To the best of our knowledge, our study is, in European pediatric literature, the first observational ED-based research analyzing the frequency, the temporal trend, and the pattern of the injuries associated with HBs in pediatric patients in an effort to recognize the principal criticalities regarding the usage of these recreational devices in the pediatric population.
We reported an increased rate of Injury associated with HBs / Injury per 1,000 from 0.8 in 2016 to 7.7 in 2017, then a gradual decline over the following year. Compared to a previous American study, in 2015 there was an average 208% increase in the rate of this type of injury compared with any of the previous 4 years [7]. Probably, this temporal difference with our data is due to a delay of 2 years of the introduction of HBs in the Italian consumer market compared with the boom in the US. Overall, our data revealed a positive trend because after a peak in 2017, the rate of injuries declined in 2018 and 2019, but this was not completely comforting. In fact, if we consider the interest of users online in HBs by Google Trends, we noticed that the popularity in the Lazio region, after a peak during 2017, decreased over time. Therefore, the reduction of HB related injuries was, in all probability, due to a decrease in popularity after 2017, taking a back seat in the market of the electric mobility on two wheels because of the success of other, more novel and sophisticated paradigms such as the electric scooter that is now the most popular electric wheelers in European cities [8].
We observed that the frequency of HB related injuries was variable, but generally the peak of injuries was concentrated in spring and summer. This distribution not only followed the popularity trend but relies on other factors such as the seasonality and weather conditions that can influence physical activities. In fact, a systematic review reported that a seasonal effect is present as the levels of physical activity appear to be highest in spring and summer [9]. Although seasonal variation is not a set feature of the environment, numerous attributes might affect physical activity behaviors such as temperature, precipitation, and daylight hours [9]. In fact, with a longer day length in spring, undoubtedly for the child, the recreational activities increased, and there is a greater desire to run and play [10]. Instead, in 2016 we reported a peak just before December, and this data might be explained by the novel recreational product just introduced in the Italian market that year and in coincidence with Christmas sales resulting in one of the most popular and attractive gifts [4,7,11,12].
We noticed that younger children were at a higher risk of HB related injuries in 2018-2019 in comparison with 2016-2017. In the literature, many studies report that pediatric patients are more at risk of injury than adults [3,4,7,13] and generally, the use of HBs and the injuries associated with them are more common in the adolescent population [10,13-15]. Our finding draws attention to an alarming reality: the lack of the child surveillance and of the safety education efforts in our region during the most recent years.
It was surprising how a significant proportion of HBs were being used indoors, and this data has also been described in other studies [13]. Moreover, in 2018-2019 we registered a significant, greater proportion of injuries occurring indoors than in 2016-2017. This finding of extreme concern might be analyzed form different points of view. Generally, older children present a higher rate of outdoor injuries [15]. We reported a higher risk of indoor injury occurring in 2018-2019 because injuries occurred more commonly in younger children who tend to play indoors. A higher proportion of indoor injuries in the last years might also mirror the considerable evidence that the opportunities to play outdoors have steadily declined across the last generations, and the leisure lives of children appear to be moving indoors [18-21]. Some researchers have stated that social influences on parents can have influenced possibilities in outdoor play engagement of children [22-25].
However, we assume that the principal cause of this phenomenon is a shortage of an adequate awareness and education of parents and other caregiver figures about the risks related to the usage of these devices. Parents should be educated on the appropriate location for the use of this leisure device for their children, on the safety equipment that should be used at all times while on board HBs, and on the enrollment of the child in lessons. Safety policies of the governments are also important to promote preventive programs for modifying behavior. In Italy the legislative decree n° 229, 4 June 2019 [26] opens to the experimentation on the devices of the electric micro-mobility including HBs, but the age limit is a factor depending just on common sense because the current legislation does not consider this issue. The best usage of the HB has been conceived for adults for two reasons. First, children are physiologically at risk for falls because of less mature development in coordination, balance motor strength, along with their higher center of gravity [3]. The second reason is one of responsibility. In fact, Italian law establishes that in a case of a child caught in breach of the usage regulations, the penalty will be issued to the parents. The penalty is applied not because the device has been ridden by a child, but because the device circulates on a forbidden area such as a street (regulation n° 190 of the Italian Highway Code) [27]. In Italy, the driver’s “AM” license can be obtained upon reaching 14 years of age and allows riding two wheeled vehicles with a maximum engine displacement of 50 cm3, a maximum power of 4 Kw, and a maximum speed of 45 km / h. This age limit might be a compromise solution.
Analyzing the site of the injury, the upper extremity was the most common region of the body to be affected, and the fracture was the most common type of injury. These findings were replicated by other studies [4,11,12,14,16,28]. Some of these studies also detailed an increase in the wrist and forearm injuries, specifically fractures. Surprisingly, patients were almost 5 times more likely to have injured the lower extremity during the 2018-2019 period than other body regions compared with the 2016-2017 period, when, generally, younger children appear to be pre-disposed to injuries of the upper extremity [29]. We are not able to explain this data if we consider that the likelihood of injury was higher in younger children in the last biennium. Probably, we did not consider the potential confounders of the relationship between body region and injury, such as the body mass index, bone mass and bone minerality density, stature, inadequate nutrition, cognitive development, use of medication, mechanism of injury (fall or collision), fall from stationary or moving HB, fall backwards, forwards or sideways, and different kinetic energy depending on riding along a downhill or flat pathway.
Our study has some limitations. The nature of a retrospective study makes it subjected to shortcomings associated with this type of analysis: documentation omissions, missed relevant data, selection bias. The single site of our study may affect the generalizability of the results, although in the Lazio region, there are only 2 major pediatric trauma hospitals in a 17,242 km² wide region. GIPSE lacks a specific code for HBs; therefore, the diagnosis of HB related injuries was extrapolated from a narrative mention in the clinical history of the injury as reported, and some data might be missed.