Like you, I would hesitate to do spinal surgery on a 12 year old lab. Is he on any kind of anti-inflammatory? I know people sometimes do not want to put their dog on medication, but if it will give him another 6 months (or however many months) of mobility, it starts to sound worthwhile due to limited options. Examples are Rimadyl or Deramaxx, or your vet may have something newer. My one senior dog was on Rimadyl and it did eventually bother his tummy, but it gave him an extra 6 months of walking, and when we had to discontinue it, that was when he quit walking so I know it was working for him. I would recommend talking with an experienced vet you trust, maybe just your regular vet, not the specialist, and find out what s/he recommends, and give something a try to see if you see any improvement. It sounds like you are close to him not being able to get up, I went through it with a golden retriever the same age and same size. I hope this helps.