Uncapped flanker Virgile Bruni and fullback Jean-Marcellin Buttin have been added to a 30-man squad gathering on Sunday for a two-week training camp ahead of the opening match at home to England on Feb. 1, the French Rugby Federation (FFR) said.
France, who finished bottom of the Six Nations last year, have been plagued by a series of injuries and had already been deprived of several key players including centre Florian Fritz, scrumhalf Morgan Parra and winger Vincent Clerc.
"The amount of serious injuries since the start of the year is worrying," France head coach Philippe Saint-Andre said in a FFR statement.
Flanker Dusautoir, who has won 65 international caps, ruptured a biceps tendon during Toulouse's European victory against Zebre in Parma on Saturday and will be sidelined for up to four months.
"Thierry was back to his best level and had a leading role in the squad," Saint-Andre said.
Toulouse head coach Guy Noves had earlier told a local radio station that Dusautoir would be out of club competitions for the rest of the season but could recover for France's tour of Australia in June.
Lock Pascal Pape, who has already worn the France captain's armband when Dusautoir was out injured in the past two years, will lead the team in the Six Nations.
"I'm sure he will figure out how to put his troops on the right track from the start of the tournament," Saint-Andre said.
Dusautoir has been replaced in the squad by the 24-year-old Bruni, who has become a regular starter for European champions Toulon this season.
Guitoune, who made his international debut in November, ruptured his Achilles tendon in Perpignan's defeat at home against Gloucester on Sunday and is set to be sidelined until the end of the season.
Fullback Buttin, who won his first two caps in 2012, has taken Guitoune's place in the squad.