The innocuous front-end slip-off resulted in a transversal fracture of the right malleolus when the German's leg got caught up in the trackside fake grass.
It is thought he will be out of action for Phillip Island but back for Motegi.
"We are happy about the results of this operation. Stefan is doing well and now it will be a case of starting the recovery process on Monday," said team boss Lucio Cecchinello.
"He will work with the physiotherapists until we sit down once again with the MotoGP Medical Team on Thursday at Phillip Island, when we will be able to form a much clearer prognosis."
HRC boss Livi Suppo said there is no chance of Casey Stoner substituting in Australia as the team do not contractually have to run a replacement.
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