Car seats: Facing backward is the way forward

Abstract

Road traffic accidents are one of the commonest causes of death in children. Child safety car seats have played a pivotal role in reducing the mortality and morbidity associated with road traffic accidents. However, there have been some concerns about the about the design of front facing car seats versus their rear facing counterparts. Legislation governing the use of rear facing car seats is variable, with some Scandinavian countries recommending their use up to the age of four, while others mandate their use only until one year of age. We present three case narratives of patients aged under 3 years who sustained catastrophic injuries after being involved in a road traffic accident despite being placed in an appropriately sized forward facing car seat. We reviewed the literature for evidence comparing the safety and efficacy of front versus rear facing car seats. Accident registry and crash test results support the increased safety of rear facing child seats. Frontal sled test have demonstrated that forward facing car seats expose children to much higher neck loads and chest displacement resulting in higher injury scores. Epidemiological data from registries and observational studies support the experimental data and demonstrate a clear injury-reducing effect of rear facing child seats compared to their forward facing counterpart. We recommend keeping children in rear facing car seats until the age of four, which is common practice in Sweden.

Full text

Case Report
Car seats: Facing backward is the
way forward
Jo Han Gan, Caroline Davison, Nick Prince and Anami Gour
Abstract
Road traffic accidents are one of the commonest causes of death in children. Child safety car seats have played a pivotal role
in reducing the mortality and morbidity associated with road traffic accidents. However, there have been some concerns
about the about the design of front facing car seats versus their rear facing counterparts. Legislation governing the use of
rear facing car seats is variable, with some Scandinavian countries recommending their use up to the age of four, while
others mandate their use only until one year of age. We present three case narratives of patients aged under 3 years who
sustained catastrophic injuries after being involved in a road traffic accident despite being placed in an appropriately sized
forward facing car seat. We reviewed the literature for evidence comparing the safety and efficacy of front versus rear facing
car seats. Accident registry and crash test results support the increased safety of rear facing child seats. Frontal sled test
have demonstrated that forward facing car seats expose children to much higher neck loads and chest displacement
resulting in higher injury scores. Epidemiological data from registries and observational studies support the experimental
data and demonstrate a clear injury-reducing effect of rear facing child seats compared to their forward facing counterpart.
We recommend keeping children in rear facing car seats until the age of four, which is common practice in Sweden.
Keywords
Child car seat safety, paediatric intensive care, paediatric trauma
Introduction
Road traffic accidents (RTAs) are the second common-
est cause of death in children after congenital malfor-
mations.
1
The mandatory use of child car seats has
been shown to reduce mortality and serious injuries
by up to 71%.
2
Despite this clear evidence of efficacy,
there are concerns that front facing car seats are less
safe compared to rear facing seats. Accident registries
suggest that fatalities could have been avoided if rear
facing car seats were used in place of their front facing
counterparts.
3
We present a case series of three children
in front facing restraints who suffered catastrophic inju-
ries during motor vehicle accidents. The mechanism of
injury in relation to the position of the car seat is exam-
ined and literature comparing the relative efficacy of
front versus rear facing car seats is reviewed.
Case reports
Case one
A two-year-old boy was restrained in a forward facing
child seat in the rear of a car when it collided head-on
into a wall at an unknown speed. He was in cardiac
arrest on scene and cardiopulmonary resuscitation
(CPR) was commenced immediately and continued
for 20 min until he recovered spontaneous circulation.
On arrival in the emergency department (ED), compu-
terised tomography (CT) scan revealed bilateral pneu-
mothoraces, a traumatic subarachnoid bleed, possible
disruption of C1/2 and evidence of severe hypoxic brain
injury. Bilateral chest drains were inserted, and he was
managed supportively in the paediatric intensive care
unit (PICU). The following day, a magnetic resonance
image (MRI) of his brain and spinal cord revealed
extensive injury to the spinal cord parenchyma from
the cervicomedullary junction to C5 (Figure 1). His
stay in PICU was complicated by aspiration pneumo-
nia, diabetes insipidus and pressure ulcers. He remained
in a minimally conscious state, ventilator dependent
Paediatric Intensive Care, St George’s Hospital, London, UK
Corresponding author:
Anami Gour, Paediatric Intensive Care Unit, First Floor, Lanesborough
Wing, St. George’s Hospital, London SW17 0QT, UK.
Email: anamigour@gmail.com
Trauma
0(0) 1–5
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DOI: 10.1177/1460408618755811
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and quadriplegic. Intensive care was withdrawn when it
was clear that there was no potential for recovery.
Case two
A two-year-old girl was the rear seat passenger restrained
in a front facing child car seat when the car collided head-
on with another vehicle at a combined speed of 80 mph.
She was found to be in cardiac arrest and bystander CPR
was commenced immediately. She regained spontaneous
circulation after intubation and bilateral thoracostomies
by the Helicopter Emergency Medical Service (HEMS)
team with a total downtime of 20 min. In ED, CT scan
revealed a distraction injury at C5/6 with paravertebral
haematoma, plus a subarachnoid bleed associated
with hydrocephalus. Initially, an intracranial pressure
(ICP) monitoring device was sited, and later, an extra-
ventricular drain due to persistently high ICP despite full
active medical management. MRI two days later revealed
evidence of significant hypoxic ischaemic brain injury and
spinal cord injury to the thoracic level with a cord haema-
toma at C1 level. Her recovery was complicated by
intractable seizures and autonomic instability. She was
discharged to a neuro rehabilitation unit eventually and
is currently ventilator-dependent via tracheostomy with
flaccid quadriplegia.
Case three
An 11-month-old girl was in the rear of a car restrained
in a front facing child car seat when it collided with
another vehicle travelling at a combined speed of
70 mph. At the scene, she was unresponsive, and CPR
was commenced by her father. She was initially brought
to a local hospital for stabilisation before being trans-
ferred to the major trauma centre. Initial imaging
revealed significant intracranial haemorrhage especially
around the fourth ventricle and brainstem with asso-
ciated hydrocephalus. There was also subluxation of
C1 on C2 with evidence of spinal cord damage. An
extra-ventricular drain was inserted and halo traction
applied. She spent 27 days in PICU, and remained ven-
tilator dependent until her eventual death from compli-
cations of her injuries.
Discussion
Common factors
All three cases involved a frontal collision, where the
child was in the back seat of a vehicle, all restrained
appropriately in a forward facing car seat. There was
no intrusion due to the impact that may have affected
the performance of the car seats. All car seats were still
properly affixed in the car after the collision.
All three patients had significant cervical spine
injures in the absence of any abdominal injuries or
long bone fractures; all were found in cardiac arrest
at the scene, had traumatic subarachnoid haemorrhage
and subsequent hypoxic ischaemic brain injury.
This consistent pattern of injury in children during
road traffic collisions leads us to be concerned that for-
ward facing child car seats expose the occupants to a
high risk of cervical spine and intracranial injuries in a
frontal collision which contributes to a significant rise in
mortality. Knowledge of paediatric anatomy and phys-
ique, physics and the most likely vector of force in a road
traffic collision (frontal impact, forward travel of occu-
pants) would support this as a logical hypothesis.
Mechanism of injury
In a properly fitted front facing car seat, the child is
secured by a 5-point harness which anchors a child’s
shoulders and hips to the seat. This allows the rigid
bony parts to take high impact loads without damaging
any internal organs. However, the head is not, and
cannot easily be, restrained. A child’s head is supported
by a relatively weak neck whose muscles are not devel-
oped sufficiently to dampen violent head movement.
Cervical vertebrae are mainly cartilaginous in the
infant. Articular facets, the contact areas between the
vertebrae, are shallow and are orientated more horizon-
tally, therefore allowing subluxation at significantly
lower forces. Neck ligaments, as elsewhere in the
body, are weaker than in adults. The disproportionately
large head compared to older children and adults
(Figure 2), weak cervical spine musculature and laxity,
may result in an uncontrolled cervical spine movements
Figure 1. MRI image showing cervical CSF collection
compressing the damaged spinal cord.
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and compressive or distraction forces in certain impact
deceleration events.
In a frontal collision, there is a sudden deceleration
at the point of impact: with the body anchored and the
head free, the neck experiences the entire magnitude of
the decelerating force. If neck motion exceeds tolerable
limits, ligaments stretch or disrupt, resulting in disloca-
tion of vertebrae, and/or disruption of the spinal canal
and cord. The younger the child, the lower the crash
force required to cause spinal injury.
4
In addition to the physiological/anatomical nature
of small children, the design of the car may contribute
to the injuries sustained during a collision. Car manu-
facturers tend to respond to market forces generated
by consumer information programmes: European
New Car Assessment Program (Euro NCAP) is a vol-
untary vehicle safety rating system which awards rat-
ings based on the performance of the vehicle in various
collision scenarios. Higher ratings have consistently
resulted in higher car sales. By stiffening the passenger
chassis, a vehicle may improve its safety rating by redu-
cing the risk of intrusion and injury to the passenger
but at the expense of higher deceleration forces.
4
Unfortunately, the child in a front facing restraint is
very vulnerable to the high deceleration forces acting
on the unsupported head.
Evidence: Rear vs. forward facing car seats
Rear facing car seats keeps the head, neck and spine
fully aligned. In a frontal collision, the crash forces are
distributed over all of these body areas. The head in
particular is supported by the child seat and the neck
does not experience excessive flexion or extension.
This is demonstrated by frontal sled tests
comparing rear and forward facing child restraints
with 1–3-year-old dummies.
5
Thirty-one frontal crash
tests with 12-month, 18-month, and 3-year-old dum-
mies restrained in both US and European rear facing
and forward facing seats were performed to measure
neck load and chest displacement. Chest displacement,
upper neck tension and lower neck flexion moments
were all substantially lower with both rear facing
restraint types, compared to the forward facing
restraints. This resulted in significantly lower injury
measures for rear facing restraints, particularly the
European rear facing seats.
5
A review of the US National Highway Traffic Safety
Administration vehicle crash database from 1988 to
2003 revealed that children under the age of two
years are 75% less likely to die or sustain serious
injury when they are in a rear facing seat.
6
This finding
was particularly true for frontal impact collisions where
children in forward facing car seats were much more
likely to be injured (OR ¼5.53, 95% CI: 3.74 to 8.18).
The odds of severe injury for forward facing infants
<12 months of age were 1.79 times higher than for
rear facing infants. For children 12 to 23 months old,
the odds were 5.32 times higher.
A Swedish epidemiological study examined accident
data involving Volvo cars to evaluate child safety with
respect to age, size and impact situation.
7
A total of
3670 children, aged 0–15 years, were involved in car
crashes during 1987–2004. The injury-reducing effect
Figure 2. Comparison of the relative size of head to body from infant to adulthood
4
(Copyright: Association for the Advancement of
Automotive MedicineßAAAM 1998).
Gan et al. 3

of any child restraint systems was high overall. The high-
est injury-reducing effect was found in rearward facing
child restraints for children up to four years of age,
offering an injury-reducing effect of 90% compared to
an unrestrained child. This is in contrast to booster seats
for 4–10 year olds which reduce the risk of injury by
77%. A tendency of higher injury risk was found when
the growing child switches from one restraint to another,
i.e. when the child is at the youngest age approved for
the restraint. It was worth noting that forward facing
child seats for ages 1–4 with integrated child harness
are very rare in Sweden as the official recommendation
is to keep children rear facing until four years old, and
therefore not included in this study.
This finding has been confirmed by the reviewing the
Swedish Fatal Accidents database.
3
There were 17 fatal
accidents involving children from 1999 to 2006. Six
cases were excluded as they were due to unrestrained
children and misidentified cases. Of the remaining 11
fatalities, four were in a rear facing seat. Those who
died were due to excessive intrusion, fire and drowning
where the choice of child restrain would not have made
a difference. On the other hand, of the six fatalities
involving children in a front facing restraint, three
cases were deemed to have been survivable if the child
was in a rear facing car seat.
Current UK legislation allows a front- or rear facing
child seat to be placed in the front seat of the car if the
airbag is turned off. However, the risk of significant
injury is much higher if the child is in the front seat.
A matched cohort analysis found the risk of death for a
front passenger, compared with a rear passenger of the
same age, was increased most among children.
8
For
rear seat passengers younger than 13 years compared
with front seat passengers of the same age the adjusted
mortality risk ratio was 0.71 (95% CI: 0.64 to 0.79).
Conclusion
We have presented a case series of three paediatric
trauma patients suffering catastrophic spinal cord
injuries in an otherwise properly restrained forward
facing child seat. The literature review provides evi-
dence that front facing car seats expose children to a
greater risk of spinal injuries and death when com-
pared to rear facing car seats. Clinicians should have
a high index of suspicion for spinal injuries despite
appropriate restraints in forward facing car seats.
We recommend keeping children in rear facing car
seats until the age of 4, which is common practice in
Sweden, where practical.
Acknowledgements
We would like to thank Ms Rachel Neal, Data Manager,
PICU, St George’s Hospital for helping us accessing the
patient details.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with
respect to the research, authorship, and/or publication of this
article.
Funding
The author(s) received no financial support for the research,
authorship, and/or publication of this article.
Ethical approval
Not applicable.
Informed consent
Written informed consent was obtained from the patient
(Cases 1 and 2) for their anonymised information to be pub-
lished in this article. Consent for Case 3 was unavailable as
patient was deceased and parents were no longer contactable
despite attempts through multiple avenues.
Guarantor
AG.
Contributorship
JHG wrote the first draft of the manuscript. All authors
reviewed and edited the manuscript and approved the final
version of the manuscript.
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