European Journal of Trauma and Emergency Surgery (2020) 46:413–418
Injuries related tobicycle accidents: anepidemiological study inThe
LiviaE.V.M.deGuerre1· SaidSadiqi2· LoekP.H.Leenen1· CumhurF.Oner2· StevenM.vanGaalen3
Received: 29 May 2018 / Accepted: 8 October 2018 / Published online: 15 October 2018
© The Author(s) 2018
Background This study aims to analyze the incidence and outcomes of bicycle-related injuries in hospitalized patients in
Methods Bicycle accidents resulting in hospitalization in a level-I trauma center in The Netherlands between 2007 and 2017
were retrospectively identiﬁed. We subcategorized data of patients involved in a regular bicycle, race bike, oﬀ-road bike or
e-bike accident. The primary outcomes were mortality rate and incidence of multitrauma. Secondary outcomes were diﬀer-
ences between bicycle subcategories. Independent risk factors were identiﬁed using multivariable logistic regression. All
variables with a p value < 0.20 in univariable analysis were entered in multivariable analysis.
Results We identiﬁed 1986 patients. The mortality rate after emergency room admission was 5.7%, and 41.0% were multi-
traumas. A higher age, multitrauma and cerebral haemorrhages were independent risk factors for in hospital mortality. Inde-
pendent risk factors found for multitrauma were a higher age, two-sided trauma, e-bike accidents and cerebral haemorrhage.
Conclusion Bicycle accidents resulting in hospitalization have a high mortality rate. Furthermore, a high incidence of mul-
titrauma, fractures and cerebral haemorrhages were found. Considering the increasing incidence of bicycle accident victims
needing hospital admission, new and more eﬃcient prevention strategies are essential.
Keywords Bicycle· Bike· Traﬃc accident· Traﬃc injury· E-bike· Epidemiology
Cycling is a popular means of transportation and leisure
activity with many health and environmental advantages.
However, simultaneously with the increasing popularity of
cycling, concerns for road safety have grown. A recent Aus-
tralian study estimated that per 1000km cycled 0.29 crashes
occur . Also, a Dutch study showed that in 2012, 31% of
the lethal traﬃc accidents and 59% of the traﬃc accident
victims treated in the emergency room were cyclists .
Parallel to the regular city bicycles, other bicycle types have
gained popularity and sales of race bikes, oﬀ-road bicycles
and e-bikes have grown . Each subtype is known for its
speciﬁc end users and preferred cycling environment but
little is known about the diﬀerences in injury risks with spe-
ciﬁc morbidity and mortality.
Biking is rooted in Dutch culture and every year approxi-
mately one million bicycles are sold in The Netherlands .
Compared to other European countries, The Netherlands has
a higher prevalence of cycling as a mode of transport but
also a higher incidence of severe bicycle crash injuries .
Yearly costs of bicycle-related accidents in The Netherlands
are estimated to be 402million euros .
Several studies have been conducted to assess bicycle-
related injuries in the general population; however, studies
regarding bicycle-related injuries treated in the emergency
room are lacking. A clear understanding of the epidemiol-
ogy of this group will permit better emergency care and
aid to implement eﬀective injury prevention strategies.
Therefore, the objective of this study is to gain insight in
the epidemiology of bicycle accidents in a level-I trauma
* Said Sadiqi
1 Department ofSurgery, University Medical Center Utrecht,
2 Department ofOrthopaedics, University Medical Center
Utrecht, HP G05.228, P.O. Box85500, 3508GAUtrecht,
3 Departement ofOrthopaedics, Diakonessenhuis
Utrecht/Zeist, Utrecht/Zeist, TheNetherlands
414 L.E.V.M.de Guerre et al.
center in The Netherlands, as well as the identiﬁcation of
trauma patterns and factors that may predict the outcomes.
All patients who were admitted to the University Medical
Center Utrecht (a large level-I trauma center in The Neth-
erlands) after emergency care following a bicycle accident
between 2007 and 2017 were retrospectively identiﬁed in
a well-established trauma care database.
Data were obtained for patients that were involved in
a regular bicycle, race bike, oﬀ-road bike or e-bike acci-
dent. The data collected included patient characteristics
(age, gender), trauma mechanism (vehicle, one-sided or
two-sided injury mechanism, helmet protection), injury
characteristics [diagnosis, fractures, haematomas, injury
severity score (ISS)] and mortality. The injuries were clas-
siﬁed as minor or multitrauma according to the ISS score.
In line with the available literature, the cut-oﬀ point for a
multitrauma patient was settled as > 15 for the abbreviated
injury severity (AIS)-98 classiﬁcation system, or > 12 for
the AIS-08 system .
The primary outcome measures of the study were mortal-
ity between the arrival at the emergency department and
hospital discharge, and the occurrence of multitrauma.
Secondary outcomes were the diﬀerences between regular
bicycles, race bikes, oﬀ-road bikes and e-bikes.
Statistical analyses were performed using SPSS. Normally
distributed and non-normally distributed continuous vari-
ables were expressed as mean (± SD) or median (range).
Categorical data was presented as total counts and per-
centages. The incidence of all accidents was calculated
for each subgroup. The relation between survival and
the baseline variables were evaluated by Chi square test,
Fisher exact test or Mann–Whitney U test. A multivari-
ate logistic regression analysis was performed to identify
independent predictors for survival. All variates with a
p value < 0.2 in the univariate analysis were included in
the multivariate analysis. Associations were considered
signiﬁcant when the p value was < 0.05.
A total of 1986 bicycle-related accidents were identiﬁed in
the database, out of which 1655 concerned regular bicycle
accidents (83.3%), 195 race bikes (9.8%), 78 oﬀ-road bicy-
cles (3.9%) and 58 e-bikes (2.9%) (Table1). Of all patients
presented in the emergency department, 41.0% were mul-
tiply injured. The recorded mortality was 5.7%. The mean
age at diagnosis was 45 years, 61.1% of the patients were
male and the majority did not wear a helmet (92.5%). The
accidents were one-sided in 49.6% of the cases and 73.0%
had at least one fracture (Table2). As shown in Fig.1,
83.7% of the patients with a multitrauma suﬀered from
a head or neck injury, 39.4% had thoracic trauma, 10.5%
abdominal injuries, 9.0% pelvic injuries, 10.9% upper
extremities, 14.9% lower extremities and 17.8% spine
injuries. In patients with a minor trauma, signiﬁcantly
less patients had a head or neck injury (68.3%), thoracic
trauma (18.0%), abdominal injuries (3.8%), pelvic injuries
(5.8%) and spinal injuries (10.4%); however, signiﬁcantly
more had a lower extremity injury (21.0%) and a similar
percentage had upper extremities injury (11.6%). Table3
shows a stratiﬁcation of the sustained fractures, with the
most prevalent being facial fractures (28.2%), skull frac-
tures (19.8%) and rib fractures (17.2%). Cerebral haem-
orrhages were common: 16.6% suﬀered from a subdural
haematoma and 17.0% from a subarachnoid haemorrhage
(SAH). Less common were epidural haematomas (5.4%)
and intracerebral haemorrhage (5.5%).
Risk factors formortality
Age, gender, multitrauma, non-regular bicycle accidents,
one- or two-sided accidents and cerebral haemorrhages
were identiﬁed as possible risk factors for mortality. These
risk factors were included in the multivariate logistic
regression model. The analysis identiﬁed a higher age,
multitrauma and cerebral haemorrhages as independent
risk factors for mortality.
Table 1 Incidence of bicycle
traumas per subgroup Bicycle subgroup N (%)
Regular bicycle 1655 (83.3)
Race bike 195 (9.8)
Oﬀ-road bicycle 78 (3.9)
E-Bike 58 (2.9)
415Injuries related tobicycle accidents: anepidemiological study inThe Netherlands
Risk factors formultitrauma
Independent risk factors for multitrauma were higher age,
two-sided trauma, bicycle type and cerebral haemorrhage.
Univariate analysis for multitrauma accidents identified
age, e-bike accidents, one- or two-sided accidents and
occurrence of cerebral haemorrhages as possible risk
An increase in the total number of accidents was seen
between 2009 and 2012. From 2012 onwards, the inci-
dence of bicycle traumas has been relatively stable. The
incidence of minor traumas increased over the years,
Table 2 Baseline characteristics
SD standard deviation, DOA death on arrival, ICU Intensive Care
Unit, MCU Medium Care Unit, OR operating room, Aftermath admis-
sion location after emergency room treatment
Male 1213 (61.1)
Female 767 (38.6)
Missing 6 (0.3)
Age Mean 45.0 (SD 24.1)
One-sided 985 (49.6)
Two-sided 1001 (50.4)
ISS Mean 13.6 (SD 10.6)
No 1860 (93.6)
Yes 114 (5.7)
Missing 12 (0.6)
No 1838 (92.5)
Yes 148 (7.5)
None 536 (27.0)
At least 1 1450 (73.0)
Epidural 95 (5.4)
Subdural 295 (16.6)
Subarachnoidal 304 (17.0)
Intracerebral 96 (5.5)
Home 5 (< 1)
Hospital ward 1080 (54.4)
Transferred out 83 (4.1)
MCU 275 (13.8)
ICU 358 (18)
OR 178 (9.0)
Deceased in the emergency room 3 (2.0)
Missing 1 (< 1)
Fig. 1 a Anatomical distribution of the injuries in multitrauma
patients. b Anatomical distribution of the injuries in patients with
minor trauma. Since multiple patients had more than one body part
aﬀected the total is > 100%
Table 3 Incidence of fractures Fracture N (%)
Skull 393 (19.8)
Skull base 87 (4.4)
Facial 561 (28.2)
Spine fractures 252 (12.7)
Humerus 58 (2.9)
Lower arm 73 (3.7)
Scapula 48 (2.4)
Sternal 21 (1.1)
Clavicle 168 (8.5)
Rib 342 (17.2)
Pelvis 127 (6.4)
Femur 140 (7.0)
Lower leg 185 (9.5)
416 L.E.V.M.de Guerre et al.
whereas the multitrauma incidence remained relatively
Compared to patients sustaining trauma with regular bicy-
cles, race bike trauma patients were older, more often male
and the accidents were more often one-sided. Oﬀ-road bike
accidents have signiﬁcantly increased in recent years com-
pared to regular bicycles, these were more often one-sided,
and patients were more often male and younger. A speciﬁc
bicycle subgroup concerns e-bikes. Compared to classic
bicycles, e-bike trauma patients are older, mortality is more
common, more accidents include multitrauma, and the num-
ber of accidents has increased signiﬁcantly in recent years
In the small subgroup of cyclists wearing a helmet (7.5%),
2.0% of the patients died versus 6.0% of the patients who
did not wear a helmet. However, this diﬀerence was not sig-
niﬁcant. When wearing a helmet, signiﬁcantly less patients
had head and neck injuries, subdural bleedings, intracerebral
bleedings, skull fractures and skull base fractures.
The aim of this study was to gain insight in the incidence and
outcomes of bicycle-related injuries in hospitalized patients
in The Netherlands.
Fig. 2 Incidence of minor and multitrauma bicycle traumas per year
Table 4 Bicycle subgroups
SD standard deviation
Regular bicycle Race bike Oﬀ-road E-bike
Male 944 (57.0) 167 (85.6) 74 (94.9) 28 (48.3)
Female 706 (42.7) 27 (13.9) 4 (5.13) 30 (51.7)
Missing 5 (0.3) 1 (0.5)
Age 43.9 (SD 25) 50.8 (SD 15.2) 39.6 (SD 18.3) 64.3 (SD 15.8)
One-sided 762 (46.0) 114 (58.5) 75 (95.2) 34 (58.6)
Two-sided 893 (54.0) 81 (41.5) 3 (3.8) 24 (41.4)
No 1645 (99.4) 93 (47.7) 43 (55.1) 57 (98.3)
Yes 10 (0.6) 102 (52.3) 35 (44.9) 1 (1.7)
Epidural 83 (5.0) 6 (3.1) 3 (3.9) 3 (5.2)
Subdural 254 (15.4) 17 (8.7) 9 (11.5) 15 (25.9)
SAB 260 (15.7) 17 (8.7) 6 (7.7) 21 (36.2)
Intracerebral 84 (5.1) 3 (1.5) é (2.6) 7 (12.1)
No 997 (63.3) 111 (61.3) 50 (66.7) 27 (58.7)
Yes 579 (36.7) 70 (38.7) 25 (33.3) 19 (41.3)
No 1544 (93.3) 189 (96.9) 77 (98.7) 50 (86.2)
Yes 102 (6.2) 4 (2.1) 1 (1.3) 7 (12.1)
Missing 9 (0.5) 2 (1.0) 1 (1.7)
417Injuries related tobicycle accidents: anepidemiological study inThe Netherlands
Bicycle injuries resulting in hospitalization were charac-
terized by a high mortality of 5.7%, and a considerably high
multitrauma incidence of 41.0%. In a Dutch study investi-
gating bicycle-related traumatic brain injuries, 4% of the
cyclists treated at the emergency department deceased in
the hospital due to their multiple injuries . The somewhat
higher incidence found in our study could be explained by
the more severely injured patient population as we only took
into account patients who were admitted to the hospital ward
after their treatment at the emergency department. In the
present study, 73.0% of the patients presented with at least
one fracture, while 16.6% and 17.0% suﬀered from subdural
and subarachnoid haemorrhages, respectively. Injuries to the
head and thorax were the most common.
Increased age, multitrauma and cerebral haemorrhages
were found to be independent risk factors for mortality. For
multitrauma, additionally two-sided trauma and e-bike acci-
dents were found as independent risk factors. Previous stud-
ies reported not wearing a helmet, increased age and alcohol
consumption as risk factors for bicycle crash mortality [2, 7].
A systematic review showed the association between bicycle
helmet use and reduced odds of head injury, serious head
injury, facial injury and fatal head injury . Our results
indicate that the prevalence of helmet wearing in The Neth-
erlands for cyclists remains low. When wearing a helmet this
is associated with less head and neck injuries. Furthermore,
cerebral haemorrhages are a risk factor for both multitrauma
and mortality. These results support that promoting to wear
bicycle helmets is an important safety strategy opportunity
for Dutch legislators.
Recent research concerning the increasingly popular
e-bikes has raised many concerns . In The Netherlands,
27.6% of the total number of fatal bicycle accidents in 2017
were e-bike accidents . In the present study, we found a
high mortality and morbidity rate in an older patient group.
Possible contributing factors making e-bikes more prone
to severe traﬃc accidents are the speed diﬀerence between
cyclists and e-bikers using the same traﬃc lanes, increased
risk taking behaviour and misperception of the e-biker’s
approaching speed . In this group, especially the older
patients show increased use of anticoagulation drugs
which makes (more than in the other bicycle categories)
wearing helmets essential in the prevention of speciﬁcally
head related injuries. A ﬁrst step to decrease severe e-bike
accidents was recently made when a new traﬃc law in The
Netherlands made wearing a helmet compulsory in e-bikes
surpassing the speed of 25km/h (speed pedelecs). This fol-
lowed EU legislation as deﬁned in the white Paper “Rules
and Regulations on electric cycles in the EU” categorizing
this subcategory of e-bikes as a similar mode of transpor-
tation as a L1e-B moped . For this category, compul-
sory helmet wear for moped was applied. Unfortunately the
white paper stated that none of the EU member states have
imposed helmet usage on adult users of conventional bicy-
cles consequently exempting the 25km/h–250kW pedelecs
from compulsory helmet wear. However, increased road user
awareness, increased distinctiveness from other bicycles and
compulsory helmet wear for all e-bike categories would be
needed to reverse the alarming increase in both morbidity
and mortality related to e-bike accidents as found in this
Hartog etal. estimated that the beneﬁcial eﬀect of cycling
due to increased physical activity results in 9 times more
gain in life years than the loss from inhaled air pollution
and traﬃc accidents . However, bicycle crashes are still
signiﬁcant contributor to traﬃc accident-related mortality
and morbidity, while often being considered as prevent-
able. Therefore, stronger injury prevention strategies are
needed such as education by promoting safety measures
and to increase awareness concerning upcoming new (often
faster) bicycle subtypes. Secondly, stricter traﬃc laws may
be needed in The Netherlands to stop the current negative
trend of increased accidents.
This study has several limitations. The patient group only
represents a percentage of all bicycle-related injuries, as
only the patients admitted after emergency room care were
included. The minor injuries not requiring hospital admis-
sion and on site fatal bicycle accidents are not represented
in this study creating somewhat a selection bias. It is also
conceivable that the incidence of accidents with race bikes,
oﬀ-road bicycles and e-bike might be much higher, since
not all of these accidents will be registered as such but as
regular bicycle accidents instead at the emergency room.
Furthermore, this is a regional study and our results might,
therefore, not apply to other regions with diﬀerent bicycle-
related infrastructure, traﬃc laws and cycling popularity.
However, since the investigated trauma center is one of the
largest in The Netherlands, we expect the results to be rep-
resentative for other Dutch trauma regions. A previous study
showed that bicycle crash prevalence and severity in The
Netherlands is among the highest in Europe . Therefore,
the results of this study might not be comparable to countries
with diﬀerent cycling cultures. Historically, the Dutch adult
cyclists seems to be rather reluctant in voluntary use of hel-
mets on regular bicycles but the data from this study should
emphasize that the class L1e-A 25km/h–250kW pedelec
is not a regular bicycle. Further data collection would be
required to better understand inﬂuencing factors leading to
bicycle accidents such as the crash mechanism, speed, infra-
structure, alcohol or smartphone use, and more complete
data regarding protective gear and the type of bicycle .
In conclusion, this study investigated the epidemiology of
bicycle accidents in a large level-I trauma center and found
a high mortality rate, many multitrauma cases, a high inci-
dence of fractures and cerebral haemorrhages. Considering
the increasing incidence of bicycle crash victims needing
418 L.E.V.M.de Guerre et al.
hospital admission, prevention strategies such as protective
gear, better infrastructure and more strict traﬃc laws are
essential. Furthermore, more extensive national databases
should be implemented to enable more speciﬁc research
and gain new insights. The authors make a strong recom-
mendation for stronger legislation on the use of protective
helmets especially when e-bikes are involved in the elderly
Compliance with ethical standards
Conflict of interest All authors declare that they have no conﬂict of
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Creative Commons license, and indicate if changes were made.
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