. The use of kinematic parameters of the head to predict brain injury has been suggested because they are indicative of the inertial response of the brain. The objective of this study is to characterize the rotational kinematics of the head associated with concussive impacts using a large head acceleration dataset collected from human subjects. The helmets of 335 football players were instrumented with accelerometer arrays that measured head acceleration following head impacts sustained during play, resulting in data for 300,977 sub-concussive and 57 concussive head impacts. The average sub-concussive impact had a rotational acceleration of 1230 rad/s2 and a rotational velocity of 5.5 rad/s, while the average concussive impact had a rotational acceleration of 5022 rad/s2 and a rotational velocity of 22.3 rad/s. An injury risk curve was developed and a nominal injury value of 6383 rad/s2 associated with 28.3 rad/s represents 50% risk of concussion. These data provide an increased understanding of the biomechanics associated with concussion and they provide critical insight into injury mechanisms, human tolerance to mechanical stimuli, and injury prevention techniques.

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Rotational Head Kinematics in Football Impacts: An Injury Risk Function for Concussion

Anthropometry is the technique of expressing quantitatively the form of the body. Hrdlicka (1947) defines it as a system of techniques, the systematized art of measuring and taking observations on man, his skeleton, his brain, and other organs, by the most reliable means and methods for scientific purposes. It is limited only by the problems to which it is applied and no treatise, however large, can account for all the factors present in an original study. Time and again the anthropometrist will be presented with problems for which there are no guidelines, and he, alone or in discussion with his colleagues, must find satisfactory solutions.

The Methods of Auxological Anthropometry

This study was conducted to determine the biomechanics of the human head under quasistatic and dynamic loads. Twelve unembalmed intact human cadaver heads were tested to failure using an electrohydraulic testing device. Quasistatic loading was done at a rate of 2.5 mm/s. Impact loading tests were conducted at a rate of 7.1 to 8.0 m/s. Vertex, parietal, temporal, frontal, and occipital regions were selected as the loading sites. Pathological alterations were determined by pretest and posttest radiography, close-up computed tomography (CT) images, macroscopic evaluation, and defleshing techniques. Biomechanical force-deflection response, stiffness, and energy-absorbing characteristics were obtained. Results indicated the skull to have nonlinear structural response. The failure loads, deflections, stiffness, and energies ranged from 4.5 to 14.1 kN, 3.4 to 16.6 mm, 467 to 5867 N/mm, and 14.1 to 68.5 J, respectively. The overall mean values of these parameters for quasistatic and dynamic loads were 6.4 kN (+/- 1.1), 12.0 mm (+/- 1.6), 812 N/mm (+/- 139), 33.5 J (+/- 8.5), and 11.9 kN (+/-0.9), 5.8 mm (+/- 1.0), 4023 N/mm (+/- 541), 28.0 J (+/- 5.1), respectively. It should be emphasized that these values do not account for the individual variations in the anatomical locations on the cranium of the specimens. While the X-rays and CT scans identified the fracture, the precise direction and location of the impact on the skull were not apparent in these images. Fracture widths were consistently wider at sites remote from the loading region. Consequently, based on retrospective images, it may not be appropriate to extrapolate the anatomical region that sustained the impact forces. The quantified biomechanical response parameters will assist in the development and validation of finite element models of head injury.

Biomechanics of skull fracture

Infants and children in the adult world of automobile safety design: Pediatric and anatomical considerations for design of child restraints☆

Basic physical characteristics of the neck have been defined which have application to the design of biomechanical models, anthropometric dummies, and occupant crash protection devices. The study was performed using a group of 180 volunteers chosen on the basis of sex, age (18-74 years), and stature. Measurements from each subject included anthropometry, cervical range-of-motion (observed with both x-rays and photographs), the dynamic response of the cervical flexor and extensor muscles to a controlled jerk, and the maximum voluntary strength of the cervical muscles. Data are presented in tabular and graphic form for total range-of-motion, cervical muscle reflex time, decelerations of the head, muscle activation time, and cervical muscle strength. The range-of-motion of females was found to average 1-12 deg greater than that of men, depending upon age, and a definite degradation in range-of-motion was observed with increasing age. Average neck muscle reflex times range from 56-92 ms for flexors and 54-87 ms for extensors, with males being generally slower-reacting. This finding means that the cervical muscles generally cannot be activated in sufficient time to mitigate the hyperextension effects of a surprise rear-end collision. Reflex time becomes significantly longer after middle c.g. in the range of 0.3-0.5 g. The time required to stop the head after initial detection of the muscle reflex was slightly longer for neck extensors. Strength tests revealed that males are on average stronger than females in both flexor and extensor strengths. Males and females also exhibit different aging characteristics, and a slight stature effect was noted for the younger and shorter portions of the population. Age and sex were found to be important factors in cervical flexibility and response characteristics, and they should be included whenever accurate representation of neck parameters is desired.

Cervical range of motion and dynamic response and strength of cervical muscles

A total of 87 traditional and functional body measurements were taken on a sample of 4,127 infants, children and youths representing the United States population aged 2 weeks through 18 years. Measurements were taken throughout the United States by two teams of anthropometrists using an automated anthropometric data acquisition system. Standard anthropometers, calipers, and tape devices were modified to read electronically and input dimensional data directly to a mini-computer for data processing and storage. Summary statistics of measurement results are reported for 16 age groups along with scatter plots of the data points for the sexes combined and males and females separately. Each measurement is described alog with a photgraph and illustration. In addition, bivariate relationships of selected functional measurements with weight or stature are provided along with regression data.

Richard G. Snyder

Papers

Biomechanics of skull fracture

Infants and children in the adult world of automobile safety design: Pediatric and anatomical considerations for design of child restraints☆

Cervical range of motion and dynamic response and strength of cervical muscles

Anthropometry of infoants, children, and youths to age 18 for product safety design

Impact injuries in pregnancy: I. Experimental studies☆☆☆