The centre-back suffered the injury while clearing the ball during Newcastle's 4-2 win over Southampton at St James' Park on February 24 and has not featured for the club since.

The 31-year-old has returned to Argentina to be assessed by his national team's medical staff, and could be out until May.

"Colo has gone back to Argentina," Newcastle manager Alan Pardew said.

"There's no treatment he can have, he's broken two of the bones in his back.

"We think it's going to be anything between three and seven weeks. He's gone back for a week."

Newcastle play Anzhi Makhachkala in the Europa League on Thursday, before hosting Stoke City in the Premier League three days later.