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Injury reconstruction is a process of injury analysis which combines both medical and engineering technology to produce a composite picture of injury causation. The process is outlined and the potential applications of this analysis are detailed.

Nineteen sled impact tests were conducted simulating a frontal collision exposure for an unrestrained driver. The deceleration sled buck configuration utilized the passenger compartment of a late model compact passenger vehicle, a rigid driver's seat, and a custom fabricated energy-absorbing steering column and wheel assembly. Sled impact velocities ranged from 24.1 to 42.6 km/hr. The purpose of the study was to investigate the kinematic and kinetic interaction of the driver and the energy-absorbing steering assembly and their relationship to the thoracic/abdominal injuries produced. The similarities and differences between human cadaver and anthropomorphic dummy subjects were quantified.

This paper represents a continuation of previous research on closed head impact in the human cadaver and an associated mathematical model. The long term goal of the study is to describe the relationships between head impact events which might be useful in understanding what takes place in the living human. In the current study, two different sets of experiments were conducted 1) sequential impacts on a single embalmed helmeted specimen and 2) impact experiments on individual helmeted unembalmed specimens. Impact parameters and intracranial pressures were measured and discussed. A finite element model is presented which can predict the intracranial pressures throughout the brain for the first 8 msec. It is apparent that the helmet prevents high magnitude, short duration intracranial pressures and that posterior pressures develop after the, acceleration phase and helmeted impacts.

Two series of cadaver head impact experiments are presented. Series I consists of individual experiments and Series II multiple sequential impacts on a single specimen. Measured intracranial pressures were correlated with other impact parameters. The use of a linear finite element model is also presented.

A series of blunt head impacts has been performed on stationary unembalmed human cadavers. The specimens were prepared to simulate realistic fluid pressures within the cerebrospinal fluid space and cerebral blood vessels. Translational acceleration-time histories of the head were recorded by biaxial accelerometers attached to the skull. Peak resultant head accelerations in excess of 3,000 m/s2 and pulse durations of 5 ms. or less were observed in a series of 10 experiments. The cerebral vascular system was perfused with a carbon particle tracer solution. Following impact, careful gross and microscopic pathologic studies of the cranial soft tissues were performed to assess vascular hemorrahage as represented by extravasation of tracer solution into the brain tissue. Data is presented describing the input forcing function, resultant head acceleration, and detailed necropsy findings.

Sternal and/or spinal acceleration data from eighteen of the unembalmed cadaver, blunt thoracic impact experiments reported by the authors at the Eighteenth Stapp Conference have been analyzed and several related response parameters computed. High acceleration levels, rates of onset, and Gadd Severity Indices were found in sternal acceleration measurements, whereas quite low values were obtained from the spinal regions in the same tests. A Severity Index value of 1000, computed from a sternal acceleration measurement, would be associated with only a mild exposure; whereas for a spinal measurement, the same value would reflect an extremely severe exposure. Correlation matrices which include cadaver characteristics, input and response parameters, and Abbreviated Injury Scale ratings show that none of the sternal acceleration parameters correlate well with AIS rating in the analyzed data base.

Previous studies of human thoracic injury tolerance and mechanical response to blunt, midsternal, anteroposterior impact loading were reported by the authors at the 1970 SAE International Automobile Safety Conference and at the Fifteenth Stapp Car Crash Conference. The present paper documents additional studies from this continuing research program and provides an expansion and refinement of the data base established by the earlier work. Twenty-three additional unembalmed cadavers were tested using basically the same equipment and procedures reported previously, but for which new combinations of impactor mass and velocity were used in addition to supplementing other data already presented. Specifically, the 43 lb/11 mph (19.5 kg/4.9m/s) and 51 lb/16 mph (23.1 kg/7.2 m/s) conditions were intercrossed and data obtained at 43 lb/16 mph (19.5 kg/7.2 m/s) and 51 lb/11 mph (23.1 kg/4.9 m/s).

This paper presents conclusions of a study of rollover collisions and the injuries resulting from them. The injury severity, the type of injury, the body region injured, the frequency of injury, and the injury mechanism are all indicated. The study includes statistics on both restrained and unrestrained occupants, and shows that ejected occupants usually sustain more severe injury than contained occupants. Several conclusions are presented as to automobile structures in relation to injury.

At the 1970 SAE International Automobile Safety Conference, the first experimental chest impact results from a new, continuing biomechanics research program were presented and compared with earlier studies performed elsewhere by one of the authors using a different technique. In this paper, additional work from the current program is documented. The general objective remains unchanged: To provide improved quantification of injury tolerance and thoracic mechanical response (force-time, deflection-time, and force-deflection relationships) for blunt sternal impact to the human cadaver. Fourteen additional unembalmed specimens of both sexes (ranging in age from 19-81 years, in weight from 117-180 lb, and in stature from 5 ft 1-1/2 in to 6 ft) have been exposed to midsternal, blunt impacts using a horizontal, elastic-cord propelled striker mass. Impact velocities were higher than those of the previous work, ranging from 14-32 mph.

Automobiles damaged in collisions in which the main vehicle structure has been underridden or overridden were studied, as well as injuries to occupants of the automobiles. The parameters that affect injuries are listed and discussed, as are the effects of these parameters for each case example. Recommendations are made for modifications of passenger cars, trucks, trailers, and highway furniture to mitigate the severity of injury in underride-override collisions.

Utilizing unembalmed cadaver test subjects, a series of tests was carried out to characterize quantitatively the resistance of the skin, the soft underlying tissue of the scalp, and certain other typical areas of the body to impact loading. The impacts were delivered by the use of an instrumented free-fall device similar to that previously employed for facial bone fracture experiments. In one group of tests, metal and glass edges were affixed to the impacting device to produce localized trauma under conditions which were standardized with respect to variables affecting the degree of the injury. In the second group of experiments, specimens of skin, together with underlying tissue of uniform thickness, were subjected to compressive impact between the parallel surfaces of the impacting weight and a heavy metal platen. From these latter experiments the force-time histories, coefficient of restitution, and hysteresis loops of load versus deflection were obtained for the specimens.

The paper represents a distillation and analysis of collision injury cases collected by the UCLA Trauma Research Group from 1960-1969. Injuries are interpreted with relation to specific variables which are thought to represent important factors in collision injury causation and prevention. The methodology is presented as one possible way to view transportation trauma in terms of factors which can be isolated and may lend themselves to manipulation in the cause of traffic safety.

Restraining devices continue to be the most effective means of lessening injuries in automobile collisions. Evidence from the Trauma Research Group's case files illustrates how injury is avoided or minimized by use of lap, shoulder, and diagonal seat belts in several types of crashes, under various angles of impact. Prevention of fatal ejection, the improved chances a restrained driver has of retaining control of his car, and the attenuation of interior collision forces, such as result in jackknifing, are topics discussed, as well as the contribution of major automobile design improvements.

By duplication of glass fracture patterns, the feasibility of relating 22 lb headform impacts to head injuries sustained by occupants contacting the windshield in crashed vehicles has been established. For each suitable windshield sample selected from available 1966 to 1969 crashed automobiles, a vehicle analysis was performed. The unbroken sections of 33 selected windshields were subjected to dynamic loads using the 22 lb portable headform. This portable device mounted in a van is described. At impact, the deceleration and velocity were measured and lacerations rated on the basis of damage to simulated tissue and moist chamois. Achievement of duplication between headform and occupant head impacts permits a numerical assessment of windshield lacerative injuries and presents a tentative method for future programs involving correlation between laboratory and service performance.

A study was made of 290 collisions containing 464 front seat car occupants. Of the 405 injured occupants, 141 received their lower extremity injuries against the instrument panel. The occupant’s most serious injury was related to car model year, age of occupant, vehicle weight, and estimated impact speed. Statistically, a regression analysis shows a very strong correlation of these variables and collision injury. It is significant that the number of lower extremity injuries drops steeply for vehicles from 1957 through 1967. Rear seat occupant injuries were not considered in this paper.

Forces necessary for fracture under localized loading have been obtained experimentally for a number of regions of the head. Three of these, the frontal, temporoparietal, and zygomatic, have been studied in sufficient detail to establish that the tolerances are relatively independent of impulse duration, in contrast with the tolerance of the brain to closed-skull injury. Significantly lower average strength has been found for the female bone structure. Other regions reported upon more briefly are mandible, maxilla, and the laryngotracheal cartilages of the neck. Pressure distribution has been measured over the impact area, which has been 1 sq in. in these tests, and the relationship between applied force as measured and as predicted from a head accelerometer is examined.

The types and mechanisms of head injury are reviewed, and then the findings of a UCLA study on the electrophysiology of primate concussion is presented. It was found that g loadings, as measured by a triaxial accelerometer attached to the skull of an impacted monkey, correlated well with severity of concussion. Deep and superficial cerebral electrodes were implanted to monitor electroencephalographic and impedance changes after concussion. Resistance dropped and capacitance rose in the impedance electrodes in direct proportion to the severity of concussion. Deep electroencephalographic recordings showed a high amplitude low frequency charfge in the reticular formation areas after impact. Superficial electroencephalographic recordings did not correlate with clinical states. Applications of these data are presented as they relate to the prevention and treatment of head injury.

Forty-six automobile collisions with 82 child occupants have been studied. Emphasis was placed on the mechanism of injury production and child collision kinematics. A number of case examples illustrate these injury patterns. Also included are example cases of the effects of collisions in pregnancy and cases of restrained children. Childhood growth characteristics as they affect injury patterns and restraint systems are discussed in detail. An analysis of current types of restraint systems is included and recommendations are made. Collision and comfort-convenience requirements of an “ideal” restraint system are listed.

Cardio-thoracic injuries comprise a significant segment of the injuries sustained in automobile collisions. Because of the urgent need for additional information which can lead to prevention of these injuries, The Vehicle Trauma Research group at the UCLA School of Medicine has instituted a medical-engineering study of these injuries. The study has attempted to correlate pathophysiologic aspects of the injuries with the kinematics and biomechanics of the collision. Particular attention has been paid to the effects of restraining devices and the relationship of injuries of various wheel-column configurations including “energy absorbing” designs. Sixty-seven cases have been completely analyzed to date and are presented as a preliminary pilot study illustrating the value of this type of approach to auto collision injuries.

A study was made of 54 collisions resulting in injuries to rear-seat occupants unrestrained by seatbelts. It was determined that children (who represent a disproportionate percentage of rear-seat occupants) tend to become airborne and to incur severe injuries against the windshield, miror, dashboard and header. Adults tend to injure the face and head against the front seat and to sustain typical leg fractures from trapping their feet under the front seat. The occupants seated at the outside edges of the rear seat sustain dangerous injuries from metal ashtrays and window crank handles out of proportion to the severity of the collision. All unrestrained rear-seat occupants add to the injuries of front-seat occupants by hurtling into them. Terminology to describe the types and severity of collisions is offered to facilitate medical and engineering evaluation of injuries. Recommendations are made for design changes to lessen hazards.