I had butt implant surgery about 1 year ago but I'm not sure if my prothesis moved or are badly located. (Photos)

This is why its EXTREMELY important to choose a Board Certified Plastic Surgeon who specializes in buttock implants.  If you do that you will not have this type of result.  This is a poorly placed implant and can be revised by a board certified plastic surgeon who specializes in buttock implants.  

It looks like your buttocks implant is malpositioned and will have to be removed prior to either revision or fat grafting. Revision includes:

1) Removal of implants - this will allow your tissues to heal

2) Revision placement of implants in the proper plane (in the muscle) this will keep them in place and prevent implant migration.Fat grafting is a great alternative but you should wait at least six months after implant removal to allow your buttocks shape to return to baseline and to improve your fat graft take.