I have seen patients who did not have leg pain prior to a surgery develop leg pain after due to the retained pars fragments. That is not always the case and remember that I have a reputation of seeing patients with failed prior surgeries. The ones that did well would not obviously come to see me after a successful surgery.
Nonetheless, it makes no sense to me not to decompress the nerve roots. In addition, the pars fragments make excellent bone graft which is the requirement for a good fusion in the first place.
Neurosurgeons who think TLIF cages are “not big enough” have never performed a TLIF. They are speaking from inexperience. I have a 99% fusion rate and I would like to see the ALIF surgeons demonstrate a rate close to that.
When a TLIF is performed, the entire nucleus and cartilagenous endplate is removed. This allows the bone graft and BMP to fully engage these bone surfaces. BMP mixed with autograft (your own bone) goes in the front of the disc space. The TLIF cage with only autograft goes in the back of the disc space.
When you remove the pars defect, there will always be a spur that develops off of the pedicle. This spur grows into the nerve root and is the primary cause of nerve compression in this disorder. Removing the pars defect and then this spur decompresses the root (along with the placement of the cage to raise up the disc space).
The cages for PLIF first started about 15 years ago. At this point they were metal (Moss Miami cages). The PEEK cages started to be used somewhat later and the TLIF technique was started by Harms about 12 years ago.
I cannot recommend anyone in your area. It sounds like your research has been thorough.