Ok vet staff here - I see you say there is no way you can afford the surgery even on a PP, but I will lay out your options in full either way as it might help someone else too. The options are PTS, I am sorry but we have it happen a lot due to finances, it is a very, very, awful sad fact of life these days. A Humm loan or installment plan with vets, or surrender your dog to a charity for the work to be done and your pet put up for adoption afterwards or approach a charity vet ( PDSA) who may be able to do the surgery a lot cheaper, or as an alternative a training school where new grad vets do the surgery much cheaper for learning experience, while supervised closely by experienced vets.
You could also start a GO FUND me and see if anyone is willing to donate towards the surgery, lots of people do.
Before anyone comes at me saying a vet wont PTS a healthy dog, have you any idea of the amount of dogs in rescues and shelters who will never get a home, ones that will end up PTS anyway as the charities and rescues are overflowing with much younger and more adoptable dogs.
This surgery is in the thousands and if you are in the UK great, there are a lot more options than in Ireland. You could also try a bank loan, a credit union loan, or pay the surgery cost off weekly or monthly and keep your pet on pain relief until then
.However, bear in mind once one leg goes, the other usually follows within a year as the good leg is now taking all the pain and stress of the bad leg.
I am sorry ideally we would all have our pets insured but life happens and I am not here to make you feel awful about whatever choice you make in the end.
Chat to your vets and see if they can offer any help at all, even as a training for new vets, but Ortho surgery is a very specialised market and they may not be willing to work with you on money.