I'd like to add my thoughts. If the cat doesn't appear to be in pain, and you haven't found a solution, you may want to let it heal and make it a "house cat". Lots of people and animals have limps, and live out full lives. If it's in misery, I'd do it the favor of putting him down, but if it seems to be doing OK, I'd let nature take it's course, but I wouldn't put it back outside so it can happen again, or get into fights with other cats, and not be able to defend itself or get away.