In a method for determining a deviation of a medical instrument from a target position, in an image of an implant located in the body of a patient created with an imaging system, a virtual model of the implant is fitted at the correct location and thus a location of the implant is determined in the imaging system. On a basis of the location of the virtual model in the imaging system and a target position for an instrument selected as a fixed position relative to the virtual model, the location of the target position in the imaging system is determined. A video image of the instrument is created by a recording device and its current location in relation to the recording device is determined from this. By a geometrical relationship between the recording device and the imaging system, a deviation of the instrument from the target position is determined.
