Abstract: Method for planning implant placement, the implant comprising a first implant in a first limb and a second implant in a second limb, the first and the second implant forming an artificial structure joining the first and second limb, the method comprising the steps: a) providing a first limb data set representing a first reference system in which the first limb is fixed; b) providing a second limb data set representing a second reference system in which the second limb is fixed; c) providing a representation of the implant for the head of the second limb in a known position in the second reference system; d) providing relative pose data representing a plurality of different relative positions and/or orientations, referred to as relative poses, of the first and second reference system; e) determining a data set representing a plurality of envelope points, said envelope points being generated by calculating the locations of a point of the second implant representation in the first reference system for the plu

Abstract: A method and a computer system for executing the method is provided for pre-operatively determining a degree of deformity of an anatomical structure joining a first and second limb, the method comprising the steps: a) providing data representing the pose of a first axis of the first limb in a first reference system in which the first limb is fixed; b) providing data representing the pose of a second axis of the second limb in a second reference system in which the second limb is fixed; c) providing force orientation data representing a relative pose between the first and second reference system with the first and second limb in extension, and with an external force being applied to eliminate or reduce the deformity of the anatomical structure; and d) determining a relative angular orientation between the first axis of the first limb and the second axis of the second limb based on the force orientation data, said relative angular orientation being referred to as force relative angular orientation.