He can go on LTIR, but assuming he will stay on LTIR for 51 games is completely unrealistic,Surgery is not required to go on LTIR. A player can treat an injury with a lengthy rehab program that doesn’t involve surgery and go on LTIR.
A back injury could keep a player out for months without requiring surgery, and they could go on LTIR.
This is where you seem to be missing the point,
1. He and the team likely believe he will be back before the end of the season, if they didn't, it's highly likely theyd have chosen the surgery route.
2. You can't keep healthy players on LTIR, at least not without lying.
As much as you want to disappear Perron and his cap hit, the team and player expects him back before the end of the year. A conversation with the player to agree to stay in LTIR when nothing about his timeline suggests he is expected to miss the remainder of the season to accommodate a trade is cap circumvention, hence my original point about faking it.