Richard G. Snyder

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

U.S.A. Abstract-The infant and child differ structurally from the adult in a number of ways which are critical to the design for protection against impact forces and for adequate occupant restraint systems. The purpose of this paper is to bring together a profile of the anatomy, anthropomctry, growth, and development of the infant and child. Age differences related to the proper design of child restraint systems are emphasized. Problems discussed include child-adult structural differences, center of gravity of the body, the head mass in relation to the neck and general body proportions, positions of key organs, and biomechanical properties of tissues.

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

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.

IMPACT INJURIES IN PREGNANCY. I: EXPERIMENTAL STUDIES,

Abstract Eleven pregnant baboons were subjected to 12 experimental impacts. At the 20 g level of decelerative force, maternal injuries were minimal. Fetal death occurred in association with traumatic head injury, placental separation, and maternal shock. Although prevention of body flexion during impact did not prevent elevation of intrauterine pressure, fetal injury, or placental separation, the number of animals is too small to draw conclusions regarding the superiority of one restraint system over another. The lap belt should be worn by pregnant women, and it should be snugly placed across the pelvis and not over the fundus.

A Biomechanical Analysis of Head Impact Injuries to Children

Head-first free-falls of 30 children, 1-10 years old and one adult, 21 years old, were studied to determine fall circumstances and injuries sustained. The falls of six children and one adult were simulated using the MVMA Two-Dimensional Crash Victim Simulator computer model. The data shows that head-first falls of children onto rigid surfaces from heights as low as 2 meters can result in serious injuries. Conservative head injury tolerance limits are estimated to be 200-250g for peak head acceleration. /Author/

SEATED POSTURE OF VEHICLE OCCUPANTS

This paper describes the methodology and results from a project involving development of anthropometrically based design specifications for a family of advanced adult anthropomorphic dummies. Selection of family members and anthropometric criteria for subject sample selection were based on expected applications of the devices and on an analysis of U.S. population survey data. This resulted in collection of data for dummy sizes including a small female, a mid-sized male, and a large male. The three phases of data collection included: 1. In-vehicle measurements to determine seat track position and seating posture preferred by the subjects for use in development of laboratory seat bucks; 2. Measurement of subject/seat interface contours for fabrication of an average hard seat surface for use in the buck; and 3. Measurement of standard anthropometry, seated anthropometry (in the buck), and three-dimensional surface landmark coordinates using standard and photogrammetric techniques. For the covering abstract of the conference see HS-036 716. (Author/TRRL)

DOOR CRASHWORTHINESS CRITERIA

The object of the program was to make long duration head impacts and to develop scaling relationships to allow extrapolation of impact data for infra-human primates to living humans. A series of primate side impacts, to the head and body was conducted in parallel with a series of impacts to human cadavers. Dimensional analysis techniques were employed to estimate in vivo human tolerance to side impacts. The threshold of closed brain injury to humans was found to be 76Gs for a pulse duration of 20 msec and an impact velocity of 29.5 mph. The maximum tolerable penetration to the chest was found to be 2.65 inches for both the left and right sides. Scaling of abdominal injuries to humans was accomplished by employing a factor which relates impact contact area, animal mass, impact force, and pulse duration, to injury severity. The maximum tolerable contact pressure to the upper abdomen of a human was found to be 32 psi.

ANTHROPOMETRY OF U. S. INFANTS AND CHILDREN.

This report presents the results of a three-year study designed to collect, analyze and reduce selected anthropometric data on 4,027 infants and children representative of the current U.S. population ranging in age from newborn to 12 years of age. Since the major purpose was to provide basic measurement data most useful and critical to consumer product design, regulatory consideration, or other direct applications, 12 of the 41 measurements taken were applied measurements which have not been previously available. A substantial portion of the study involved the design, fabrication, development, and testing of a new generation of anthropometric measuring devices which transmit measurement signals to a portable mini-computer data acquisition system or to a set of readout meters. The results presented in this report summarize the complete data which have been provided on magnetic tape for automated data analysis and retrieval. Each of the 41 measurements is defined and illustrated, and tabular charts are provided listing the mean, standard deviation, 5th, 50th and 95th percentiles by age and sex, and for combined sexes. In addition, the mean, 5th and 95th percentiles are shown graphically. /Author/

Joint Range of Motion and Mobility of the Human Torso

THE OBJECT HAS BEEN TO DEVELOP A QUANTITATIVE DESCRIPTION OF THE MOBILITY OF THE HUMAN TORSO, INCLUDING THE SHOULDER GIRDLE, NECK, THORACIC AND LUMBAR VERTEBRAL COLUMN, AND PELVIS. THIS HAS BEEN ACCOMPLISHED BY A SYSTEMATIC MULTIDISCIPLINARY INVESTIGATION INVOLVING TECHNIQUES OF CADAVER DISSECTION AND MEASUREMENT, UTILIZING CINERADIOFLUOROSCOPY FOR JOINT CENTER OF ROTATION LOCATION, ANTHROPOMETRY, RADIOGRAPHY AND PHOTOGRAMMETRY FOR SELECTED POSITIONS AND MOTIONS OF LIVING SUBJECTS, AND COMPUTER ANALYSIS. THE MAJOR RESULTS OF THE STUDY ARE PREDICTION EQUATIONS AND GRAPHS DESCRIBING HOW THE BASE OF THE SPINE REFERENCE POINT (FIFTH LUMBAR SPINAL SURFACE MARKER) MOVES IN RELATION TO DEFINED SEATED AND STANDING REFERENCE POINTS FOR GIVEN REACHES, AND THE DEVELOPMENT OF TECHNIQUES BY WHICH THE LENGTHS AND EXCURSIONS OF TORSO AND LIMB LINKS MAY BE ESTIMTED AND LOCATED. IT WAS FOUND THAT THE SURFACE LANDMARKS SELECTED COULD PREDICT PRECISE LOCATION OF THE UNDERLYING ANATOMICAL LANDMARKS. THE RESULTS PROVIDE INITIAL BASIC DATA REGARDING HUMAN TORSO MOTION, JOINT CENTER OF MOTION, AND LINK RELATIONSHIPS. /SAE/

Response of human larynx to blunt loading

Direct impact to the larnyx is usually prevented in accidents by ths]protective nature of the chin. In some situations, the occupant motions leave the larnyx unprotected and susceptible to impact by the steering wheel rim or instrument panel. As one of the unpaired vital organs of the body, there is no easy way to provide an alternative for its functions when the larnyx is lost or damaged. Information available on the tolerance of the unembalmed human larnyx to force is quite limited. This paper describes a multidisciplinary study to determine the response of unembalmed human larynges to blunt mechanical loading and to interpret the response with respect to clinical data. Fresh intact larynges were obtained at autopsy and tested at either static or dynamic loading conditions utilizing special test fixtures in materials-testing machines. Load and deformation data were obtained up to levels sufficient to produce significant fractures in both the thyroid and cricoid cartilages. Additional information was obtained in the form of permanent dimensional changes through direct measurements and location of fracture sites by use of xeroradiography. Final evaluation of the damage was performed following dissection of the laryngeal structure. The results of the tests are analyzed and interpreted in relation to establishing tolerance criteria for laryngeal loading.

Fundamentals of Anthropometric Survey Measurement Techniques

In the modern technologically based society there is increased recognition of the basic importance of human population dimensional measures. This is reflected in the observation that some 85% of the major anthropometric studies world-wide have been completed during the past 20 years. The emphasis on military population studies has resulted in models for the increasing number of civilian-based surveys. But as the need for population surveys increases, new techniques and methods must be developed to increase the accuracy, quality and quantity of measures, and the means to quickly reduce and interpret these data. Bioanthropologists have greatly benefited from the technical contributions of other disciplines, particularly that of bioengineering, biostatistics, and biophysics. In reviewing recent technological advances and some current survey problems, this paper presents a brief overview of the state-of-the-art of anthropometric survey techniques and methods.