Epidemiology and patterns of musculoskeletal motorcycle injuries in the USA

Introduction

Injury secondary to motorcycle crashes is a major problem in the United States of America (USA). In 2007, the number of registered motorcycles in the USA totaled 7,138,476, of which 387,915 were registered in Texas^19,21. That same year, 103,000 Americans were injured in motorcycle crashes, with 5,154 of them killed. Texas ranked third in terms of fatalities behind Florida and California¹⁸.

In recent years, the annual incidence of automobile-related fatalities in the USA has progressively decreased, while the annual incidence of motorcycle crash fatalities has progressively increased¹⁹. However, despite the expanding use of motorcycles, there has been a paucity of orthopedic epidemiological studies related to motorcycle crash in recent years. Our institution has been the primary Level I trauma facility for Galveston County and the surrounding region. The area is one of the most popular motorcycle destinations in Texas, and Galveston is home to the state’s largest motorcycle rally¹. The purpose of this study was to review a single-institution experience with MIs in regard to the epidemiology and patterns of both musculoskeletal and non-musculoskeletal injuries. In addition, this study will compare our modern USA motorcycle injury data with those of earlier international reviews^2,27.

Materials and methods

The study was conducted in compliance with the University of Texas Medical Branch policies and regulations regarding human subject research following study protocol review and approval by the Institutional Review Board (approval IRB #09-259). Study data were derived from a prospectively collected injury database at our Level I trauma center. The data sampling included 1,221 patients injured in motorcycle crashes for the 10-year period ending August 31, 2008. Each motorcycle trauma event was considered separately and evaluated independently; patients with more than one motorcycle trauma event evaluation during the study time period had each event considered as a separate incident.

This retrospective analysis included data on patient age, gender, race/ethnicity, documentation of helmet use, Glasgow Coma Scale (GCS) score at the time of presentation in the emergency department, injury severity score (ISS), length of hospital stay (LOS), specific injury diagnosis, and mortality.

Descriptive statistics were used to describe the sample characteristics (age, gender, race) and distribution of the outcome variables (GCS, ISS, LOS, type of injury, and death). Non-parametric methods (Spearman correlation coefficient and Kruskal-Wallis tests) were used to test the association between the general patient demographic data, helmet use, and the outcome variables ISS and LOS. Logistic regression analyses were used to test the association of the general patient demographic data and helmet use with patient GCS classification (mild vs. moderate/severe), vital status at discharge and type of injuries (with/without central nervous system injury, dislocation, fracture, and thorax injury). All tests were two-sided with alpha of 0.05 and were performed using SAS 9.3 (SAS Institute Inc, Cary, NC, USA).

Results

Discussion

Many epidemiological studies have addressed motorcycle crash injuries, in particular the effect of helmet use^3,5,6,9,25. There has been a relative paucity, however, of new information regarding orthopedic motorcycle crash injuries in USA over the last 30 years. Unfortunately, during this period motorcycle crashes continued to be a major cause of accident-related morbidity and mortality. It has been reported that in 2007 motorcyclists were 37 times more likely to die in a motor vehicle traffic crash than passenger car occupants, and nine times more likely to be injured²⁰. Whereas car and truck fatality rates have decreased for the past 6 and 3 years, respectively, 2008 marked the eleventh consecutive year in which the annual motorcycle fatality rate increased¹⁹. Yet, to our knowledge, the most recent epidemiological studies on orthopedic motorcycle crash injuries in the USA were by Bried et al.⁶ in 1987 and Peek et al.²² in 1994.

According to our data, the rates of skull, face, spine, rib, and pelvis fractures have increased in the USA motorcycle crashes compared with historical reports^9,11,28. The rates of skull and face fractures in our study are substantially higher than in recent European studies (Table VI), whereas the rates of spine and pelvis fractures have remained similar. The higher incidence of some of the injuries documented in our study may be attributed to better injury detection. In the USA, whole-body computed tomography has become a routine trauma screening tool²⁴. Moreover, European riders are more likely to wear a helmet², and their lower incidence of skull and face fractures and death might be attributed to this protective device. The protective nature of helmets has been described in a number of studies^13,16.

In contrast to Ankarath et al’s² and Robertson et al’s²³ studies from 2002 that analyzed similar patient populations from the Yorkshire region of the United Kingdom from the mid to late 1900s and Kupferschmid et al.¹⁵ study from 1989, we found lumbar spine fractures to be more common than thoracic. This is in agreement with Goslar et al.’s¹² study (2008) that looked at spine fractures in motorcycle accident victims in Arizona. However, the incidence of facial fractures in the present study was nearly twice that reported by Kraus et al. (13.66% vs. 7.10%) in a study using early 1990s data¹⁴, when routine computed tomography was not as common a procedure.

Injuries and death among older motorcyclists has recently become a focus topic of motorcycle crash studies. It has been reported that the age of motorcyclists has been increasing⁷. The Motorcycle Industry Council found the mean age of motorcycle ownership to rise from 33.1 years in 1998 to 40.2 years in 2003¹⁷. Our study of patients aged 4 to 83 years (mean 36 years) joins other studies of motorcycle crash victims that have shown increased risk for a longer hospital stay, more severe injuries, and death among older patients. Brown et al., using 1996–2005 National Trauma Databank statistics on 61,689 motorcycle operators involved in crashes, found the average age to increase steadily over the study period, from 33.9 years to 39.1 years⁷. The fastest growing age group in relative frequency was that of 50 to 59 years, whereas the most rapidly declining was that of 20 to 29 years. Operators 40 years of age or older had higher ISS, LOS, intensive care unit LOS, and death rate compared with operators younger than 40 years. Brown et al. found significantly higher rates of severe thoracic and head injuries and rib fractures, as well as more complications and more than twice the rate of pre-existing comorbidities among motorcyclists aged 40 years or older⁷. Whereas their data indicated no difference in helmet use between younger and older injured operators, we found older patients significantly less likely to use a helmet, with lack of helmeting linked to skull fracture and death^3,25. In contrast, in a 1981 NHTSA treatise Hurt et al. described younger patients as less likely to wear a helmet¹³.

Dischinger et al. found that older riders (40 years or older) have significantly higher incidence of thoracic injury, specifically multiple rib fractures¹⁰. Talving et al. investigated the relation of age to injury type, distribution, and the severity of motorcycle crash patients in a Los Angeles County-wide trauma registry study (N = 6,530) including data from 1995 to 1997²⁶. Age was classified as 18 years or younger, 19 to 55 years, or older than 55 years. Older patients were significantly more likely to suffer severe trauma, severe head and chest injuries, and spinal fractures. Death was 3-fold higher in the oldest age group compared with the youngest.

The limitations of our study include its retrospective nature and the fact that it relies upon a trauma database. Although the data were collected prospectively, they were not specifically designed for this study. Orthopedic injuries were grouped by anatomic location as opposed to specific fracture type to control for small errors of injury classification (e.g., injury was classified as a radial shaft fracture as opposed to a Galeazzi or simple distal radius fracture). However, these injury classifications are similar to those employed in prior studies^{2,6,8,9,11,22,27,28}, and many of those study data were also derived from existing databases^2,4,12.

Although the motorcycle fatality rate continues to increase, we did not see a similar increase in in-hospital mortality rate, indicating that more of the involved participants are likely being declared dead at the scene. The increase in the incidence of skull, spine, and face injuries noted in the study may be attributed to better injury detection (routine CT and/or MRI). The higher incidence of USA skull and facial fractures, as compared to other countries, may also be attributed to differences in compulsory helmet wearing laws. Older MI patients are a higher risk for serious injury and mortality, and this is further potentiated by not wearing a helmet.

Data availability

Figshare: Raw data used for the analysis in the study on epidemiology and patterns of musculoskeletal injuries. Doi: http://dx.doi.org/10.6084/m9.figshare.1402186²⁹