In this study, we undertook a scoping review of the current literature on electric scooter-related injuries to evaluate injury patterns, circumstances and outcomes. With evidence pertaining to trauma associated with electric scooters still emerging, this review aimed to identify gaps in the current body of literature and suggest areas for further investigation.
The incidence of electric scooter-associated injuries has increased considerably since the expansion of electric scooter sharing companies in late 2017. 3 So far, research on electric scooter injuries has been conducted in major urban areas across Europe, Asia and Oceania. 4 In some emergency departments, the number of injuries associated with electric scooters is now similar to that of cycling injuries. 5 Legislators have struggled to adapt road safety regulations to mitigate injuries due to the recent influx of electric scooters. Some jurisdictions have mandated use of protective equipment such as helmets. 6 Additional evidence on injury patterns and circumstances associated with electric scooter collisions is needed to guide clinical management and inform development of policy and interventions that target modifiable risk factors for these events.
Electric scooters are personal mobility devices that have been adopted as a convenient, environmentally friendly alternative to traditional modes of inner-city transportation. These scooters are typically comprised of a shaft that connects handlebars to a thin metal deck with two wheels, leaving riders only a few inches from the ground. 1 Electric scooters can reach speeds up to 25 km/hour which allow the rider to travel on roadways or bicycle lanes. Conversely, the compact size of electric scooters also allows riders to easily manoeuvre through pedestrian traffic. 2 Thus, electric scooter riders can switch between different types of road infrastructure, leaving them and other road users, including cyclists and pedestrians, vulnerable to traumatic injuries in the case of a collision.
Two reviewers (MT, SM) independently screened titles and abstracts for eligible articles from the initial search. For articles that were unclear for eligibility, consensus was made through discussions among all team members. The selected articles were then reviewed in detail using standardised inclusion and exclusion criteria by MT and SM. Disagreements were resolved through discussions among all team members. Inter-rater reliability was measured with Cohen’s kappa coefficient. For each included study, the following data were independently extracted by the two reviewers: study title, first author, year of publication, data collection period, study aims, study methodology, country, participant demographics, sample road user type (ie, electric scooter driver, non-driver), injury distribution, injury type, injury rate, injury severity, clinical care in emergency department, emergency department disposition, hospital admission length, mechanism of injury, collision road type, helmet use and substance use.
Grey literature was identified through a TRID search, a Google Scholar search, a general Google search and a Google custom search. The Google custom search focused on government documents. In all cases, the following terms: (“Scooter” or “Micromobility”, or “Personal Mobility”) and (“Injury” or “Trauma” or “Accident”) were used to search for exact terms. Searches were conducted up to 31 December 2020.
The quality of studies was independently assessed by two reviewers using the National Heart Lung, and Blood Institute (NHLBI) assessment tools for evaluating observational studies. The specific tool applied was chosen based on study design. 8 This ensured that the internal validity and risk of bias of each study were assessed in a similar manner irrespective of study design. Disagreements were resolved through discussions between two reviewers (MT, SM) and by consulting a third reviewer when needed.
Studies and documents were excluded if: (1) only injuries requiring a specific medical treatment were included; (2) only the treatment or management of injuries was reported; (3) case series included fewer than 20 cases; or (4) studies were reported as an abstract only.
To be included, studies and documents needed to: (1) examine the injuries of patients following electric scooter-associated injury events; (2) have electric scooter-specific data; (3) have electric scooter-associated injury events comprise at least 25% of the study sample; and (4) be published between January 2010 and December 2020.
The first two concepts (electric scooter and injury) were combined to examine injury patterns specifically regarding severity, type and location of injury. The first and third concepts (electric scooter and circumstances) were combined to examine the injury circumstances specifically regarding the street/road environment, motor vehicle traffic and causes of the events. A sample search is included in online supplemental table 7 . References from selected articles were examined to look for relevant articles that were not included in the database search.
A systematic search of English-language peer-reviewed studies was conducted using four databases: Medline, Embase, SafetyLit, and the Transport Research International Documentation (TRID). The TRID database also includes non-peer reviewed ‘grey literature’ such as reports (see below). As the popularity of electric scooters is fairly recent, the search was limited to articles published between January 2010 and December 2020. Keywords and/or subject headings were used to define three concepts (electric scooter, injury and circumstances) as per online supplemental table 6 .
Data from 16 studies (n=1656) showed that only 4.5% of electric scooter riders were helmeted ( table 5 ) at the time of their injury, while 67.5% were unhelmeted, and the remaining 28.0% had unknown helmet status. 4 5 10 11 13–17 19 22 23 26 28 29 32 A protective effect of helmets on the incidence of head injuries was noted in the sole study where this association was examined. 13
Ten studies (n=1214 participants) reported mechanism of injury ( table 5 ) in all patients with electric scooter-related trauma. 4 10 11 15–19 28 33 These studies report that 92.8% of riders were injured in single road user events, while 7.1% were injured in multiple road user events. Single user events included falls, collisions with objects, excessive speed and unfavourable road conditions, with falls (94.6%) being the most common ( table 5 ). Five of these 10 studies included injury circumstances for non-electric scooter riders ( table 5 ), namely pedestrians and cyclists (n=44). In these five studies, the most common mechanisms of injury to non-riders included being struck by an electric scooter (26/44=59.1%) and tripping over a stationary electric scooter (13/44=29.5%). 4 5 14 18 28
The number of patients who underwent imaging procedures ( table 4 ) in the emergency department was reported in six studies. 5 11 13 16 18 28 Two-thirds of all patients in these six studies required a procedure (480/696=68.9%; range: 32.6%–90.3%). Consistent findings between these six studies, and in two additional studies that focused on imaging, suggest that radiographs account for the majority of these procedures. 30 31
The distribution ( table 2 ) of electric scooter-associated injuries was reported in 25 separate studies (counting the NEISS studies as one study), but the categorisation of injuries varied between studies. Thirteen studies categorised all injuries into the same six body regions (ie, head, face, chest, upper extremity, abdomen and lower extremity). 3 4 9–19 In these studies, the most commonly injured regions were the upper extremity (one of three most frequently injured regions in 12 studies), head (11 studies) and lower extremity (10 studies) whereas the chest and abdomen were the least frequently injured regions ( table 2 ). Eight studies looked specifically at craniofacial injuries and all reported that the upper and mid regions of the face as well as the orbit were especially vulnerable to injuries ( table 2 ). Dental injuries were also noted as being common in patients with craniofacial injuries. 19–26
The majority of studies sampled patients retrospectively through emergency department or trauma services databases ( table 1 ). All studies reported electric scooter riders as part of their sample, eight studies also reported non-riders injured in an electric scooter collision. Data collection ( table 1 ) was performed through retrospective medical chart reviews for 20 studies. Four studies used NEISS data. Four studies were based on interviews with injured electric scooter riders, including one study that conducted interviews during participants’ emergency department visits.
Twenty-eight peer-reviewed studies were included, of which 25 were retrospective case series and three were prospective observational studies. No scoping or systematic reviews related to electric scooter trauma were identified. Twenty-three studies were conducted in urban regional trauma centres: 11 single-site studies and 12 multisite. Of these studies, 13 were conducted in the USA, 3 in New Zealand and 1 each in Singapore, Australia, Denmark, France, Finland, South Korea and Germany. Four nationwide studies were conducted in the USA through analyses of the United States Consumer Product Safety Commission National Electronic Injury Surveillance System (NEISS). These four studies were counted as a single study when reporting injury patterns and circumstances in the following sections as they used the same database. Additionally, one study employed information from a city-wide database in the USA. Publication dates ranged from 2019 to 2020. No included studies were published between 2010 and 2018. The NHLBI assessment of the included studies ranged from ‘Fair’ to ‘Good’. A summary of the study designs can be found in table 1 .
The search strategy yielded 614 unique records. Twenty-eight peer-reviewed studies and nine grey literature records were included in the final review following the title, abstract and full-text eligibility review ( figure 1 ). Cohen’s Kappa coefficient between the two reviewers (MT and SM) was 0.83. There were no disagreements between the two reviewers in the quality assessment of selected studies.
To the best of our knowledge, this is the first scoping review of electric scooter trauma. All 28 included peer-reviewed studies were published between 2019 and 2020, which suggests research in this area is recent and may increase rapidly in the coming years. The recent literature may be in response to the recent proliferation of shared electric scooter schemes leading to increases in related emergency department visits.3
The most commonly injured body parts following electric scooter-associated trauma were the head, upper extremities and lower extremities as expected. The chest and abdomen were consistently the two least common injured regions. This injury pattern is similar to that observed in certain non-motorised mobility devices such as skateboards and non-motorised scooters.42 However, electric scooter injuries are likely more severe due to their increased speeds, as noted in two included studies.4 34 Falls were the leading cause of injuries in electric scooter riders, and many upper extremity injuries result from falls on an outstretched hand, a common reaction used to break the impact of a fall.43 Electric scooters’ low height off the ground along with riders’ reflex to step off the scooter in risky situations may explain the high frequency of lower extremity injuries.1
Low rates of helmet use among riders were noted in several studies, which may be linked to the high prevalence of head injuries following electric scooter-associated trauma. Moreover, one study noted a protective effect of helmets on craniofacial injuries suggesting many of these injuries may be preventable.13 This assertion is supported by a large body of work showing the effectiveness of helmets in preventing head injuries in cyclists.44 This evidence is relevant for many cities that are considering helmet laws for electric scooter users.6 A 2019 study in Brisbane, Australia found that previously low rates of helmet use increased to 64% among electric scooter riders following the introduction of a mandatory helmet law.45 More broadly, helmet use among electric scooter riders should be promoted in public health messaging as an effective means to reduce the high incidence of head injuries.
While the majority of electric scooter riders were injured in single road user events, a considerable portion were injured through collisions with other vehicles. Moreover, in some cases, cyclists and pedestrians were injured through collisions with electric scooter riders. These findings may in part be due to the scooters’ high speeds and small size allowing them to be used on different types of road infrastructure.2 The five studies that reported location found that streets and sidewalks were common locations where these events occurred.17 18 24 32 34 This suggests that policies restricting electric scooter use to specific road infrastructure such as bicycle lanes should be considered as both devices operate at similar speeds.6
Multiple findings highlight a large healthcare burden in cities where electric scooters are popular. For instance, although the majority of patients seen in the emergency department were discharged home, a considerable portion required admission to hospital. Moreover, over two-thirds of patients (68.9%) required at least one procedure during their emergency department visit. These findings are supported by a New Zealand study which found that the introduction of electric scooters had a large impact on regional healthcare costs.46 This may be of particular interest to cities considering the adoption of shared electric scooter schemes, as the introduction of such services may increase the demand of already-stretched emergency services.47
Our findings are affected by the limitations of the included literature. The majority of included studies were retrospective case series in design that only reported on clinically relevant variables present in medical charts or databases. Additionally, most studies only reported the clinical course of the patients’ emergency department visits; information on long-term health outcomes is lacking. Metrics used to report important factors such as injury distribution and severity were heterogenous across studies, limiting the scope of comparisons. Factors relating to the circumstances of the injury such as the location of the event and substance use were inconsistently reported, while helmet use was difficult to ascertain due to high rates of unknown helmet status.
The three studies with prospective observational designs benefitted from emergency department clinicians consistently documenting circumstances of the incidents as well as patients’ clinical course and outcome.15 Future research on electric scooter trauma would benefit from a similar prospective observational design with an emphasis on using standard metrics such as ICD-10 body regions for reporting injury distribution, and ISS or Abbreviated Injury Scale for injury severity. Such research would provide better evidence on the injury patterns and severity of electric scooter-associated trauma. Details of the injury circumstance, such as time of day, road infrastructure (eg, sidewalk, roadway, bike path), involvement of other road users, and contributory factors should be systematically collected in order to identify modifiable risk factors for electric scooter injuries. Similarly, as electric scooter use increases, it is important for injury surveillance databases to capture electric scooter injuries, including injuries to other road users resulting from collisions with electric scooters. Moreover, as many urban areas lack legislation mandating the use of protective equipment by electric scooter riders, future evaluations of interventions for preventing electric scooter injuries, especially measures to increase helmet use, will help inform policy decisions.
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