When Rob told me a couple weeks ago that one of his colleague's 2-year old kid's leg broke going down a playground slide with his mom, I thought it was some sad, fluke thing. Then I read this article, which reports that leg breaks and fractures of this kind are pretty common. It basically says it's dangerous going down a slide with your kid because if their shoe or leg gets caught, the adult's weight keeps propelling them forward, making the kid's leg twist even more forcefully. If the kid was alone, his own weight would stop him or atleast slow him down.
I'm so glad I read that! I don't think we'll stop going down the slide with him completely, especially at this age when Greyson can't go on slides on his own, but we'll be hyper-vigilant about limbs being tucked in.