Robert Kaufman

Pedestrian crashes: higher injury severity and mortality rate for light truck vehicles compared with passenger vehicles.

Introduction: During the last two decades changes in vehicle design and increase in the number of the light truck vehicles (LTVs) and vans have led to changes in pedestrian injury profile. Due to the dynamic nature of the pedestrian crashes biomechanical aspects of collisions can be better evaluated in field studies. Design and settings: The Pedestrian Crash Data Study, conducted from 1994 to 1998, provided a solid database upon which details and mechanism of pedestrian crashes can be investigated. Results: From 552 recorded cases in this database, 542 patients had complete injury related information, making a meaningful study of pedestrian crash characteristics possible. Pedestrians struck by LTVs had a higher risk (29%) of severe injuries (abbreviated injury scale ⩾4) compared with passenger vehicles (18%) (p = 0.02). After adjustment for pedestrian age and impact speed, LTVs were associated with 3.0 times higher risk of severe injuries (95% confidence interval (CI) 1.26 to 7.29, p = 0.013). Mortality rate for pedestrians struck by LTVs (25%) was two times higher than that for passenger vehicles (12%) (p<0.001). Risk of death for LTV crashes after adjustment for pedestrian age and impact speed was 3.4 times higher than that for passenger vehicles (95% CI 1.45 to 7.81, p = 0.005). Conclusion: Vehicle type strongly influences risk of severe injury and death to pedestrian. This may be due in part to the front end design of the vehicle. Hence vehicle front end design, especially for LTVs, should be considered in future motor vehicle safety standards.

THE RELATIONSHIP BETWEEN BODY WEIGHT AND RISK OF DEATH AND SERIOUS INJURY IN MOTOR VEHICLE CRASHES

We sought to investigate the effect of increased body weight on the risk of death and serious injury to occupants in motor vehicle crashes. We employed a retrospective cohort study design utilizing data from the National Automotive Sampling System, Crashworthiness Data System (CDS), 1993-1996. Subjects in the study included occupants involved in tow-away crashes of passenger cars, light trucks, vans and sport utility vehicles. Two outcomes were analyzed: death within 30 days of the crash and injury severity score (ISS). Two exposures were considered: occupant body weight and body mass index (BMI; kg/m2). Occupant weight was available on 27263 subjects (76%) in the CDS database. Mortality was 0.67%. Increased body weight was associated with increased risk of mortality and increased risk of severe injury. The odds ratio for death was 1.013 (95% CI: 1.007, 1.018) for each kilogram increase in body weight. The odds ratio for sustaining an injury with ISS > or = 9 was 1.008 (95% CI: 1.004, 1.011) for each kilogram increase in body weight. After adjustment for potentially confounding variables (age, gender, seatbelt use, seat position and vehicle curbweight), the significant relationship between occupant weight and mortality persisted. After adjustment, the relationship between occupant weight and ISS was present, although less marked. Similar trends were found when BMI was analyzed as the exposure. In conclusion, increased occupant body weight is associated with increased mortality in automobile crashes. This is probably due in part to increased co-morbid factors in the more overweight occupants. However, it is possibly also due to an increased severity of injury in these occupants. These findings may have implications for vehicle safety design, as well as for transport safety policy.

An Evaluation of the Association Between Vehicle Type and the Source and Severity of Pedestrian Injuries

To evaluate the effect of vehicle type (passenger vehicle vs. light truck vehicle) on crash trajectory and on the consequent source and severity of pedestrian injury, we analyzed data from the Pedestrian Crash Data Study (PCDS), conducted by National Highway Traffic Safety Administration (NHTSA) from 1994 to 1998. While 62% of the adults in PV (passenger vehicle)-related crashes were carried by the vehicle, such pedestrian-vehicle interaction was observed only in 28% of LTV (light truck vehicle)-adult crashes. Being thrown forward or knocked down were the most common (65%) type of pedestrian-vehicle interactions for LTV-adult crashes. For children, 93% of those struck by LTVs and 46% of those struck by PVs were thrown forward or knocked down. For adults, LTVs were more likely than PVs to cause thorax (37% vs. 20%) and abdomen injuries (33% vs. 18%). For children, LTVs were more likely than PVs to cause injuries to the upper extremity (71% vs. 56%) and abdomen (14% vs. 8%). For adults struck by PVs the most common sources of injury were windshield for head injuries (63%), hood surface for thorax (67%), abdomen (58%), spine (30%), and upper extremity (36%) injuries, and bumper for the lower extremity injuries (60%). The leading causes of injury for adult-LTV crashes were ground for head (39%) and upper extremity (37%) injuries, hood edge for thorax (48%) and abdomen (56%) injuries, hood surface for spine injuries (36%), and bumper for lower extremity injuries (45%). For child-PV crashes, ground was the most common source of face (37%) abdomen (83%), spine (43%), and upper extremity injuries (54%). For children hit by LTVs, 52% of face, 67% of abdomen, 100% of spine, and 60% of upper extremity injuries were attributed to ground contacts. Altogether, the major sources of injury were hood surface and windshield for PV-pedestrian crashes and hood surface and hood edge for LTV-pedestrian crashes. Changes in design, such as altering the geometry and stiffness of front-end structures, might be associated with considerable decrease in the frequency and severity of pedestrian injury.

Severity of injury and outcomes among obese trauma patients with fractures of the femur and tibia: a crash injury research and engineering network study.

Objective: To understand the influence of obesity on the morbidity and mortality outcomes of patients who have sustained fractures of the femur and tibia. Design: Retrospective review. Setting: Multicenter level I trauma facilities. Patients/Participants: Motor vehicle crash victims enrolled in multicenter databases were reviewed. Main Outcome Measurements: Outcome measurements for obese (body mass index, BMI ≥ 30 kg/m2) versus nonobese (BMI < 30 kg/m2) patients included Injury Severity Score, Abbreviated Injury Scores, OTA fracture types, length of hospital stay, disposition, complications, and 36-Item Short Form Survey Instrument. Results: We included 665 cases from the database, of which 461 (69%) were nonobese and 204 (31%) were obese. There was no difference in sex, mechanism of injury, Injury Severity Score, and Abbreviated Injury Score. The obese population was older with a mean age of 44 years compared with 41 years for the nonobese (P < 0.01) and had a greater incidence of reported baseline cardiac disease (P < 0.01) and diabetes (P < 0.01). Obese patients had more severe injury patterns (OTA B and C type) in the distal femur fractures (90% versus 61%, P < 0.01). Mortality rates did not show a statistically significant difference (5.6% versus 9.4%, P = 0.07). The baseline physical component on the 36-Item Short Form Survey Instrument was lower among the obese but not statistically different (P = 0.08). At 6 and 12 months post injury, a decline was noted in both groups; however, no differential decline was noted between the groups (P > 0.05). Conclusions: Obese patients are significantly more likely to have more severe distal femur fractures compared with nonobese when involved in motor vehicle crashes. In this study, there was no statistically significant difference in length of stay, complications, or mortality in obese patients.

Mortality and injury patterns associated with roof crush in rollover crashes

BACKGROUND In the United States, a significant number of spine injuries, traumatic brain injuries (TBI), and deaths result from motor vehicle rollover crashes each year though they make up a small percentage of total crashes. We sought to explore the relationship between these injuries and the degree of roof crush. METHODS We searched the NASS CDS database for belted, adult (> or =16), non-middle seat passengers involved in rollover crashes from 1993 to 2006. We also searched the CIREN database for illustrative cases. Logistic regression was used to evaluate the relationship between different levels of roof crush and mortality, severe injury (AIS > or = 3) to the spine, spinal cord, and head injury. RESULTS The risk of mortality, TBI, and spine injury all increased as the degree of roof crush increased. For mortality increased risk occurred at >15 cm [15-30 cm: OR 2.089 (95% CI: 1.461-2.987); >30 cm: OR 6.301 (95% CI: 4.369-9.087)]. For TBI, increased risk was seen above 15 cm crush [15-30 cm: OR 1.52 (95% CI: 1.045-2.21); >30 cm: OR 3.672 (95% CI: 2.456-5.490)]. For spine injury increased risk was seen above 8 cm crush [8-15 cm: OR 1.968 (95% CI 1.273-3.043); 15-30 cm: OR 2.530 (95% CI 1.634-3.917); > or =30 cm OR 2.682 (95% CI 1.474, 4.877). Results were similar across the different statistical models. CONCLUSION There is an association between the degree of roof crush and mortality, spine injury, and head injury in rollover crashes.

Childhood crash injury patterns associated with restraint misuse: implications for field triage

INTRODUCTION Restraint misuse is a common problem leading to increased morbidity and mortality for children involved in motor vehicle crashes. The purpose of this project was to describe the injury patterns associated with restraint misuse in the pediatric population, with particular focus on clues to significant injury that can be identified by the prehospital provider that may impact subsequent triage decisions. METHODS This is a case series presentation that illustrates the injury patterns associated with various types of restraint misuse in infants (ages 0-1 years), toddlers (age 1-4 years), young children (ages 4-8 years), and pre-teens (ages 8-14 years). Cases were identified from the Crash Injury Research and Engineering Network (CIREN) database. RESULTS Six cases are presented that illustrate the injury patterns associated with misuse of rear-facing infant car seats (0-1 years), forward-facing child seats (1-4 years), booster seats (4-8 years), and shoulder belts (8-14 years). Prehospital assessment of appropriate restraint use is described. CONCLUSIONS Restraint misuse in children is a common problem. Emergency medical services providers need to be aware of these issues when assessing children and determining appropriate triage to a trauma center. Ongoing educational efforts also are vital to inform parents regarding the risks of inappropriate restraint use and can encourage legislators to better define appropriate restraint use for older children.

FEMUR FRACTURES IN RELATIVELY LOW SPEED FRONTAL CRASHES: THE POSSIBLE ROLE OF MUSCLE FORCES

In a sample of relatively low speed frontal collisions (mean collision speed change of 40.7 kph) the only major injury suffered by the partly or fully restrained occupant was a femur fracture. However, femur load measurements from standardized barrier crash tests for similar vehicles at a greater speed change (mean of 56.3 kph) showed that in almost all the cases, the occupants femur would not have fractured because the loads were below fracture threshold. In order to address this discrepancy, the load in the femurs of the occupants in the crash sample were estimated and compared with the femur fracture threshold. Femur load was estimated by inspecting the scene and measuring deformations in each vehicle, defining occupant points of contact and interior surface intrusion, and calculating crash change in velocity and deceleration. From this data, the measured femoral loads from standardized crash test data in a comparable vehicle were scaled to the actual crash by considering crash deceleration, occupant weight, and restraint use. All the occupants (7 males, average age 26.7 years, 13 females, average age 36 years) sustained at least a transverse midshaft fracture of the femur with comminution, which is characteristic of axial compressive impact, causing bending and impaction of the femur. However, the estimated average maximum axial load was 8187 N (S.D. = 4343N), and the average probability for fracture was only 19% (based on the femur fracture risk criteria). In 13 crashes the fracture probability was less than 10%. Two factors were considered to explain the discrepancy. The occupants femur was out of position (typically the drivers right front leg on the brake) and did not impact the knee bolster, instead hitting stiffer regions of the dashboard. Also, since most victims were drivers with their foot on the brake to avoid the collision, additional compressive force on the femur probably resulted from muscle contraction due to bracing for impact. Adding the estimated muscle load on the femur to the estimated external load increased the femur loads beyond threshold, explaining the fracture in all but one case. Since crash tests using dummies cannot simulate out of position occupants or muscle contraction loading, they may underestimate the total load acting on the femur during actual impacts where the driver is bracing for the crash. These results may have implications for altering knee bolster design to accommodate out of position occupants and the additional load caused by muscle forces during bracing.

The effect of air bags on pregnancy outcomes in Washington state: 2002-2005

OBJECTIVE: To estimate whether air-bag deployment is associated with an increased risk of adverse pregnancy outcomes. METHODS: We performed a retrospective cohort study to assess the effect of air-bag availability and air-bag deployment on the risk of adverse pregnancy outcomes among pregnant, front-seat occupants in motor vehicle crashes in Washington State. Pregnant women involved in motor vehicle crashes were identified by linking birth and fetal death certificate data with Washington State Patrol crash data, which reported air-bag availability and deployment. We calculated relative risks (RRs) of adverse maternal and perinatal outcomes and 95% confidence intervals (CIs) using Poisson regression, adjusted for maternal age, seatbelt use, and vehicle model year. RESULTS: We found no increased risk of adverse maternal or perinatal pregnancy outcomes among occupants of air-bag–equipped vehicles in all collisions (n=2,207) compared with those in vehicles without air bags (n=1,141). Among crashes in which air-bag deployment would be likely, we found a nonsignificant 70% increased risk of preterm labor (RR 1.7, 95% CI 0.9–3.2) and a nonsignificant threefold increased risk (RR 3.1, 95% CI 0.4–22.1) of fetal death among occupants in vehicles with air-bag deployment compared with occupants in vehicles without air bags, although fetal death results were limited by small numbers (2/198 [1.0%] in pregnant women whose air bags deployed; 2/622 [0.3%] in pregnant women whose air bags did not deploy). CONCLUSION: Our findings provide clinicians with evidence to advise women that air bags do not seem to elevate risk of most potential adverse outcomes during pregnancy. LEVEL OF EVIDENCE: II

Validation of prehospital trauma triage criteria for motor vehicle collisions

BACKGROUND Triage of an injured patient to an appropriate trauma center can have an impact on morbidity and mortality. We sought to validate the 2012 national field triage guidelines for motor vehicle crashes. METHODS This is a retrospective cross-sectional study using the National Automotive Sampling System Crashworthiness Data System. Vehicle damage criteria proposed as prehospital triage guidelines were correlated with injury severity. RESULTS There were 85,761 individuals representing 29,397,234 occupants in car crashes from 2003 to 2008. Of the patients, 3.8% met physiologic Step 1 criteria with a mean Injury Severity Score (ISS) of 9.1 (95% confidence interval [CI], −3.1 to 20.9); Step 1 had a positive predictive value (PPV) of 20.8% (95% CI, 20.1–21.4%) for severe injury (ISS > 15). Of the patients, 0.43% met anatomic Step 2 criteria alone, with a mean ISS of 18.1 (95% CI, 16.4–19.8) and a PPV of 48.5% (95% CI, 46.8–50.1%). Step 3 criteria include injury mechanism; 3.7% of the patients met one of these criteria alone with a mean ISS of 5.1 (95% CI, 4.4–5.8) and a PPV of 9.7% (95% CI, 9.3–10.2%). Patients who met only Step 3 criteria were examined to determine crash characteristics that predict severe injury. Intrusion of greater than 12 inches had a PPV of 10.4% (95% CI, 9.5–11.3); steering wheel collapse had a PPV of 25.7% (95% CI, 23.0–28.4%). Older patients (age > 55 years) who met Step 3 mechanism criteria had higher predictive values for injury for nearly all crash characteristics. CONCLUSION Injury mechanism criteria alone predict significant injury in a substantial proportion of patients who did not meet the physiologic or anatomic criteria. Vehicular crash data could improve the ability of emergency medical service providers to triage injured occupants. Consideration of transport to a trauma center should be given for elderly patients and drivers with steering wheel collapse. LEVEL OF EVIDENCE Epidemiologic study, level III.

Do initial radiographs agree with crash site mechanism of injury in pelvic ring disruptions? A pilot study.

Objective: Direction of injury force inferred from pelvic radiographs may be used in trauma care to predict associated injuries and guide intervention. Our objective was to compare injury direction determined from anteroposterior (AP) pelvic radiographs with injury forces determined from crash site investigation. Materials and Methods: We studied all 28 subjects from the Crash Injury Research Engineering Network (CIREN) database who met inclusion criteria of pelvic ring disruption, single-event crash, restrained front-seat occupant, diagnostic-quality pelvic radiography, and complete crash investigation data. Assessment of diagnostic quality of pelvic radiography was made by 2 radiologists who were blinded to all other subject information. Crash site investigation data included principal direction of force (PDOF), crash magnitude, and passenger compartment intrusion. An orthopedic trauma surgeon and a fellowship-trained emergency radiologist independently assessed the pelvic radiographs to determine the injury PDOF and the Young-Burgess and Tile fracture classifications, with disputes resolved by an additional emergency radiologist. Agreement between injury forces and pelvic radiographs was assessed using the kappa statistic. Results: The PDOF was anterior in 9 (32%) and lateral in 19 (68%) subjects. The readers agreed with the crash primary direction of force in 21 (75%) subjects (κ = 0.42). In subjects with lateral PDOF, agreement was 89% (17/19) compared to 44% for anterior PDOF (4/9). Interobserver agreement for the Young and Tile classification schemes was moderate (weighted kappa 0.44 and 0.54, respectively). Conclusion: Crash site investigation and pelvic radiography may provide conflicting information about primary direction of injuring forces. Presumed anterior impact based on PDOF is not in consistent agreement with the pattern of injury evident on the AP pelvic radiograph.