Joint implant placement

1. A computer-implemented 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 positions and/or orientations, referred to as relative poses, of the first reference system relative to the second reference system;

e) determining, using a processor, a data set representing a plurality of envelope points, said envelope points being generated by calculating for the plurality of relative poses locations of a point of the representation of the implant provided in step c in the first reference system; and

f) placing, using a processor, a representation of the first implant in the first reference system by adjusting and/or matching pose of the representation of the first implant to the plurality of envelope points.

2. Method according to claim 1 , wherein one representation out of a plurality of representations of first implants is placed in the first reference system and is adjusted and/or matched with respect to the plurality of envelope points and out of the plurality of representations of first implants that representation is selected for which a desired adjustment and/or matching is achievable.

3. Method according to claim 1 wherein the plurality of envelope points are calculated by correcting the location of the point of the a second implant representation in the first reference system for the plurality of relative poses in case of an uncorrected deformity of the anatomical limb by means of a correction vector which describes the correction of the relative pose of the first and second reference system in case of a corrected deformity.

4. Method according to claim 1 wherein providing relative pose data representing the plurality of different poses of the first and second reference system comprises detecting reference arrays attached to the first limb and the second limb during movement of the second limb relative to the first limb, said movement includes flexing and/or extending the second limb relative to the first limb.

5. Method according to claim 1 wherein the implant placement is suitable for total knee arthroplasty, the artificial structure joining the first and second limb comprises an artificial knee joint and the first and second limb comprises femur and tibia, respectively.

6. Method according to claim 1 wherein the placing step further comprises:

displacing the representation of the first implant along an axes of the first limb and/or tilting the representation of the first implant relative to the axis of the first limb.

7. Method according to claim 1 the method further comprising:

registering an axis of the first limb in the first reference system and an axis of the second limb in the second reference system.