The Bio-mechanics of Kids in Car Crashes

Little Kids in Big Crashes

Lisa Schwing, RN

Trauma Program Manager

Dayton Children’s

Very Little Research

• There has been very little research on the forces a crash has on a child’s body.

• Most research has occurred on scaled down models of the adult body.

Kids are not little adults • Because children are smaller than

adults, traumatic forces in children usually affect a larger region of the body. Multisystem injuries are more common among pediatric patients.

• High incidence of pulmonary contusion, liver and spleen injuries.

• Compact - organs are more tightly packaged.

• Most often, less fat, less muscular, therefore less protection.

Speed vs Velocity

• Kenetic Energy = ½ mass X velocity E=½ MV • When mass is doubled, so is the energy. • When velocity is doubled, energy is quadrupled.

• Bottom line – speed kills!

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• In comparison to body size, the child’s head is larger in size and weight.

• A child’s neck ligaments

are weaker.

Children have big bobble heads

Child Thrown from a Vehicle During a Crash

• Any child that goes airborne up to the age of 10 will land on their head.

The Child’s Skull is Thinner • Predisposing the

skull to fractures that are often accompanied by epidural or subdural bleeding. Head injury is the number one cause of death in children involved in car crashes.

Epidural or subdural bleeding on the Brain Can be fatal

• An epidural bleed is usually the result of a torn artery (the middle meningeal artery) in the brain that bleeds under pressure.

A Child’s Ribs are Made of Cartilage.

• Adult ribs are at an angle, are calcified and hard and provide better protection in a crash.

Chest radiograph taken 6 days after injury reveals multiple healing fractures at costovertebral junction and lateral ribs bilaterally.

• Ribs of a child are horizontal and have little calcium. • Fractures are difficult to identify, but underlying organs are easily injured.

Lungs are Smaller and Respiratory Rates Higher

• The lungs have disproportionately smaller inside surfaces for oxygen exchange compared to an adult. Depleted oxygen and fatal chemical changes in the blood occur very quickly in children without adequate oxygen.

• Abdominal Muscles are less

developed.

“Baby Buda belly”

• Think potential for multisystem injuries.

What we do know

Motor Vehicle Crashes – Put Children at Risk for Abdominal Injuries

High velocity crashes cause extreme energy transfer to the body. The combination of tightly packaged abdominal organs and in some cases ill fitting safety restraints put a child at increased risk for abdominal injuries.

Excessive Energy Transfers to a Small Area

Flexion injury around the lap belt. Chance fracture

Airbag injuries to children

Back to the math

• E=½ MV

2 5 kg baby 50 mph

921 pound force/foot

Zero chance you will hold this child in a 50 mph crash.

Chest and Abdominal injuries • Chest and Abdominal Injuries are the second leading cause

of death in pediatric trauma associated with car crashes. • Because the physical exam is often not reliable and the history may be incomplete, missed injuries can lead to increased morbidity and mortality.

FAST Exam in Children

• Negative predictability fairly reliable

• Positive predictability about 56% and uncertain due to modest sensitivity.

• Varying study results

Ruptured Spleen Goal – Children keep their spleens.

•The 2 children requiring splenectomies due to trauma done at DC in the last 12 years were both in MVC’s and both inappropriately restrained. (3yo in booster and 6 yo in seatbelt ) Both had ruptures with massive bleeding. Both had multisystem injuries with ISS >40. Both recovered completely.

Blunt Abdominal Injuries – Hollow Organs

• Hollow organ injuries usually require urgent surgical intervention. • Esophageal and stomach • Bowel • Bladder

Skeletal Differences • Children have

incomplete bone calcification. Children’s bones are still growing. Injuries to growth plates can arrest bone growth.

Penetrating vs. Blunt Abdominal Trauma • Penetrating trauma accounts for < 4% of all

injuries seen at Dayton Children’s.

•Blunt trauma is common. • While falls are the most

common cause of injury,

severe injuries related to

blunt force trauma are

usually associated with

motor vehicle crashes (not accidents) or children hit by a car while riding a bike or walking.

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Percent of Injury Types at Dayton Children's

BurnsPenetrating InjuriesBlunt Injuries

How bad was the crash? – “Delta v” • Consider the crashworthiness of the vehicle, the passenger characteristics, and restraint usage. • Factor in the speed change of the vehicle as a result of the crash – known as the Delta v. • This is the measure of the severity of the impact. • However, mechanism is not always a factor in the severity of

the injury and at Dayton Children’s was found to be a poor indicator for predicting injuries.

Disbursing the energy in a crash

• When the energy transfer is isolated to one line or one spot, the impact to that line or spot is greater.

• Take the energy and spread it out across a larger surface and the energy transfer to any one spot is .

• A helmet absorbs the energy, spreads it out and protects the head much like seatbelts protect the body.

Seatbelt stats

• Children 4-8 years old restrained in seatbelts are 3 times more likely to be admitted for injuries from a motor vehicle crash than children from birth-4 years. They are too big for car seats and too little for seatbelts. Ohio legislators passed a law October 7, 2009 requiring booster seats for all children 4 to <8 years-of-age and shorter than 4’9”.

No Perfect

What is wrong here?

• The neck • The lap belt / buckle • The position of the legs

What’s wrong here

• The lap belt • The shoulder

harness • The 5 point restraint

buckle • Transfer of crash

energy to a single area

What’s wrong here?

• Too small/young for seatbelts.

• Shoulder strap across abdomen.

• No neck protection.

What’s wrong here?

• Nothing

Seat Belt Injury = Tier II Trauma Activation

Though seat belts contribute to a number of predictable injury patterns, proper use of seat belts is statistically the single best prevention for motor vehicle crash fatalities. • Note the lack of shoulder strap markings.

What’s wrong here?

• Lucky baby involved in a roll over crash.

5-Point Restraints Spread the Crash Impact

Seatbelt Sign

Seat Belt sign with associated lumbar

compression fracture

Dayton Children’s admitted 65 children with positive seatbelt signs in the last 2 years. The most common injuries associated with seat belt sign:

deaths 0 spleen lacerations 11 liver laceration 1 renal lacerations 4 perforated bowel 1 intracranial bleeds 3 concussion 8 skull fracture 2 lumbar fracture 1 femur fracture 5 humerus fracture 3 pelvis fractures 4 pulmonary contusions 4 rib fractures 3 clavicular fracture 3 facial injuries 3

There is No Substitute for Good Judgment

Kids can Survive Most Car Crashes if Properly Restrained

Summary • Researchers are striving to develop accurate ways to

predict a child’s injuries in a motor vehicle crash. • Kids are not little adults.

• Prevention is key.

• Thank you for all you do!