Oh how sad. Just a thought! Can they not operate on a cat for this? I know it can be done on dogs and the outcome can be very sucessful. My mini doxie had disc operation and had several of them fused when he was 6 years old. He was in terrible pain at the time and was even loosing the ability to walk. He is now going on 9 and you should see this guy run. I just don't allow him to climb stairs or jump up on anything anymore. It was extremely expensive, about $8000.00 CDN as I recall but he is worth every penny of it for the joy he gives me. Perhaps you can check out specialists in your area and/or the local veterinary college to see if it has ever been performed on cats. It is just so heart wrenching to seem them in pain and 6 years old is still young for a cat. I wish you luck!
Pat