I Have Isthmic Spondylolithesis. I've Had Two Spinal Operations. Three

I have isthmic spondylolithesis. I've had two spinal operations. Three months post op I had urgent MRI Scan which showed the vertebrae had slipped back to it pre operative stage. My surgeon has recommended that I would be best served by posterior approach with pedicle screw fixation at L5/S1 exploration of L5 roots and distraction across the foramina and then later on an anterior approach with an interbody fusion and planting. I am not happy about interbody fusion (ALIF/PLIF and plating). I would rather have Motion Preservation Spine Surgery as possible to fusion. The question I have - bed wetting & spondylolisthesis are they linked? I have been told that I don't have cauda equina syndrome (but my Urologist says I have neurogenic bladder)