Guy S. Nusholtz

Cervical Spine Injury Mechanisms

A test series using eight unembalmed cadavers was conducted to investigate factors affecting the creation of cervical spine damage from impact to the crown of the head. The crown impact was accomplished by a free-fall drop of the test subject onto a load plate. The load plate striking surface was covered with padding to vary the contact force time characteristics. The orientations of the head, cervical spine, and torso were adjusted relative to a laboratory coordinate system to investigate the effects of head and spinal configuration on the damage patterns. Load and acceleration data are presented as a function of time and as a function of frequency in the form of mechanical impedance. For the covering abstract of the conference see HS-036 716. (Author/TRRL)

RESPONSE OF THE CERVICAL SPINE TO SUPERIOR-INFERIOR HEAD IMPACT

A test series using 12 unembalmed cadavers was conducted to investigate factors affecting the creation of cervical spine damage due to impact to the top of the head. The test subjects were instrumented to measure head, T8 thoracic spine, and sternum acceleration responses. Photographic targets on the head and torso allowed analysis of impact motions from high-speed movies. The stationary test subject was struck by a guided, moving impactor mass of 56 Kg at 4.6-5.6 m/s. The impactor striking surface consisted of a biaxial load cell with padding to vary the contact force-time characteristics of the head/impactor. The orientation of the head, cervical spine, and torso was adjusted relative to the impactor axis to investigate the effect of spinal configurations on the damage patterns. Load and acceleration data are presented as functions of time and as functions of frequency in the form of mechanical impedance. Damage to the cervical spine was produced in all but one test, including fractures of the spinous processes, laminae, transverse processes, and the bodies of the vertebrae as well as ruptured discs and torn ligaments. Both anterior and posterior damage was produced and the sites of the damage ranged from C2 to T4. The peak forces produced during the impacts ranged from 1.8 kN to 11.1 kN. The limited response data of this pilot study do not allow any specific conclusions with regard to cervical spine tolerance levels. However, it does attest to the influence of spinal configuration and impact conditions on both response and damage of the spine due to crown impact.

HEAD AND NECK RESPONSE TO AXIAL IMPACTS

Two series of impacts to the head in the superior-inferior direction using 19 unembalmed cadavers are reported. The first series of five tests was aimed at generating kinematic and dynamic response to sub-injurious impacts for the purpose of defining the mechanical characteristics of the undamaged head-neck-spine system in the S-I direction. The second series of fourteen tests was intended to define injury tolerance levels for a selected subject configuration. A 10-kg impactor was used to deliver the impact to the crown at a nominal velocity of 8 m/s for the first series, and between 7 and 11 m/s for the second series. Measurements made include the impact velocity, force, and energy, the head three-dimensional kinematics, forces and moments at the occipital condyles, and accelerations of the T1, T6, and T12 vertebrae.

Head impact response - skull deformation and angular accelerations

The response of the head to impact was investigated using live anesthetized and post-mortem Rhesus monkeys and repressurized cadavers. The stationary test subject was struck by a guided moving impactor. The impactor striking surface was fitted with padding to vary the contact force-time characteristics. The experimental technique used a nine-accelerometer system rigidly mounted on the head to measure head motion, transducers placed at specific points below the skull to record epidural pressure, repressurization of both the vascular and cerebral spinal systems of the cadaver model, and high-speed cineradiography of selected test subjects. The results of the tests demonstrate the potential importance of skull deformation and angular acceleration on the injury produced in the live Rhesus and the damage produced in both the post-mortem Rhesus and the cadaver as a result of impact. Language: en

REPEATABILITY EVALUATION OF THE PRE-PROTOTYPE NHTSA ADVANCED DUMMY COMPARED TO THE HYBRID III

A comparison of the NHTSA advanced dummy and the Hybrid III is presented in this paper based on their performance in repeated sled tests under 3 different restraint systems. The restraint systems considered are: the airbag alone, the 3-point belt alone, and a combined use of the airbag and the 3-point belt. Various time-histories pertaining to accelerations, angular velocities, deflections and forces have been compared between the two dummies in order to study their repeatability. The Hybrid III appears to be more repeatable than the NHTSA advanced dummy in its response in one case, that of restraint with the 3-point belt alone. The response of the NHTSA advanced dummy in two other restraint modes, the airbag alone and the combination of 3-point belt and airbag, appears to be no less repeatable than that of Hybrid III in this series of tests. The variability in the sled pulse appears to mask the differences, if any, in the variability of response between the two dummies in two later cases. Under some restraint configurations, for some body segments, the NHTSA advanced dummy appears to show better repeatability. In addition, it appears that the read-out of the chest-deflection measurement system in the NHTSA advanced dummy is not well defined because it is influenced by the rotation of the upper spine relative to the lower spine. (A) For the covering abstract see ITRD E106439.

Head impact response comparisons of human surrogates

The response of the head to impact in the posterior-to-anterior direction was investigated with live anesthetized and post-mortem primates. The purpose was to relate animal test results to previous head impact tests conducted with cadavers and to study the differences between the living and post-mortem state in terms of mechanical response. The three-dimensional motion of the head, during and after impact, was derived from experimental measurements and expressed as kinematic quantities in various reference frames. This paper uses an additional method for describing the kinematics of head motion through the use of Frenet-Serret frame fields. The experimental technique used a nine-accelerometer system, mounted rigidly to the head, to measure head motions. Additional measurements included impact force, epidural pressure, and strains in the skull bone. Language: en

COMPARATIVE PERFORMANCE EVALUATION OF THOR AND HYBRID III

A comparison of the NHTSA advanced dummy, THOR, and the Hybrid III dummy is presented in this paper, based on their performance in four vehicle barrier tests, six HYGE sled tests and twenty-two pendulum chest-impact tests. Various time-histories pertaining to accelerations, angular motions, deflections, forces and moments are compared between the two dummies in light of their design difference. In general, in the vehicle crash tests, the resultant head acceleration and chest deflection in THOR are greater than those in the HYBRID III. The shear, axial force and lateral moment in THORs lumbar are less than those in the Hybrid III in frontal impacts. The differences in the head/chest acceleration and chest deflection could be due to the differences in the construction of the neck and the thorax of the THOR when compared to those of the Hybrid III. The THOR and the Hybrid III have the same level of repeatability in the rear impact sled tests. The THOR is less repeatable in tests involving pendulum impacts on the chest. No major durability problems were identified in the THOR. The construction of the THOR is much more complex than that of the HYBRID III. In order for the THOR to be as easy to use as the HYBRID III, greater effort is needed to improve convenience in terms of data processing, documentation and handling. (A) For the covering abstract see ITRD E106349.

TECHNICAL SPECIFICATIONS OF THE SID-IIS DUMMY

A new dummy, the SID-IIs, a small (s) second generation (II) side impact dummy (SID) is reported. The SID-IIs is being developed to: 1) help evaluate proposed side impact countermeasures, such as side airbags, for the smaller segment of the population. This smaller segment includes both children and small adults; 2) help harmonize between existing side impact dummies toward one design worldwide by offering the begining of a family of biofidelic Anthropomorphic Test Devices (ATD) with as much worldwide input as possible. The dummy weighs 43.5 kg, is 790 mm high and has over 100 data channels available.

THE INFLUENCE OF IMPACT ENERGY AND DIRECTION ON THORACIC RESPONSE

A test series using unembalmed cadavers was conducted to investigate thoracic response differences in lateral impacts between high energy (rib fractures produced) and low energy (no rib fractures produced) testing and also the response to low energy impacts for different impact directions (frontal, 45 degrees, and lateral). Five of the test subjects were instrumented with a nine-accelerometer package and an eighteen-accelerometer array to measure thoracic response. Seven of the test subjects were instrumented with a triaxial accelerometer on the head and a six-accelerometer array to measure thoracic response. Impact events were performed with either the UMTRI pendulum impact device or the UMTRI pneumatic impact device. The subject was struck with a free-travelling mass (25 or 56 kg) which was fitted with either a 15 cm round or 20 cm square rigid metal surface. For different impact tests this surface had affixed to it various materials which would produce different force-time and load distribution characteristics. For the covering abstract of the conference see HS-036 716. (Author/TRRL)

Use of quadruped models in thoraco-abdominal biomechanics research

Pigs and dogs have become common models of human thoraco-abdominal impact response. This paper summarizes a comparative analysis of the dog and pig to the live human accomplished through a series of necropsies performed on pigs and dogs. The results are summarized below. Emphasis is placed on specific aspects which are felt to be important for impact biomechanics. In particular, emphasis is placed upon the effect of tethering structures because of their potential in explaining mechanisms of injury for specific types of trauma such as aortic and certain liver injuries. Some aspects of tethering in the pig and dog are significantly different from that of the live human so care should be taken when using these animals in thoraco-abdominal biomechanics experiments.