We found that 69 % of patients admitted to hospital with cycling-related injuries had minor/moderate injuries. Despite 10 % having very severe and critical injuries, only four adult patients were reported to have significant sequelae after their accident.
Our data represent an almost complete overview of all patients admitted to hospital for cycling-related injuries for a four-year period at a medium-sized Norwegian hospital. We believe we have captured the vast majority of cycling injuries due to the hospital's secondary control of the data. The main weaknesses are that we have not registered injuries treated at outpatient clinics either in our own hospital or in the remainder of the catchment area, and that the patients were not systematically followed up.
In two similar hospital studies from Trondheim in 1984 and Harstad in 1990, patients treated at outpatient clinics were also included, which means it is difficult to make direct comparisons (7, 8). In addition, both the diagnosis and treatment of injuries have changed significantly since then. CT and MRI are now available at all Norwegian hospitals, enabling a quick and detailed overview of injuries. Interdisciplinary trauma teams have also been established as standard at all Norwegian hospitals. Both Lereim's and Wasmuth's studies describe a cyclist population that is appreciably different from today, especially in view of the fact they found the highest injury rate among children. Lereim also identified a risk group among patients in their 30s, possibly as a result of a growing percentage of adult cyclists in a more urban setting. As in our study, they observed that approximately 15–20 % of injuries were related to training or racing. This is probably a minimum figure, as a large number of cyclists use their daily commute to and from work as a training session. We have not specifically registered the percentage of journeys to and from school and work, but the 24 % reported for the two peak injury times during the morning and afternoon rush hours (figure 1c) is in accordance with figures from the national cycling accounts report from 2016 (11) and Leirem's figures.
In Melhus' data from the Oslo University Hospital's Orthopaedic Emergency Section in 2014 (5), more than 2000 people were treated at the emergency clinic itself, while 2 % were transported to the trauma team at Ullevål Hospital. The Orthopaedic Emergency Section in Oslo has facilities that far exceed a normal emergency clinic, and a large number of our injuries could probably have been treated at an institution similar to this.
Four out of five accidents did not involve any other road users, according to the national cycling accounts report (11). Our age distribution corresponds to this report, but the mean age is somewhat higher than for the patients at the Oslo Orthopaedic Emergency Section; 41 years compared to 32 years (5). The city's younger population and the increased traffic may explain some of the age disparity. The seasonal and daily profiles correspond to the Oslo data (5), but the high percentage of alcohol/drug intoxication of almost 20 % among adults in our data is striking. In Swedish and Finnish studies, corresponding figures confirm our finding (12, 13), while the TØI states that among those requiring medical treatment for their injuries, 6 % were intoxicated (4).
Our data show a range in the extent of injuries, from thumb fractures to multi-traumas whose complexity necessitated an immediate transfer to Ullevål Hospital. Fractures and head injuries predominated, but injuries to virtually all body organs were registered. As with comparable literature, we found that collisions, especially with heavier vehicles, cause the most extensive injuries (14).
Our figures on helmet use are incomplete, with approximately half unknown. Among those with a known helmet status, around 60 % used a helmet. This is probably comparable to the data from Oslo's Orthopaedic Emergency Section, where approximately half used a helmet. A meta-analysis by Olivier & Creighton showed that helmet use halved the odds of head injuries in cyclists and reduced the odds of severe head injuries by two-thirds (15). Similarly, Høye et al. found that severe head injuries were halved where helmet use was mandatory (16). One third of our patients had damage to the head region, and the low percentage of helmet use therefore represents a clear challenge to injury prevention work.
Only four of the accidents involving adults occurred on an electric bicycle. The figure is probably lower than what might be found today as sales and the use of electric bicycles have increased significantly since the completion of our study. We believe it would be useful to monitor the panorama and extent of injuries in this group. In the Netherlands, where the percentage of cyclists is high and the use of electric bicycles is rapidly increasing, both the media and medical publications warn about the risk of injury. In 2017, more cyclists than motorists were killed in the Netherlands, and the increase in fatalities occurred mainly in the electric bicycle group (17).
The injury panorama itself is affected by the cyclist's speed, clothing/protection, physique, helmet use and the surface/object being hit. Not surprisingly, children's injuries were less severe than those in adults. This is reflected in the shorter hospital stays and absence of serious sequelae. It is also worth noting that no children had chest injuries, but eight had abdominal trauma, with several needing an emergency laparotomy. The broad injury panorama and significant percentage of multi-organ injuries in children in our data are evidence that children who are injured in cycling accidents should be examined in the same way as adults. This involves a complete body examination and treatment by a trauma team if the criteria so dictate. The anatomical and physiological differences that separate children from adults must also be taken into account.
With the increased focus on the bicycle as a means of transport, the extent of injuries may change. Continuous registration of injuries and their circumstances, such as that established in, for example, Sweden in 2013 (18), could make an important contribution to the municipal and national cycling strategy. More focus on national registration of injuries has been sought for decades (19). As far back as 1995, Ytterstad showed that targeted interventions can reduce traffic accidents (20).