A method and a system assess a relative pose of an implant and a bone of a patient. The method includes: acquiring multiple medical X-ray images of the bone with the implant preliminarily mounted to the bone providing a database of virtual 3D implant models and selecting the implant used fitting the virtual implant to the medical X-ray image selecting a bone model and fitting the chosen bone model to the medical X-ray image. The system and method now allow directly in the operation room to assess the relative pose of the implant and the bone/bone fragments by a comparison of the medical image and the respective virtual image both having the same orientation in view. The resulting image is an image of the matching virtual 2D image of the implant used and the real medical image taken from the C-arm X-ray device.
