1. A non-transitory computer readable storing machine readable instructions for generating a patient specific instrument (PSI) for use as a surgical guide, the machine readable instructions comprising: a region modeling component configured to provide a three-dimensional model of a region of interest within a body from at least one imaging scan of the region of interest; a surgical planning component configured to display a model of a selected implant and the three-dimensional model of the region of interest to a first user and allow the first user to position the model of the selected implant within the three-dimensional model of the region of interest, the model of the selected implant having at least one hidden attribute that is not visible to the first user; and a PSI design component configured to provide a patient specific instrument model from a generic PSI model according to the position of the model of the selected implant within the three-dimensional model of the region of interest and the at least one hidden attribute.