Biomedical subjects

G S Nusholtz

Publications and source records attributed to G S Nusholtz.

9 recordsLinked to original sources

PubMed2003

Studies of neck injury criteria based on existing biomechanical test data.

The mechanisms of injury of the human neck are potentially related to the forces and bending moments acting on the spinal column. An injury criterion that combines the effects of the time history of force and moment, N(ij), has been adopted by the USA federal government for vehicle crash regulations. This paper presents two analytical approaches to evaluate the N(ij) injury criterion using previously published biomechanical data: a direct fit optimization analysis and a statistical analysis. The results show that no values used in the N(ij) criterion corresponding to compressive force, extension moment and flexion moment will optimally separate the injury and non-injury cases in the biomechanical data set. Only the tensile force allows identification of the injury risk. All indications are that increasing the weight given to moment decreases the accuracy of the prediction.

Accidents, Traffic↗

PubMed2003

Air bag effectiveness as function of impact speed.

An investigation was conducted to estimate the effectiveness of air bags as a function of velocity. The study consisted of three parts: a theoretical idealization, an analysis of National Automotive Sampling System/Crashworthiness Data System (NASS/CDS), and a reanalysis of previously published Fatality Analysis Reporting System (FARS) data. The theoretical analysis looked at idealized risk curves as a function of velocity; assuming that the air bag offers a benefit for both belted and unbelted occupants. Analysis of the NASS/CDS data looked at the effectiveness of air bags as a function of velocity for Maximum Abbreviated Injury Scale (MAIS) 3+ injuries. The reanalysis of the previously published FARS data looked at the effectiveness of the air bag as a function of velocity for fatalities. The theoretical analysis indicates that the air bag effectiveness should be greatest at the low velocities. The field data analysis of both NASS/CDS and FARS were consistent with the theoretical analysis, indicating that air bags are most effective at the lower velocities, below 40 kph (25 mph), for both belted and unbelted occupants. Although it was not possible to estimate a different effect for belted and unbelted for fatalities using FARS, it was possible for MAIS 3+ using NASS/CDS. For unbelted occupants the effectiveness goes to zero or becomes negative above 40 kph (25 mph) for MAIS 3+, and for belted occupants the effectiveness stays positive but with significantly lower magnitude for speeds above 40 kph (25 mph).

Abbreviated Injury Scale↗

PubMed1995

Internal cavitation in simple head impact model.

A two-dimensional computational model is used to evaluate the potential for cavitation to occur inside the brain material during head impact. The model represents a simple water-filled 14-cm-diameter, 5-cm-deep cylinder. For the purpose of our study, this cylinder represents the skull while the water inside the cylinder represents the brain material. To ensure that the stress predicted by the model is realistic, it has been calibrated against experimental data. When the cylinder is struck by a free-flying mass cavitation is initiated at the boundary opposite impact. Significant vaporous regions may develop at the boundary, while only limited vaporization occurs internally. Higher accelerations, or an additional loading of the domain by a constant acceleration perpendicular to impact, adds to the likelihood and to the severity of internal cavitation. This indicates that preexisting conditions or complex loading conditions of the head during an impact event may affect the cavitation response. Such conditions could be the result of angular velocity, angular accelerations, or head accelerations as a result of neck loading.

Brain↗

PubMed1995

Cavitation/boundary effects in a simple head impact model.

An experimental and numerical analysis of the impact response of a simple model of the human head is presented. A water-filled 14-cm diameter cylinder was struck by a 10 kg free flying mass. Rigid-body acceleration-time-history and the pressure at the fluid-cylinder interface were monitored during the impact event. Comparisons between the experimental results and the results of a computational model were made. The computational model used is a two-dimensional finite difference code simulating the physical experiment. The code incorporates a thin layer of air and the potential for vaporization along the inside of the cylinder. The study indicates that during a severe impact to the human head, the stresses generated within the brain can result in cavitation on the far side of impact followed by a sudden cavity collapse which can be quite violent. The study identifies how a skull-brain interface and cavitation can potentially affect the internal pressure response of the brain when subjected to a sudden impact.

Acceleration↗

PubMed1987

Two factors critical in the pressure response of the impacted head.

The response of the head to blunt impact in the posterior-to-anterior direction (+Gx) was investigated using anesthetized Macques (Macaca mulatta). Three-dimensional motion and epidural pressures were measured. The data were analyzed in the time domain using time histories and auto- cross-correlation functions; in the frequency domain, transfer functions were used. The results of the tests demonstrate that: 1) the thermodynamic response (fluid vaporization) of the cerebrospinal system is an important consideration when the impact produces significant tension, and 2) the interaction of the neck and the skull affects both the stresses produced in the brain and the injury response. These results are important for both the mathematical modeling of head trauma and establishing the injury tolerance of the head.

Acceleration↗

PubMed1987

Comparison of epidural pressure in live anesthetized and post-mortem primates.

The response of the head to impact in the posterior-to-anterior direction was investigated with live anesthetized and post-mortem primates. The study was conducted at the University of Michigan Transportation Research Institute (UMTRI) under the sponsorship of the Motor Vehicle Manufacturers Association. 3-D motion and epidural pressures were experimentally measured. Interpretation of the results by simulating the tests using a 3-D mathematical model of the primate brain was done by Dr. C. Ward. The results of the tests and the simulation are presented to demonstrate the differences found between live and post-mortem primate brains.

Animals↗

PubMed1986

Cervical spine biomechanics: a review of the literature.

This article reviews the many clinical and laboratory investigative research reports on the frequency, causes, and biomechanics of human cervical spine impact injuries and tolerances. Neck injury mechanisms have been hypothesized from clinically observed cervical spine injuries without laboratory verification. However, many of the laboratory experiments used static loading techniques of cervical spine segments. Only recently have dynamic impact studies been conducted. Results indicate that crown-of-head impacts can routinely produce compression of the neck with extension or flexion motion. However, the two-dimensional (midsagittal) movement of the head bowing into the chest does not routinely produce flexion/compression type damage to the cervical spine. Flexion/compression damage to the cervical spine can be produced by prepositioning the subject so that upon impact, a three-dimensional motion of the head and neck occurs. Future laboratory research is needed to determine the forces and impact directions required to produce the various known fracture types and dislocations for a clear, accurate description of the cervical spine impact dynamics.

Accidents, Traffic↗

PubMed1986

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.

Abdomen↗

PubMed1986

Pelvic stress.

Biomechanics testing simulated stress concentrations in the acetabulum resulting from a blow to the right trochanter, as commonly occurs in recreational and passenger contexts. Developing tolerance criteria for the pelvis is addressed in this paper in terms of the load distribution and energy transmission to the pelvis via both soft tissues and the femur, the instability of the femur-pelvis complex, and the difficulty of predicting stress using simple, experimentally derived, parameters.

Biomechanical Phenomena↗