If you wondered how a little old "bike spill" could be serious enough to keep U2 from showing up for their scheduled week-long residency on 'The Tonight Show,' well, we don't blame you -- but it sounds like Bono's accident was really rather serious.

Rolling Stone reports that five hours of surgery were required to mend Bono's injuries, sustained in what doctors are calling a "high energy bike accident" that occurred when the singer swerved to avoid hitting another cyclist in New York's Central Park on Nov. 16.

The article says Bono's list of ailments included "a 'facial fracture involving the orbit of his eye,' three separate fractures of his left shoulder blade and a fracture of his left humerus bone in his upper arm" -- and the fracture shattered the bone "in six different places ... tearing through his skin."

Three metal plates and 18 screws later, Bono's back on the mend, but the report cautions that he'll need to undergo "intensive and progressive therapy" before he's completely back in shape. The band hasn't commented on how this might affect its plans to tour in 2015, but it seems pretty likely that the group will need to scale back or reschedule any further promotional plans for its new 'Songs of Innocence' LP.

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