Luthi was collected by Ratthapark Wilairot's bike when the Gresini rider crashed on the final afternoon of the first pre-season test at Valencia on Thursday.
The Swiss rider was flown back to Zurich on Thursday night and spent Friday in surgery in Munsingen hospital.
Plates and screws were fitted to multiple fractures in his right arm during a five-hour operation.
Doctors predict Luthi, who has finished in the top five in Moto2 for the past three years and will stay with the Paddock team for 2013, will make a full recovery.
The team confirmed that Luthi was likely to miss at least the rest of pre-season testing and that his appearance at round one in Qatar was "in jeopardy".
But boss Daniel M Epp said the main priority was his rider's health.
"This accident was very, very unlucky," said Epp. "But the initial report of the doctors after surgery took a big weight off our shoulders since Tom will, in all likelihood, recover completely from his injuries.
"At the moment, this is all that counts."
The Moto2 season will begin at Losail on April 4-7.