Front Passenger Research Articles

An unusual case of irreducible knee dislocation

A 37-year-old man presented to the Accident and Emergency Department following a high-velocity road traffic accident in which he was thrown out of the front passenger seat of a car. His injuries included a ruptured left hemidiaphragm, ruptured spleen, open left forearm fracture, multiple fractured ribs and degloving of the left thigh extending to the perineum. His left knee was clinically dislocated with no palpable distal arterial pulses and poor capillary return in that foot. There was no neurological deficit. Following resuscitation, urgent attempts at closed reduction of the knee under general anaesthesia and full muscle relaxation failed. Radiographs of the knee showed interposition of the patella into the lateral compartment of the knee joint (Figure 1). After surgical treatment of the thoracoabdominal injuries, an open reduction of the knee through a midline incision was therefore carried out. There were complete ruptures of both the cruciate ligaments and the posterolateral structures, including the lateral collateral ligament of the knee. Vastus medialis, the anteromedial capsule and the medial part of the quadriceps tendon were torn. The patellar tendon and the medial collateral ligament were intact. The patella was retracted to allow reduction of the knee joint and the quadriceps tendon was repaired. Arterial pulses in the leg subsequently became palpable and digital subtraction arteriography was normal. The knee was stabilized using an anteriorly placed Shearer external fixator in 20” flexion. Four compartment fasciotomies were also performed. Postoperative radiographs confirmed successful reduction (Figure 2). Discussion

Airbags and children: A spectrum of C-spine injuries

Over 30 children who were improperly restrained or in rear facing safety seats have been reported killed in motor vehicle accidents (MVA) involving airbags. The authors report one minor and two major injuries in properly restrained children in the front passenger seat. In case 1, A 10-year-old seatbelted boy was involved in an MVA (40 km/h) with deployment of both airbags. Physical examination findings showed right hyphema with corneal abrasion, right cheek abrasion and minimal cervical tenderness. C-spine x-ray was normal. He was treated for whiplash and facial burns resulting from contact with hot gas released by the airbags and discharged. In case 2, a 4-year-old boy wearing a lapbelt was in a MVA (20 km/h) with airbag deployment. On arrival, his Glasgow coma score was 3 and he was hemodynamically unstable. Secondary survey after stabilization showed left neck abrasions and ecchymoses, quadraplegia, priapism, and absent rectal tone. C-spine x-ray showed atlanto-occipital dislocation with possible complete spinal cord transection at C 1. Aggressive maneuvers were witheld, and the patient was pronounced dead. Autopsy findings confirmed the clinical diagnosis. In case 3, a 3-year-old boy in a forward-facing safety seat was in a MVA (60 km/h) with air bag deployment. The patient was fully awake. C-spine x-rays were normal. Because of fluctuating level of consciousness, he underwent head computed tomography (CT) scan, which demonstrated a posterior fossa subarachnoid hemorrhage and a hematoma posterior to the odontoid, suggesting a ligamentous tear. He remained asymptomatic and was discharged on day 6. A head CT scan at 1 month showed a periosteal reaction in the area of the alar ligament suggestive of partial ligamentous avulsion; this injury was the forerunner of atlanto-occipital dislocation. Airbags deploy by releasing a hot effluent at 300 km/h. Mechanisms of injury include direct contact of hot gas with facial skin and energy transmitted directly from the airbag system to the child's head and neck. These cases illustrate a spectrum of C-spine injuries caused by airbag deployment and support the recommendation that children under 12 years of age travelling in a car equipped with dual airbags be seated in the back.

Reductions in Deaths in Frontal Crashes Among Right Front Passengers in Vehicles Equipped With Passenger Air Bags

Virtually all new cars now are equipped with passenger air bags. Determining whether passenger air bags are saving lives is important, particularly because passenger air bags have caused some deaths among children and adults. To assess the effectiveness of passenger air bags in reducing the risk of death in frontal crashes for right front passengers. Air bags are designed to protect occupants in frontal crashes. Using Fatality Analysis Reporting System data for calendar years 1992 through 1995, the relative frequency of right front passenger deaths in frontal vs nonfrontal fatal crashes was compared for cars with dual air bags and for cars with driver-only air bags. Odds of right front passengers dying in frontal compared with nonfrontal fatal crashes were computed for 1992 through 1995 model year cars with dual air bags and for cars with driver-only air bags. Percentage reductions in right front passenger deaths in dual air bag vehicles were estimated. Right front passenger fatalities were 18% lower than expected in frontal crashes of cars with dual air bags and 11% lower in all crashes. An estimated 73 fewer than expected right front passengers died in 1992 through 1995 model cars with dual air bags during 1992 through 1995. The risk of frontal crash death for right front passengers in cars with dual air bags was reduced 14% among those reported to be using belts and 23% among belt nonusers. Children younger than 10 years in cars with dual air bags had a 34% increased risk of dying in frontal crashes. Passenger air bags were associated with substantial reductions in fatalities among right front passengers in frontal crashes. However, more children are being killed than are being saved by air bags. Immediate countermeasures to reduce the dangers of air bags to children and adults are suggested.

The Cost-effectiveness of Air Bags by Seating Position

Motor vehicle crashes continue to cause significant mortality and morbidity in the United States. Installation of air bags in new passenger vehicles is a major initiative in the field of injury prevention. To assess the net health consequences and cost-effectiveness of driver's side and front passenger air bags from a societal perspective, taking into account the increased risk to children who occupy the front passenger seat and the diminished effectiveness for older adults. A deterministic state transition model tracked a hypothetical cohort of new vehicles over a 20-year period for 3 strategies: (1) installation of safety belts, (2) installation of driver's side air bags in addition to safety belts, and (3) installation of front passenger air bags in addition to safety belts and driver's side air bags. Changes in health outcomes, valued in terms of quality-adjusted life-years (QALYs) and costs (in 1993 dollars), were projected following the recommendations of the Panel on Cost-effectiveness in Health and Medicine. US population-based and convenience sample data were used. Incremental cost-effectiveness ratios. Safety belts are cost saving, even at 50% use. The addition of driver's side air bags to safety belts results in net health benefits at an incremental cost of $24000 per QALY saved. The further addition of front passenger air bags results in an incremental net benefit at a higher incremental cost of $61000 per QALY saved. Results were sensitive to the unit cost of air bag systems, their effectiveness, baseline fatality rates, the ratio of injuries to fatalities, and the real discount rate. Both air bag systems save life-years at costs that are comparable to many medical and public health practices. Immediate steps can be taken to enhance the cost-effectiveness of front passenger air bags, such as moving children to the rear seat.

Reductions in deaths in frontal crashes among right front passengers in vehicles equipped with passenger air bags

Reductions in deaths in frontal crashes among right front passengers in vehicles equipped with passenger air bags

Auto safety advice

There has been increasing media coverage about the dangers of air bags when infants, small children, pregnant women and short stature drivers are placed in the front passenger seat. Although it is fitting that the public be aware of such risks, we are deeply concerned that the well-established benefits of air bags are being overlooked by this intense media coverage. Air bags are performing well overall. They saved an estimated 1,100 lives during 1986-1995. Driver side air bags in passenger cars reduce overall fatality risk by an estimated 11 percent, including a 30 percent reduction in fatalities in head-on crashes.

The use of feedback signs to increase observed daytime seat belt use in two cities in North Carolina

Well publicized enforcement programs in North Carolina have raised seat belt use to about 80%. In an effort to find techniques to raise belt use further, signs providing feedback to drivers on belt use rates were introduced in two communities, Asheboro (population 18,000) and Greensboro (population 183,000). Feedback signs remind motorists about belt use and imply a constant and vigorous enforcement presence. The signs were prominently posted by the roadside at high volume locations; belt use information was changed weekly based on observational surveys. Observed daytime driver belt use in Asheboro increased from an average of 75% before the signs to 89% after the signs were established. At urban sites in Greensboro, driver belt use increased from 80% to 86%. Right front passenger belt use increased significantly in Asheboro but not in Greensboro. There were no changes in belt use at two interstate exit sites in Greensboro. Reasons for the differential success rates may relate to differences in initial belt use rates, community size, amount of publicity, and numbers of encounters with the signs. It is clear, however, that feedback signs can be an important supplement to belt use enforcement programs.

Age Differences in Visual Abilities in Nighttime Driving Field Conditions

This study was conducted to provide field data on age differences in sign legibility and object detection. Two age groups of healthy drivers with normal vision were tested for nighttime visual ability. The older group had an average age of 65.6 years and the younger group averaged 22.5 years. The field study was conducted on a private road with the subjects seated in the front passenger seat. Subjects performed a Landolt ring legibility task for four types of signs; positive and negative contrast, new and worn material. Subjects also performed object detection tasks using a small object and a pedestrian target appearing in average and low reflectance. In addition, sign legibility and object detection were completed for some trials using a simulated inclement weather visor to create a worst-case scenario. The object detection task was also completed in the presence of glare from oncoming headlamps. Results showed that older driver's legibility distances were 65% those of the younger drivers. Age differences in the object detection task ranged from a 20% to a 45% reduction for older drivers across visibility conditions.

Foot-ankle injuries: Influence of crash location, seating position and age

Foot-ankle injuries have increased in relative importance in recent years. As a basis for future countermeasures, an epidemiology study has been undertaken using Swedish accident data from Folksam Insurance. The database consists of 805 foot-ankle injuries out of 57,949 car occupant injuries reported from 1985 to 1991. The influence of crash location, seating position and occupant age is determined for the frequency, incidence and rate of foot-ankle injury in car crashes. Frontal car crashes produce 76% of the AIS 2–3 foot-ankle injuries with 13% in side impacts and 8% in roll-overs. The rate of AIS 2–3 foot-ankle injury is 24.7 per 1000 occupants injured in all crash locations and is similar irrespective of seating positions. Ankle fractures and sprains both occur at an incidence of 3.7 per 1000 injuries, followed by malleolus fractures at 2.7 and midtarsal fractures at 2.4. The foot-ankle injury incidence and rate are significantly greater ( p<0.01) in near oblique-frontal crashes than for 12 o'clock frontals. For drivers in 11 o'clock and front passengers in 1 o'clock, the incidence is 27.8 per 1000 injuries as compared to 17.5 for drivers and front passengers in 12 o'clock crashes. Occupant age is not as significant as seating position and crash location; however, there are higher incidences for rear occupants ⩾60 years old in oblique frontal crashes. Using the new AAAM Impairment Injury Scale (IIS), 48% of the foot-ankle injuries are rated with residual impairment IIS 1–2. The incidence in near-seated occupants is 1.5 times greater in oblique frontal crashes than in frontals. The incidence for IIS 1–2 impairment in near oblique-frontal crashes is 12.8 per 1000 occupant injuries as compared to 8.3 in frontal crashes.

Protection for Thorax Injury Severity in 90° Lateral Collision

The thoracic trauma index (TTI) and the viscous criterion (VC) are injury criteria intended for the prediction of torso injury severity. The criteria were assessed in two series of experiments: 90° (lateral) car to car collisions and controlled left trunk impacts against either a rigid or padded wall. Forty-two belt restrained human cadavers in the age range 18–65 years, located in the near-side front passenger seat, were used. The impact velocity was between 40 and 60 km/h. Left and right side impacts were simulated using standard or modified car side structures. With the second series of experiments, the left side of each subject was impacted under one of two different test conditions: 24 km/h rigid wall or 32 km/h padded wall. The thorax deformation was evaluated through the double integration of the accelerated difference at the fourth and eight ribs, near and far side. Deformation maxima of 6–138 mm (mean 69 mm), VC values of 0.3–4.7 m/s (mean 1.6 m/s), and TTI values of 85–252 (mean 63) occurred. Torso abbreviated injury severity (AIS) values were between 0 and 5. Statistical analyses showed a stronger influence of age on injury severity than the injury criteria or biomechanical responses in the two series of experiments. The TTI showed the highest correlation with thoracic AIS and the number of rib fractures, while VC was the better predictor of abdominal AIS. The results are discussed critically and the strength and robustness of the injury criteria analyzed.

Protection for Thorax Injury Severity in 90° Lateral Collision

The thoracic trauma index (TTI) and the viscous criterion (VC) are injury criteria intended for the prediction of torso injury severity. The criteria were assessed in two series of experiments: 90° (lateral) car to car collisions and controlled left trunk impacts against either a rigid or padded wall. Forty-two belt restrained human cadavers in the age range 18–65 years, located in the near-side front passenger seat, were used. The impact velocity was between 40 and 60 km/h. Left and right side impacts were simulated using standard or modified car side structures. With the second series of experiments, the left side of each subject was impacted under one of two different test conditions: 24 km/h rigid wall or 32 km/h padded wall. The thorax deformation was evaluated through the double integration of the accelerated difference at the fourth and eight ribs, near and far side. Deformation maxima of 6–138 mm (mean 69 mm), VC values of 0.3–4.7 m/s (mean 1.6 m/s), and TTI values of 85–252 (mean 63) occurred. Torso abbreviated injury severity (AIS) values were between 0 and 5. Statistical analyses showed a stronger influence of age on injury severity than the injury criteria or biomechanical responses in the two series of experiments. The TTI showed the highest correlation with thoracic AIS and the number of rib fractures, while VC was the better predictor of abdominal AIS. The results are discussed critically and the strength and robustness of the injury criteria analyzed.

From the Centers for Disease Control and Prevention. Air-bag-associated fatal injuries to infants and children riding in front passenger seats--United States

From the Centers for Disease Control and Prevention. Air-bag-associated fatal injuries to infants and children riding in front passenger seats--United States

Air-Bag—Associated Fatal Injuries to Infants and Children Riding in Front Passenger Seats—United States

Air bags, when used as a supplement to safety belts, effectively prevent deaths and serious injuries in frontal motor-vehicle crashes. Air bags are standard equipment in most new cars; federal safety standards require that all new passenger cars and light trucks be equipped with both driver- and passenger-side air bags by 1999. The safety of air bags is well documented, and air bags have saved an estimated 900 lives since the late 1980s (1); however, special precautions are needed to safely transport children in vehicles equipped with air bags. Reports of eight deaths of child passengers in crashes involving air-bag deployment are of special concern because they involved low-speed crashes that the children otherwise might have survived. This report summarizes three of these eight cases (2).

Comparison of motor vehicle occupant injuries in restrained and unrestrained 4-to 14-year-olds

This study compares injuries of restrained and unrestrained 4- to 14-year-olds in nine emergency rooms and the Coroner's office in Orange County, California from 1983 to 1989. Analyses were performed separately for 4- to 9- and 10- to 14-year-olds because of differences related to the fit of the seat belt. Significantly fewer intracranial injuries and a significantly lower mean Injury Severity Score (ISS) were seen between the restrained and unrestrained for 10- to 14-year-olds in the front passenger and back seats; but for 4- to 9-year-olds in the back seat only. These same differences were noted between restrained 4- to 9-year-olds in the back compared with those in the front passenger seat. Except for 4- to 9-year-olds in the front passenger seat, our findings are consistent with similar studies of occupants of all ages. Our results suggest that lap-shoulder belts (primary restraint in front seat) may provide less protection for 4- to 9-year-olds than for 10- to 14-year-olds and adults.

Comparison of motor vehicle occupant injuries in restrained and unrestrained 4- to 14-year-olds

This study compares injuries of restrained and unrestrained 4- to 14-year-olds in nine emergency rooms and the Coroner's office in Orange County, California from 1983 to 1989. Analyses were performed separately for 4- to 9- and 10- to 14-year-olds because of differences related to the fit of the seat belt. Significantly fewer intracranial injuries and a significantly lower mean Injury Severity Score (ISS) were seen between the restrained and unrestrained for 10- to 14-year-olds in the front passenger and back seats; but for 4- to 9-year-olds in the back seat only. These same differences were noted between restrained 4- to 9-year-olds in the back compared with those in the front passenger seat. Except for 4- to 9-year-olds in the front passenger seat, our findings are consistent with similar studies of occupants of all ages. Our results suggest that lap-shoulder belts (primary restraint in front seat) may provide less protection for 4- to 9-year-olds than for 10- to 14-year-olds and adults.

Restraint effectiveness, occupant ejection from cars, and fatality reductions

The effectiveness of air cushion restraint systems, or airbags, in preventing fatalities is estimated by assuming that they do not affect ejection probability, and protect only in frontal, or near frontal, crashes with impact-reducing effectiveness equal to that of lap/shoulder belts. In order to compute airbag effectiveness, lap/shoulder belt effectiveness and the fraction of fatalities preventable by eliminating ejection are estimated using Fatal Accident Reporting System (FARS) data. Ejection prevention is found to account for almost half of the effectiveness of lap/shoulder belts (essentially all for lap belts only). Airbag effectiveness is estimated as (18 ± 4)% in preventing fatalities to drivers and (13 ± 4)% to right front passengers. Drivers switching from lap/shoulder belt to airbag-only protection increase their fatality risk by 41%.

Relative risk of death from ejection by crash type and crash mode

In virtually all circumstances, the chance of survival in a crash is much greater if the occupant is not ejected from the vehicle. Several estimates of the increased risk of death as a result of ejection (ranging from 2.5 to 25) have been made, but none were specific to the crash mode and most did not control for crash severity. The current study examined the relative risk of fatality due to ejection, by crash type and crash mode, using the Fatal Accident Reporting System data from the years 1982 through 1986. Crash type was defined as either single vehicle or multivehicle and crash mode included rollover, nonrollover, and/or direction of impact. Crash severity was controlled for using a paired comparison method of analysis. Both crash type and crash mode were found to have substantial effects on the relative risk of death due to ejection. In addition, risk differences across seating position exist. Depending on crash mode or type, the risks ranged from about 1.5 to 8. Single-vehicle rollover crashes have the highest increased risk of death due to ejection: about eightfold for the driver and sevenfold for the right front passenger.

Potential fatality reductions through eliminating occupant ejection from cars

The percent of occupant fatalities preventable by eliminating ejection is calculated using Fatal Accident Reporting System (FARS) data for 1975 through 1986. The calculation requires estimates of two quantities. First, the fraction of all fatally injured occupants who were ejected; this is obtained directly from the FARS data. Second, the probability that an ejected occupant was killed compared to the probability that the occupant would have been killed in a similar crash in the absence of ejection; this quantity is estimated using the double pair comparison method, and its dependence on occupant age and sex and on car mass and model year is examined. High precision estimates of the reduction in fatalities that would result from eliminating ejection as functions of these same variables are thereby obtained. These estimates depend on assuming that whatever method is used to prevent ejection would cause the formerly ejected occupant to acquire the same fatality risk as a nonejected occupant in a similar crash; the study does not address how to prevent ejection. It is concluded that ejection elimination would decrease fatalities to unrestrained car occupants by 18 ± 1%. The fatality reductions are independent of car seating position (19%, 19%, 17%, 16%, 19%, and 18% for drivers, middle front, right front, left rear, middle rear, and right rear passengers, respectively); they decrease with driver age, from 25% at age 18 years to 7% at 70 years; they decrease with increasing mass, but remained relatively independent of car model year since the early 1970s, being somewhat higher for earlier model years.

Chest Injuries Sustained in Severe Traffic Accidents by Seatbelt Wearers

In Finland during the period 1972-1985, there occurred 3,468 severe traffic accidents in which one or more of the drivers or passengers sustained an injury leading to a fatal outcome within 30 days. Of the victims who had been wearing seatbelts, 207 had fatal and 73 had severe chest injuries. The four leading causes of fatalities resulting from chest injuries were ruptures of the aorta (37%), ruptures of the heart (28.4%), and bilateral lung contusions (31.1%) or lacerations (15.5%). Seatbelt wearers with heart ruptures more often had concomitant rib fractures, lung injuries, and sternum fractures than those who had sustained ruptures of the aorta. The side of rib fractures was associated with the victim's location in the car, drivers seated on the left having more right-sided and right front passengers more left-sided rib fractures. In addition to chest injuries, 87% of the victims had other concomitant injuries, the most common abdominal injuries being liver injuries (40.2%) and spleen ruptures (26.5%). In seatbelt wearers chest injuries with a fatal outcome appear to be caused by impacts of exceptional severity, since in more moderate accidents seatbelt wearing has proved to save lives.

Seating position in cars and fatality risk.

Fatality risk in passenger cars according to seating position (front versus rear; left versus center or right) was examined using Fatal Accident Reporting System (FARS) data for 1975 through 1985. Comparing the fatality risk of unrestrained occupants matched in sex and age (within three years) revealed effects attributable to seating position, and not to occupant characteristics correlated with use of different seats. Fatality risk to drivers was the same as fatality risk to right front passengers to within 1 per cent; this was so for crashes in all directions and for frontal crashes. Fatality risk in rear seats was (26 +/- 2) per cent lower than in front seats, and lower in center compared to outboard seats by (22 +/- 4) per cent for front seats and (15 +/- 4) per cent for rear seats. The center rear seat was associated with the lowest fatality risk.