Can I suggest some up to date x-rays with a referral to the super vet Noel Fitzpatrick. I have just watch one of his programs and a dog had this problems for several years and nobody had found the issue, Noel did and operated, after the recovery weeks there was no sign of any mishaps. ( this was an op on the spine)
The only other thing would be to invest in a mountain of news paper spread down and around the house,which would be easier to clean up, also plastic sheeting under soft furnishings ie: actual duvets, cushion foam etc. I did this for one of my old cats but unfortunately she past away.