Dad may require more surgery. Will the Medicare benefit for rehab start over?

Just when my brother and I came up with a date to rescue Dad from the rehab facility (next week), we learned that the pins used to repair his broken hip have become displaced. He has been in the rehab facility for 60 days. I know Medicare pays up to 100 days. If he has more surgery, will the benefit start over? If it does, he will NOT be going back to the rehab facility he in which he is currently confined. I'm not sure he will be able to come home either so we are looking into some, hopefully, better options.