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Evidence-based justification for extended rear-facing

It’s all the rage among parents nowadays: extended rear-facing. If you’re turning your child to face forward before age 2, then you’re old-schooling it and increasing your child’s risk of injury in a crash. Many pediatricians still hold onto the now ancient recommendation of turning kids forward-facing at age 1 and 20 lbs., even though their own professional organization, the American Academy of Pediatrics, hasn’t recommended that since before 2002. You were probably in grade school then.

Why is it so critical for kids to stay rear-facing?

When you use the carseat right, it protects them and you from potentially being forever changed if you get into a crash.

Simple Physics Lesson

A carseat will always move toward the point of impact (Newton’s 1st Law). In a frontal collision—statistically the most common type of severe/fatal crash—the entire back of a rear-facing carseat will protect the head, neck, and spine of a child as it rotates down toward the front of the vehicle. Even in a side impact, which is a more serious type of crash due to its proximity to passengers, there is usually an element of frontal movement, such as a vehicle moving forward through an intersection, as it’s hit from the side. So a rear-facing carseat will rotate down and forward, then toward the side where the impact occurs.

Click each graphic to see the motion:

rf-physics-animation ff-physics-animation

Compare this to a forward-facing child in a harnessed carseat. In a frontal crash, the carseat still rotates down and forward toward the front of the vehicle, and the child will be flung forward into the harness and forward of the carseat shell. In a side impact, again the carseat rotates down and forward toward the front of the vehicle; the child comes forward into the harness and out of the carseat shell and there is rotation toward the vehicle door where the impact occurs. Because the harness is holding only the shoulders and hips, the head, arms, and legs are flung violently forward. If the harness is loose, which is one of the most common mistakes a caregiver makes, there’s a high likelihood of the child hitting the vehicle seat in front or the side pillar. According to this study, rear-facing children 12-23 months are 5.53 times safer in a side impact than forward-facing children and there’s no indication that safety magically disappears at 24 months.

Anatomy 101

The folklore is that a child’s neck muscles aren’t developed enough to keep a baby’s neck safe in a car crash, which is why they have to face the rear of the vehicle. I suppose that’s true in a way: it does take babies time to develop their musculature so they can hold their heads up to keep their airways open. But the muscles don’t protect the fragile spinal cord, which is the bundle of nerve fibers that forms the central nervous system and is connected to the brainstem. No amount of baby push-ups will strengthen your child’s muscles to the point of protecting his spinal cord.

The bones of the spinal column are what actually protect the spinal cord and in infants and young children; they aren’t completely fused together for years. One of the most important cervical bones, the Atlas (C1), is what attaches the head to the spinal column. Drawings show where it ossifies, or fuses, at varying times: the anterior arch fuses around age 7, while the posterior neural arches fuse around age 3. Before it fuses, the Atlas and Axis (C2), the 2nd vertebra that the Atlas nestles into, are made of bone and cartilage, which is very pliable. These two vertebrae are held in place by ligaments, which are very elastic (lax) to allow the child to grow.

atlas-side-view axis-side-view simplified-upper-cervical-spine

Studies of infant cadavers have shown that vertebral columns can stretch up to 2” but that the spinal cord is damaged after only ¼”. Given that a baby’s head accounts for ¼ of its total body size versus 1/7 an adult’s size, plus the immaturity of its vertebrae and laxity of the ligaments holding those vertebrae together, rear-facing seems the obvious choice.

The child’s large head shifts the fulcrum of movement, where the head swings forward, higher, elongating the spinal column and potentially causing catastrophic damage to the spinal cord. Before age 8, this fulcrum is in the upper cervical spine, at C2-C3. After age 8, the fulcrum shifts down to C5-C6, where it stays into adulthood. When you hear the term “internal decapitation,” it encompasses this movement of the upper cervical spine since the head swinging forward must happen in order for the ligaments to stretch and pull the head from the Atlas.

Another devastating injury that doesn’t show up on x-ray is called Spinal Cord Injury without Radiographic Abnormality (SCIWORA). This is when the spinal cord stretches because of the elasticity of the ligaments and cartilage in the spinal column. An x-ray will show normal bone alignment and no fractures, but the spinal cord may be irreversibly damaged. Remember that this bundle of fibers can only stretch up to ¼” before having catastrophic damage.

The evidence is clear. Rear-facing carseats protect the most fragile part of a developing child’s body: the head and spinal column. The American Academy of Pediatrics recommends rear-facing to a minimum of age 2 and instructs their pediatricians to counsel parents about rear-facing to age 2 and longer as the carseat allows. The National Highway Traffic Safety Administration (NHTSA) recommends rear-facing  as long as possible.

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The American Academy of Pediatrics (AAP) has recommended since 2002 that after age 1 and 20 lbs., children should ride in a rear-facing convertible seat until reaching the weight limit of that carseat. They amended that policy in March 2011 to recommend rear-facing to age 2 or until they reach the “highest weight or height allowed” by that convertible carseat.

 

Note how the legs fly away from the back of the vehicle seat during the test. In the forward-facing seat, the properly secured dummy bends nearly in half during the crash test. Photo courtesy Kathy Weber, ret., UMTRI, and SafetyBeltSafe USA.

Note how the legs fly away from the back of the vehicle seat during the rear-facing test on the left. In the forward-facing seat, the properly secured dummy bends nearly in half during the crash test.  Photo courtesy Kathy Weber, ret., UMTRI, and SafetyBeltSafe USA.

Forward-facing children under the age of 2 are 75% more likely to be injured.  (Car Safety Seats for Children: Rear Facing for Best Protection

Here’s an article showing why children up to the age of 2 are more than 5 times safer riding rear-facing.  (Rear-Facing Car Safety Seats Getting the Message Right)

SafetyBeltSafe USA’s opinion on how long children should ride rear-facing. (How Long Should Children Ride Facing the Back of the Car?)

After reviewing studies from the U.S. and Sweden, a study published in the highly regarded British Medical Journal advises keeping children rear-facing until age 4.  (www.bmj.com/cgi/content/full/338/jun11_2/b1994?view=long&pmid=19520728)

Leg injuries account for 28% of significant injuries faced by forward-facing children in crashes  (Jermakian, J.S., et al. “Lower Extremity Injuries in Children Seated in Forward Facing Child Restraint Systems.” Traffic Injury Prevention 8 (2007): 171-179.)

This analysis shows how leg injuries are common among forward-facing children (Bennett, T.D., et al. “Crash Analysis of Lower Extremity Injuries in Children Restrained in Forward-facing Car Seats During Front and Rear Impacts.” Journal of TRAUMA® Injury, Infection, and Critical Care 2006;61:592-597

A tightly installed rear-facing carseat allows the vehicle and carseat to absorb crash forces and increases “ride down,” the amount of time it takes a body to come to a stop in a crash.  The longer the ride down time, the less chance of injury.  (http://www.car-safety.org/rearface.html)

Rear-facing carseats provide excellent protection in side impacts as well.  Because there’s usually a vehicle moving forward, as through an intersection, that element of forward motion can easily throw a child’s head clear of the carseat if he’s forward-facing.  If rear-facing, his head will stay protected inside the carseat.  (http://www.carseatsite.com/rf.htm)

Infants and young toddlers have spines made of soft bone and cartilage that doesn’t begin to harden until around age 3.  As a result, the spinal column can stretch up to 2 inches; however, the spinal cord will rupture after being stretched after only ¼ inch.  This damage cannot be repaired.  (http://www.carseat.org/Technical/tech_update.htm#rearfacFF)

Evenflo is now requiring that children be age 2 before forward-facing in their convertible and combination carseats.
 

Approximately 75% of kids in Sweden rear-face until at least age 4.  From 1999-2006, only 4 rear-facing children under age 4 were killed in crashes and their deaths were due to circumstances unrelated to the direction the carseat was facing (fire, drowning, excessive intrusion).  During that same timeframe, 6 kids under age 4 facing forward in booster seats were killed; 3 of these crashes were potentially survivable crashes had the children been in rear-facing carseats.  (http://www.bmj.com/cgi/content/full/338/jun11_2/b1994)

Anecdotal evidence suggests that infants around ages 10 mos.-18 mos. enter a fussy stage that makes it difficult to put them into any carseat, rear- or forward-facing.  Many parents prematurely switch the rear-facing carseat forward-facing thinking that the child is objecting to riding rear-facing, when the child is objecting to being restrained at all.  Visit the Car Seat Safety forums at www.car-seat.org and you’ll hear from other experienced parents regarding this phase.

The above video shows how the dummy stays contained in the seat during a rear-facing crash test.  The tape on the dummy’s head is for measurement and doesn’t affect its head during the test.

This video is the companion video to the one above and shows a side view of the crash test.  Note how little the head moves.

The above video shows a properly installed forward-facing seat.  Note the seat belt stretch and how far forward the dummy bends.

The above video from Norway shows the differences between rear- and forward-facing carseats in an animated crash.

The above video from the Buckle Up Brutus at Ohio State University demonstrates the difference between rear-facing and forward-facing in crash tests.

If you need more convincing, take it from Dr. Marilyn Bull, a noted pediatrician from one of the country’s best pediatric hospitals, Riley Children’s Hospital in Indiana. This video was produced for, and used in, the current Child Passenger Safety Technician course.

Vehicle crashes are the number 1 killer of children.  Protect your children to the best of your ability.  Follow best practice.