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Epidemiology of skateboarding-related injuries sustained by children and adolescents 5-19 years of age and treated in US emergency departments: 1990 through 2008 Abstract Background: The goal was to examine the patterns and trends of skateboarding-related injuries sustained by children and adolescents in the United States.


Background
Skateboarding has evolved from sidewalk-surfing, on primitive skateboards which were constructed from planks of wood with metal roller skate wheels (Hawkins and Lyne 1981), into a dynamic, adrenaline-filled sport with advanced gear, ramps, skate parks, and extremetype competitions (Brooke 1999). Skateboarding is a popular recreational sport and participation has increased the last several decades, faster than any other sport or recreation activity between (National Sporting Goods Association 2008. Previous reports have estimated~50 000 emergency department (ED) visits and 1500 hospitalizations among children and adolescents annually in the United States (US) (Committee on Injury and Poison Prevention 2002). The most common skateboarding-related injuries include fractures, (Hawkins and Lyne 1981;Banas et al. 1992;Sheehan et al. 2003;Zalavras et al. 2005) wrist and ankle strains and sprains, (Kyle et al. 2002) and traumatic brain injuries (TBIs) (Schleimer 2002).
Studies on skateboards injuries have focused on a single year of data, (Kyle et al. 2002;Nathanson et al. 2015) or specific types of injuries such as epiphyseal injuries, (Adams 1979) knee injuries, (Shapiro 1994) fractures (Hawkins and Lyne 1981;Banas et al. 1992;Sheehan et al. 2003;Zalavras et al. 2005), minor TBIs (Schleimer 2002), or head injuries (Tominaga et al. 2015). Other research have only considered injuries treated in a single medical facility or trauma center (Sheehan et al. 2003;Hawkins and Lyne 1981;Banas et al. 1992;Adams 1978;Cass and Ross 1990;Christian and Khan 1980;Forsman and Eriksson 2001;Fyfe and Guion 1978;Hassan and Dorani 1999;Illingworth et al. 1978;Kemm 1978;Kirkpatrick 1980;Macdonald et al. 2006;Maitra 1979;McGeehan et al. 2004;Morgan et al. 1980;Rethnam et al. 2008). Previous case series studies (Burt and Overpeck 2001;Finch et al. 1998;Kyle et al. 2002;Osberg et al. 1998;Powell and Tanz 2004;Schieber et al. 1994;Shapiro 1994;Zalavras et al. 2005) have looked at skateboarding injuries treated in EDs, but have only done so for limited time periods (i.e., two years or less) or longer periods of time but the data are now dated. A more recent study by Keays and Dumas (Keays and Dumas 2014) compared cases of longboarding, a sport that uses longer and wider boards than traditional skateboards, and skateboarding-related injuries. These prior studies do not represent the cyclical nature of skateboarding-related injuries. The variation in participation (estimates range from 5.8 million participants <18 years to 74 million participants >7 years) and rates of injury from skateboarding can only be accurately described by examining multiple years of data. Previous research has found that most injuries occur when a skateboarder loses balance leading to a fall (Clark et al. 2011).
To the best of our knowledge, this is the first nationally representative study to examine the epidemiology of skateboarding-related injuries treated in EDs in the US over a 19-year study period from 1990 through 2008, further the current study extends the age groups under examination to include participants up to 19 years of age. The purpose of this current research was to examine injury rates and long-term epidemiologic trends in skateboarding-related injuries by age and sex.

Data source
Data for children and adolescents who were treated in an US ED, from January 1, 1990 through December 31, 2008, were obtained through the National Electronic Injury Surveillance System (NEISS) operated by the US Consumer Product Safety Commission (CPSC). The NEISS provides data on consumer product-and sportsrelated injuries treated in US EDs. The NEISS receives data from a network of~100 hospitals, representing a stratified probability sample of 6 100 hospitals with ≥6 beds and a 24-h ED, including urban, suburban, rural, and children's hospitals (US Consumer Product Safety Commission 2001). Sample weights, based on the inverse probability of selection, were assigned to each case by the CPSC and were used to generate national estimates. At sampled hospitals, ED medical charts are reviewed by professional NEISS coders, and patients' age and sex, injury diagnosis, body part injured, locale where the injury occurred, product(s) involved, and disposition from the ED, as well as a narrative describing the incident, are recorded. Population estimates from the US Census Bureau (2011) were used to calculate injury rates per 10 000 children/adolescents 5 to 19 years of age.

Case selection criteria
All NEISS cases for children/adolescents 5 to 19 years of age with a product code of skateboards (code 1333) were reviewed (n = 36 862). Inclusion and exclusion criteria and variable categories were developed after a review of a subset of case narratives. All case narratives were reviewed by 1 or more authors to ensure that cases met inclusion criteria (i.e., involved the active use of a skateboard). A total of 6 936 cases were excluded because the narratives revealed that the injury did not occur during active use of a skateboard. In addition, all five fatalities were excluded. All fatalities involved patients who were struck by motor vehicles while skateboarding. The final number of actual cases was 29 921.

Variables
Data regarding patient sex, age, injury diagnosis, body part injured, locale, and disposition were coded as categorical variables. Patients were categorized according to age (5-10, 11-14, and 15-19 years of age). Locale (location where the injury occurred) was categorized as home (including home, apartment, mobile home, and farm), street and/or highway, sports and/or recreation place, school and other (including other public property and industrial space). The body parts injured were grouped according to region, in categories of head (including head and neck), face (including eyes, ears, mouth, and face), upper extremity (including shoulder, upper arm, lower arm, elbow, wrist, hand, and finger), lower extremity (including upper leg, knee, lower leg, ankle, foot and toe), trunk (including upper trunk, lower trunk and pubic region), and other (including "25 %-50 % of the body" and "all parts of body"). Diagnosis was grouped according to injury type, in categories of soft tissue injuries (including contusions, abrasions, and hematomas), lacerations (including lacerations, punctures, and avulsions), fractures and dislocations, internal injury, sprains and strains, traumatic brain injuries (TBIs) (including concussions, fractures of the head, and internal organ injuries of the head), (Xiang et al. 2007) and other (including crushing, foreign body, dental injury, nerve damage, amputation, burns, hemorrhage, and other/not documented). Disposition was categorized as hospitalized (including treated and transferred to another hospital, treated and admitted for hospitalization, or held for observation <24 h) or not hospitalized (including treated and released or examined and released without treatment).

Statistical analyses
All statistical testing and variance estimation accounted for the complex sampling frame of the NEISS using SURVEY procedures in SAS version 9.3 (SAS Institute, Inc, Cary, NC). Bivariate comparisons were conducted by using Rao-Scott design-corrected chi-square likelihood-ratio χ 2 . Linear regression was used to determine change in the rate of skateboarding-related injuries over the study period. Logistic regression was used to identify characteristics of skateboarding-related injuries associated with age. Statistical significance was assessed at α = 0.05 from the Wald χ 2 with the magnitude of association evaluated using odds ratios (ORs) and 95 % confidence intervals (CIs) from univariate logistic regression. All data reported in this article are national estimates unless specified as unweighted cases. The Nationwide Children's Hospital institutional review board approved this study (approval number 0403HSX066).
Children/adolescents 15-19 years of age had the lowest proportion of females (7.2 %), the highest proportion of males (92.8 %), and were most commonly injured in the street and/or highway (32.9 %) or a sports and/or recreation place (28.3 %) ( Table 2). Children/adolescents 15-19 years of age most commonly injured the lower (42.1 %) or upper extremities (38.3 %), and the most common diagnoses were sprains or strains (33.8 %) and fractures or dislocations (38.3 %).
The odds of injury for each characteristic, across age groups, are shown in Table 3. For females, as age increased, the proportion of injuries sustained at home decreased, while injuries sustained in the street and/or highway or sports and/or recreation place increased. Children/adolescents 11-14 years of age had greater odds of hospitalization compared to younger children (OR: 1.42 (1.17-1.73)), while older and younger children/adolescents had similar odds of hospitalization (OR: 1.09 (0.89-1.33)). Lower extremity injuries increased with age, while face and head or neck injuries decreased with age. TBIs were higher for children/adolescents 5-10 years of age than older children/adolescents, but this difference was not statistically significant (OR: 1.17 (0.96-1.42)).

Discussion
During the 19-year study period, more than 1.2 million skateboarding-related injuries were treated in US EDs. Population-based rates of skateboarding-related injuries among children and adolescents 5-19 years of age have increased since 1994 for both males and females and among all age groups. Similar to previously published studies, the majority of skateboarding-related injuries occurred to males. Children and adolescents 11-14 years of age were the age group most affected, comprising almost one-half of the total injuries (44.9 %), which may reflect an increase in participation in skateboarding and/or a lower skill level than older children/adolescents. Despite the lack of specific injury severity data in the NEISS dataset, using hospitalization as a proxy for severity, the vast majority of skateboarding-related injuries in the current study were not severe as they were able to be treated in the ED and not hospitalized (96.9 %). Similar to previous research that found that upper extremity and lower extremity injuries were the most common injury (Clark et al. 2011), most injuries in this study were to the upper extremities (44.1 %) and many were fractures and dislocations (32.1 %). A study published in 2002 also utilizing the NEISS data found the most frequent injuries were ankle strains/sprains and wrist fractures; injury rates were twice as high as in-line skating and one-half as high as basketball-related injuries during the same period (Kyle et al. 2002).

Rate per 10 000 population
Year 5-10 11-14 15-19 Age group, (years) Fig. 2 Rates of skateboarding-related injury per 10,000 population estimate by age group, 1990-2008 and diagnoses. Younger children/adolescents 5-10 years of age sustained more injuries to the face. Children/adolescents 11-14 years of age sustained the most upper extremity injuries; and 15-19 year olds sustained the most lower extremity injuries. Overall, most skateboarding-related injuries occurred at home (37.3 %) or in the street and/or highway (29.3 %), places that were likely easily accessible. Older children/adolescents were more likely to be injured at school, street and/or highway, and at sports and/or recreational facilities. If they were injured in the street, they were more likely to be hospitalized. Females were more likely to be injured at home.
Recommendations exist to reduce and prevent injuries associated with skateboarding. The extent to which these recommendations are followed is, unfortunately, unable to be determined with the NEISS data. It is worth noting that current recommendations suggest that children/adolescents <5 years of age should not ride skateboards and children/adolescents between 6 and 10 years of age be closely supervised while skateboarding (Committee on Injury and Poison Prevention 2002). Many skateboarding-related injuries may be able to be prevented if protective gear such as helmets, wrist guards, elbow pads and knee pads are worn. Helmets that comply with the CPSC-standard or a multi-sport helmet that complies with the N-94 standard should be worn while skateboarding (Consumer Product Safety Commission 1998). We found that one-third of injuries to adolescents 15-19 years of age, and one-quarter of injuries to younger children/adolescents occurred in the street and/or highway, therefore it is recommended that skateboarding parks (in particular ones that mandate protective equipment use) be developed. Further, skateboarders should not ride in traffic. The fatalities (although not included in these analyses) involved children/adolescents who were struck by motor vehicles. There may have been other fatalities that occurred at the scene and would not be counted in the NEISS. In the current analyses skateboarding-related fatalities were excluded, however, this may be worthy of exploration in future work, as each fatality in the data set was related to a collision with a motor vehicle and injuries that occurred in the street or highway were associated with hospitalization.

Limitations
This study has several limitations. This study underestimates the total number of injuries because the sample includes only injuries treated in US EDs. Case narratives often did not include whether protective equipment such as helmets, elbow pads, or wrist guards were being worn at the time of the injury. Despite these limitations, the strengths of this study are its large, nationally representative sample and its 19-year study period.

Conclusions
Skateboarding-related injuries continue to be an important source of injury for children and adolescents. Population-based rates of skateboarding-related injuries among children and adolescents age 5-19 in the US have been increasing since 1994. Further research using more rigorous study designs is required to develop a broad perspective of the incidence and determinants of injury, and to further identify risk factors and viable injury countermeasures while simultaneously promoting participation in skateboarding.
Abbreviations CI: confidence interval; CPSC: consumer product safety commission; ED: emergency department; NEISS: National Electronic Injury Surveillance System; TBI: traumatic brain injury; US: United States.

Competing interests
The authors have no competing interests relevant to this article to disclose.