Varus shearing force is a main injury mechanism of pediatric trampoline-related injury in addition to compressive axial loading

Abstract

Background Many case studies have been published about trampoline-related injury (TRI); however, a comparative study could allow a more specific analysis of the characteristics of TRI, and enable more differentiated approaches to prevent such injuries. We investigated the injury mechanism of TRI in children compared with other pediatric trauma. Methods Of 35,653 children (age 0–18 years) who visited the pediatric emergency department after traumatic injuries from January 2011 to June 2017, 372 patients with TRI (TRI group) were retrospectively identified. Among the remaining 35,281 patients with other trauma (non-TRI group), 372 were 1:1 matched to the TRI group according to sex, age, injured body part, and body weight (matched-control group). The patients’ data, injured site, and injury patterns were compared between the groups. Results The most frequently injured body part was the knee/lower leg in the TRI group and the head in the non-TRI group. The most frequent injury types were fractures in the TRI group and open wounds in the non-TRI group. In the comparison between the TRI and matched-control groups, the most common lower-extremity fractures were proximal tibial fractures with varus angulation in the TRI group and tibial shaft spiral fractures in the matched-control group. For the upper extremities, the risk of lateral condylar humeral fracture was higher in the TRI group. The TRI group presented more physeal involvements. Conclusions The risks of varus stress injury (proximal tibial fracture with varus angulation in lower extremity and lateral condylar humeral fracture in upper extremity) were higher in the TRI group than in matched-control group. Thus, varus shearing force seems to be an important injury mechanism in TRI in addition to compressive force. This varus force may increase the risk of physeal injury by generating additional shear force on the physis.

Trampoline-related proximal tibia impaction fractures in children: A population-based approach to epidemiology and radiographic findings between 2006 and 2017

“…29 Bearing this in mind, all bone fractures in the upper part of tibiae should be considered as clinically significant, and follow-up is recommended. 30 A particular fracture in this area is the 'trampoline leg fracture', which is an impaction fracture of the cortices caused by high landing force on an upward impacting trampoline mat. There are not usually any fissures that reach the physis, however, anterior depression of the physis is usual, resulting in the tilting of the growth plate.…”

Initial angular deformity and its recovery of the proximal tibial metaphyseal fracture according to the cause: Trampoline-related injury versus other injuries

“…In concordance with the present results, varus force during trampoline injury has been suggested as a possible mechanism of injury. 9 …”

“… 3 , 12 , 21 For this reason, anterior tilting of proximal tibial epiphysis and/or buckling of the anterior cortex are regarded as one of the important radiological findings in trampoline fractures. 9 , 11 Despite these findings, little research has been done on the recurvatum deformity and its recovery. The present results show that there were recurvatum deformity in both TRI and non-TRI groups at the initial presentation; and it was more severe and showed incomplete recovery after two years of follow-up in the TRI group.…”

“…7 , 8 However, it is currently suggested that the degree of valgus deformity would be minimal or absent in patients with proximal metaphyseal fracture by TRI. 2 , 9 Therefore, this underscores the need to investigate the fractures separately based on the cause of injury (TRI versus non-TRI).…”

“… 3 , 10 Several studies on proximal tibial metaphyseal fractures as a type of TRIs have reported characteristic radiological findings that involve the anterior cortex due to axial loading on the hyperextended knee, such as buckling of the anterior apophysis of the tibia and anterior tilt of the proximal tibial epiphyseal plate. 9 , 11 , 12 Despite reports stating that recurvatum deformity is one of the important features of proximal tibial metaphyseal fracture due to TRI, there has been a paucity of follow-up studies on sagittal deformity, unlike coronal deformity.…”