Ozzy Osbourne and Black Sabbath’s farewell concert featured an all-star lineup of some of the biggest names in classic rock, but one notable band was missing. Now, Mötley Crüe’s Nikki Sixx has revealed why the ‘80s icons weren’t there.

The bassist did not elaborate on the health issues, but in March, Motley Crue posted to Instagram to announce that lead singer Vince Neil, 64, underwent a "required medical procedure,” forcing a postponement of the band’s planned spring Las Vegas Residency at Dolby Live at Park MGM.

Ozzy Osbourne is saying goodbye to the stage after performing what has been billed as his final show with the original members of Black Sabbath.