The Swiss rider suffered multiple fractures of his arm and shoulder when he was collected by Ratthapark Wilairot's bike in a crash at Valencia.
Luthi underwent surgery last week and will start his rehabilitation soon, but his team said on Wednesday he will not return to action until the third round of the season at Jerez.
He will miss the races in Qatar and Texas.
"Of course this injury is a big disappointment for me," said Luthi. "But with my doctor of confidence, Dr Marc Mettler, I am in the best hands and I am optimistic to be able to start the rehab programme and the work toward my comeback very soon.
"It was very nice to feel so much compassion, which motivates me even more to work hard for a speedy recovery."