I'll be brief, because there isn't a lot of hard, clear information and because speculation makes me nervous.
The farrier tried to pull Tristan's shoes and begin to trim without sedation. No dice. Tris started flipping around as soon as the farrier picked up his foot. So he got tranq'd. I'm not sure how to solve this one now. He's been good as gold for me, and I can't in good conscience ask the farrier to expose himself to physical danger and take up large amounts of time working through this. He wasn't being pushy, unusually quick, or really anything - steady, gentle, purposeful movement and Tris just did. not. want.
So farrier pulled the front shoes and did an initial trim, and then the vet shot x-rays of the RF. She did quite a few, including a navicular series, and determined two things based on x-rays. First, medial lateral balance was off, but not spectacularly so. Second, she did not like the look of the navicular bone. She thought she saw a loss of bone density and possibly some changes toward the back that were new bone growth in compensation for out of balance foot. She also thought she saw some deterioration of the bone in his toe - third phalanges - but couldn't make a clear determination because the bad hoof from the abscess was so junky it was obscuring the x-ray. She's going to keep looking at them with more leisure on a bigger screen, and in comparison with all the other previous x-rays, and possibly send them out to a specialist.
X-rays also showed that the LF is clean as a whistle, so any damage to the navicular in the RF is because of the poor balance there. That says to me at least - though vet was being admirably circumspect and cautious - that the damage was caused externally and is, while clearly not reversible, able to be stopped.
Joints continue to look good, and sole depth is remarkable, so those are two things not to worry about. The hoof growing down behind the abscess is straight and solid. With the x-rays the farrier and the vet both agreed he could take off much more toe than it looked like he could from an external view, so Tris's foot got trimmed back again. The bottom holes are alllllmost to the ground now. He also set the hoof back fairly significantly to move the breakover back and ease pressure on the heel. With the vet's input, we left shoes off his hind feet, so hooray for that.
When the farrier pulled the shoe from his RF, the abscess hole was clearly visible from the bottom, and HUGE. I am really regretting not taking a picture. I could easily have put my index finger into it up to the first knuckle. It was awful. Vet and farrier were duly impressed, and said they could smell not current infection but a sort of rank smell from old, dank infection. Ugh. I can't wait until the whole thing is gone. At this rate, the upper hole will be probably another 3 trims away from the bottom, maybe 4.
So. Plan going forward. I'll send all previous x-rays to the vet for comparison (she's already got the fall's, but I'll send her the views from a few years ago). She'll let me know if she wants to send them out. Tris has dramatically shortened feet but better balanced feet, and he'll be on 2g of bute a day until Tuesday to help him adjust. Next Friday I'll drag M. to the barn and jog him out and get a video to send to the vet.
I am still hopeful. Perhaps foolishly at this point. I'm not exactly cheerful - I've been close to tears basically since Tris started flailing at the farrier yesterday afternoon, and that doesn't look like it will go away soon. But I have a sort of internal logic worked out in my head that says that if any damage to the navicular was caused by bad balance, we can correct the balance and compensate, and keep an eye on him. It may mean we don't jump any more, it may mean I get picky about footing, it may mean he's shod up front for the rest of his life. Whatever it takes to keep him comfortable and happy is what I'll do. I just hope that happens to coincide with being able to ride him again.