Bono was already partly paralyzed by the time doctors performed the emergency operation last week.
German neurosurgeon Professor Jeorg Tonn said the U2 star had already suffered paralysis in his leg by the time he was rushed to hospital.
Tonn - who operated on Bono - said the star couldn't walk when he came into the hospital.
"He was already in severe pain with partial paralysis in the lower leg," he said.
"This surgery was the only course of treatment for full recovery and to avoid further paralysis. Bono is now much better, with complete recovery of his motor deficit.
"The prognosis is excellent but to obtain a sustainable result, he must now enter a period of rehabilitation."
The doctors are saying that Bono needs a minimum of eight weeks to recover from the surgery but Professor Tonn cautioned that it might take more.
Sports injury specialist Dr Hans-Wilhelm Muller-Wohlfahrt, agreed.
Muller-Wolfahrt was the first doctor to see Bono in Germany after he injured himself.
"Bono suffered severe compression of the sciatic nerve. On review of his MRI scan, I realized there was a serious tear in the ligament and a herniated disc, and that conservative treatment would not suffice," he said.
He recommended that Bono seek emergency surgery with Tonn at the Munich hospital and says the star needs at least eight weeks to recover.
"In our experience, this is the minimum time," Muller-Wohlfahrt said.
Meanwhile, Bono says he is heartbroken at being forced to pull out of Glastonbury and the North American leg of the 360 Tour.
Sixteen shows have been canceled from Salt Lake City on June 3 through to New Jersey's Meadowlands Stadium on July 19.
The band is now also out of next month's 40th anniversary of the Glastonbury Festival which they were due to headline.
"I'm heartbroken. We really wanted to be there to do something really special -- we even wrote a song especially for the festival," Bono said on the band's webs
Guinness is good for you, say medical experts