Bicycle Injuries—A Modern Perspective
Laura Q. Wu, BS¹, Daniel C. Jupiter, PhD², William J. Mileski, MD³,Elissa Dabaghi, MS⁴, Zbigniew Gugala, MD,PhD¹
¹Department of Orthopaedic Surgery & Rehabilitation²Department of Preventive Medicine & Community Health³Department of Surgery⁴School of MedicineUniversity of Texas Medical Branch; Galveston, TX, USA
Corresponding Author:Zbigniew Gugala, MD,PhD, Orthopaedic Surgery & Rehabilitation, University of Texas Medical Branch, 301 University Blvd., Galveston TX 77555, USA, e-mail: zgugala@utmb.edu
DOI: 10.18600/toj.050101
INTRODUCTION
Bicycling is a popular recreational activity and means of transportation among people of all ages. A national survey by the Outdoor Foundation in 2013 identified bicycling as the most popular outdoor activity among U.S. children and the third most popular among U.S. adults [1]. Although various personal and structural safeguards have been studied and implemented, data from the Centers for Disease Control and Prevention (CDC) show that cycling-related injuries still send half a million people to the emergency room and cause 900 fatalities every year [2]. Furthermore, reported numbers likely underestimate the true incidence of bicycle injuries, because not all injuries are documented in police or hospital records. Children are the most commonly injured age group, but the elderly sustain injuries with higher morbidity and mortality [3]. This suggests that bicycle injury patterns may vary with demographic and behavioral factors, and that prevention strategies can be differentially adjusted for each target population.
Current injury prevention methods include protected bicycle lanes, cyclist visibility, cyclist education, and protective equipment (eg, helmets) [3]. Of these, helmet use is by far the most extensively studied and commonly recommended. Many cities and states have enacted local helmet laws, most of which are limited to riders under the age of 18 [4]. These laws have been controversial, with one side citing the number of studies indicating reduction of head injury and mortality with helmet use, and the other side pointing out the lack of high quality evidence that show helmet laws can effectively change injury patterns without also decreasing ridership [5-7]. Compliance with helmet-wearing is low, as low as one quarter of cyclists, which is especially true among young riders [8-9].
Many studies on bicycle ridership have previously identified risk factors for injury and mortality [3,10-15]. Additionally, other studies have focused on helmets, examining rates of, barriers to, and effectiveness of helmet use [3,8-9,16-18]. Yet, despite the published research and public reports, bicycle injuries have not seen a dramatic decline. Understanding factors associated with cycling-related injury severity and mortality may potentially help establish effective policy countermeasures. More importantly, further research can bring awareness to this ongoing issue that is both deadly and costly. The objectives of the current study were to examine cycling-related injuries from both local and national trauma databases and identify cyclist- and injury-related risk factors, and to compare the two sets of results to determine whether guidelines for bicycle safety can be adjusted for local communities.
PATIENTS & METHODS
Study Design
The National Trauma Data Bank (NTDB) and a local Level I trauma center database were separately queried for bicycle injury data from January 2007 to December 2012. NTDB is managed by the American College of Surgeons and contains prospectively collected, de-identified data from over 700 trauma centers across the USA. The local trauma database contains similar information and contributes data annually to the NTDB. Approval was obtained from the University of Texas Medical Branch’s Institutional Review Board for this patient population.
Patients with bicycle-related injuries were retrospectively identified using ICD-9 E-codes (800-807[.3], 810-825[.6], 826.1). All external causes in which the patient was a bicyclist, such as collisions with motor vehicles, were included. Each bicycle trauma event was considered independently, even if a patient was involved in more than one accident during the study period. Patient characteristics (demographics, drug use), injury factors (mechanism, location, body region, helmet use), and short-term outcomes (severity, complications, number of procedures, length of stay, death) of interest were extracted. Patients under the age of 3 were excluded due to low likelihood of independent riding.
Statistical Methodology
Data sets from the 2 databases were separately analyzed and then compared. Univariate analyses were carried out to describe each variable, using means (standard deviations) or proportions, as appropriate. Bivariate categorical comparisons were performed using the Pearson Chi-square test or Fisher’s exact test. Groups were compared using the Student’s t-test or analysis of variance (ANOVA). Multivariate models (logistic regressions) were built based on the bivariate analyses in order to relate predictor variables to outcome variables and control for confounding variables. In general, the variables with a bivariate analysis P-value <0.2 were included in the multivariate models. Odds ratios were determined for each predictor variable in the multivariate analyses. All tests were two-sided, and a P-value <0.05 considered significant. All analyses were completed using the R statistical package version 3.2.5 (R Developmental Core Team; R: A Language and Environment for Statistical Computing, 2009; available from: http://www.R-project.org).
RESULTS
National Database Summary
The NTDB query identified 113,623 bicycle trauma event evaluations in the years 2007-2012. Males made up 80% of injury evaluations (Table 1). The average patient age was 32.8 years (range 3-89). There was a 7:1:1 White:Black:Hispanic ratio. Of those patients whose alcohol and drug usage status were recorded (92,561 and 86,649, respectively), 9.7% were found to be using alcohol above the legal limit, and 9.2% were found to be using either illegal drugs or using prescription drugs illegally. Among the injured cyclists whose helmet status was recorded (92,209 incidents), 32% reported wearing helmets.
Motor vehicle accident was the mechanism behind 34% of injury evaluations, while bicycle-only accident was behind 64% of injuries identified. The most common location for injury was on the street (72%), and the second most common was recreation areas (10%). The average Injury Severity Score (ISS) was 9.8 (SD=8.3, range 1-75), and the mortality (at arrival and/or post-admission) was 1.9%. Average length of stay was 3.9 days (SD=7.1, range 0-314).
Head and neck injuries occurred in 65,413 (57.6%) injury evaluations, and traumatic brain injuries occurred in 48,317 (42.5%; Table 2). Fractures, the most common injuries, were sustained by 66% of injured cyclists (Table 3).
Compared to helmeted cyclists, the non-helmeted cyclists were younger, used more alcohol and illegal drugs, and were disproportionately male, Hispanic or non-Hispanic black, and Medicaid-insured (p<0.001; Table 4). Non-helmeted cyclists also suffered higher rates of head and neck injuries, traumatic brain injuries, and mortality (p<0.001).
Compared to helmeted cyclists, the non-helmeted cyclists were younger, used more alcohol and illegal drugs, and were disproportionately male, Hispanic or non-Hispanic black, and Medicaid-insured (p<0.001; Table 4). Non-helmeted cyclists also suffered higher rates of head and neck injuries, traumatic brain injuries, and mortality (p<0.001).
Local Database Summary
In the local trauma registry, 240 bicycle trauma event evaluations were identified in the years 2007-2012. Males made up 74% of injury evaluations. The average patient age was 34.7 years (range 3-88). There was an 8:2:3 White:Black:Hispanic ratio (Table 1). Of those patients whose alcohol and drug usage status were recorded (203 and 147, respectively), 0.97% were found to be using alcohol above the legal limit, and none were found to be using either illegal drugs or using prescription drugs illegally. Of those injured cyclists whose helmet status was recorded (163 incidents), only 10% reported wearing helmets. Compared to helmeted cyclists, the non-helmeted cyclists were younger (p=0.010) and Hispanic or non-Hispanic black (p<0.014).
Comparison of Databases
Only 10% of local database cyclists were reported to have been wearing a helmet, compared to 32% in the national database (p<0.001; Table 1). Compared to the national database, local trauma database cyclists were proportionally more female (p=0.00944) and black or Hispanic (p<0.001). Alcohol and drug use were significantly lower in the local database (p<0.001). Local cyclists were more likely to be injured in the street and by motor vehicle accidents (p<0.001). Extremity injuries were less common in local evaluations (p<0.001). However, local cyclists had lower average injury severity score (p<0.001), higher Glasgow Coma Scale (GCS) upon emergency room arrival (p=0.0168), and shorter length of stay (p<0.001).
DISCUSSION
Bicycle injuries today remain high in number and can cause significant morbidity and mortality. Especially controversial is the effect of helmets in preventing severe injury [5-7]. Demographic groups such as children and the elderly are especially at risk, and efforts must be made to identify modifiable risk factors in order to reduce bicycle injuries [3]. It is possible that bicycle injury patterns vary with demographic and behavioral factors, and that prevention strategies can be differentially adjusted for each target population.
The comparison of national and local trauma databases is an important objective of this study. Recent literature has shown that large databases used in trauma research may sample different populations and produce different conclusions [19]. Therefore, we hypothesized that our local trauma database population could also differ and produce different conclusions than the National Trauma Data Bank. When creating policy toward public safety, it could be difficult to choose between national data that is generalized and supported by a large sample size, versus local data that is more relevant but much smaller in sample size. In the present study, the local data differed from the national data not only in demographics, but also in helmet-wearing status and injury patterns. Therefore, it is advisable to analyze local data when available, so as to note any unique patterns of the regional population.
Our results show the number of bicycle injuries reported in the U.S. remains high, with around a third caused by motor vehicle accidents. Our results indicate that helmets offer effective injury prevention for cyclists, and that the level of compliance was lowest in teenagers and highest in the elderly. Alcohol and drug use were common in injured cyclists, and these behaviors were associated with worse outcomes.
There are several limitations to this study. First, as a retrospective, observational study, it is not able to uncover any causative relationships or make predictions. Second, the local database is from a single center and may not be representative of other regions. The region surrounding the local trauma center does not have any helmet laws, whereas areas surrounding other trauma centers may have distinct regulations. Third, the local database is not independent of the national database because it contributes annually to the national database. And lastly, state and local bicycle and helmet laws vary by region, and cyclist compliance with any existing laws is unknown. The present study summarizes data from a national trauma database, which unifies areas with differing laws through de-identification of trauma centers. Therefore, given this data, it is impossible to determine the effect of existing bicycle laws around the country on helmet wearing compliance and injury characteristics.
CONCLUSIONS
Efforts to improve availability of cyclist-friendly infrastructure, compliance with helmet-wearing, and cyclist injury awareness should be continued or increased to reduce the number of bicycle-related injuries. National databases may not be representative of local populations, and local policy could be informed by looking at regional data, if available.
ACKNOWLEDGMENTS
We would like to thank the American College of Surgeons and the National Trauma Data Bank for access to the national database. The NTDB remains the full and exclusive copyrighted property of the American College of Surgeons. The American College of Surgeons is not responsible for any claims arising from studies based on the original data, text, tables, or figures. We would also like to thank everyone involved in the creation and maintenance of the local trauma database, without whom this study would not be possible. In the present study, 2007-2012 editions of the databases were utilized.
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