Radiological trends in trampoline-related paediatric injuries in a major paediatric trauma centre: a 6-year experience

Recreational trampoline-based activities have increased in recent years. Articles mostly from the United States and Australia report higher volumes of injury, increased severity, and increased hospitalisation rates (Kasmire et al. 2016; Sharwood et al. 2018; Rao et al. 2019; Paul et al. 2016; Purcell and Philpott 2007; Ashby et al. 2015). The National Electronic Injury Surveillance system database recorded 288,876 trampoline fractures with an estimated 1,002,735 visits to emergency departments in the US from 2002 to 2011 (Loder et al. 2014). The American Academy of Pediatrics, Safe Kids Canada, the Canadian Paediatric Society and Canadian Academy of Sport and Exercise Medicine released policy statements and safety recommendations with regard to recreational trampoline use (Purcell and Philpott 2007; Briskin and LaBotz 2012). At the turn of the century, the sales of domestic garden trampolines rose, but in recent years the focus has shifted to newly setup trampoline parks. Reports in the scientific literature and mainstream press have warned about injuries sustained in trampoline parks, raising questions about safety regulations (Kasmire et al. 2016; Sharwood et al. 2018; Rao et al. 2019; Paul et al. 2016; Wootton and Harris 2009; BBC News 2018; Mulligan et al. 2017; The Guardian 2017). Only a small number of older studies, examining limited numbers of patients with trampoline-related injuries, are available from the UK and Europe (Wootton and Harris 2009; Bhangal et al. 2006; Eberl et al. 2009; McDermott et al. 2006; Klimek et al. 2013). Our study aims to assess the workload in the radiology department related to these injuries, in a large tertiary referral major trauma centre in the UK, to identify trends in number of attendances, injury type, and severity.

A retrospective search of the local radiology information system (RIS) for emergency department (ED) requests and reports between January 2012 and December 2017, containing the search term “tramp*” with an age of < 18 years was used. Modalities included were radiography, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound (US) and nuclear medicine (NM).

Radiological reports were reviewed and categorised as positive or negative for injury. Fractures and soft-tissue injury (including soft-tissue swelling and joint effusions) were regarded “positive”. Radiological reports identifying a fracture with associated soft-tissue injury were counted as a single injury (‘fracture’), as were recognised patterns of injury,e.g., concomitant fractures of the distal radius and ulna.

All other reports were classed “negative” for injury. The date of injury was recorded for each attendance to the radiology department as well as patient demographic data; age, sex, body part injured, and number of body parts imaged. For any reports where clinical correlation was advised for equivocal findings, the follow-up imaging and records were reviewed. Any patients treated clinically as fractures, with or without imaging evidence for injury, were counted as positive.

Cross-sectional imaging and NM reports were categorised as positive or negative, and the injury type recorded along with the demographics.

Multiple publications warn of the dangers related to recreational trampoline use (Sharwood et al. 2018; Purcell and Philpott 2007; Briskin and LaBotz 2012; Rättyä and Serlo 2008; AAOS 2015). The American Academy of Pediatrics, Safe Kids Canada, the Canadian Paediatric Society, and Canadian Academy of Sport and Exercise Medicine have issued statements against the use of trampolines in the home environment (Purcell and Philpott 2007; Briskin and LaBotz 2012; CPS 2017). Efforts to make trampoline use safer through improved design, such as the inclusion of safety nets, and recommending adult supervision have not had the desired impact (Wilson et al. 2018; Paker 2017). Trampoline safety knowledge among parents remains low, despite parents being in the best position to promote safer recreational use of trampolines (Beno et al. 2018). Our study confirms that trampolining’s popularity in a large city in the UK is on the increase, mirroring findings from the US, Canada, and Australia (Kasmire et al. 2016; Sharwood et al. 2018; Rao et al. 2019; Ashby et al. 2015). Our results show a significant year-on-year increase in trampoline-related injuries starting around the same time that the first trampoline park opened nearby in 2015. In 2017, there were at least 3 trampoline parks in our region.

In our study, the upper extremity was more commonly injured with most injuries at the elbow (18.5%), followed by the wrist (18%), ankle (15.4%), and knee (14%). This corresponds to findings from previous studies (Loder et al. 2014; Klimek et al. 2013). There is new evidence to suggest that the patterns of injuries are different depending on the location of the trampoline, with upper limb and head injuries being more common in a backyard setting, and lower limb injuries in the indoor setting (Kasmire et al. 2016). This might be related to inadequate padding and netting used in the backyard setting; and new indoor trampoline sites are often ‘wall-to-wall’ reducing the risk of a hard landing. It was not possible to observe this trend in our study due to the lack of data relating to the location of the trampoline where the injuries occurred.

In our cohort, the number of injuries over the winter months increased, which may be linked to the fact that indoor trampoline parks allow sporting activity regardless of the season. Interestingly, a Korean study reported no seasonal variation in trampoline-related injuries, which was attributed to the high number of injuries sustained in trampoline parks (67%) (Choi et al. 2018). However, like most studies from America and Australia, the spring and summer months remain a peak time for injuries in our study (Eberl et al. 2009; Yule et al. 2016). The injuries sustained in winter are not simply ‘replacing’ the injuries sustained in summer, but adding to them, leading to an overall increase in visits to the radiology department over the study period. This could however also be related to more children taking up exercise in form of trampolining in the winter months rather than being more sedentary, or that other sporting activities are replaced by trampolining.

Our results show that younger patients (7 years of age and less) are more likely to have sustained an injury when they present to imaging departments. This was also observed in a limited number of previous studies (Ashby et al. 2015; Choi et al. 2018). Smaller children are up to 13.6 times more likely than larger children to sustain injuries on a trampoline (Hurson et al. 2007). A study by Choi et al. (2018) reports that more than half of the injured children in multi-user events were the youngest on the trampoline at the time. This is most likely related to the lower body weight and less developed motor skills of small children. Multiple organisations have advocated specific paediatric limitations on trampoline use, and called for no participation by children younger than 6 years of age (Purcell and Philpott 2007; AAOS 2015; Health Canada 2005).

Thirty-nine of 1871 patients (2.1%) had severe enough clinical injury to undergo cross-sectional imaging, acutely or in the sub-acute setting with CT or MR. Of these, 21/39 (54%) had clinically important findings — overall 21/1871 (1.1%) — which are often occult on plain radiographs. Hauth et al. (2017) reviewed MR scans of 20 children with trampoline-related injuries, and suggested ‘generous use of MR imaging’ in children with ongoing pain after trampoline injury and negative initial plain radiographs. Such injuries, especially of the head and spine, can have life-changing consequences (Wechsler et al. 2001; Leonard and Joffe 2009).

Published statements and recommendations on the recreational use of trampolines have advised caution and restrictions on its use (Purcell and Philpott 2007; Briskin and LaBotz 2012; AAOS 2015; Health Canada 2005; CPSC 2012; Government of Western Australia 2015; Murphy 2000). This includes advice that trampolines should not be regarded as play equipment, requiring adequate constant adult supervision, strictly one person jumping at the time, use of shock-absorbing pads and enclosure netting, and no somersaults or tricks. The use by children less than 6 years of age is discouraged. Ideally, trampolines should only be used in a supervised setting with trained personnel in a recognised training environment such as the British Gymnastic Program (British Gymnastics 2009). The Royal Society for the Prevention of Accidents (2011, 2015) aided by National Health Service Trusts in the UK have published advice on garden trampoline safety.

Supervision at indoor parks currently has no mandatory regulation and can vary from site to site. To participate, parents or guardians must sign waivers for their children, which provide safety rules for the park, but do not always outline potential injuries that may be sustained (Bounce 2018). Due to increasing numbers of injuries seen in indoor trampoline parks in Australia, Sharwood et al. (2018) have called for national mandatory safety standards that apply to indoor trampoline park operators and might help to reduce injuries. General guidelines and standards for the UK and Europe aiming to increase public awareness and to prevent injury while using trampolines recreationally appear to be limited.

Our study was retrospective, with limited information on trampoline location at the time of injury. We could not establish a definite causative link for the rise in injuries. Another limiting factor was the use of a key term search in reports and requests. The true incidence of injury may have been underestimated if clinicians did not mention the key search term ‘tramp*’ in their clinical details. Cross-sectional imaging was used as a radiological surrogate for a potentially severe injury, but this did not consider clinically severe orthopaedic injury, for example open or markedly displaced fractures, separately. Therefore, the 1.1% of severe injuries in our study is probably an underestimate. Finally, this study only deals with imaging at initial acute presentation, and therefore does not consider the protracted clinical and imaging follow-up that may be required in a significant proportion of cases.

The number of trampoline-related injuries has increased over the study period. Higher injury rates are seen in younger children. Seasonal trends appear to be altering as access to indoor trampolines widens. This leads to more emergency and radiology department visits all year round and places an increased burden on the healthcare system. More campaigns are needed to improve public awareness on how to prevent trampoline-related injuries by providing guidance to parents and carers and influence national policies to set safety standards.