Bitmerkle, have you read the literature on Dr. Corenman’s site, it’s very useful info on spondy.
I’m not answering for Dr. Corenman by any means, but I also have l5 pars fracture, bilateral. My fracture is also very old, since I’m 42 now and it probably happened around 15 years old I believe. The bottom line is, is somewhat healed itself over the years by scarring up. So you and I have pannus or scar/bony tissue that is holding that lower pars joint together.
You can get it fixed now, with surgery, more than likely a TLIF, fusion. That is my option too. My pain is from muscle fatigue, 24/7 the low back muscles spasm from trying to hold that joint together. I work out and try to keep the low back strong without overdoing it but, honestly anything much more than sedentiary lifestyle will overwork the low back. I’m trying to deal with it as long as I can before I give in to surgery, due to the task that surgery will impose on ones personal life, job, finances, etc.
I have changed my profession from a physically demanding mechanic job to an office job, as well as modifying my habits, like bending over, I bend down, etc.
I hope this helps some and you can get some relief. The shots, did nothing for me, corisone, epidurals, nothing. Trigger point injections helped calm the muscles down but that’s just a temporary bandaid, at least in my case.