I've not read about this commonly occurring and have not experienced it, but I have two frienRAB that are currently having similar problems. Both have had a one level fusion at L4-5 and both are having issues with possible non-union. One gal has pain that kind of wraps around from the back to the sides and to the front. The other has recently been complaining of pain in her abdominal area. Neither understanRAB what is going on.
Sorry I don't have any possible answers to share with you. Hopefully someone who has experienced this will see your post and respond back to you.