Wales flanker Dan Lydiate added to head coach Warren Gatland's back row problems on Tuesday after being ruled out for the rest of the season with a bicep injury that will also see him miss the upcoming Six Nations.

The 30-year-old is to go under the knife after injuring his bicep in Ospreys' PRO14 22-9 win over the Dragons on December 31, his club side Ospreys announced.

Lydiate, who has 62 caps but started just one of Wales' Tests in 2017, joins fellow flanker Sam Warburton in missing the tournament.

"After speaking to consultants and seeking specialist opinion, the decision has been taken in Dan's best interests to undergo surgery," said Ospreys medical performance manager Chris Towers.

"That process will take place this week, ruling him out of consideration for the rest of the current season."

Aside from Lydiate and Warburton's absences, Gatland also has concerns over No8 Taulupe Faletau, who is recovering from knee trouble and won't be back until late February or early March.

Ross Moriarty, another back row forward, is also sidelined through injury.

The Six Nations gets underway on February 3.