My cousin has chron's and implants. Over the years she seems to keep developing more and more autoimmune issues, like her body won't stop attacking different parts of her. I don't think that doctors ever actually finally pointed to the implants being the problem, but I know it has been a consideration b/c of the same "foreign object" you mentioned.
Sorry - probably not the answer you were hoping for, she is only one case though, and also the only person I know well that has implants!