Vahaamahina out of SA tour
The news is a blow for the 25-year-old, who will miss Clermont's final games of the season and France's three-Test tour of South Africa in June.
Vahaamahina was substituted after 45 minutes in Clermont's European Champions Cup Final defeat to Saracens in Edinburgh at the weekend.
"Tests confirmed a fracture to the lower part of the tibia," the club said, adding: "An absence of several months" was expected for the 25-times capped player.
Clermont play the semifinals of the Top 14 on May 27 in Marseille against either Montpellier or Racing 92.
France are also scheduled to play Tests against the Springboks on June 10, 17 and 24.
* Meanwhile French No.8 Louis Picamoles has signed a pre-contract to return to Montpellier from Northampton.
"We've signed a pre-contract and Louis Picamoles should join up with us after the France tour [to SA in June]," Mohed Altrad told French television.
Montpellier only has to wrap up some "administrative issues with his current club which it's in the process of doing", said Altrad, Picamoles having signed a three-year deal with Northampton last summer.
Picamoles, capped 61 times by France, came through the Montpellier youth section and quickly made his name at the southern club before leaving for Toulouse in 2009.
Altrad, dubbing Picamoles the "world's best No 8", said the transfer would also be helpful for the France team, "which wants to have (its players) close by to find the same rhythm".