Crash Scene Photography in Motor Vehicle Crashes without Air Bag Deployment

Transcription

1 924 Newgard et al. CRASH SCENE PHOTOGRAPHY Crash Scene Photography in Motor Vehicle Crashes without Air Bag Deployment Craig D. Newgard, MD, MPH, Katherine A. Martens, MD, Evelyn M. Lyons, RN, MPH Abstract Objective: To determine whether vehicle characteristics, measured using crash scene photography, are associated with anatomic patterns of injury and severity of injury sustained in motor vehicle crashes (MVCs) without air bag deployment. Methods: A prospective observational study was conducted over 22 months, using 12 fire departments serving two hospitals. Two vehicle photographs (exterior and interior) were taken at each MVC. Vehicular variables were assigned by grading the photographs with a standardized scoring system, and outcome information on each patient was collected by chart review. Results: Five hundred fifty-nine patients were entered into the study. Frontal crashes and increasing passenger space intrusion (PSI) were associated with head, facial, and lower-extremity injuries, while rear crashes were associated with spinal injuries. Restraint use had a protective effect in head, facial, and upper and lower extremity injuries, yet was associated with higher odds of spinal injury. Lack of restraint use, increasing PSI, and steering wheel deformity were associated with an increased hospital length of stay and hospital charges, yet only steering wheel deformity was associated with increasing injury severity when adjusting for other crash variables. Conclusions: Out-of-hospital variables, as obtained from crash vehicle photography, are associated with injury site, injury severity, hospital length of stay, and hospital charges in patients involved in MVCs without air bag deployment. Key words: crash photography; motor vehicle; trauma. ACADEMIC EMERGENCY MEDICINE 2002; 9: Mechanism of injury is recognized as a potential predictor of injury in motor vehicle trauma (MVT). 1 While associations between vehicular damage and injury severity 2 4 and between impact site and injury site 1,5 have been demonstrated, a method of accurately recording predictive variables in a timely manner by on-scene personnel has not been developed. 2,6,7 On-scene photographic documentation of damage from motor vehicle crashes (MVCs) has been suggested as a potentially effective means From the Department of Emergency Medicine, Harbor UCLA Medical Center, Torrance, CA (CDN); the Division of Emergency Medicine, Loyola University Medical Center, Maywood, IL (CDN, KAM, EML); and EMS & Highway Safety, Illinois Department of Public Health, Maywood, IL (EML). Dr. Newgard is currently in the Department of Emergency Medicine, Oregon Health & Science University, Portland, OR. Received January 7, 2002; revision received April 23, 2002; accepted April 29, Presented at the annual meeting of the Society for Academic Emergency Medicine, Denver, CO, May 1996, and the annual meeting of the Illinois College of Emergency Physicians, Chicago, IL, June Supported in part through funding from the Emergency Medicine Education & Research Group (EME&RG), grant number F32 HS00148 from the Agency for Healthcare Research and Quality, and the SAEM Research Training Grant. Polaroid provided the cameras used in the study. Address for correspondence and reprints: Craig D. Newgard, MD, MPH, Department of Emergency Medicine, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Mailcode CR-114, Portland, OR Fax: ; e- mail: newgard@ohsu.edu. of obtaining accurate and timely out-of-hospital information. 6,8 To date, no study has linked injury pattern and injury severity to data from crash scene photographs. In this study, we assess crash vehicle photographs taken by out-of-hospital personnel for site and severity of impact, passenger space intrusion (PSI), steering wheel deformity, and windshield condition in vehicles without air bag deployment. These vehicle characteristics were examined to determine their relationship to anatomic injury patterns, severity of injury, length of hospital stay, and hospital charges. We hypothesized that such photographs could provide an objective tool that could be used to help predict injury patterns and injury severity in MVT patients. METHODS Study Design. This was a prospective, observational study. The study was approved by our hospital institution review board (IRB), who waived the requirement for informed consent. Study Setting and Population. The population consisted of mixed urban/suburban communities served by 12 fire departments in the western suburbs of Chicago transporting patients to one of two participating hospitals, a Level I trauma center in a

2 ACAD EMERG MED September 2002, Vol. 9, No university hospital setting and a Level II trauma center in a community hospital setting. Study Protocol. Specialized, durable instant cameras produced by Polaroid were distributed to 12 fire departments. Members of each department received instruction on camera use and appropriate documentation of on-scene variables prior to implementation of the study. Emergency medical services (EMS) personnel were instructed to take one photograph of the primary point of external vehicular impact and a second photograph of the occupant compartment at the scene of passenger vehicle crashes when patients were transported to participating hospitals. If there was any question of compromising patient care or transport time, the photographs were not taken unless backup firefighters or police were available. The photographs were collected over a 22-month period (April 1993 January 1995) for patients taken to one of the two participating hospital emergency departments (EDs). Measurements. The photographs were scored as to primary site of impact (18 options) and severity of impact (mild, moderate, or severe) based on a standardized grading tool produced by the National Safety Council. 9 The pictures were also graded for PSI, steering wheel deformity, and windshield integrity. PSI was defined as any encroachment of vehicle deformity into the passenger compartment, regardless of proximity to the occupant. Minor compartment intrusion was defined as less than 18 inches and major intrusion was greater than or equal to 18 inches of encroachment, as assessed from the photographs. Vehicle structures were used as points of reference to estimate the extent of encroachment in the photographs (e.g., intrusion beyond the midway point of a given seat location, measured from the door in a lateral collision, from the dash in a frontal collision, or from the rear seatback in a rear collision, was defined as major intrusion). Steering wheel deformity was noted if any angulation or deformity was seen in the photograph. A nonintact windshield was defined as any windshield encompassing a crack, spidering, or blowout. Each photo was independently graded by two of four researchers [two emergency medicine (EM) attendings, an EM registered nurse, and a medical student/emergency medical technician]. A third researcher arbitrated any significant discrepancies in the observations. Kappa scores were calculated to assess interrater agreement. Because there was a very low prevalence of air bag deployment and because injury patterns may differ with air bag deployment, vehicles with air bag deployment were excluded from the analysis. We conducted a chart review to determine patient demographic information, Abbreviated Injury Scale (AIS), Injury Severity Score (ISS), length of hospital stay, and total hospital charges. A single researcher, blinded to the accompanying photograph, assigned AIS codes and the resulting ISS. Data Analysis. To assess the relationship between out-of-hospital variables and anatomic injury, we used logistic regression models. Seven different models (one for each type of anatomic injury by AIS code: head, face, spine, thorax, abdomen, upper extremity, and lower extremity) were analyzed using five variables obtained from the photographs (type and severity of external vehicle damage, PSI, steering wheel deformity, and windshield damage) and three variables from out-of-hospital providers (restraint use, seat location, and patient age). Variable selection was performed using a backward stepwise selection process and a p < 0.15 for significance to allow for improved model fit and for an appropriate number of predictor variables used to model a given outcome. Five predictor variables were included in the final models (crash type, PSI, restraint use, seat location, and patient age) for all injury types. Due to the high prevalence of certain anatomic injury types in certain types of crashes, crash type was modeled as a specific type of collision versus all other types. Each type of collision (i.e., frontal, lateral, or rear) was tested in each model for association with the anatomic injury and for model fit. In vehicles with more than one impact site, the site with the greatest amount of external damage was considered the main impact site for purposes of the analysis. The 18 regions of external damage originally used to grade the photographs were categorized into three regions for the analysis: frontal (front-center, front-distributed, front-left, and frontright), rear (rear-center, rear-distributed, rear-left, and rear-right), and lateral (left-back-quarter, leftdistributed, left-front-quarter, left-middle, left-top, right-back-quarter, right-distributed, right-frontquarter, right-middle, and right-top). Models using two different definitions of seat location (front versus rear seat position or drivers versus non-drivers) were compared. Injuries within a given anatomic region were analyzed without respect to injury severity due to the variable number of injuries with AIS 2 severity by body region, and no adjustment was made for clustering of patients within vehicles. Proc LOGISTIC (SAS 8.1, SAS Institute, Cary, NC) was used to compute the models and the Hosmer Lemeshow goodness-of-fit test was used to assess model fit.

3 926 Newgard et al. CRASH SCENE PHOTOGRAPHY We analyzed ISS, total hospital stay, and hospital charges for differences with respect to restraint use, PSI, steering wheel deformity, and windshield damage using the nonparametric methods of SAS Proc NPARLWAY (univariate analysis). The reported unadjusted p-values are products of the Wilcoxon rank sum test or the Kruskal-Wallis test, based on the number of groups being compared. Adjusted p-values were calculated using three multivariate linear regression models, each modeling a separate continuous variable as an outcome (ISS, hospital stay, and hospital charges) using seven predictors (restraint use, PSI, steering wheel deformity, windshield damage, age, seat position, and external vehicle damage). Models using two different definitions of seat location (front versus rear seat position or drivers versus non-drivers) were compared. All reported p-values are two-sided. Proc REG was used to compute the models. RESULTS There were 559 patients included in the study. Patient and vehicle characteristics of the sample are included in Table 1. We analyzed 502 automobile photographs, and 28 photographs were used to assess more than one patient. Impact site was unable to be categorized in 18 photographs (3%), while impact severity could not be categorized in six photographs (1%), due to poor quality. These photographs were excluded from the respective analyses. Fifteen percent of patients (83/559) had at least one injury of moderate severity or greater (AIS 2), while 2% of the patients studied (11/559) were severely injured (ISS 16), and four patients died (0.7%). All MVT patients transported by participating fire departments to one of the two study hospitals were tracked for a six-month period during the study to monitor out-of-hospital personnel compliance. Of the 377 total MVT patients transported during this six-month period, 224 (59%) had photographs taken and were included in the study. Information on MVT patients who did not have photographs taken was unavailable for comparison. Interrater reliability scores (kappa scores) were calculated for primary vehicular impact site (18 categories) and damage severity (3 categories), as determined in the photograph. The overall kappa scores for impact site and impact severity were 0.59 and 0.52, respectively, indicating fair reliability. Kappa scores were not calculated for assessment of PSI, steering wheel deformity, or windshield damage. The association between anatomic injury and out-of-hospital variables is seen in Table 2, and the TABLE 1. Patient and Vehicle Characteristics Variable Sample size 559 Age median (interquartile range) 29 (21 41) yr Gender male 48% Restrained 56% Windshield damage 59% Steering wheel deformity 23% Drivers 71% Front seat position 91% Impact type Frontal 49% Rear 16% Lateral 35% External vehicle damage None 3% Mild 29% Moderate 36% Severe 33% Passenger space intrusion (PSI) None 81% <18 inches 13% 18 inches 6% Anatomic injury types All Injuries* AIS 2(%) Head 84 (15%) 35 (42%) Face 172 (31%) 8 (5%) Spine 110 (20%) 2 (2%) Thorax 38 (7%) 15 (39%) Abdomen 15 (3%) 7 (47%) Upper extremity 97 (17%) 20 (4%) Lower extremity 127 (23%) 23 (18%) *Percentages of each injury are calculated as a percentage of the entire sample, and do not add to 100% due to some patients with multiple anatomic injury types. Percentages of Abbreviated Injury Scale (AIS) 2 are calculated by row, as a percentage of a given type of anatomic injury. relationship between ISS, hospital length of stay, hospital charges, and out-of-hospital variables is presented in Table 3. Steering wheel deformity, windshield damage, and external vehicle damage did not have associations with any injury types and were excluded from the final anatomic injury models. Only steering wheel deformity was associated with an increasing ISS in the multivariate model, while lack of restraint use, PSI, and steering wheel deformity were all associated with an increase in hospital stay and charges. Associations in all models (i.e., anatomic injury, ISS, length of stay, and

4 ACAD EMERG MED September 2002, Vol. 9, No TABLE 2. Multivariate Analysis of Predictors of Anatomic Injury in Motor Vehicle Crashes (7 Separate Models Assessing Odds Ratios with 95% Confidence Intervals) Outcome Injury* Crash Type PSI Restraint Use Front Seat Age Head Frontal 2.2 ( ) 2.8 ( ) 0.4 ( ) 2.0 ( ) 1.1 ( ) Face Frontal 2.1 ( ) 1.8 ( ) 0.5 ( ) 1.6 ( ) 1.0 ( ) Spine Rear 5.8 (3.3 10) 0.2 ( ) 3.0 ( ) 1.4 ( ) 1.0 ( ) Thorax Lateral 1.6 ( ) 1.5 ( ) 0.7 ( ) 1.2 ( ) 1.4 ( ) Abdomen Lateral 2.8 (0.6 12) 0.7 ( ) 0.4 ( ) 0.2 ( ) 1.6 ( ) Upper extremity Frontal 0.9 ( ) 1.6 ( ) 0.5 ( ) 1.6 ( ) 1.1 ( ) Lower extremity Frontal 2.8 ( ) 2.2 ( ) 0.7 ( ) 1.1 ( ) 1.3 ( ) *Anatomic injury outcomes refer to all injuries in a given anatomic location, regardless of severity. PSI = passenger space intrusion. Age was coded as a continuous variable in increments of ten years. charges) remained unchanged whether seat location was coded as front versus rear seat position or as drivers versus non-drivers. A nonintact windshield was not associated with injury severity, hospital stay, or hospital charges in the multivariate models. All logistic regression models were well-fit using Hosmer Lemeshow goodness-of-fit testing. DISCUSSION In this study, we demonstrate associations between MVT mechanism of injury, as ascertained through on-scene photographs, and specific injury patterns and injury severity. These results complement results found in other studies, l,5,10,11 yet this analysis is distinguished by the communication of on-scene vehicular information via photographs. Although specific biomechanical injury patterns associated with impact type have been established, 1,5,10,11 the inaccuracy of reporting and charting by out-of-hospital providers has made this information difficult to apply clinically. When using EMS run sheets from MVCs, Hunt et al. noted that the area and severity of vehicle damage could be determined in only 52% and 39% of cases, respectively. 6 However, assessment of photographs from the same vehicles provided accurate information for these variables in 100% of cases. 6 In a subsequent study assessing the time needed for out-of-hospital personnel to take photographs (1 interior, 1 exterior of the vehicle), 96% of the photos required less than 2 minutes and there was no difference in on-scene times compared with a prior control sample. 8 Other studies have documented the inaccuracy of information obtained by emergency physicians regarding vehicle collision factors when compared with police accident reports, with 74% of cases having at least one discrepancy and 46% having multiple discrepancies. 7 Furthermore, verbal depiction of collision details is often inefficient and ineffective in the clinical setting, especially in a high-volume ED or where multiple physicians care for the patient. Because of these deficiencies, on-scene photography of vehicular damage has the potential to serve as an efficient, practical, and accurate method of conveying information on mechanism of injury in MVT patients. We found frontal crashes and increasing PSI (as graded from crash photographs) to be associated with head, facial, and lower extremity injuries, when controlling for the protective effect of restraint use. Increasing age was associated with thoracic, abdominal, and lower extremity injuries. The lack of any additional associated predictors for thoracic or abdominal trauma may have been a reflection of the smaller number of patients in these injury groups. Restraints proved most beneficial in reducing head, face, and upper extremity injuries. Spinal injuries had a strong association with rear crashes, as well as associations with PSI and restraint use different from that of other injury types. Our results suggest that increasing PSI and lack of restraint use have protective effects in spinal injuries. While these findings seem counterintuitive, there may be a biomechanical explanation to partly explain these associations. The spinal injuries included in our sample were primarily minor severity injuries (98% AIS 1, indicating acute strains with no fracture or dislocation), so the associations we demonstrate can be considered only with respect to minor spinal injuries. In rear impacts, the vehicle is accelerated forward, while the occupant moves rearward within the vehicle. As the head and neck are extended, the seat is flexed posteriorly to accommodate the rearward movement of the occupant. In lower-speed crashes, there may be minimal posterior movement of the seat, forcing the soft tissues of the neck to absorb all the energy incurred during hyperextension of the head and neck. 11 The impact speed necessary to initiate structural deformity of the vehicle (approximately 9 mph) is greater than that needed to induce cervical soft-tissue injury in healthy people with proper head support. 12 As the energy in a rear collision increases

5 928 Newgard et al. CRASH SCENE PHOTOGRAPHY TABLE 3. Relationship between Out-of-hospital Variables Obtained through Crash Vehicle Photographs [Passenger Space Intrusion (PSI), Steering Wheel Deformity, and Windshield Deformity] and Out-of-hospital Provider Reports (Restraint Use), and Injury Severity Score (ISS), Hospital Stay, and Hospital Charges ISS Hospital Stay Hospital Charges Variable* Mean (Median) Unadj. p-val Adj. p-val Mean (Median) Unadj. p-val Adj. p-val Mean (Median) Unadj. p-val Adj. p-val Restraint use Yes 1.6 (1) (0) < $1,983 (0) < No 2.7 (1) 1.5 (1) $7,074 (3,047) PSI None 1.7 (1) < (0) < $2,651 (0) < <18 in 3.0 (1) 2.1 (1) $9,368 (3,566) 18 in 6.4 (2) 3.5 (1.5) $15,594 (5,707) Steering wheel deformity Yes 4.2 (1) < (1) < $10,527 (4,416) < No 1.5 (1) 0.7 (0) $2,734 (0) Windshield deformity Yes 2.7 (1) < (1) < $7,144 (3,497) No 2.0 (1) 0.7 (0) $2,501 (0) *Results for seat position, external vehicle damage, and age are omitted from the table for clarity. Of these three variables, only age was associated with ISS (p = ), hospital stay (p = ), and hospital charges (p = ) in the multivariate models. Unadjusted p-values were calculated by the Wilcoxon rank sum test or the Kruskal-Wallis test, based on the number of groups being compared. Adjusted p-values were calculated by multivariate linear regression models, including predictors: restraint use, PSI, steering wheel deformity, windshield deformity, age, seat position, and external vehicle damage. Outcome variables were modeled as continuous variables without categorization. Adjusted R-squared values ranged from 0.11 to (i.e., as the PSI increases, if one considers PSI a surrogate marker for the severity of collision), there is more posterior movement of the seat, which may buffer the amount of stress placed on the soft tissues of the neck, 11 thus potentially reducing the likelihood of soft-tissue trauma. Restraint use has not been shown to reduce spinal injuries in rear crashes due to an inability to restrain the head and neck. 11 Whether the positive association between restraint use and minor spinal injury in our sample suggests a cause-and-effect relationship or a protective effect (i.e., that restraint use reduced the severity of injury from potentially severe to minor) is unknown. The effect of restraint use on more serious spinal injuries is unclear. Only steering wheel deformity was associated with increased injury severity (ISS), while steering wheel deformity, lack of restraint use, and increasing PSI were associated with longer hospital stays and greater hospital charges. These findings persisted after controlling for age, seat position, and external vehicle damage. If we consider increasing hospital stay and higher charges as markers of more severe injuries, then steering wheel deformity, PSI, and lack of restraint use may serve as indicators of injury severity. The lack of association between windshield damage and injury severity in the multivariate models may be explained by the many other objects and forces involved in a collision that can disrupt windshield integrity without adversely affecting occupants. LIMITATIONS Photographs accompanied only 59% of the MVT patients transported to the participating hospitals. This finding may represent a selection bias toward less severely injured subjects if out-of-hospital providers were less likely to provide photographs for severely injured patients, and may partly explain the lower percentage of severely injured patients in our sample (2%). We did not restrict the analysis to patients with higher severity injuries due to smaller numbers of patients with severe injuries. Future studies that include a higher percentage of patients with moderate-severe injuries will be needed to affirm our findings. In addition, there was only moderate interrater agreement when grading the pictures independently. The kappa scores would likely improve with simplification of categories for impact site and impact severity. Because vehicles with air bag deployment were

6 ACAD EMERG MED September 2002, Vol. 9, No excluded from the analysis, our findings cannot be generalized to those occupants. Although the use of air bags in newer model vehicles will become increasingly important with respect to new patterns of injury, the majority of vehicles on the road today are not equipped with air bags. Other studies have reported specific injuries (e.g., thorax, abdomen, and pelvis) associated with lateral crashes 1,5 ; however, we did not find such associations. This discrepancy may have been a result of not linking the side of impact to the occupant s location within the vehicle or due to an inadequate number of patients with these injury types. Finally, the lack of association between PSI or restraint use and ISS in the multivariate models may have been the result of an inadequate number of severely injured patients to detect an association with these variables. CONCLUSIONS Variables obtained through crash vehicle photographs are associated with anatomic injury patterns, injury severity, hospital length of stay, and hospital charges in subjects involved in MVCs without air bag deployment, and may provide a useful means of communicating objective information from the crash scene to the clinician in a timely manner. To define the usefulness of crash photography in patient management, in patient outcomes, and in vehicles with air bag deployment, further studies are needed. The authors acknowledge the participation of the following Illinois fire departments in this study: Berwyn, Broadview, Brookfield, Cicero, Forest Park, Forestview, Hillside, Lyons, Maywood, North Riverside, Oak Park, and Westchester. In addition, they acknowledge Maureen A. Phelan, MS, for her statistical assistance and Roger J. Lewis, MD, PhD, for his assistance with manuscript preparation. References 1. Dischinger PC, Cushing BM, Kerns TJ. Injury patterns associated with direction of impact: drivers admitted to trauma centers. J Trauma. 1993; 35: Jones IS, Champion HR. Trauma triage: vehicle damage as an estimate of injury severity. J Trauma. 1989; 29: Newman RT. A prospective evaluation of the protective effect of car seatbelts. J Trauma. 1986; 26: Henry MC, Hollander JE, Alicandro JM, Cassara G, O Malley S, Thode HC Jr. Incremental benefit of individual American College of Surgeons trauma triage criteria. Acad Emerg Med. 1996; 3: Siegel JH, Mason-Gonzalez S, Dischinger P, et al. Safety belt restraints and compartment intrusions in frontal and lateral motor vehicle crashes: mechanisms of injuries, complications, and acute care costs. J Trauma. 1993; 5: Hunt RC, Brown RL, Cline KA, Krohmer JR, McCabe JB, Whitley TW. Comparison of motor vehicle damage documentation in emergency medical services run reports compared with photographic documentation. Ann Emerg Med. 1993; 22: Santana JR Jr, Martinez R. Accuracy of emergency physician data collection in automobile crashes. J Trauma. 1995; 38: Hunt RC, Whitley TW, Allison EJ Jr, et al. Photograph documentation of motor vehicle damage by EMTs at the scene: a prospective multicenter study in the United States. Am J Emerg Med. 1997; 15: Traffic Accident Data Project Steering Committee. Vehicle Damage Scale for Traffic Accident Investigators, ed. 3. Traffic Accident Data Project Technical Bulletin No. 1. Chicago, IL: National Safety Council, Parenteau CS, Viano DC, Lovsund P, Tingvall C. Foot ankle injuries: influence of crash location, seating position and age. Accid Anal Prev. 1996; 28: Severy DM, Mathewson JH, Bechtol CO. Controlled automobile rear-end crashes, an investigation of related engineering and medical phenomena. Can Serv Med J. 1955; 11: Miller DB. Low velocity impact, vehicular damage and passenger injury. Cranio. 1998; 16:226 9.