The German doctor who repaired rocker Bono's back last year told the U2 star that his pioneering operation might wreck his performance in the bedroom. Dr. Hans-Wilhelm Muller-Wohlfahrt was candid with the singer and humanitarian when he first asked for help after cancelling tour dates because of his back pain - and told him there may be life-changing after effects. Bono explains, "The guy's a genius. I was told he was the best and that I was in deep trouble - and now I'm not... I'm very well, rebuilt by German engineering. "But he said, 'For this procedure... there is some risks... (like) the dropped foot... you might walk with a limp, and also the sexual dysfunction.' And my wife Ali was there and she said, 'Great!'."But I am very pleased at this great German care; I have neither of those problems."