Although it is nice to think of kids as just little adults, that is just not true. In fact, doctors are taught the differences so that these differences can be taken into account, when treating kids.
Fractures in adults require splinting and at times surgeries. The bones have stopped growing so the idea is to put the bones back together and make sure that the nerves and blood vessels are in line.
However, with kids their bones are still growing. Certain fractures are like breaking a green stick. The stick bends and then breaks only part way. These fractures often require nothing more than a ace wrap. Since the bones are growing healing is fast.
Other fractures are not so easily treated. If a bone breaks through the growth plate, then there may be a risk of permanently damage to the growth plate, unless the pieces of bone are line up very carefully. These fractures called growth plate fractures must be diagnosed correctly so that the right treatment can happen. To be sure sometimes with minor breaks in the growth plate, only a splint or cast is needed. However, for other such fractures surgery is needed.
Because kids bones are much softer than adults, it often takes more force to break (fracture) them. Some of that force may end up wreaking havoc in the soft tissues such as organs. For example, a fall from a height in an child may result in fewer fractures but more internal injury than an adult. Furthermore, ligaments are not as strong as adults so serious spinal cord injury can be seen without any spinal fractures. This is only rarely seen in adults.
Bottom lines, children are not little adults and fractures are just one example of this.