Maxwell, who returned to international duty with the All Blacks on their end-of-year tour last November, consulted a surgeon following the team's return to New Zealand.
Crusaders doctor Deb Robinson said: "He's decided to have the surgery and will need five to six weeks with the finger in a splint to recover."
The second rower will miss the four remaining round-robin matches in this season's Super 12 but could possibly return for the semi-finals if, as expected, the four-time champions finish in the top four.
They are currently second in the table with only the Cats, Sharks, Highlanders and Hurricanes to play.
Maxwell's injury will be of concern to All Blacks coach Graham Henry, with an already short supply of experienced international locks to partner Chris Jack further reduced ahead of a big international season that includes the British & Irish Lions tour, Tri-Nations and end of season tour of Britain.
Ali Williams is part-way through a six-week suspension for stamping, while Keith Robinson has not played rugby for over 10 months following persistent back problems which eventually required surgery.