Trampoline Fracture of the Proximal Tibia in Children

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                                                            Trampoline   Fracture of the
                                                            Proximal Tibia in Children

                           Richard     S. Boyer1’2             Seven children (aged 2-5 years) sustained fractures       of the proximal tibial metaphysis
                               Richard    B. Jaffe1         while jumping on a trampoline       with a heavier child or adult. Most impaction     fractures
                             George     W. Nixon1           were transverse      and neither angulated    nor displaced. None of the children developed
                                                            permanent    disability  or impairment.    Parents and physicians     should be aware of the
                              Virgil R. Condon1
                                                            possible danger to small children while tandem jumping on a trampoline           with a heavier

                                                               New types of injuries peculiar                to specific recreational      activities   are recognized
                                                            with increasing        frequency       in our society,       which devotes       considerable        time and
                                                            resources      to recreation.        It is often helpful to associate            a typical     injury with a
                                                            particular    activity    and attempt          to elucidate    its underlying       mechanism        to aid in
                                                            recognizing      and preventing          injury to persons        engaged     in that activity.      We have
                                                            recently    observed       fractures      of the proximal        tibia in several children         who were
                                                            jumping     on a trampoline          with another       person (usually older and/or heavier).             We
                                                            report our findings and propose                the underlying      mechanism     of injury.

                                                            Subjects      and Methods
                                                               During 1981 through 1 984, we observed similar tibial fractures in seven children                     that were
                                                            sustained while jumping on a trampoline. Original radiographs of the fracture                            site were
                                                            examined by one of us (A. B.). Aefemng physicians and/or parents were contacted                        at intervals
                                                            from 2 months to 3 years after the injury to confirm the circumstances       of the                     injury and
                                                            assess subsequent impairment.


                                                                Seven children, aged 2-5 years (mean, 3.9), sustained                         fractures     of the proximal
                                                            tibia while jumping on a trampoline               with another person. In five of seven cases, the
                                                            child was jumping with an older child or an adult. The seven children weighed                                1 1 #{149}7
                                                            25 kg (mean,       1 7.9) compared         to their jumping        partners    who weighed         22.7-1 00 kg
                                                            (mean, 52.3). One child was jumping                   with several children            of the same age, and
       Received June 24, 1985; accepted after revision      another with a child of the same age who was 5 kg heavier.
August 28, 1985.
                                                                The typical fracture that was observed,               a linear transverse        fracture of the proximal
   I All authors: Department      of Radiology,   Univer-
                                                            tibia metaphysis        (fig. 1), was seen in five children.               In one child, the fracture           was
sityof Utah Medical Center, and Primary Children’s
Medical Center, 320 Twelfth Ave., Salt Lake City,           comminuted        but nondisplaced          (fig. 2). In another child, the radiographs                showed        a
UT 84103. Address reprint requests to A. B. Jaffe.          cortical buckle (torus) fracture without a visible fracture line (fig. 3). The fracture                             in
   2Psern     address: Department of Radiology,             one child was mildly angulated             and displaced       (fig. 4). None of the fractures extended
Hospital for Sick Children, Toronto, Ontario, Can-          to the articular surface.
ada M5G 1X8.
                                                                After a follow-up          period    of 2 months          to 3 years,         parents     and/or     referring
AJR     146:83-85,   January   1986
0361 -803X/86/1 461-0083                                    physicians     indicated      that each child had recovered               without      apparent    deformity       or
C American Roentgen Ray Society                             limitation.  No follow-up         radiographs      are available for confirmation.
84                                                                       BOYER      ET   AL.                                                              AJR:146, January 1986

                                                                                                                   Fig. 1 .-Anteropostenor    view. Linear transverse
                                                                                                               fracture of proximal tibial metaphysis.

                                                                                                                   Fig.   2.-Anteroposterior          view. Comminuted         frac-
                                                                                                               bore of proximal tibia.
1                                                       2

                                                                                                                   Fig. 3.-Anteroposterior    view. Cortical          buckle    (to-
                                                                                                               rus) fracture of proximal tibia.

                                                                              1;                                   Fig. 4.-Lateral
                                                                                                                                     view. Mild displacement
                                                                                                                         at fracture site.
                                                                                                                                                                           and an-

Discussion                                                                           seen in the trampoline         injuries.
                                                                                         It should      be emphasized         that the tibial fracture       we are
                                                                                     reporting     is not a stress fracture        [1 -4]. There is no history of
     We propose        that a fracture       of the proximal        tibia is an      repetitive     stress to the proximal         tibia, nor is there the typical
understandable         occurrence     in young children (aged 2-5 years              history of pain relieved by rest and exacerbated                 by activity as
in our patients) who jump on a trampoline               with another person          seen with stress fractures.            Furthermore,      in none of the chil-
if the second      person is heavier. As the heavier person jumps                    dren who sustained           fractures       was there radiographic          evi-
(fig. 5), the trampoline         mat recoils upward from its stretched               dence of underlying        bone abnormality          or history of metabolic
downward       position.     If the smaller child lands on the upward-               bone disease.
 moving mat at the time when its elasticity             is reversed     by recoil        The   outcome     of fractures          in the        children      we   report       was
and the springs         are shortening       to their unstretched         length,    uniformly   good. No child developed              deformity    or disability
there is significant         upward     impaction    force applied         to the    after treatment     with routine immobilization.          Genu valgum did
descending       child’s legs. The force applied             at just the right       not develop as a complication          of these tibial fractures,      as has
time and angle of impact may be sufficient                 to cause the tibial       been reported      in some children with tibial metaphyseal              frac-
fractures    we have observed.                                                       tures [4, 5].
     We recently      observed      a similar injury in a child who was                  We suggest      that radiologists,     pediatricians,     and orthope-
jumping     on the top mattress            of a bunk bed. The fracture               dists who are aware of the possibility              of a “trampoline     frac-
occurred    when another child lying on the bottom bunk pushed                       ture” of the proximal        tibia may be in a better position               to
upward with his feet on the upper mattress                 as the child above        recognize    this injury and correctly        identify its mechanism         of
landed on it. We propose a similar effect to that of the recoiling                   injury. Parents and other adults should discourage                   tandem
trampoline     mat in causing         an identical   tibial fracture      to that    jumping,   especially    by children of different       sizes, to avoid the
AJR:146, January 1986                                   TRAMPOLINE           FRACTURE       IN CHILDREN                                                       85

                                                                                     potential   of this injury   with its associated   pain and inconveni-
                                                                                        We thank Valone Kemp and Deborah Villeneuve for secretarial
                                                                                     assistance. Figure 5 was drawn by Marilou Kundmueller, Primary
                                                                                     Children’s Medical Center.
                                                                                      1 . Salter RB. Textbook of disorders    and injuries of the musculo-
                                                                                          skeletal system 2d ed. Baltimore: Williams & Wilkins, 1985
                                                                                      2. Grusel A. Pseudofractures     and stress fractures. Semin Roent-
                                                                                           genol 1978;13:81-82
                                                                                        3. Belkin SC. Stress fractures in athletes. Orthop Clin North Am
                                                                                        4. Aogers LF. Radiology     of skeletal trauma. New York: Churchill-
                                                                                           Livingstone, 1982
                                                                                        5. Curranno G, Pinckney LE. Genu valgum after proximal tibial
                                                                                           fractures in children. AJR 1980;136:915-918

                                                                                        Since submission    of this manuscript,      we have seen eight
                                                                                     additional  cases of similar “trampoline     fractures” of the prox-
                                                                                     imal tibia. We thank Richard Keller of Cottonwood           Hospital,
    Fig. 5.-Mechanism     of injury in trampoline  fracture.” As mat recoils, pro-
pelling heavier person upward, it strikes descending smaller person (child) with     Salt Lake City, UT, for providing        four of these cases for
sufficient force to cause fracture of proximal tibia.                                review.

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