"He hasn't recovered the way that we've liked or the way that he's liked in the conservative route, so the next logical step is surgery," Hinch said.
Hinch said the surgery is likely a season-ending measure, but wouldn't confirm it until the surgery was completed.
Deduno appeared in nine games before his injury, making two starts and accruing a 6.86 ERA in 21 innings.
"It's unfortunate because that means he probably won't be able to participate in the rest of the season or postseason should it come to that, but it's in his best interest," Luhnow added.
The prognosis is similar for fellow righty Brad Peacock, who went on the DL for a second time on April 15 with a left intercostal strain and is still experiencing symptoms after the club tried to ramp him up and get him to throw off the mound.
"He's not doing any better," Hinch said. "We're searching for answers. We're going to send him to another specialist in the next week or so to hope for a better diagnosis or hope for a clearer path as to how to get him back to health."
Peacock, who made only one five-inning start before the injury, will not throw for the foreseeable future, leading Luhnow to believe the time may be running out on the possibility of a return.
"I'm not optimistic he's going to make it back anytime soon, and we still don't know what the right course of action is," Luhnow said. "We'll have to figure out what the best path is for him. It, unfortunately, looks like a lost year for him."
Chandler Rome is an associate reporter for MLB.com.