As any parent or teacher knows, children are different - in so many ways. One of them is the way their bodies, especially the skeletal structure and internal organs, react to the massive forces present in a vehicular crash.
Extensive work has been done over the past several decades on passive safety - protecting the occupants after a crash. The vehicle itself has been engineered to collapse in a controlled manner to absorb energy. Airbags and seat belts have been steadily improved and even the seats themselves and the head restraints have been radically improved.
Many of these advances have been possible because of data gathered from instrumented dummies subjected to actual crashes. They are also as close to anatomically representative of the human body as money and brains can make them.
One area of crash testing and data gathering that has not developed as well as others is that of child safety and crash dummies. To this point, the dummies used to gather data about children have essentially been downsized version of "adult dummies" that don't allow for the differences in body composition between adults and children.
Children are especially susceptible to the forces of gravity. The head of a newborn child accounts for almost half of its body weight. At the age of nine months, it still makes up about 25 per cent of the total weight. By the age of three, it has fallen to only 18 per cent and at six years the head accounts for 16 per cent of a child's total weight. By comparison, an adult male head makes up only 6 per cent of total weight, on average.
The infant skull is more flexible than that of an adult because the bones are still relatively soft and there are numerous fibrous "joints" where the growing sections come together. On the other hand, the brain tissue of infants is stiffer and more resistant to deformation than a toddler and adult brain tissue is even softer yet. Thus infant brains are especially susceptible to injury in a crash.
Another area of difference is the spine. Those of scaled-down test dummies do not allow for the big differences in spine development and flexibility as we grow from child into adulthood and the resulting head movements that can occur in crashes.
The cervical vertebrae of a child remain as separate bones until the age of four to six when they fuse. The ligaments of that area are much more loose than those of an adult and the joints are mostly horizontal - all of which means the skeletal components of a young spine move around a lot in a crash, allowing more head movement and creating greater risk of spinal cord and brain damage.
Researchers at the Center for Injury Research and Prevention at the Children's Hospital of Philadelphia (CHOP) have studied more than 7,000 children between the ages of four and eight involved in real-world crashes in the last decade. They have found that brain and skull injuries are the most common type of injury among children involved in a crash.
They say belts, bags and other advances reduce the likelihood of head injuries for adults but no accurate model exists to represent the developing skull and brain tissue of a child beyond toddler age.
To address this, researchers at CHOP and the University of Pennsylvania are working to establish brain injury criteria for six- to 10-year-old children. This data will allow development of an accurate computational model that could be used to mimic the reaction of young skulls and brains to the forces of a crash.
With financial and scientific support from the Association of Import Automobile Manufactures, CHOP is doing cutting-edge work on the development of accurate crash test dummies, called child Anthropometric Test Devices or ATDs.
These new devices are expected to result in innovative restraint systems and changes to vehicle design that will help prevent injuries and save more young lives.
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