Patent ID: 7209776

Claim:
A method of obtaining preoperative information determining the position of an articular point of a central joint for guiding orthopaedic surgery performed on said central joint, said central joint being between two substantially rigid bodies, the central joint being located between first and second outer joints located at the ends of said first and second rigid bodies distal to said central joint, respectively, said method comprising the steps of: identifying the position of a first point on said first rigid body located substantially at said central joint; determining the position of a first articular point of said first rigid body at said first outer joint; defining a first axis between said first articular point and said first point; identifying the respective positions of a second and a third point on said first rigid body on opposite sides of said central joint; defining a plane substantially perpendicular to said first axis and at substantially equal respective rectangular distances to said second and third points, the intersection of said plane and said first axis being an initial estimate of said articular point of said central joint; determining the position of a second articular point of said second rigid body at said second outer joint; defining a region in said plane having a predetermined size, said region including said initial estimate of said articular point of said central joint; moving said second articular point relatively to said first rigid body by rotating said second rigid body about said central joint; identifying a multiplicity of different positions of said second articular point during said rotation of said second rigid body; determining one point among a multiplicity of points within said region for which the position is substantially invariant for each of said positions of said second articular point, said one point being said articular point of said central joint; and using the position of said articular point to guide an orthopaedic surgical procedure.