Ferris suffered a tendon problem which occurred as a consequence of ankle damage sustained during Ulster's fixture against Edinburgh.
He missed Ireland's entire autumn Test programme as a result, with the operation coming just over eight weeks before the RBS 6 Nations opener against Wales in Cardiff.
In a statement, Ulster said: "Stephen will be reviewed in the coming weeks to establish an accurate time period for recovery and to assess when he will be fit to return to play."
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