Apparently it's not the height that makes heels dangerous, it's angle your foot is at. So although Gaga wears really tall high heeled shoes, they are normally platforms and that means her feet aren't at a really dangerous angle, unlike the shoes in the x ray.
The platform actually makes all the difference, though. Her foot is not on a great of an incline as the X-ray photo. The incline is what will kill your feet. So she's wearing the right kind of heels, no matter how many inches that platform is :)
I think the plateau heals are better than the high heels you showed in X-ray, because in plateau ones the heel is not so high compared to the sole of foot!