Method of determining the position of the articular point of a joint
AssigneeAesculap AG
InventorFrancois Leitner
Life of this patent
Estimating the term…
Abstract
A non-invasive method for determining the articular point of a joint is disclosed. The method uses a surgical navigation system having a stereoscopic cameras which tracks the positions of infrared emitting or reflecting markers attached to appendages on either side of the joint. A movable marker is used to palpate known landmarks on the appendages to determine their positions. The appendages are moved to determine the trajectories of the landmarks relative to the joint. Positional information from the cameras is fed to a data processing system with resident software which uses the positional information and trajectories to mathematically determine the position of the joint articular point according to the laws of kinematics.
Claims18
A method of determining the position of an articular point of a central joint 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;
- and
- 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.
A method of determining the position of an articular point of a knee joint between the femur and the tibia, the knee joint comprising a patella and medial and lateral epicondyles and being located between a hip joint and an ankle joint located at respective ends of said femur and said tibia distal to said knee joint, said method comprising the steps of:
- identifying the position of said patella;
- determining the position of an articular point of said femur at said hip joint;
- defining a femoral axis extending between said femur articular point and said patella;
- identifying the positions of said medial and lateral epicondyles;
- defining a plane substantially perpendicular to said femoral axis and at substantially equal respective rectangular distances to said positions of said medial and lateral epicondyles, the intersection of said plane and said femoral axis being an initial estimate of said articular point of said knee joint;
- defining a region in said plane having a predetermined size, said region including said initial estimate of said articular point of said knee joint;
- determining the position of an articular point of said tibia at said ankle joint;
- moving said tibia articular point relatively to said femur by rotating said tibia about said knee joint;
- identifying a multiplicity of different positions of said tibia articular point during said rotation of said tibia;
- and
- 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 tibia articular point, said one point being said articular point of said knee joint.
A method of determining the position of an articular point of a knee joint between the femur and the tibia of a leg, the knee joint comprising a patella and medial and lateral epicondyles and being located between a hip joint and an ankle joint located at respective ends of said femur and said tibia distal to said knee joint, said method comprising the steps of:
- fixing a first marker to a portion of said leg comprising said femur;
- fixing a second marker to a portion of said leg comprising said tibia;
- identifying the positions of said first and second markers in space using a measuring device;
- palpating said patella using a third marker;
- identifying the position of said patella using said measuring device to measure the position of said third marker in space during said patella palpating step;
- determining the position of a femur articular point using a data processing system adapted to receive signals corresponding to positional data of the markers from the measuring device;
- defining mathematically a femoral axis extending between said femur articular point and said patella using said data processing system;
- palpating said medial and lateral epicondyles using said third marker;
- identifying the positions of said epicondyles using said measuring device to measure the position of said third marker in space during said epicondyle palpating step;
- defining mathematically, using said data processing system, a plane substantially perpendicular to said femoral axis and at substantially equal respective rectangular distances to the positions of said medial and lateral epicondyles, the intersection of said plane and said femoral axis being an initial estimate of said articular point of said knee joint;
- defining a region in said plane having a predetermined size, said region including said initial estimate of said articular point of said knee joint;
- determining the position of an articular point of said tibia at said ankle joint;
- moving said tibia articular point relatively to said femur by rotating said tibia about said knee joint;
- identifying a multiplicity of different positions of said tibia articular point using said measuring device to measure the positions of said first and second markers during motion of said tibia articular point;
- and
- determining mathematically, using said data processing system, one point among a multiplicity of points within said region for which the position is substantially invariant for each of said positions of said tibia articular point, said one point being said articular point of said knee joint.
Dependencies are inferred from the claim text.