Backyard trampolines accounted for 1 million emergency room visits, reports a new study, with nearly 300,000 of those resulting in broken bones.

The Indiana University School of Medicine looked at accidents between 2002 and 2011, which researchers estimated cost about $400 million.

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The study estimates the cost over a 10-year period at more than $1 billion for ER-related expenses caused by using trampolines. Nearly all of them were caused at home and more than 90 percent of the injuries occurred in children.

Some of the most common injuries -- for upper extremities -- were the forearm (37 percent) and elbow (19 percent). The most common lower extremity injuries were the tibia/fibula (39.5 percent ) and ankle (31.5 percent ).

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"We are inundated with injuries," Dr. Randall T. Loder, chair of orthopaedic surgery at the IU School of Medicine and the study's lead author, told the Indianapolis Star. "Kids need to be healthy and active, but this is not the way to do it."