He says it was due to boxing injuries, but that sounds like a lie he made up for his horribly excessive plastic surgery. Mike Tyson got hit a thousand times harder than Rourke ever did, and he doesn't look like a blowup doll. Neither do any other famous professional boxers. Plastic surgery to repair damage doesn't include jumbo XXX sized lip injections.
Mostly due to the boxing. Had several facial injuries, had to have reconstructive surgery on his nose and cheekbone which didn’t work, and had to teturn to surgery several times.