Hi Charlie, welcome!
I have a Zimmer ceramic/ceramic THR, supposedly the Rolls-Royce of hip replacements, and I am confident that it will outlast me (I’m 70). I also have a metal/metal resurfacing and I get checked for chromium and cobalt levels every 3 years because metal bearings do wear. From the Smith and Nephew website, the oxinium coating with cross-linked polyethylene would be expected to both remove the risk of metal poisoning and the risk of ceramic shattering so I would vengure to suggest that your surgeon is probably right on the money.
Not sure how the oxinium bearing is sized but the ball/socket combination ought to be bigger than a ceramic equivalent as the socket could be thinner, allowing a bigger ball and making dislocation less likely – and it’s not likely anyway.
Sorry to hear about your Parkinson’s, I don’t think either a ceramic or oxinium device will affect it.
Good Luck,
Pete