Seems there are two versions of the above image being distributed. The first, sent out by Greg Kadel's studio, with the ribs intact (full editorial here). And the second, photoshopped/printed by Numéro, in which they smoothed them out.
This is another case of a magazine being extra cautious (or lack taste), and I prefer Kadel's original to Numéro's manipulation. Anyone who stretches back like that will have their ribs show through. It's natural; unlike the edited image.
Last year Vogue Italia also freaked out about their image of Karlie.
Update: Kadel responds to this.