@retreat1 The only other information that I can add would be the lab in Chicago that does testing for immune reactions to metals and implants. Here is the link.
https://www.orthopedicanalysis.com/
They have you send a blood sample that this kept warm in transit. This is their page about metal testing.
https://www.orthopedicanalysis.com/page/metal-sensitivity
This page is interesting that shows what metals are in an implant.
https://www.orthopedicanalysis.com/page/what-are-the-metals-in-my-implant

I did this test for metals and surgical implant materials prior to my spine surgery and it did not indicate any sensitivity for me which surprised me, and my insurance did not cover it. I was able to have spine surgery without hardware so that didn't matter anyway. It was after I received titanium plates after an ankle fracture that I began to have problems, and thankfully, I could have them removed. At the time I did this blood test, it cost around $500.

The Environmental Health Center in Dallas also does extensive testing, but I have not been a patient there. My environmental medicine doctor highly recommended them.

In regard to your comment about titanium screws being the only screws available, my comment is that I have zirconium screws holding a zirconium bridge to my zirconium dental implants. That is all ceramic and doesn't have metals in it. I don't know if there is anything similar for joint replacement. I don't know if the material is strong enough for knee replacements, etc.

I did a little searching and found this research article that may be of interest. You may be able to contact the authors and locate doctors who may help.

Research work from Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA
"Allergy in Total Knee Replacement. Does It Exist?"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5264571/

The results state: There is consensus that patients with self-reported allergies against metals or bone cement and positive patch test should be treated with hypoallergenic materials or cementless TKA. Treatment options include the following: coated titanium or cobalt-chromium implants, ceramic, or zirconium oxide implants."

If you scroll to the end, all of the research is referenced and there you can click on links to that literature and find the authors. This may lead to a connection to a doctor at an institution that may help. They may know about safer implants if revision surgery is needed. Of course that is another big surgery if it is possible. The practice in Dallas does allergy shots for treatment of immune reactions. I'm sure this is a difficult decision as to what to do.