no matter if it did crack the concrete - presumably the soil around the concrete is pretty firm anyway.

depending on cost and labor availability they might be worth trying as opposed to full post replacement and the attendant hole digging/new concrete pour.

if the concrete is already cracked and/or the post is just leaning and yet fully intact, those things wouldn't help at all.

This device would be useful if the needs help because of cracking or deterioration or shrinkage, but not if the lean is due to movement of the concrete in the soil.

In the first case, there should be space for the plate to fit without stressing the concrete.

I'd at least try one plate on one post.

Cool device!

The only way I can think of that the concrete might have shifted is from frost heaves, but the rest of the fence is largely straight. It may be water from the adjacent garden that has had an effect on the posts over the past 20+ years. We also had some large Virginia Creeper vines covering the fence along this stretch, which may have had something to do with it. They were dug out last week by me using my trusty digging bar ("Texas toothpick&quot .

I've been looking at various post pulling devices and most appear either expensive, unreliable or simply a lot of work.

find a kid (teenager) and put them to work is my advice

that or replant the creeper vines LOL

not sure where you are, but with some soils "they" say using concrete is pointless so the post may just be in the ground.

from experience, the worst situation is the bright idea of some ancestor who thought it would be a good plan to toss a bunch of rock in the hole.

then you're going to have a potential rot problem where the post enters the concrete.

If you use concrete to anchor the posts, it's best to have the concrete come above the ground a little so that the surface of the concrete doesn't stay wet.

If the concrete meets the post at, or worse below ground level, then you're going to have a lot of moisture entering and leaving the wood. That leads to a crack forming between the wood and the concrete as the wood expands and contracts. Water can then get into that crack, and you add freeze-thaw damage too.

Basically, there's two good ways to use concrete on a fence:
1) build it like a deck, where the concrete comes above the ground.
2) You're in a very loose, sandy soil where the post won't stand up on its own.

If those don't apply, concrete generally doesn't make the posts last any longer than just sticking a below-grade-rated pressure-treated post in the ground.

So back to the original problem and what to do now (This assumes your concrete is at or below grade):
The metal plate in your OP works, in that it provides a stop-gap solution that will last bit, if the problem is the post leaning and not the concrete leaning. It won't last nearly as long as a new post. It won't damage the concrete in any relevant way - for the post to lean the concrete has to already be damaged, or the post has to be broken or rotted significantly.

Your other option is to replace the post - but consider whether you should bother with new concrete. It costs less to just stick the pressure-treated post in the ground, and post-in-the-ground will generally last longer than using below-grade concrete.

You get the old post out by disconnecting the fence, and then digging around the post with a shovel. You can generally get it out by digging a bit, and then levering the post back and forth until it's loose. You don't need a puller or other fancy mechanism.

If you replace the post without concrete, you're going to need to add a bunch of dirt to fill the space that used to be filled with concrete. Make sure you pack that dirt in very firmly - don't add more than 2" at a time, and smash the hell out of the dirt as you backfill.