Injury in America A Continuing Public Health Problem (1985) / Chapter Skim
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4 Injury Biomechanics and the Prevention of Impact Injury
4 Injury Biomechanics and the Prevention of Impact Injury
Pages 48-64
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From page 48... ...
Even if there is recovery from structural injury, normal physiologic function does not always return. For example, bony fractures can heal, but associated damage to the central nervous tissue might result in a permanent loss of motor and sensory function.
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From page 49... ...
· Impulsive impact, such as by violent sternal motion that deforms the heart beyond its viscous tolerance and causes contusion and rupture. · Acceleration of the skeleton and tearing of internal organs, because of their inertia; for example, during head impact, the skull accelerates and the loosely attached brain lags,..
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From page 50... ...
Knowledge of injury mechanisms is fundamental to the science of in jury biomechanics, because it points to the appropr late biomechanical measurements that characterize injuries. The human body has viscoelastic tissues that absorb energy and protect vital organs from the effects of impact.
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From page 51... ...
6 2 The two main types of strain (Figure 4-2) that can damage tissue are tensile strain and shear strain; a third type is compressive strain, which is responsible for crushing injuries.
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From page 52... ...
Axial impact on the femur causes an increase in its curvature, tensile strain on its enter for surface, and compressive strain on its posterior surface. Midshaft failure of the femur occurs when the tensile strain exceeds the recoverable limit.
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From page 53... ...
RESEARCH NEEDS Injury Mechanisms Gaining knowledge of the mechanisms of injury is the first step in injury biomechanics research. It permits an understanding of the deformations associated with gross anatomic lesions or damage to biologic tissues that result in functional change.
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From page 54... ...
Although noninjurious responses can be measured in volunteer experiments, the basic study of impact responses must use surrogate humans. The primary research tools to evaluate injurious biomechanical responses are human cadavers and anesthetized animals that are exposed to impact and detailed response measurement.
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From page 55... ...
Determination of human tolerances to impact is complicated by many factors, including the magnitude, direction, distribution, duration, and pulse shape of the force of the impact; the body orientation; tightness and configuration of restraint; and structure of the striking object. Biologic factors may also influence human tolerance, including sex, age, physical and mental condition, and body size.70 ~° i94 Individual variability must be considered, because tolerance under identical test conditions can vary in the same person, as well as from one person to another.
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From page 56... ...
For anatomic injur ies , the predictive capacity of dummy tests is marginal. More important, current dummies cannot be used to evaluate functional changes that result in severe cognitive dysfunction, in quadriplegic, or in fatal ventricular fibr illation .
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From page 57... ...
Alcoholic beverage use that produces even moderate or low blood alcohol concentration can signif icantly increase the fatality rate associated with cardiac injury and the debilitating effects associated with CNS damage. Physiologic experiments have demonstrated a higher fatality rate associated with a combination of acute alcoholic-beverage use and blunt thoracic impact than that associated with impact alc~ne.~°' A
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From page 58... ...
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From page 60... ...
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From page 61... ...
The frequency of head impact is high, and the consequences of brain damage are severe.'s ' t ~ 2 ~ ~ ~ O ~ ~ ~ ~ S 7 Of similar importance is development of response and tolerance data on the spinal cord. The seriousness of quadriplegic is obvious, and useful measures of the r isk of damage to the central nervous system are needed.
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From page 62... ...
A multidisciplinary approach to injury biomechanics research should be coordinated to include: · Injury investigation, in jury-mechanism study, biomedical research on response and tolerance, study of pathophysiologic response to impact, and research on disabling injuries, particularly to the central nervous system. · Support for the training of scientists and engineers in injury biomechanics, to overcome a serious shortage of such workers.
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From page 63... ...
Central nervous system, where the accurate measurement of linear and angular acceleration is needed for use in b~omechanics exper iments . · Thoracic viscera, including motion of internal organs and vessels that leads to injury.
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From page 64... ...
64 · Survival of extreme impact, to provide a better basis for understanding the limits of tolerance.
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