IIHS research bibliography

The Insurance Institute for Highway Safety (IIHS) has been measuring head injury criterion (HIC), a measure based on linear impact skull fracture data, to assess head injury risk in its front crash tests since 1995. In 2012, IIHS added instrumentation to measure brain injury criterion (BrIC), a rotationally based injury measure derived from animal data correlated to humans through computational modeling. BrIC is intended to complement HIC rather than replace it. Head injury risk associated with HIC and BrIC values measured with a Hybrid III dummy in 138 front crash tests was compared with real-world injury rates in similar frontal crash configurations calculated from the National Automotive Sampling System Crashworthiness Data System (NASS CDS) database. NASS CDS identified 1.3-5 percent AIS3+ head injury rates in crashes similar to the test configurations. The mechanisms of injury represented by HIC and BrIC are a subset of all head injuries; therefore, the NASS-indicated head injury rates inherently may be an overprediction of injuries directly applicable to these formulas. In crash tests, HIC AIS3+ head injury risk ranged 0-22 percent and BrIC AIS3+ head injury risk ranged 3-85 percent. BrIC AIS3+ head injury risk greater than 50 percent was associated with a variety of head kinematic events including front airbag loading, head contact with instrument panel, and non-contact forward excursion. The published injury risk curve for BrIC indicates that crash tests represent significantly higher serious head injury risk than observed in real-world crashes of similar configurations. Hybrid III may produce exaggerated measures of BrIC or, if accurate, the BrIC formula may need to be reexamined against the underlying animal test data to determine the limitations of BrIC, and the proposed injury risk curves need to be re-evaluated against real human injury risk. Despite its origins as an indicator of skull fracture risk, the range of HIC-based head injury risk observed in crash tests more closely reflects the real-world head injury rates than the range of BrIC-based head injury risk.

An estimated 3,000 fatalities and 8,000 serious head injuries result from head impacts with vehicle upper interior surfaces during crashes each year in the United States. Sun visors occupy a strategic location in motor vehicles for potentially reducing head injuries. Current U.S. regulations require only that sun visors use energy-absorbing padding, allowing manufacturers to specify the characteristics of the padding. In constrast, Australia has a design rule for sun visors with specified performance criteria. Sun visors from 26 different vehicles were tested to compare the relative head injury protection offered by Australian market cars and compariable American market cars. The average head injury criterion (HIC) scores reflect a wide disparity in the energy managing capabilities of the tested visors, ranging from 568 to 2765. Five of the Australian sun visors that produced HIC scores of less than 1000 had U.S. counterparts that produced HIC scores double to quadruple those of the Australian sun visors. The finding of the study clearly indicate that the technology and manufacturing ability exists to produce sun visors that can reduce head impact severity.

Head injuries are the most frequent and most costly of all severe injuries to occupants of motor vehicles, and the upper interior structure of the vehicle is the largest cause of head injury. To reduce the violence of head impacts during crashes, sun visors are required to be covered or constructed with energy-absorbing materials, bur current regulations do not provide a method for evaluating these materials. This paper describes a test method for evaluating the head protective padding in sun visors. The head of a Hybrid III dummy is impacted against the sun visor and the resulting HIC is used to measure head injury potential. Preliminary test results of 20 sun visors from 1991 model cars show a wide variation in the HIC readings measured by the dummy head. 

We collected data on all residents of San Diego County, California who were hospitalized for or died from a brain injury in 1981. The objectives were to assess the frequency of blood alcohol concentration (BAC) testing and the associations of BAC prevalence with the external cause of the brain injury and case outcome. We found that high BAC levels were most frequent among brain-injured subjects between the ages of 25 and 44 and among those subjects involved in motor vehicle crashes and assaults. Contrary to expectations, injury severity and hospital mortality were inversely related to BAC level, controlling for other predictors. We believe that these inverse associations might be due to differential rates of BAC testing by severity. Among brain-injured survivors with more severe injuries, however, we found that BAC level was positively associated with the prevalence of physician-diagnosed neurological impairment at discharge and with the length of hospitalization.

Mild brain injury accounts for a substantial proportion of all persons admitted to a hospital for brain trauma, yet the amount of information on the epidemiology of this problem is quite sparse. Data on mild brain injuries for San Diego County residents injured in 1981 were analyzed for incidence, external cause, prehospital factors, diagnoses, alcohol use, and in-hospital treatment costs. More than 80% of all San Diego County residents hospitalized for an acute brain injury had a mild uncomplicated brain injury: a rate of 130.8 per 100,000 per year. Three quarters of these had an ER Glasgow Coma Scale of 15. Rates are twice as high for males compared to females, with peak occurrence for males at ages 15-19 years. More than 40% of mild brain injuries are caused by motor-vehicle-related events. The most common diagnosis was concussion (80%) or other intracranial injury (14%). Median length of hospital stay was 2-3 days and depended on brain injury diagnosis or Glasgow Coma Scale. Although less than 30% of those aged 15 years and older were blood tested for alcohol, two thirds of those tested had a level of 100 mg% or higher. In-hospital treatment costs for concussion or other mild intracranial injury for San Diego County residents exceeded six million dollars in 1981.

Acute brain injury is the cause of approximately 100,000 pediatric hospital admissions per year in the United States. This report examines the nature of the brain injury, clinical diagnosis, hospital course, and discharge outcome of all pediatric cases in the population of San Diego County, California, for 1981 (N = 709). Brain-injured children were identified from hospital records, death certificates, and coroners' records. Severity of injury was determined using the Abbreviated Injury Scale and the Glasgow Coma Scale. Three percent of brain-injured children died at the accident site; an additional 3% died in the hospital. All in-hospital deaths occurred among the 5% of children with Glasgow Coma Scale scores of 8 or less, and in this group the case fatality rate was 59%. Fractures of the skull, present in 23% of cases, seemed to be associated with excess mortality even after type of lesion was considered. Type of lesion, but not presence or absence of a skull fracture, had some predictive power for disability among survivors. Concussion was the most frequent diagnosis. Mildly brain-injured children accounted for 93% of all cases and about 90% of all hospital days.

We performed a population-based study of bicycle-related brain injuries in San Diego, California, residents during 1981. Incidence rates among males were three times higher than for females and were highest at ages 10-14 years for males. Only one-third of bicycle-related brain injuries involved collision with a motor vehicle, and this proportion was independent of age or gender. Brain injuries from motor-vehicle collisions were more severe than those resulting from other causes. Over half the brain-injured bicyclists aged 15 and older who were blood alcohol tested were legally intoxicated.

Among residents of San Diego County, California the incidence and external causes of serious brain injury were related to the median family income of the census tract of residency. Low income tracts had high incidence rates--a finding not changed by adjustment for age and race/ethnicity. For those injured, the type of emergency transport, time from injury to treatment, and outcome of treatment were not related to the median income of the census tract of residency.

Hospital discharge summary data were used to identify and study all 2,870 Rhode Island residents hospitalized in-state with head injuries during 1979 and 1980. The overall hospitalized incidence rate was 152 per 100,000 of population per year with age and sex variations similar to those found in other studies. This is consistent with the observation that fatal injury rates in Rhode Island are only 75 per cent of the United States average. Hospitalized incidence rates of head injury for the census tracts in the lowest decile of median income were twice those for census tracts in the highest decile. Smaller increases were also observed with increasing population density. Length of hospital stay increased with age. Discharge to chronic care facilities plus in-hospital deaths increased 20-fold with increasing age. In each age group, in-hospital deaths and discharge to chronic care facilities were associated with long hospital stays.

The number of fatal brain injuries and hospital admissions for brain injuries in children up to 15 years old in San Diego County, California, were ascertained from emergency room and hospital records, coroners' reports, death certificates, and nursing home and extended-care records for 1981. The annual brain-injury rate per 100 000 children was 185 (235 for boys and 132 for girls). The major causes of pediatric brain injury were falls (35%), recreational activities (29%), and motor vehicle crashes (24%). The case-fatality ratio was six deaths per 100 injured children. Of those children admitted to a hospital alive, 88% had a mild brain injury and 44% had no evidence of loss of consciousness. Two thirds of children with mild brain injuries and one third of those with serious brain injuries were transported to a hospital in private nonemergency vehicles.

Most studies of head injury incidence have been limited to head-injured people who died or were admitted to a hospital. In the present study, all people with head injuries (skull fracture or injury to the cranial contents resulting in a physician visit or at least one day of disability) regardless of treatment or hospital admission status, were identified from National Health Interview Survey data for the years 1977-1981. Only 16 percent of all head injury cases were admitted to hospitals. Cases not admitted included one-half of those with 3-7 days of bed disability and one-third of those with more than 7 days of bed disability and accounted for one-half of all disability days. Children; members of low income families; and those injured at home, school, or in a recreational setting were less likely to be admitted than others. These finding suggest that current head injury incidence data are markdely incomplete and may contain substantial biases.

Survival time after injury (the time from injury to death) imposes an important constraint on the timing of the delivery of postinjury medical care. From a population-based study of brain-injured people, the survival times in 542 cases with fatal outcomes were studied. Prehospital deaths as well as hospital deaths were included. Survival times were considerably shorter for 95 people with untreatable injuries (Abbreviated Injury Scale level 6) than for the remaining 447 whose injuries were potentially treatable. For the former group, the median survival time was 10 minutes; for the latter, it was 2 hours. For those with potentially treatable injuries, the median time from injury to receiving medical assistance was approximately 30 minutes and 82% received medical assistance within 1 hour of injury. Short survival time was associated with prehospital death, young age, high Injury Severity Score, and having a nonbrain injury as the most severe injury. For patients who arrived alive at a hospital, intracranial surgery was associated with increased survival time.

Little published information is available on the incidence of brain injury from work-related activities. A study of brain injury of residents of San Diego County, California, showed that the overall work-related injury rate for males was 19.8 per 100,000 workers (45.9 per 100 million hours). The incidence rates for male civilian and military personnel were 15.2 and 37.0 per 100,000 workers, respectively. In addition, the annual incidence of such injuries was 9.9 per 100 million work hours for males in the work force (18.5 per 100 million hours for military personnel and 7.6 per 100 million hours for civilians). Among military personnel, more than half of all work-related brain injuries were transportation related, primarily from off-road vehicles. Among civilians, more than half were due to falls. For both the military and civilian groups, work-related brain injury rates were markedly higher among young workers than among older ones.

A survey of 93 nursing homes in and near Rhode Island in May 1982 identified all head-injured patients who were State residents. Nineteen were identified, of whom ten were injured in motor vehicle crashes. The median age was 35 years. The median time since injury was 3 years and increased with age. The prevalence of such patients was 2 per 100,000 population. Except for a recent survey by the Connecticut Department of Health, little is known about the prevalence or duration of nursing home residency after head injury. To obtain such data, nursing homes in and near Rhode Island were surveyed for State residents who were patients because of head injury.

It is axiomatic that decreasing the time from injury to emergency medical treatment will lower the probability of death. However, studies have never addressed total lapsed time as opposed to time from summoning help until medical treatment begins. A population-based study of all incident brain injury cases in San Diego County, California, in 1981 provided this opportunity. Time from injury to initial treatment (whether during emergency transport by paramedics or upon arrival at the emergency room was determined for all persons with a physician-diagnosed brain injury. Outcomes included age- and injury severity-adjusted case fatality rates, neurological limitation rates, and unsatisfactory outcome rates based on the Glasgow Outcome Scale. Time from injury to treatment varied by external cause of injury and method of emergency transport. The most favorable outcome rates were not found among those receiving emergency care in the shortest time (i.e., less than 30 minutes). However, the evidence suggests that those with the most severe brain injuries received emergency care in the shortest time from injury.

Because alcohol intoxication is common among brain-injured patients, we performed this study to determine the extent to which alcohol alters the initial assessment of brain injury severity in these patients by depressing the level of consciousness. The Glasgow coma scale was used to measure the level of consciousness of 257 brain-injured adults admitted to the University of Virginia Hospital, both on arrival in the emergency room and 6 to 10 hours later. Improvement in the level of consciousness between the first and second measurements was significantly related to the blood alcohol concentration on admission. Patients with the highest blood alcohol concentrations showed the greatest improvement. Most of this effect occurred in patients with a blood alcohol concentration of 0.20% or higher. Alcohol intoxication is a potential source of bias in the clinical classification of brain injuries according to severity.

Forty-seven tests were run in which a baseball was pitched at an anthropometric dummy head at speeds of between 95 and 100 mph. Impact configurations included impacts to the front and side of the head with direct and indirect impacts. Tests were run with an unprotected dummy head and with the head protected with various helmets including baseball, football, hockey, bicycle, and motorcycle helmets. Head accelerations were measured for each test and maximum accelerations and Head Injury Criterion (HIC) values computed. The values of maximum acceleration and HIC for the tests to the unprotected dummy head were then correlated with actual injuries received by professional baseball players (without helmets) hit by fast pitches. Head accelerations and HIC values for helmeted tests are also compared to the results for the unprotected head to determine the relative effectiveness of each helmet design in attenuating impact.

Studies on the incidence and epidemiologic features of brain injury and the immediate medical outcomes are few, and published results have serious methodological inconsistencies which prohibit comparisons. This study provides incidence rates of brain injury among the residents of San Diego, California. Cases had clinical confirmation and onset of injury occurred during 1981. The 3,358 cases identified represent a rate of 180/100,000 with males having a 2.2 times higher rate than females. Rates were highest for males aged 15-24 years and, for both genders, those over age 70. Forty-eight per cent of all cases were from transport-related causes, followed by falls (21%) and assaults (12%). Over 11% were dead-on-arrival, and 16% were classified as having moderate or severe brain damage on admission to a hospital. Age- and sex-specific incidence rates varied according to external cause of injury. For example, for most subcategories of motor vehicle crashes and for assaults, the incidence rate was highest among males aged 15-24, while for brain injuries from falls or firearms, highest incidence rates were observed in older age groups. Almost 7% of all cases discharged alive from an acute care hospital had significant neurologic sequelae. The impact of brain injury is discussed as a major unresolved public health problem.

Nursing instructors, aware of the problems in describing levels of consciousness, know how difficult this process can be for inexperienced nurses and nursing students. The authors discuss the Glasgow Coma Scale, a simple, objective, clinical tool for assessing levels of consciousness in head-injured patients. Using this scale should increase the accuracy of neurologic assessments and provide useful clinical information.

The annual incidence rate of facial injuries from vehicle crashes, 278 per 100,000 residents, was determined from a population-based study involving all Dane County, Wisconsin, hospitals with emergency departments. Applying this figure to the U.S. population yields an estimated 625,000 hospital-treated facial injuries from vehicles occurring in the United States each year. Vehicle crashes were the source of a substantial proportion of facial injuries from all causes, and were found to be the single leading cause of the most severe facial lacerations and facial fractures. The majority of injuries were sustained by drivers and other vehicle occupants, and others by bicyclists, motorcyclists, and pedestrians struck by vehicle. Vehicle occupants' faces were most commonly injured by steering wheels and windshields. Technologies which are thought to protect occupants include airbags and nonlacerating windshields, but neither is available in vehicles currently manufactured for sale in the United States.

Head-first free falls of 30 children, 1-10 yr old, and one adult, 21 yr old, were studied 10 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 show that head-first falls of children onto rigid surfaces from heights as low as 2 m can result in serious injuries. Conservative head injury tolerance limits are estimated 10 be 200-250g for peak head acceleration.

Provisional data from the National Center for Health Statistics (42) indicate over 155,000 U.S. deaths in 1975 from all external causes (accidents, suicides, homicides, etc.). The National Health Interview Survey (48) revealed 62,186,000 acute injuries of all types and causes in fiscal year 1974. About 38.4% of those required only medical attention, 16.9% required only restriction of activity, and 44.7% required both medical attention and restriction of activity. Of all acute injuries, about 14% were to the head, including contusion and laceration of surface structures other than the eye, concussion, skull fractures, brain hemorrhage, and intracranial injury plus contusion and laceration (50). The National Center for Health Statistics ( 49) indicates that 1,392,000 uninstitutionalized civilian persons had complete or incomplete paralysis in 1971, with 157,000 of the cases being due to spinal cord injuries, ranking third in importance behind poliomyelitis and stroke. Injuries to the head and spinal cord often result in death or irreversible motor and sensory deficits, epilepsy, psychiatric and emotional disturbances, and a wide variety of neurologic residua. In many respects, persons who survive head and spinal cord injuries present monumental medical problems. Not only are current methods of treatment and restoration limited, but the impact on society is enormous in terms of costs and uses of medical resources. This chapter summarizes head and spinal cord injuries under two aspects: (a) incidence, prevalence, mortality, geographic distributions, time trends in occurrence, and groups at high risk; (b) the areas where knowledge is needed to improve the clinical practice of neurology and neurosurgery. Head injuries are covered first, and then spinal cord injuries.

Some of the problems that currently plaque emergency rooms are outlined, as well as possible solutions. Steps in the emergency room management of maxillofacial injuries are also presented.