It's capsular contracture. The body forms a capsule of scar tissue around the implant, and in this case, it's resulted in what's called "upward displacement", where the capsule has adhered to the pectoral muscles.

It can be fixed, but if porn stars are anything like strippers (well, most of them start out that way) they don't choose their surgeons carefully and don't give themselves enough time to heal or follow pre- or post-operative instructions. It's so counterintuitive, because all that ends up happening is spending more money and more recuperation time on yet another surgery.

It's not uncommon to meet strippers who've had their breasts done 4-7 times.