The 63-year-old, who has performed his own stunts in the movie, was left reeling in pain after a fight with wrestling star Stone Cold Steve Austin turned dangerous.
"My fight with Stone Cold Steve Austin was so vicious that I ended up getting a hairline fracture in my neck. I haven't told anyone this, but I had to have a very serious operation afterwards. I now have a metal plate in my neck,” contactmusic.com quoted him as saying. Stallone stars alongside fellow tough guys Bruce Willis, Jet Li, Mickey Rourke and Jason Statham in the movie, in which a group of mercenaries attempt to overthrow a South American dictator.