England and Wasps lock Joe Launchbury is to undergo surgery on a neck injury and will miss the 2015 Six Nations.
The 23-year-old, who has been sidelined since the beginning of November, is now expected to be out for a further three to four months.
Wasps director of rugby Dai Young told the club website: "We have consulted specialists and they have recommended surgery as the best option for him."
Launchbury has won 22 caps for the national team.
When fit, he has been a regular starter for England during Stuart Lancaster's reign as head coach.
The neck problem kept him out of the recent autumn internationals and, with Leicester's Geoff Parling also injured, Bath's Dave Attwood and Northampton's Courtney Lawes were Lancaster's preferred second-row pairing.
England begin their Six Nations campaign away to Wales on 6 February.
Launchbury, who has been with Wasps since 2010, signed a new contract with the club in October.
He will miss their debut at the Ricoh Arena in Coventry on Sunday, where a crowd of around 27,000 is expected to watch their Premiership fixture against London Irish.