Surgery should be your last resort. Your pattern you describe almost fits my path except mine was in 1988 and running was not a part of my regime. You are typically born with a defect causing spongylolithisis, although mine was aggravated by a fall down a flight of stairs. I should have stuck with PT more. My surgery fusion with stainless steel bars was a partial success. They now know that stainless steel causes damage to vertebrae above and below the bars, hence my ongoing chronic pain, stenosis, peripheral neuropathy. They now use titanium cages with bone that works much better, heals quicker and less long term complications. But I’m now a firm believer in PT and the longer the better. If you are a runner you’re most likely in better health than I was back then and your chances of success with PT stand a better chance of staving off surgery.