A data processing method performed by a computer for judging implant orientation data representing an orientation of a first implant part relative to a first bone, the first implant part being part of an implant pair which further comprises a second implant part for a second bone, the implant pair being envisaged to be implanted in a patient, comprising the steps of: —acquiring the implant orientation data, -acquiring second implant orientation data representing the orientation of the second implant part relative to the second bone, -acquiring implant shape data representing the shapes of the first and second implant parts, —acquiring activity data representing at least one desired activity of the patient to be possible after implanting the implant, wherein each desired activity has an associated range of motion between the first bone and the second bone, —calculating a range of motion volume, which represents possible orientations between the first bone and the second bone over three rotational axes, from the implant orientation data, the second implant orientation data and the implant shape data, and —judging the implant orientation data to be feasible if the ranges of motion of all desired activities lie within the range of motion volume.