Ch
ance fr
actures of the skelet
ally imm
ature spine cl
assic
ally occur in front
al motor vehicle
accidents (MVAs) when the occup
ants
are restr
ained by
a l
ap belt only
and undergo tr
aum
atic hyperflexion of the torso during the imp
act. We retrospectively ex
amined
all MVA-rel
ated Ch
ance fr
actures
at British Columbi
a's Children's Hospit
al since 1986, by collecting injury
and se
at-belt use inform
ation from ch
art d
at
a and im
aging studies. Twenty-six p
atients were included in the study, 14 wore
a l
ap belt only, seven wore
a three-point restr
aint properly,
and five were reportedly misusing the shoulder portion of
a three-point restr
aint. The subjects r
anged in
age from 3 to 16 with
a me
an
age of 10.6 ye
ars. Eleven of the 26 (42 % ) p
atients sust
ained
abdomin
al viscer
a injuries, seven of the 26 p
atients suffered neurologic injury (spin
al cord
and/or spin
al nerve injury)
associ
ated with their spin
al fr
acture, with two c
ases of complete p
ar
alysis,
and there w
as
a 38 % incidence of he
ad injury. Concomit
ant injuries (i.e. to the he
ad,
abdomen
and
abdomin
al contents) tended to be mitig
ated by the presence of
a properly worn shoulder restr
aint.
This leads to the conclusion that Chance fractures can be sustained even when the occupant is using a shoulder belt to restrain their torso. The mechanism responsible for this is unknown. This may indicate that Chance fractures can be caused by a lesser degree of torso hyperflexion than previously thought. Alternatively, we also speculate that Chance fractures can occur while the torso is restrained by the shoulder belt if the hips submarine beneath the lap belt and the torso experiences hyperflexion secondary to forward excursion of the pelvis and legs during the collision. Future work is necessary to confirm these mechanisms and to find ways to prevent them. These studies will need to use computational or experimental child surrogates that can sit in a slouched posture and submarine during a collision.