The band was about to get back on the road when its front man’s back gave out.

U2’s lead singer, Bono, underwent an “unexpected” back surgery in a Munich hospital on Friday, May 21. This was after the magnanimous rocker suffered an injury during “tour preparation training,” according to the band’s own website.

The emergency surgery dampens fan excitement, as the band is forced to postpone the first date of its upcoming world tour. The 50-year-old rock star and his band had been preparing to launch the North American leg of their “360 Degree” world tour, the kick-off of which would have been in Salt Lake City on June 3.

Paul McGuinness, the band’s long-time manager, hinted that the injury could cause further postponements.

As reported on Reuters, McGuinness said in an audio message: "It's unfortunate that we're inconveniencing fans. We will make plans to reinstate these dates as soon as possible.”

More than fan inconvenience, however, it’s the poor man’s health that’s at stake. But realistically, any lengthy disruption of the schedule would be a major blow not just to fans but also to Live Nation, the concert company handling U2’s tour, as well as its merchandising, digital, and branding rights.

McGuinness also admitted, “Obviously, it's been very disruptive to our crew. We have over 400 people converging on Salt Lake City. Some of those have been told to turn around and told to stay at home until we make our new plan."

But the band and its management are playing it safe.

"Once his condition has been assessed further, a statement will be made regarding the impact on forthcoming tour dates," the band said on its website.

"Bono will spend the next few days there (Munich), before returning home to recuperate. Once his condition has been assessed further, a statement will be made regarding the impact on forthcoming tour dates," a spokesperson for Bono said, as reported by Reuters.

U2 is estimated to have sold more than 150 million records in their career and remains a big concert draw—earning around $109 million in 2009, as reported by Billboard.

The U2 360 Tour, so-called because fans surround a giant circular platform, has been predicted to become the highest-grossing tour in history.