Dunne has yet to play under Lambert in the Barclays Premier League since the Scot took charge in the summer, having initially suffered his fitness setback during the Republic of Ireland's Euro 2012 campaign.
The 33-year-old former Manchester City player underwent two rounds of surgery before it was determined he would need to go overseas for the treatment that would get him playing again. Villa manager Paul Lambert said: "'Dunny' got hurt at the Euros and it's never really cleared up. I think that's where it's come from."
Lambert continued: "He had another operation yesterday in America so hopefully once and for all that will be cleared up.
"I think America was the only place he could get that done. He'll come back in the next few days and hopefully then start his rehab and get going again. It's all stemmed from his hip area.
"We tried to sort out one thing and then it went to another, then it's gone to another thing. I've never seen anything like this. I don't think the medical people have seen anything like this."
Lambert insists Villa have not looked at trying to obtain compensation from the Football Association of Ireland over the matter.
He said: "I've not gone down that road. Injuries can happen to players, sometimes you get to the bottom of it, sometimes it takes longer than you think.
"As a footballer you get frustrated because you can't put your finger on what's gone wrong with you. Hopefully this time this has worked."
Lambert was hoping a sickness bug at the club this week would be under control ahead of Saturday's clash at Liverpool.
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