When I told my surgeon about my high levels of Cobalt in my blood test, he told me that he didn't think that metal allergies were a serious problem. We didn't talk about what he was using in the revision surgery. But now I have an implant with a hinge - that's lotsa metal.
Had to have the revision because of severe Arthrofibrosis. Since my first knee replacement in 2016, have dealt with that Arthrofibrosis, and never ending pain. Can only hope he is right, and I will recover.