Purpose or Case Report: Trampoline-related injuries in children are a common cause for presentation to the Emergency Department, and their incidence is increasing. Injuries to the lower limb are the most common. Transverse fractures of the proximal tibial metaphysis are a well-described classic fracture. These fractures may be subtle, only diagnosed at the time of follow up x rays. When reviewed at Radiology Quality Assurance meetings, these missed fractures were perceptible on the original imaging. We sought to examine the characteristics of fractures that were missed, and elucidate measures that could improve diagnostic accuracy.
Methods & Materials: All patients who received conventional x rays of the lower limb for trampoline-related injuries at the Mater Children's Hospital during the six year period January 2009 - December 2014 were reviewed. Patient demographics included gender and age. The referring department and mechanism of injury was determined from the request form. The regions x rayed and the views obtained were noted. All imaging was reviewed to assess for fracture and for any complications such as non union or angulation. Where fractures were present, reports were reviewed to determine the timing of fracture diagnosis. The fractures were classied as to bone, location (diaphysis, metaphysis), involvement of growth plate, and type: complete/incomplete. Particular attention was paid to those fractures within the proximal tibial metaphysis.
Results: 250 patients (102 male, 148 female) underwent x rays of the lower limb for trampoline-related injuries. The vast majority (242) were referred by the Emergency Department, the remainder from primary care or outpatient clinics. The average age was 3.6 years (range 1 - 15 years). Fractures were present in 45% patients. Of these, 62% were located in the proximal tibial metaphysis. While the majority were diagnosed at the time of original injury, in our series, 10% were not. These fractures were subsequently diagnosed at the time of first follow up x ray. The fractures that were missed were subtle: either undisplaced linear fractures of the "hairline" variety or incomplete, buckle type fractures. The buckle fractures that were not perceived commonly occurred in a region of overlap between the proximal tibia and fibula on the AP projection. When femoral x rays were also performed at the time of injury, this improved conspicuity of proximal tibial fractures, particularly those of the buckle type. There were no complications of non union or significant angulation, with mean follow up duration of 4.7 weeks.
Conclusions: Trampoline-related injuries are increasing in frequency, despite measures to improve product design and safety standards. The proximal tibial metaphysis is the classic site of trampoline fracture, however these may be subtle. Delayed diagnosis has obvious implications on patient management. In our review, the most commonly missed fracture types were undisplaced linear and buckle fractures, particularly those with isolated angulation of the lateral tibia. Buckle fractures often occured in a region of overlap between the proximal tibia and fibula on the AP projection. When x rays of the femur are also performed, re-assessment of the tibia is recommended, as this view may result in increased conspicuity of proximal tibial fractures compared with images of the tibia/fibula alone, due to differences in centring of the x ray beam. Windowing of images may improve conspicuity of subtle, undisplaced linear fractures. In order to reduce delayed diagnosis, the proximal tibial metaphysis should be an area of review when reporting x rays for patients with trampoline injuries. Specific attention to any region of overlap of the proximal tibia/fibula on the AP projection and re-assessment of the proximal tibia on any femur x rays (if these were also performed) can improve diagnostic accuracy.