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!
Dx: UC in 1997 at 14 with pan colitis, but it hasn't been that far up since.
Meds: Asacol (400mg x12 daily)
6mp (50mg from Aug06 to Dec07)
Prednisone (20mg currently tapering)