Comparisons of the Outcome Prediction Performance of Injury Severity Scoring Tools Using the Abbreviated Injury Scale 90 Update 98 (AIS 98) and 2005 Update 2008 (AIS 2008)

The Abbreviated Injury Scale (AIS) was revised in 2005 and updated in 2008 (AIS 2008). We aimed to compare the outcome prediction performance of AIS-based injury severity scoring tools by using AIS 2008 and AIS 98. We used all major trauma patients hospitalized to the Royal Perth Hospital between 1994 and 2008. We selected five AIS-based injury severity scoring tools, including Injury Severity Score (ISS), New Injury Severity Score (NISS), modified Anatomic Profile (mAP), Trauma and Injury Severity Score (TRISS) and A Severity Characterization of Trauma (ASCOT). We selected survival after injury as a target outcome. We used the area under the Receiver Operating Characteristic curve (AUROC) as a performance measure. First, we compared the five tools using all cases whose records included all variables for the TRISS (complete dataset) using a 10-fold cross-validation. Second, we compared the ISS and NISS for AIS 98 and AIS 2008 using all subjects (whole dataset). We identified 1,269 and 4,174 cases for a complete dataset and a whole dataset, respectively. With the 10-fold cross-validation, there were no clear differences in the AUROCs between the AIS 98- and AIS 2008-based scores. With the second comparison, the AIS 98-based ISS performed significantly worse than the AIS 2008-based ISS (p<0.0001), while there was no significant difference between the AIS 98- and AIS 2008-based NISSs. Researchers should be aware of these findings when they select an injury severity scoring tool for their studies.

Identification and validation of a logistic regression model for predicting serious injuries associated with motor vehicle crashes

A multivariate logistic regression model, based upon National Automotive Sampling System Crashworthiness Data System (NASS-CDS) data for calendar years 1999-2008, was developed to predict the probability that a crash-involved vehicle will contain one or more occupants with serious or incapacitating injuries. These vehicles were defined as containing at least one occupant coded with an Injury Severity Score (ISS) of greater than or equal to 15, in planar, non-rollover crash events involving Model Year 2000 and newer cars, light trucks, and vans. The target injury outcome measure was developed by the Centers for Disease Control and Prevention (CDC)-led National Expert Panel on Field Triage in their recent revision of the Field Triage Decision Scheme (American College of Surgeons, 2006). The parameters to be used for crash injury prediction were subsequently specified by the National Expert Panel. Model input parameters included: crash direction (front, left, right, and rear), change in velocity (delta-V), multiple vs. single impacts, belt use, presence of at least one older occupant (≥ 55 years old), presence of at least one female in the vehicle, and vehicle type (car, pickup truck, van, and sport utility). The model was developed using predictor variables that may be readily available, post-crash, from OnStar-like telematics systems. Model sensitivity and specificity were 40% and 98%, respectively, using a probability cutpoint of 0.20. The area under the receiver operator characteristic (ROC) curve for the final model was 0.84. Delta-V (mph), seat belt use and crash direction were the most important predictors of serious injury. Due to the complexity of factors associated with rollover-related injuries, a separate screening algorithm is needed to model injuries associated with this crash mode.

Quantification method analysis of the relationship between occupant injury and environmental factors in traffic accidents

Injury analysis following a vehicle crash is one of the most important research areas. However, most injury analyses have focused on one-dimensional injury variables, such as the AIS (Abbreviated Injury Scale) or the IIS (Injury Impairment Scale), at a time in relation to various traffic accident factors. However, these studies cannot reflect the various injury phenomena that appear simultaneously. In this paper, we apply quantification method II to the NASS (National Automotive Sampling System) CDS (Crashworthiness Data System) to find the relationship between the categorical injury phenomena, such as the injury scale, injury position, and injury type, and the various traffic accident condition factors, such as speed, collision direction, vehicle type, and seat position. Our empirical analysis indicated the importance of safety devices, such as restraint equipment and airbags. In addition, we found that narrow impact, ejection, air bag deployment, and higher speed are associated with more severe than minor injury to the thigh, ankle, and leg in terms of dislocation, abrasion, or laceration.

Effects of osteoporosis on AIS 3+ injury risk in motor-vehicle crashes

Older occupants in motor-vehicle crashes are more likely to experience injury than younger occupants. One possible reason for this is that increasing age is associated with increased prevalence of osteoporosis, which decreases bone strength. Crash-injury data were used with Bayes' Theorem to estimate the conditional probability of AIS 3+ skeletal injury given that an occupant is osteoporotic for the injury to the head, spine, thorax, lower extremities, and upper extremities. This requires the conditional probabilities of osteoporosis given AIS 3+ injury for each of the body regions, which were determined from analysis of the Crash Injury Research and Engineering Network database. It also requires information on probability of osteoporosis in the crash-involved population and the probabilities of AIS 3+ skeletal injury to different body regions in crashes. The latter probabilities were obtained from the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) database. The former was obtained by modeling the probability of osteoporosis in the US populations using data from the 2006 National Health Examination Nutrition Survey and applying this model to the estimate of the crash-involved population in NASS-CDS. To attempt to account for the effects of age on injury outcome that are independent of osteoporosis, only data from occupants who were 60 years of age or older were used in all analyses. Results indicate that the only body region that experiences a statistically significant change in fracture injury risk with osteoporosis is the spine, for which osteoporosis increases the risk of AIS 3+ fracture by 3.28 times, or from 0.41% to 1.34% (p<0.0001). This finding suggests that the increase in AIS 3+ injury risk with age for non-spine injuries is likely influenced by factors other than osteoporosis.

Injury risk to specific body regions of pedestrians in frontal vehicle crashes modeled by empirical, in-depth accident data

Evaluation of safety benefits is an essential taskduring design and development of pedestrian protection systems. Comparative evaluation of different safety concepts is facilitated by a common metric taking into account the expected human benefits. Translation of physical characteristics of a collision, such as impact speed,into human benefits requires reliable and preferably evidence-based injury models. To this end, the dependence of injury severity of body regions on explanatory factors is quantified here using the US Pedestrian Crash Data Study (PCDS) for pedestrians in frontal vehicle collisions. The explanatory and causal factors include vehicle component characteristics, physiological and biomechanical variables, and crash parameters. Severe to serious injuries most often involve the head, thorax and lower extremities. In terms of causing components; severe head and thorax injuries occur mainly on the windshield and hood region; serious lower extremity injuries usually occur on the front bumper. In order to formulate a common metric for evaluating the effect sizes of distinct causal factors, multivariate models of injury severity are obtained by binary logistic regression. Impact speed is clearly the most important injury severity predictor for every body region, although biomechanical and physiological variables as well as geometrical characteristics of the vehicle are also significant in multivariate analysis, even controlling for speed. The injury-metric approach is illustrated in a comparison of hypothetical active and passive safety measures. The relative risk reduction to various body regions by this reduction is formulated as a benchmark for comparison of benefits from proposed structural changes to individual vehicle components.

Priorities of pedestrian protection--a real-life study of severe injuries and car sources

The aim of this study was to aid the optimisation of future, vehicle based, pedestrian injury countermeasures. The German In-Depth Accident Study (GIDAS) database was queried for pedestrians impacted by the front of a passenger car or van. A total of 1030 cases from 1998 to 2008 were studied including 161 severely (AIS3+) injured pedestrians. Considering the severe injuries, the most frequent injury mechanisms were "leg-to-front end", "head-to-windscreen area", "chest-to-bonnet area", and "chest-to-windscreen area". For children, a "head-to-bonnet area" impact was the second most common source of injury. With safety systems targeting these five injury mechanisms, 73% (95% confidence interval [CI], 65-81%) of the severely injured pedestrians would be provided protection from all of their vehicle-induced severe injuries. Omitting the windscreen area, this figure is decreased to 44% (CI, 36-53%). Furthermore, 31% of the surviving pedestrians were estimated to sustain a permanent medical impairment at any level. For more severe impairment, head was the dominating body region. The study shows that when developing countermeasures for the windscreen area to mitigate head injuries, attention should be paid to the structural parts of the windscreen area with a special focus on brain injuries. Finally, the incidence and risk of severe injury were derived as functions of impact speed for different body regions and injury sources.

Does health care insurance affect outcomes after traumatic brain injury? Analysis of the National Trauma Databank

Increasing evidence indicates insurance status plays a role in the outcome of trauma patients; however its role on outcomes after traumatic brain injury (TBI) remains unclear. A retrospective review was queried within the National Trauma Data Bank. Moderate to severe TBI insured patients were compared with their uninsured counterparts with respect to demographics, Injury Severity Score, Glasgow Coma Scale score, and outcome. Multivariate logistic regression analysis was used to determine independent risk factors for mortality. Of 52,344 moderate to severe TBI patients, 41,711 (79.7%) were insured. Compared with the uninsured, insured TBI patients were older (46.1 +/- 22.4 vs. 37.3 +/- 16.3 years, P < 0.0001), more severely injured (ISS > or =16: 78.4% vs. 74.4%, P < 0.0001), had longer intensive care unit length of stay (6.0 +/- 9.4 vs. 5.1 +/- 7.6, P < 0.0001) and had higher mortality (9.3% vs. 8.0%, P < 0.0001). However, when controlling for confounding variables, the presence of insurance had a significant protective effect on mortality (adjusted odds ratio 0.89; 95% confidence interval: 0.82-0.97, P = 0.007). This effect was most noticeable in patients with head abbreviated injury score = 5 (adjusted odds ratio 0.7; 95% confidence interval: 0.6-0.8, P < 0.0001), indicating insured severe TBI patients have improved outcomes compared with their uninsured counterparts. There is no clear explanation for this finding however the role of insurance in outcomes after trauma remains a topic for further investigation.

Double coding and mapping using Abbreviated Injury Scale 1998 and 2005: identifying issues for trauma data

INTRODUCTION

The 2005 version of the Abbreviated Injury Scale (AIS05) potentially represents a significant change in injury spectrum classification, due to a substantial increase in the codeset size and alterations to the agreed severity of many injuries compared to the previous version (AIS98). Whilst many trauma registries around the world are moving to adopt AIS05 or its 2008 update (AIS08), its effect on patient classification in existing registries, and the optimum method of comparing existing data collections with new AIS05 collections are unknown. The present study aimed to assess the potential impact of adopting the AIS05 codeset in an established trauma system, and to identify issues associated with this change.

METHODS

A current subset of consecutive major trauma patients admitted to two large hospitals in the Australian state of Victoria were double-coded in AIS98 and AIS05. Assigned codesets were also mapped to the other AIS version using code lists supplied in the AIS05 manual, giving up to four AIS codes per injury sustained. Resulting codesets were assessed for agreement in codes used, injury severity and calculated severity scores.

RESULTS

602 injuries sustained by 109 patients were compared. Adopting AIS05 would lead to a decrease in the number of designated major trauma patients in Victoria, estimated at 22% (95% confidence interval, 15-31%). Differences in AIS level between versions were significantly more likely to occur amongst head and chest injuries. Data mapped to a different codeset performed better in paired comparisons than raw AIS98 and AIS05 codesets, with data mapping of AIS05 codes back to AIS98 giving significantly higher levels of agreement in AIS level, ISS and NISS than other potential comparisons, and resulting in significantly fewer conversion problems than attempting to map AIS98 codes to AIS05.

CONCLUSIONS

This study provides new insights into AIS codeset change impact. Adoption of AIS05 or AIS08 in established registries will decrease major trauma patient numbers. Code mapping between AIS versions can improve comparisons between datasets in different AIS versions, although the injury profile of a trauma population will affect the degree of comparability. At present, mapping AIS05 data back to AIS98 is recommended.

Logistic regression analysis of pedestrian casualty risk in passenger vehicle collisions in China

A large number of pedestrian fatalities were reported in China since the 1990s, however the exposure of pedestrians in public traffic has never been measured quantitatively using in-depth accident data. This study aimed to investigate the association between the impact speed and risk of pedestrian casualties in passenger vehicle collisions based on real-world accident cases in China. The cases were selected from a database of in-depth investigation of vehicle accidents in Changsha-IVAC. The sampling criteria were defined as (1) the accident was a frontal impact that occurred between 2003 and 2009; (2) the pedestrian age was above 14; (3) the injury according to the Abbreviated Injury Scale (AIS) was 1+; (4) the accident involved passenger cars, SUVs, or MPVs; and (5) the vehicle impact speed can be determined. The selected IVAC data set, which included 104 pedestrian accident cases, was weighted based on the national traffic accident data. The logistical regression models of the risks for pedestrian fatalities and AIS 3+ injuries were developed in terms of vehicle impact speed using the unweighted and weighted data sets. A multiple logistic regression model on the risk of pedestrian AIS 3+ injury was developed considering the age and impact speed as two variables. It was found that the risk of pedestrian fatality is 26% at 50 km/h, 50% at 58 km/h, and 82% at 70 km/h. At an impact speed of 80 km/h, the pedestrian rarely survives. The weighted risk curves indicated that the risks of pedestrian fatality and injury in China were higher than that in other high-income countries, whereas the risks of pedestrian casualty was lower than in these countries 30 years ago. The findings could have a contribution to better understanding of the exposures of pedestrians in urban traffic in China, and provide background knowledge for the development of strategies for pedestrian protection.

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.

Severe-to-fatal injury risks in crashes with two front-seat occupants by seat belt use

PURPOSE

This study investigates the risk of severe-to-fatal injury (Maximum Abbreviated Injury Score, MAIS 4+F) in crashes with two front-seat occupants. It determines the relative risk of injury in the same crash by belt use and seating position.

METHODS

1993-2008 NASS-CDS was analyzed for crashes with occupants in both front-outboard seats. The effect of belt use was investigated for the driver and passenger. Light vehicles were included with model year 1990+. Injury severity was subdivided into MAIS 0-2 and 4+F in NASS-CDS to compare no-to-moderate injury with severe-to-fatal injury. Standard errors were calculated in SAS and the z-test was used to determine the significance of differences in risk. Relative risks were determined by seat belt use and seating position; odds ratios were determined for one or both occupants being severely injured.

RESULTS

In 76.7 percent of the MAIS 4+F crashes, either the driver (32.4%) or passenger (44.3%) was severely injured, rather than both occupants (23.3%). When both were belted, one occupant was severely injured in 86.5 percent of crashes. When both were unbelted, both occupants were severely injured in 68.9 percent of the crashes. Both occupants were belted in 74.7 percent of the cases and unbelted in 18.6 percent. In 6.7 percent of crashes, either the driver (4.4%) or passenger (2.3%) was unbelted when the other was belted. The highest risk occurred with an unbelted driver and belted passenger (4.98 +/- 0.73% vs. 1.97 +/- 0.38%, z = 3.65, p < .05). When both occupants were belted, the driver and passenger injury risk was similar (0.459 +/- 0.098% vs. 0.449 +/- 0.047%, z = 0.10, ns).

CONCLUSIONS

In crashes with two front occupants, typically one occupant was severely injured, not both. Overall, the odds ratio was 3.28 for one compared to two occupants being severely injured; and, risks vary by seat belt use and seating position. The highest relative risk for unbelted versus belted occupants was 9.22 when both occupants were severely injured in the same crash.

[Usefulness of selected microscopic morphological changes in determining the age of subdural hematomas]

The objective of the study was to assess the usefulness of selected microscopic changes for determining the age of subdural hematoma (SDH). The research was based on microscopic examination of histopathological preparations representing SDHs collected in the course of 76 forensic autopsies performed in the Chair and Department of Forensic Medicine, Warsaw Medical University, Poland. The deceased had SDH after head injuries and the time of injury was known. H.E. and Masson's staining was employed for qualitative and quantitative determinations. The presence of hematoma capsules, as well as hematoidin and hemosiderine deposits were analyzed. The results suggest that microscopic SDH examinations based on the afore-said features is a helpful method for determining the age of SDHs. Additionally, the results of this study indicate that qualitative techniques of SDHs dating are more accurate than quantitative ones.

Injury patterns in frontal crashes: the association between knee-thigh-hip (KTH) and serious intra-abdominal injury

Safety belts protect occupants in frontal impacts by reducing occupant deceleration and preventing the occupant from hitting interior vehicle components likely to cause injury. However, occupants moving forward during the impact may contact the safety belt webbing across their chest and abdomen. We hypothesized that if the occupant loaded their knee-thigh-hip (KTH) region with enough force to result in injury to this region-it might prevent compression (and injury) of their abdomen by the safety belt. Crash Injury Research and Engineering Network (CIREN) data were used to test the association between KTH and intra-abdominal injury related to safety belts. Odds ratios with 95% confidence limits (CL) and logistic regression models were used to assess statistical significance. Analyses were based on 706 CIREN adult, front seat occupants using their safety belt and injured in frontal crashes. Occupants with KTH injury were four times less likely (adjusted odds ratio=0.25, 95% CL 0.10, 0.62) to have concomitant serious intra-abdominal injury caused by the safety belt. Although safety belts save lives and prevent serious injury, some occupants may sustain serious intra-abdominal injury when the abdomen is loaded by the safety belt during a frontal impact. These results may be useful to motor vehicle manufacturers and others who design and test motor vehicle safety systems.

The association of weight percentile and motor vehicle crash injury among 3 to 8 year old children

The use of age-appropriate child restraint systems significantly reduces injury and death associated with motor vehicle crashes (MVCs). Pediatric obesity has become a global epidemic. Although recent evidence suggests a possible association between pediatric obesity and MVC-related injury, there are potential misclassifications of body mass index from under-estimated height in younger children. Given this limitation, age- and sex-specific weight percentiles can be used as a proxy of weight status. The specific aim of this study was to determine the association between weight percentile and the risk of significant injury for children 3-8 years in MVCs. This was a cross-sectional study of children aged 3-8 years in MVCs in 16 US states, with data collected via insurance claims records and a telephone survey from 12/1/98-11/30/07. Parent-reported injuries with an abbreviated Injury Scale (AIS) score of 2+ indicated a clinically significant injury. Age- and sex-specific weight percentiles were calculated using pediatric norms. The study sample included 9,327 children aged 3-8 years (weighted to represent 157,878 children), of which 0.96% sustained clinically significant injuries. There was no association between weight percentiles and overall injury when adjusting for restraint type (p=0.71). However, increasing weight percentiles were associated with lower extremity injuries at a level that approached significance (p=0.053). Further research is necessary to describe mechanisms for weight-related differences in injury risk. Parents should continue to properly restrain their children in accordance with published guidelines.

The AIS-2005 Revision in Severe Traumatic Brain Injury: Mission Accomplished or Problems for Future Research?

The Abbreviated Injury Scale (AIS) is commonly used to score injury severity and describe types of injuries. In 2005, the AIS-Head section was revised to capture more detailed information about head injuries and to better reflect their clinical severity, but the impact of these changes is largely unknown. The purpose of this study was to compare AIS-1998 and AIS-2005 coding of traumatic brain injuries (TBI) using medical records at a single Level I trauma center. We included patients with severe TBI (Glasgow Coma Scale 3-8) after blunt injury, excluding those who were missing medical records. Detailed descriptions of injuries were collected, then manually coded into AIS-1998 and AIS-2005 by the same Certified AIS Specialist. Compared to AIS-1998, AIS-2005 coded the same injuries with lower severity scores [p<0.01] and with decreased mean and maximum AIS-Head scores [p<0.01]. Of the types of traumatic brain injuries, most of the changes occurred among cerebellar and cerebral injuries. Traumatic hypoxic brain injury secondary to systemic dysfunction was captured by AIS-2005 but not by AIS-1998. However, AIS-2005 captured fewer loss of consciousness cases due to changes in criteria for coding concussive injury. In conclusion, changes from AIS-1998 to AIS-2005 result in significant differences in severity scores and types of injuries captured. This may complicate future TBI research by precluding direct comparison to datasets using AIS-1998. TBIs should be coded into the same AIS-version for comparison or evaluation of trends, and specify which AIS-version is used.

A reexamination of the small overlap frontal crash

The objective of this study was to examine and rank the Small Overlap Frontal Crash as one of the eight-group taxonomy proposed by Ford. The Ford taxonomy classifies real-world frontal-impact crashes based on the National Automotive Sampling System (NASS). Frontally-impacted vehicles were identified for 1985 - 2008 model year passenger vehicles with Collision Deformation Classification (CDC) data from the 1995 - 2008 years of NASS. Small overlap frontal cases were identified where there was no engagement of the vehicle frame rails, and the direct damage was located entirely outside of the vehicle frame rails. The results are that full engagement and offset (offset category means the direct damage overlaps the vehicle frame rail, with the center of direct damage between the frame rails) were the most frequent crashes contributing 35% each. The frequency of the small overlap frontal was 6%. The risks of injury (AIS ≥ 2) for the full engagement, offset, and small overlap were 8%, 6%, and 3% respectively. For this study, the number of small overlap vehicles was 1,118 and the number of injured nearside occupants was 100. This study-following the Ford approach and reasonably identifying the location of the longitudinal rails based on CDC-suggests that the small overlap is at worst a moderately dangerous crash in the overall scheme of frontal crashes. The implications of this study are that the safety community should reexamine the significance of the small overlap frontal crash against an overall taxonomy of crashes.

The utility of seat belt signs to predict intra-abdominal injury following motor vehicle crashes

OBJECTIVE

Safety belts are the most important safety system in motor vehicles and should always be worn to prevent serious injury. The purpose of this study, using Crash Injury Research Engineering Network (CIREN) data, was to assess occupant and crash factors associated with minor contusions and abrasions caused by the safety belt (commonly referred to as seat belt signs) and their association with serious intra-abdominal trauma.

METHODS

CIREN data were used to determine which factors are associated with seat belt signs. Occupant variables (age, gender, body mass index, proper safety belt use, driver v. passenger status) and crash variables (crash type, crash severity, and airbag deployment) were compared for occupants with seat belt sign who had serious (AIS 3 or greater) intra-abdominal injury and those who did not have intra-abdominal injuries. Adjusted odds ratios were used to quantify the independent association between predictive factors for serious intra-abdominal injury for occupants with seat belt signs.

RESULTS

Of 1539 occupants included in this study, 419 had a positive seat belt signs. Of those 419 occupants, 100 had serious intra-abdominal injury and 319 did not. Being in the passenger seat position increased the odds, whereas front airbag deployment and frontal impact were associated with decreased odds of serious intra-abdominal injury for occupants with seat belt signs. However, multivariate analysis showed only that being a passenger increased the odds (OR = 2.64) of having serious intra-abdominal injury for occupants with seat belt signs when other factors, including crash severity and type of impact, were controlled for in the analysis.

CONCLUSIONS

Seat belt signs remain an important physical finding in patients with intra-abdominal injury following motor vehicle crashes. Front seat passengers presenting with seat belt signs were more than twice as likely to sustain intra-abdominal injury; thus, emergency physicians and trauma surgeons should be aware of passenger position when evaluating a seat belt sign.

Making the most of the worst-case scenario: should belt-positioning booster seats be used in lap-belt-only seating positions?

OBJECTIVE

Examine real-world crash injury data to determine whether children seated with lap belts only are better protected with or without belt-positioning booster seats.

METHODS

Crash injury rates among booster-age children were examined for three restraint categories: lap belt only, belt-positioning booster seat with lap belt, and booster seat with lap/shoulder belt. Data were drawn from the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) and the Partners for Child Passenger Safety (PCPS) crash surveillance system for years 1997-2006 and 1998-2006, respectively. Main outcome measures were the percentage of crash-involved booster-age children with moderate or greater injury (maximum abbreviated injury score [MAIS] 2+).

RESULTS

The estimated risk of MAIS 2+ injury among children restrained with lap belts and boosters was 0.12 percent (NASS-CDS) and 0.96 percent (PCPS), compared with 1.21 and 1.74 percent, respectively, for lap belts only. This difference was not significant due to small numbers of children in lap belts with boosters. In PCPS, children restrained by lap/shoulder belts and boosters had lower injury risk than children restrained by lap belts, with or without boosters.

CONCLUSIONS

Although data for children secured in lap belts with boosters are limited, the results suggest that boosters are not harmful. This finding is inconsistent with the current recommendation that booster seats not be used when children must be buckled with lap belts only. Data also confirm that booster seats with lap/shoulder belts remain the optimal protection for booster-age children.

Belt use: comparison of NASS-CDS and police crash reports

OBJECTIVE

This study compares belt use in police reports with NASS-CDS investigator-determined belt use. The NASS-CDS cases were analyzed by severity of occupant injury and the crash type.

METHODS

1993-2007 NASS-CDS was analyzed for occupant injury severity and crash type. Light vehicles were included with model year 1994+. Injury severity was subdivided by MAIS 0, 1-2, 3, 4+F, and fatal. Crash types were frontal, side, rear, and rollover. The NASS-CDS determination of belt use was assumed the gold standard used to determine miscoding by the police.

RESULTS

The fraction of unbelted occupants increased with the severity of injury from 3.8 percent with no injury to 53.9 percent with fatalities in the police reports. NASS-CDS reported no belt use of 7.9 percent (2.18 times greater than the police) with no injury to 58.2 percent (1.08 times) with fatalities. In side impacts, severely injured occupants were unbelted in 46.9 percent of NASS-CDS cases. This was 1.35 times greater than the 34.7 percent unbelted reported by the police. For severely injured occupants (MAIS 4+F), 18.4 percent of the police reported cases with belt use were actually unbelted occupants by NASS-CDS. The reporting error decreased to 5.0 percent for uninjured occupants (MAIS 0). For uninjured occupants, 35.7 percent of the police-reported cases of no belt use were coded as belted by NASS after inspecting the belt system. This difference decreased to 2.6 percent for fatally injured occupants.

CONCLUSIONS

For occupants with serious-to-fatal injury, the error in police reporting belt use was 13-18 percent. The police often rely on self-reported belt use, which overestimates actual belt wearing and they do not always conduct in-depth investigation of vehicle, seat belt, and occupant injury to reach a conclusion of belt use. The police generally overreport belt use in motor vehicle crashes.

A study of impairing injuries in real world crashes using the Injury Impairment Scale (IIS) and the predicted Functional Capacity Index (PFCI-AIS)

The ability to predict impairment outcomes in large databases using a simplified technique allows researchers to focus attention on preventing costly impairing injuries. The dilemma that exists for researchers is to determine which method is the most reliable and valid. This study examines available methods to predict impairment and explores the differences between the IIS and pFCI applied to real world crash injury data. Occupant injury data from the UK Co-operative Crash Injury Study (CCIS) database have been coded using AIS 1990 and AIS 2005. The data have subsequently been recoded using the associated impairment scales namely the Injury Impairment Scale (IIS) and the predicted Functional Capacity Index (pFCI) to determine the predicted impairment levels of injuries at one year post crash. Comparisons between the levels of impairment were made and any differences further explored. Injury data for the period February 2006 to September 2008 from the CCIS database were used in the analysis which involved a dataset of 2,437 occcupants who sustained over 8000 injuries. This study found some differences between the impairment scales for injuries coded to the AIS 1990 and AIS 2005 coding dictionaries. The pFCI predicts 31.5% of injuries to be impairing in AIS 2005, less than the IIS (38.5%) using AIS 1990. Using CCIS data the pFCI predicted that only 6% of the occupants with a coded injury would have an impairing injury compared to 24% of occupants using the IIS. The main body regions identified as having the major differences between the two impairment scales for car occupants were the head and spine. Follow up data were then used for a small number of cases (n=31, lower extremity and whiplash injuries) to examine any differences in predicted impairment versus perceived impairment. These data were selected from a previous study conducted between 2003 and 2006 and identified the discrepancy between predicted impairment and actual perceived impairment as defined by the participant. Overall the work highlights the variation between the pFCI and IIS and emphasises the importance and need for a single validated impairment scale that can be universally applied. This would allow emphasis to be directed towards preventing injuries that are associated with the most significant impairment outcomes.

Rear seat occupant thorax protection in near side impacts

Thoracic side-airbags (SAB) have proven to protect front seat occupants in side impacts. This benefit has not been evaluated for rear seat occupants who are typically small statured. The objective was to analyze field data from rear seat occupants in near side impacts, and evaluate the effect of a SAB in the rear seat, through full scale vehicle tests. A field study using the NASS-CDS database was performed to review rear seat crash characteristics, occupant injuries (Abbreviated Injury Scale 3+, AIS3+) and injury sources. Full scale tests were performed with the side impact dummy SID-IIs at two different crash severities, with and without SAB in a midsize passenger car. Field data showed that of all AIS3+ injured restrained occupants 13 years and older, 59% had AIS3+ thoracic injuries and 38% had AIS3+ head injuries. The thoracic injuries were distributed to lungs (60%), skeletal fractures (38%) and injuries to arteries (1,26%) and heart (0,1%). For AIS3+ injured children, age 4-12, 51% had AIS3+ thoracic injuries and 54% had AIS3+ head injuries. Compared to adults, children sustained less fractures and more lung injuries. The rear side interior was the main injury source regardless of age group. In the full scale tests, the thoracic side-airbag reduced the average rib deflection by 50% and resulted in an AIS3+ injury risk reduction from 36% to 3%. At the higher impact speed, SAB reduced the injury risk from 93% to 24%. The full scale crash tests showed that SAB offer a significant potential for thoracic injury reduction in the crash severities causing the majority of serious injuries in real life crashes.

PTSD after severe vehicular crashes

PURPOSE

To describe predictors of PTSD after motor vehicle crashes (MVC).

METHODS

MVC patients were interviewed during their hospitalization and at 6 and 12 months post-injury. Interviews included information about behavioral factors, circumstances around the crash, recovery and PTSD screening. PTSD was defined as the development of 3 or more of 7 PTSD symptoms. Association of risk factors with PTSD development at 6 and 12 months was analyzed using contingency tables. Multiple regression models were built for the prediction of PTSD.

RESULTS

367 and 317 patients completed the 6 and 12 month interviews respectively. PTSD developed in 27.5 % (n=101) and 24.3 % (n=77) of the population at 6 and 12 months respectively. PTSD occurred more frequently among females, those with a previous history of depression, violent injury, or other traumatic events, and those whose crashes involved a fatality. Those who were culpable for the crash, age<30, and sustained brain injuries were less likely to develop PTSD at 6 months. Occupant position, education, marital status, alcohol problems, injury severity, heart rate, and blood alcohol + status did not show any significant association with PTSD. In the multiple logistic regression, female gender, history of depression, culpability, prior violent injury, and a fatality in the crash were associated with PTSD at 6 months. Only prior violent injury, and a death in same crash were predictors at one year.

CONCLUSION

PTSD occurs frequently after MVCs. Female gender, prior violent injury, death of another occupant and history of depression are associated with PTSD development.

Use of car crashes resulting in fatal and serious injuries to analyze a safe road transport system model and to identify system weaknesses

OBJECTIVE

The objective of this study was to evaluate a model for a safe road transport system, based on some safety performance indicators regarding the road user, the vehicle, and the road, by using crashes with fatally and seriously injured car occupants. The study also aimed to evaluate whether the model could be used to identify system weaknesses and components (road user, vehicles, and road) where improvements would yield the highest potential for further reductions in serious injuries.

METHODS

Real-life car crashes with serious injury outcomes (Maximum Abbreviated Injury Scale 2+) were classified according to the vehicle's safety rating by Euro NCAP (European New Car Assessment Programme) and whether the vehicle was fitted with ESC (Electronic Stability Control). For each crash, the road was also classified according to EuroRAP (European Road Assessment Programme) criteria, and human behavior in terms of speeding, seat belt use, and driving under the influence of alcohol/drugs. Each crash was compared and classified according to the model criteria. Crashes where the safety criteria were not met in more than one of the 3 components were reclassified to identify whether all the components were correlated to the injury outcome. In-depth crash injury data collected by the UK On The Spot (OTS) accident investigation project was used in this study. All crashes in the OTS database occurring between 2000 and 2005 with a car occupant with injury rated MAIS2+ were included, for a total of 101 crashes with 120 occupants.

RESULTS

It was possible to classify 90 percent of the crashes according to the model. Eighty-six percent of the occupants were injured when more than one of the 3 components were noncompliant with the safety criteria. These cases were reclassified to identify whether all of the components were correlated to the injury outcome. In 39 of the total 108 cases, at least two components were still seen to interact. The remaining cases were only related to one of the safety criteria, namely, the road user (26), the vehicle (19), and the road (24). The criteria for the road and the vehicle did not address multiple event crashes, rear-end crashes, hitting stationary/parked vehicles, or trailers.

CONCLUSIONS

The model for a safe road transport system was found useful to classify fatal and serious road vehicle crashes. It was possible to classify 90 percent of the crashes according to the safety road transport model. For all these cases it was possible to identify weaknesses and parts of the road transport system with the highest potential to prevent fatal and serious injuries. Injury outcomes were mostly related to an interaction between the 3 components: the road, the vehicle, and the road user.

Comparison of distributions of key predictor variables in CIREN and NASS-CDS cases meeting CIREN inclusion criteria

OBJECTIVE

The Crash Injury Research and Engineering Network (CIREN) database contains data from occupants who are seriously injured in motor vehicle crashes. Because of the number of injured occupants and the level of detail in CIREN, a number of previous studies have attempted to use CIREN data to estimate injury risk or relative risk by comparing the frequencies of CIREN occupants with an injury of interest to those without that injury. However, these comparisons provide little useful information because CIREN case occupants cannot provide the control and exposure information that is needed to appropriately estimate injury risk. One potential source of exposure/control information for CIREN is the database established by the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS). However, using NASS-CDS for this purpose requires that NASS-CDS and CIREN cases are drawn from the same source population. The objective of this article is to assess whether this requirement is met.

METHODS

Occupants from NASS-CDS that meet CIREN inclusion criteria, termed CIREN-eligible NASS-CDS cases, were selected to represent the source population for CIREN. These CDS cases were compared to CIREN cases on a number of key variables that are used in many analyses of crash injury data. Comparisons were evaluated using chi-square tests.

RESULTS

The comparisons indicate that CIREN cases are similar to CIREN-eligible NASS-CDS cases on most variables, with some important exceptions. First, CIREN contains more frontal crashes than CIREN-eligible NASS-CDS. Second, there are fewer CIREN cases with two or more AIS 2 injuries and no AIS 3+ injuries than would be expected based on CIREN-eligible NASS-CDS. Finally, on average, occupants in CIREN have a greater number of AIS 3+ injuries, are less often belted in the front seat, and tend to be in higher severity crashes than occupants in CIREN eligible NASS-CDS.

DISCUSSION

These differences suggest that analyses aimed at estimating either relative risk of injury by comparing CIREN cases to base rates from NASS-CDS, or estimating risk of injury using control information from NASS-CDS, should be limited to a specific crash type and injury definition, and should only be performed for AIS 3+ injuries. In addition, analyses should account for the greater overall crash and injury severity of CIREN cases, at least in interpretation of the results.