This study evidences significant higher percentage on the injury severity and less frequency of the injuries in road cycling-related accidents compared to the mountain bike ones.
The ISS value obtained in the present work was similar to that reported in an Australian study (10)but it was lower than that found in studies from other countries (7, 11). Significant differences in injury severity were observed between road and mountain bikers, with road cyclists showing more serious injuries and therefore higher ISS values. These results are consistent with those of a study assessing cycling crashes in Denmark (12). This could be explained by the high incidence of head injuries observed in the road cyclists which are also statistically different from those of the mountain bikers. In the Netherlands, indeed, traumatic brain injuries are the leading cause of mortality in cycling accidents (13)
Regarding the volume of emergency care attendance to injured cyclists, higher values were observed in mountain cyclists. The geographical location and the high percentage of populations practicing this sport could be the main determinants of this finding.
Our results evidenced that both road and mountain cyclists suffered more injuries to the extremities. In contrast de Guerre (7) or de Foley (11) found that the most affected anatomical region was the head. One of the possible reasons f or these differences lies in the fact that the de Guerre or Foley’s studies included only patients who were hospitalized. Regarding the involvement of the extremities and in agreement with other studies, the upper extremities were more frequently affected in both groups (8, 11, 14, 15). Furthermore, mountain bikers were more frequently injured in all body regions except the lower extremities where injuries were more prevalent in road cyclists.
As possible causes of the difference in injury severity, we consider that the mechanism of injury is a key factor that determines both the severity and location of injuries. In our study, in both groups the main cause of fall and therefore the mechanism of injury was loss of control. However, different results can be found in the literature. Some studies report collision with another vehicle as the main cause of the accident, either with a car or another bicycle (10, 16–19), others, as our study, outline that the main cause is loss of control (8, 20, 21) and other studies find no differences between the two groups (22). The high percentage of accidents involving motor vehicles in the road cycling group may be one of the main causes for the increased severity of injuries in this group. Another cause explaining the differences observed between the road and mountain biker groups could be the speed of the cyclists at the time of the accident, which may differ according to the type of cycling. Nevertheless, in the present study we found no differences in this parameter.
We also looked for other risk factors that may explain the differences in severity evidenced in both groups, such as the use of helmets. It has been shown that head injuries can be one of the main causes of morbidity and mortality in cyclists (13). On the other hand, helmets, which are effective in preventing head and facial injuries(7, 23, 24), are related to a decrease in ISS(25). In our study, no differences were found in the use of the helmet between the two groups; however, road cyclists suffered more severe head injuries than mountain bikers. Further studies on the use of the helmet should be conducted, particularly due to the fact that other studies(16) related the use of this safety device to factors such as age or severity of head injuries.
Another factor evaluated in this study was sex. Conversely to what has been reported in other studies, which observed that most accident victims are men (8, 10, 12, 14, 16, 25, 26) no differences in terms of severity or mortality of accidents according to sex were found in this study.
In addition, the level of triage or the length of stay in hospital were analyzed. These variables, unlike the ISS Score, did not provide significant differences when comparing the two groups. Structured triage systems with five levels of priority are used in our center. It allows patients to be classified according to "degree of urgency", so that the most urgent patients are seen first, and the rest are reassessed until being seen by the doctor (27). These levels are based on the concept of urgency rather than severity, and possibly due to the fact that urgent is not always severe and severe is not always urgent, the differences between triage and ISS Score results may have been observed.
No statistically significant differences were found between the severity of injuries related to the alcohol consumption in the two groups. We observed lower rates of alcohol consumption than those reported in the literature (17, 25, 28) probably because not all patients were tested for alcohol consumption or simply because certain drinks, such as a beer, are not considered as alcohol consumption.
Alcohol is a factor associated with an increased risk of crashes and more serious injuries in the event of a crash (29–31).
Finally, our results highlighted the association between the patients age and the injuries severity, especially in road cyclists. The older the patient, the more serious the injury was. Thus, the age can be considered an important risk factor in road cycling accidents. These findings are in line with other studies reporting a correlation between age and the severity of injuries(7, 22, 25, 31–33) or the type of injuries(31). Ekman et al.(32) observed that the risk of dying from a cycling-related injury was 3.5 times higher in older people and the risk of suffering a serious injury was 7.5 times higher. Some characteristics related to the age, such as a longer reaction time that makes it more difficult to avoid obstacles, bone fragility, acoustic or visual loss or higher presence of pathologies can determine the association between age and severe injuries.
A limitation of this study is that this group of patients only represents a percentage of all bicycle-related injuries. This is a regional study and therefore our results may not be applied to other regions with different cycling infrastructure, traffic laws and popularity of cycling. However, given that this trauma center is one of the largest in Catalonia, we expect the results to be representative for other regions. In 2021, the total number of fatal bicycle accidents in Spain was 63(3). Compared to previous years, there is a decreasing trend in the number of fatal accidents. Another limit (critical issue) regards the fact that patients dying at the scene of the accident did not reach the hospitals, and therefore, they could not be considered in the present study. This may affect all variables related to the severity of injuries, the frequency of patients in each group or the fact that no differences were found in the level of triage. Furthermore, the study was carried out during 2021, when some mobility restrictions caused by the COVID-19 pandemic were still in place. Therefore, the sample size may had been influenced by periods of confinement.
With respect to the use of electric bicycles, recent research shows that they are becoming increasingly popular and raise many concerns, as they have reported a higher incidence of multiple fractures compared to traditional cyclists (29, 34). However, from our study, they are not yet as widespread in our environment as in other countries. Electric bicycle accidents have reported a higher incidence of multiple fractures compared to traditional cyclists (15).