1. A computer based method for determining a correct size or shape of a surgical implant to be implanted in a patient, comprising: displaying a first fluoroscopic image taken of an anatomical feature from a first angle, the first fluoroscopic image being registered to a common three-dimensional coordinate system; receiving an indication of position within the first fluoroscopic image of a three-dimensional virtual surgical implant, the three-dimensional virtual surgical implant being defined with reference to the common three-dimensional coordinate system and having one or more attributes corresponding to one or more physical characteristics of the surgical implant to be implanted in the patient; displaying a second fluoroscopic image taken of the anatomical feature from a second angle, the second fluoroscopic image being registered to the common three-dimensional coordinate system; computer generating on the first and second fluoroscopic images two dimensional projections of the three-dimensional virtual surgical implant and updating the two dimensional projections of the three-dimensional virtual surgical implant in the first fluoroscopic image in response to a user manipulating the two-dimensional projections of the three-dimensional virtual surgical implant in the second fluoroscopic image.