Car Seats

Why Extended Rear-facing car Seats are Safer

Sarah Davis

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If you’re curious about why the AAP recommends extended use of rear-facing car seats after their 2018 research and updated recommendation, you’ve come to the right place. In this guide, I’ll explain in simple and technical terms why infants and toddlers need that extra protection while traveling. Let’s dive in!

Experts supporting an extended rear-facing car seat use:

In 2009, the British Medical Journal made a significant statement in the UK. They emphasized that rear-facing is the safest way for children under 4 years old to travel. This statement debunked the misconception that rear-facing car seats were exclusively beneficial to Swedish children. You can read the full statement here: link.

In 2011, the American Academy of Pediatrics (AAP) initially recommended that children up to 2 years old should be seated in a rear-facing position. However, in 2018, the AAP conducted further research and updated its recommendations. The current guideline states that children should remain in a rear-facing car safety seat for as long as possible, considering the limits of their car safety seat. This recommendation applies to almost all children under 2 years of age and the majority of children up to 4 years old.

Swedish law mandates that children must travel in a rear-facing car seat until at least the age of 4, or until they have outgrown the rear-facing weight or height limits specified by the car seat manufacturer. This means that children must remain in a rear-facing position longer than in many other countries. This has been the case for the last 50+ years.

Several states in the US have implemented regulations or are in the process of passing regulations that mandate the extended use of rear-facing car seats until the child reaches the age of 2.

  1. California: California Assembly Bill 53, which went into effect on January 1, 2017, requires children to remain rear-facing until at least 2 years of age, or until they reach the height or weight limit allowed by the car seat manufacturer.
  2. New Jersey: New Jersey’s child passenger safety law was updated in 2015 to require children under the age of 2 to be secured in a rear-facing car seat, following recommendations from the American Academy of Pediatrics (AAP).
  3. Oklahoma: Oklahoma Senate Bill SB164 was introduced to the State Senate in February 2023. Check progress here
  4. Pennsylvania: Pennsylvania’s child passenger safety law was updated in 2016 to require children under the age of 2 to be secured in a rear-facing car seat.

Understanding kids’ anatomy that makes them vulnerable:

Spine:

Pediatric cervical spine ossification patterns differ from those of adults due to the ongoing growth and development of the skeletal system during childhood and adolescence. This makes the pediatric cervical spine more vulnerable to certain types of injuries compared to adults. Here are some technical ways in which pediatric cervical spine ossification patterns render them more vulnerable:

  1. Incomplete ossification: Pediatric cervical spines have several ossification centers that are not fully fused, leading to areas of cartilage and growth plates (epiphyseal plates). These areas are weaker and more susceptible to fractures or injuries compared to fully ossified adult vertebrae.
  2. Higher cartilage content: Children have a higher proportion of cartilage in their skeletal structure compared to adults. Cartilage is more flexible and less dense than bone, making it more prone to injury upon impact or sudden forces applied to the spine.
  3. Greater ligament laxity: Children have more ligamentous laxity or looseness in their joints compared to adults. While this flexibility is essential for growth and development, it also means that pediatric cervical spines may be more susceptible to hyperextension or hyperflexion injuries, such as those seen in whiplash-type injuries.
  4. Different biomechanical properties: The biomechanical properties of pediatric cervical vertebrae, including bone density, elasticity, and strength, differ from those of adults. These differences can affect how the spine responds to external forces and may influence the types and severity of injuries sustained.

Cervical vertebra (C3) in children

In the development of the vertebral column, the closure of the vertebral arches occurs in two stages: primary and secondary closure. Primary closure refers to the initial fusion of the vertebral arches, including the neural arches (which form the spinal canal), while secondary closure involves the completion of this fusion process and the formation of a bony structure.

A study found that there is a 50% probability that the primary closure of the neural arches of the third cervical vertebra (C3) is complete by the age of 2 years in children. This means that by age 2, approximately half of children would have completed the fusion of the neural arches of C3.

The secondary closure of the neural arches of C3 is typically complete by the age of 3 years in children. This implies that by age 3, most children would have fully fused and formed the bony structure of the neural arches of C3.

The closure of the neural arches is significant because it contributes to the stability and protection of the spinal cord within the vertebral canal. Complete closure of the neural arches is essential for the normal function and structural integrity of the cervical spine.

The image below shows the difference between the cervical vertebra in a 1-year(left) and a 6-year-old(right);

C3 -vertical vertabra of 1 year and 6-year showing unfused bone structure in infants
Why a rear-facing seat is important to C3 in a collision:

The third cervical vertebra, like other cervical vertebrae, may be affected by hyperextension, hyperflexion, or axial compression forces during a collision impact. Injuries to C3 can include fractures of the vertebral body, transverse processes, or spinous processes. Fractures of the vertebral body can result in instability of the spine and potential damage to the spinal cord or surrounding nerves.

Axis Vertebrae(C2):

  • Primary Closure vs. Secondary Closure: As with other vertebrae, the closure of the vertebral arches of the axis occurs in two stages: primary and secondary closure. Primary closure involves the initial fusion of the vertebral arches, including the neural arches, while secondary closure refers to the completion of this fusion process and the formation of a fully developed bony structure.
  • Closure of the Axis (C2): A Study found that there is a 50% probability that the primary closure of the neural arches of the axis vertebra (C2) is complete by the age of 5 years in children. This means that by age 5, approximately half of children would have finished the fusion of the neural arches of the axis.
  • Completion of Secondary Closure: Additionally, the secondary closure of the neural arches of the axis is typically complete by the age of 6 years in children. This implies that by age 6, most children would have fully fused and formed the bony structure of the neural arches of the axis vertebra.
  • Significance of Closure: The closure of the neural arches, including those of the axis (C2), is critical for the stability and protection of the spinal cord within the vertebral canal. Complete closure of the neural arches is essential for maintaining the structural integrity and normal function of the cervical spine.

The image below shows the difference between axis vertebra in a 1-year and a 6-year-old;

Atlas vertabra C2 showing a 1-yr old and 6-year old - no closure up to 6 years
Why a rear-facing seat is important to C2 in a collision:

The axis is the second cervical vertebra and plays a crucial role in allowing the head to rotate from side to side. In a collision impact, the axis is vulnerable to fractures, particularly at the dens (odontoid process), which is a bony projection of the axis that articulates with the atlas. Fractures of the dens can occur due to hyperextension or axial compression forces, leading to instability of the cervical spine and potential damage to the spinal cord.

Atlas vertebra (C1):

  • Primary Closure vs. Secondary Closure: As with other vertebrae, the closure of the vertebral arches of the atlas occurs in two stages: primary and secondary closure. Primary closure involves the initial fusion of the vertebral arches, including the neural arches, while secondary closure refers to the completion of this fusion process and the formation of a fully developed bony structure.
  • Closure of the Atlas (C1): According to a Study there is a 50% probability that the primary closure of the neural arches of the atlas vertebra (C1) is complete by the age of 7 years in children. This suggests that by age 7, approximately half of children would have completed the fusion of the neural arches of the atlas.
  • Completion of Secondary Closure:The secondary closure of the neural arches of the atlas is typically complete by the age of 8 years in children. This implies that by age 8, most children would have fully fused and formed the bony structure of the neural arches of the atlas vertebra.
  • Significance of Closure: The closure of the neural arches, including those of the atlas (C1), is crucial for the stability and protection of the spinal cord within the vertebral canal. Complete closure of the neural arches is essential for maintaining the structural integrity and normal function of the cervical spine.

The image below shows the difference between atlas vertebra in a 1-year(left) and a 6-year-old(right);

C1 - no closure up to 8 years
Why a rear-facing seat is important to C1 in a collision:

The atlas is the first cervical vertebra, and its primary function is to support the skull and facilitate the rotation of the head. During a collision impact, forces transmitted through the skull and neck can cause hyperextension or hyperflexion of the cervical spine, leading to injuries such as whiplash. The atlas may also be susceptible to fractures or dislocations, particularly at the junction between the atlas and the base of the skull (occipital condyles).

As with other vertebrae, the closure of the vertebral arches of the axis occurs in two stages: primary and secondary closure. Primary closure involves the initial fusion of the vertebral arches, including the neural arches, while secondary closure refers to the completion of this fusion process and the formation of a fully developed bony structure.

How rear-facing seats are safer during collisions:

Airway:

Young children’s airways are smaller and more flexible than adults, which makes them prone to injuries caused by excessive forces on the head and neck. Rear-facing car seats help to protect the child’s airway during a collision, as they distribute the impact forces evenly across their back and head instead of concentrating them on their spinal column.

Protection against rotation:

The orientation of C1 in relation to C2 (axis) is critical for proper function and stability of the upper cervical spine. The rear-facing car seat position ensures that the child’s head, neck, and spine are aligned in a straight line, reducing rotational forces on C1. In contrast, forward-facing seats can induce excessive rotation of the upper cervical spine during crashes, increasing the risk of injury to C1.

Support for weak muscles:

Children have relatively underdeveloped neck muscles compared to adults, making them more vulnerable to injuries. Rear-facing car seats provide support for the child’s head and neck, reducing the strain on their muscles during a collision.

Infants have underdeveloped neck muscles compared to adults. Their heads are relatively large and heavy, which means they have less control over head movements. In a collision, the rapid acceleration or deceleration forces can cause the head to move violently, potentially resulting in hyperextension or hyperflexion of the neck. This can lead to severe injuries such as whiplash, cervical spine fractures, or spinal cord injuries.

Protection against hyperextension:

Hyperextension of the cervical spine can cause damage to the ligaments and soft tissues in the neck. In rear-facing car seats, the child’s head is supported by the back of the seat, preventing excessive extension of the neck during a crash.

Proper positioning:

Rear-facing car seats also ensure that the child’s head is well-supported and in a proper position, reducing the risk of injury to the upper cervical spine. In contrast, forward-facing seats may cause the child’s head to move violently during an accident, increasing the risk of injuries to their neck.

Promotes proper breathing:

In a rear-facing position, the child’s airway is less likely to be obstructed by their own body or any objects that may fly towards them during a crash. This allows for proper ventilation and ensures that the child can breathe freely.

Protection against ejection:

Rear-facing car seats offer better protection against ejection in case of a collision, as they distribute the impact forces more evenly across the child’s body. This reduces the risk of serious injuries, such as head trauma and spinal cord injuries.

Prevents interaction with airbags:

Forward-facing car seats can be dangerous for young children as they are designed to work with airbags, which can cause severe injuries if deployed during a crash. Rear-facing car seats eliminate this risk by keeping the child away from airbags and minimizing their impact on the child’s body.

Reduces the risk of serious injuries:

Studies have shown that children under the age of two who ride in rear-facing car seats have a 92% lower risk of being seriously injured in a car accident. This highlights the importance of using this type of car seat for young children to ensure their safety and well-being on the road.

Disproportionate Forces:

Infants have relatively large and heavy heads in proportion to the rest of their bodies. During a collision, the forces exerted on the body, particularly the head and neck, can be disproportionate due to this size differential.

This can lead to greater acceleration and deceleration forces acting on the head, increasing the risk of traumatic injuries. Studies have found that kids’ heads are 25% of its body mass and are disproportionately heavier(as adult heads are only 6% of body mass). For this reason, rear-facing car seats are recommended to better distribute these forces and protect the child’s head and neck.

Immature Spinal Development:

The spine of young children is still developing and does not have the same strength as an adult’s. In a forward-facing seat, the harness straps can put pressure on the spinal cord during a crash, potentially leading to serious injuries.

Impact with Restraints:

The larger size of an infant’s head compared to their body can increase the likelihood of impact with the internal components of a car seat or restraint system during a collision. Improperly fitted or incorrectly installed car seats may exacerbate this risk. Impact with the car seat or restraint system can cause head injuries, including skull fractures, concussions, or traumatic brain injuries.