Those backyard trampolines look fun and seem like a good idea for the kids, but newly-reported hospital numbers would suggest otherwise.

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An article in the Journal of Pediatric Orthopaedics cited more than one million trampoline-related visits to emergency rooms nationwide between 2002 and 2011. More than a quarter of those visits involved broken bones.

"The danger is significant," said Dr. Stephen Rice, director of sports medicine at Jersey Shore University Medical Center and a member of the American Academy of Pediatrics' New Jersey chapter. "The trampoline is inherently dangerous because of how it's used."

Intended for one user, a trampoline's screen can rise and fall in harmony with the jumper. However, once another person is added to the mix, the risk for injury increases.

Safety netting has certainly helped lessen the amount of serious injuries, but they don't solve the problem of multiple users at once.

"Part of the fun of the trampoline is this whole gang of kids on there at once, and that's really where you get yourself in trouble," Rice said.

For families considering a trampoline on their own property, Rice would advise against it. He said trampolines "aren't worth the risk" because most people don't use them in the way they're intended.