@seidholz You are asking good questions in trying to locate the source. You may be interested in Myofascial Release Therapy. Fascia gets tight with injuries and surgical scar tissue. Having had hip replacements, undoubtedly, you will have some scar tissue that may be adding pressure to your spine or limbs and these very small spaces where the nerves are traveling. If you can loosen all of that and relieve the pressure, it may help.

Here is our discussion where you can learn more,
https://connect.mayoclinic.org/discussion/myofascial-release-therapy-mfr-for-treating-compression-and-pain/
and there is a provider search at https://www.mfrtherapists.com/

I have had great results from MFR work and I periodically have to keep doing this to maintain the ability to move correctly and keep my body aligned like it should be. One of the other Mentors, Chris @artscaping has had benefits from MFR work for her neuropathy and I would like to invite Chris into this discussion. Have you heard about myofascial release before? Mayo does have some chiropractors who do MFR therapy in the rehab area.