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.

The objective of this paper is to investigate the difference in T1 instrumentation mount response in the -15G-sub-x human volunteer experiments and the PMHS experiments, based new film analyses to develop a method to correct for observed differences in T1 instrumentation mount rotation earlier and to define a new set of easy to measure neck performance requirements for frontal impact expressed relative to the corrected origin of the first thoracic vertebral body (T1). As in the earlier analyses the head motions will be presented with a two-pivot head-neck mechanical linkage mechanism. Language: en

The initial results of a continuing investigation into the effects of various levels of impact acceleration on the functional integrity of the motor nervous system are summarized. The results are based on the measurement of alterations in neural transmission along the motor pathway of the Rhesus monkey as revealed by latency and amplitude changes in the motor pathway evoked potential (EP) following the delivery of various levels of impact acceleration to a test vehicle. The EPs were produced by electrical stimulation of and recording from the motor pathway of experimental animals subjected to -Y (lateral impact) acceleration and animals subjected to -X (frontal impact) acceleration. High resolution latency and amplitude measures of the EP recorded from these animals before and after impact were tracked so that the time course of recovery of nerve propagation following impact could be accurately assessed. Analysis of these EP measures revealed that the time course of recovery to preimpact values is directly related to the intensity of the acceleration impulse delivered to the test vehicle.

the early somatosensory evoked potential secondary to median nerve stimulation in the human had an onset latency of 9–12 msec when recorded from scalp electrodes at vertex-to-mastoid, vertex-to-inion or at the base of the skull. Similar latencies were observed from responses recorded over the cervical dorsal columns during neurologic surgery. A latency difference of 1.5 msec was observed between the early response and the responses recorded from the junction of medial lemniscus and nucleus ventralis posterior lateralis of the thalamus during human stereotaxic surgery. Cervical cord transections and transection at the mid-pontine levels of the monkey showed that the evoked potential was due to generators between these levels. Depth recording of the monkey indicate that the early evoked potential originates in the region of dorsal column nuclei, while the later components are secondary to generators in cerebral cortex.

The response of the human head and neck to impact acceleration has been previously reported for the minus X (chest to back) and plus Y (right to left) directions. The purpose of this study is to report the initial position effect on the human head and neck response for plus Y direction experiments. Four initial positions of the head relative to the first thoracic vertebral body (T//1) have been investigated over a range of sled acceleration peaks from 2 to 7G. The data from six young adult male volunteers representative of a wide range of anthropometry are presented. The effect of initial position on the resulting head angular and linear acceleration, velocity and displacement is presented. A comparison of the initial position effect for minus X and plus Y direction experiments is made. The ability to model the initial position effect is discussed. Language: en

The report presents the first study of human and chimpanzee response to lateral (+Gy) impact acceleration with three dimensional inertial instrumentation of the head and of the first thoracic vertebral (T1) body. Thirty-four human experiments using six volunteers are reported. The experiments ranged from 2 G to 7.5G peak sled acceleration. Twelve chimpanzee experiments with head and T1 measurement systems identical to those used on human subjects were conducted, and ranged from 6 G to 20 G peak sled acceleration. The data for all experiments are presented. The human lateral response is considerably different from the -Gx response previously reported. There are also major differences between human and chimpanzee response. The implications of the data for modeling and the validation of such models are discussed.

: This paper reports on one aspect of a comprehensive program designed to investigate the effects of various levels of impact acceleration on the functional integrity of the nervous system. The results described are based on the measurement of afferent neural transmission in the Rhesus monkey as revealed by latency and amplitude changes in the evoked potential (EP). In order to track the time course of recovery of latency and amplitude with high time resolution, automated methods for detecting peak amplitude and latency of components of the evoked potential were developed. These methods were applied to EP data recorded during impact experiments on Rhesus monkeys.

Thirteen human volunteer subjects ranging from the 5th to the 97th percentile in sitting height were exposed to -Gx impact acceleration at peak sled accelerations of 6G and 10G. Two angles of the neck relative to chair and two angles of the head relative to the neck for a total of four conditions were tested for each subject for the 2 peak acceleration levels giving a total of 104 experiments. Instrumentation consisted of 6 accelerometers and two-axis rate gyro at the posterior spinous process of the first thoracic vertebral body, 6 accelerometers at the mouth, and a two-axis rate gyro at the top of the head. Three-dimensional photography from two orthogonally mounted onboard cameras was used also. The input data at T//1 along with the differential effects of initial head position relative to T//1 on the linear acceleration at the origin of the head anatomical coordinate system and on the angular acceleration and angular velocity of the head are presented along with the implications for modeling the response and a statistical comparison. Language: en

: From July through September 1975, a series of ship motion simulation experiments was conducted using the ONR Motion Generator at Human Factors Research, Inc., Goleta, California. The motions were based on the mathematical model for the 2000 ton surface effect ship (2000T-SES). Nineteen volunteer human research subjects, selected at different times from 600 naval enlisted recruits, briefed on NAMRL Detachment research, were exposed to several motion profiles. These subjects were extensively evaluated before acceptance. Those with any medical defects which would place them at extra risk of injury while undergoing biodynamic experiments were excluded. Those with anomalous vestibular response were also excluded. The motions to be experienced were those predicted for a 2000T-SES running in a bow quartering sea in 3 separate conditions: (1) sea state three at 80 knots; (2) sea state four at 60 knots; and (3) sea state five at 40 knots. The subjects were to be run in pairs for 48 hours in each of the three conditions. Performance tasks representative of shipboard activities were administered on a prescheduled basis. The 48-hour motion condition periods were alternated with 48-hour static control periods and 24-hour rest periods. The experimental design called for 12 subjects assuming no voluntary withdrawals. A total of 19 subjects was used, primarily because of volunteer withdrawals following continued emesis. Substantial alternations of the design also occurred due to operational problems with the simulator. For a variety of reasons many runs were undertaken with attenuation of the motion either by a percentage amount or to a selected rms acceleration level.

A series of human experiments has been conducted to measure the response of the head and the first thoracic vertebrae to these parameters. Each subject was run at three conditions defined as high rate of onset-long duration, high rate of onset-short duration and low rate of onset-long duration at peak accelerations of 6, 10 and 15 G. Comparison time profiles of angular acceleration, angular velocity and linear resultant acceleration at the head anatomical origin and horizontal linear acceleration at the T//1 origin are presented for 5 to 8 subjects at each of the three peak sled acceleration levels. Regression coefficients of peak values of the kinematic parameters of onset and duration as defined by the sled profile are developed, as well as coefficients based on similar parameters defined from the profile of linear acceleration at T//1. Language: en

Experimental evidence is presented to document the load-bearing capability of the articular facets which join the vertebrae of the spine together posteriorly. Contrary to the general opinion that these facets carry no vertical load, this paper gives qualitative as well as quantitative data to show that there exists a dual load path along the vertebral column. Extensively instrumented human cadavers were used as test subjects. Strain gages were used to provide qualitative evidence of facets load while a unique intervertebral load cell supplied quantitative information of the load-bearing role of the facets. The results of this study led to a clearer understanding of the mechanism of injury to the vertebral column during +Gz impact acceleration.

This paper discusses the results of a comparison of 41 previously reported test runs and human volunteer runs run by Mertz and Patrick in testing torque versus angular displacement response of the human head to -Gdx impact acceleration. Due to different instrumentation and measuring techniques, there were several differences, but large portions of the data were comparable. The paper points out the need for anatomically based three-dimensional coordinate systems to permit quantitative comparisons between human subjects.