Hi Frosty,
i am mostly a lurker on mn, but i felt I had to reply to your post.
Im sure you will do the right thing for both you and your horse. When you get a diagnosis like this it is so hard to come to terms with such wonderful animals that we build strong partnerships with having to make such drastic changes to their training, routines and plans for the future.
I agree with previous posters that there is only so much money you can throw at this kind of thing, and sometimes you have to say enough is enough. I think it depends somewhat on finances, but also on what riding goals you want to achieve, what your horse can cope with and what you are willing to compromise on.
I don't know whether this may help you, but a friend of mine had a 4 year old stallion (he is a rare breed called an Akhal Teke - they have a lot in common with TBs) who she had imported from russia.
A year or so after she first got him he was diagnosed with extremely severe kissing spines (not just the spinal processes touching along the spine, but the whole spine itself was 'wavy' up, down, left and right - iykwim)
She is not sure whether he was born with the deformity or it somehow developed, but he was one of two horses she had at that time, the other was a 25 y.o companion she had got from a rescue centre.
She had him checked by the best KS research vet in the uk, who basically said operating wouldn't fix his wavy spine or the touching spinal processes, and he was a lost cause.
She is Russian, a bit alternative and very stubborn :)
If she had listened to the vets he probably would now be in a tin or at best a field ornament.
She started off doing her best to learn what he could cope with and what he wouldnt be able to manage. he is a special personality (given the opportunity he will bite most people he meets! ) so he was quite a challenge to work with. she did a lot of research online and had his back muscles checked by a physio every 3-6 months.
To start with she gave him a break and did not ride for 6-12 months.
- it sounds like you are beyond that stage though, as your Dhorse is already fit and his back muscles are relatively strong.
She learned about a training aid called 'kavalkade rein', which she lunged him with several times a week. This made a big difference to his back muscles as it helped them to strengthen and develop. It may help your Dhorse to do this to keep his mind working and give you something to do with him? Once she had done some strengthening work, she started to bring him in to light hacking work again.
Another thing she then learned about was a different, starting off in hand, training method called 'Straightness Training'. It is a series of groundwork and ridden exercises that are used to develop your horse and allow it to carry itself better. She has found this has also made a big difference to his ability to be kept in ridden work. It keeps his mind busy as he is having to think about movements she is asking him (e.g shoulder in or quarter in from one side of the lane to to the other they are riding along), she does them mostly ridden with him as he will happily take a chunk out of you if you stand too close to him on the ground :)
She doesnt really do much if any ridden work in the arena with him as when she first had him and didn't know so much, she paid a 'dressage' trainer to come and school him. the trainer hauled his head in and 'put' him in the correct position, but this was the worst thing for his spine as he hollowed and firstly as a young horse wasnt really strong enough to immediately go like that as the rider should develop collection gradually (and not from hauling in the front end...), and also having undiagnosed KS made it a lot worse. The trainer rode him a few times, each time the horse got more and more uncomfortable and reacted to the rider trying to force him in to 'collecting' and the trainer eventually refused to come back as he said the horse was dangerous. Since then he has been quite dangerous to ride in the school, as she thinks he remembered the pain the trainer caused and connects it with ridden schooling in the arena.
So, she does all her straightness training schooling out hacking. She built him up to longer and longer hacks, and, as hacking near where she lives isn't brilliant (lots of roadwork), decided to join an endurance ride. He is now 11, and she has built up to successfully completing 40km competitive endurance rides.
Sorry - that is rather a long story! But I guess, i am trying to say that there may possibly be another way to keep doing things with your Dhorse depending on his KS development.
You may have to give up hunting him, as I think my friends KS vet said jumping is not advised due to the strain it puts on the spine. But, can you not aim for something else instead, or find someone who is happy to do that? There are other disciplines you can try if you want to keep him in work.
I used to share a 16.2 warmblood and loved nothing more than jumping (though I only got up to 2'6 as I am a wimp - the horse I shared was more than capable :D ) then my mum bought a 14.2 gaited horse which is far from a jumping type. For various reasons I took over riding it, and I now do non competitive endurance myself, and also some showing (though we are rubbish at it) and straightness training, as i have seen how much it has helped my friends horse, so I think it can do nothing but good for a 'normal' horse without any issues.
I don't miss jumping at all as I love all the scenery I see doing the endurance rides, and i love the challenge of constant learning and improvement the straightness training schooling brings (for myself and my horse!)
Anyway, I hope that helps you and your Dhorse in any way - i again apologise for being a terrible rambler. i'll shut up now!