TOP jockey Walter Swinburn underwent a 40-minute operation last night following a Sha Tin trackwork spill which left him in severe pain. Swinburn was operated on for a collapsed lung and three cracked ribs and his current Hongkong stint has ended in a hospital bed. The dual Derby-winning rider came off Super Bull on Monday and was kicked just below the shoulder blade. Although painful, popular winter visitor Swinburn was convinced nothing was broken and planning to ride out tomorrow morning. ''But when I woke up yesterday morning I was in severe pain. Mick Kinane had come to visit me the night before and suggested I get precautionary X-rays and then David Oughton suggested I see the doctor who looked after him when he was hurt at Sha Tin lastmonth. ''When they told me it was a collapsed lung and broken ribs I could not believe it although I had been having real trouble breathing,'' said Swinburn. The Irish ace underwent an operation to put tubing into the lung and blow it up again and was able to smile through the pain late last night. ''Actually, I felt better immediately I came out of the operating theatre. It was not being able to breathe properly that was most painful,'' he said. Swinburn reluctantly accepts that he will not be able to ride here again this season but will be back in trim for the start of the British season in March. ''It's bad luck but it happens that way from time to time in this game. I had a good book of rides for next Monday and I was really looking forward to it. ''I just hope that I can come back next winter because I love riding here and I haven't really had a chance this time,'' he said. Swinburn has been forbidden on medical grounds to travel for at least a fortnight and expects to stay on in Hongkong until at least early February. Meanwhile, Irish champion jockey Kinane is battling a severe dose of influenza to get ready for tonight's Happy Valley card where he has rides in five of the six races. ''The best way to put it is that I feel rotten,'' he said last night. The sudden drop in temperature caught out Kinane who rode out yesterday morning but then headed for bed. ''I am hoping that the antibiotics and a good night's sleep will do the trick but if the races had been tonight (Tuesday) there's no way I would have been riding. ''I could not have done the horses justice,'' he said.