Distractor system

1. A computer assisted orthopaedic surgery system for performing joint replacement of a joint that is defined by a first bone and a second bone comprising:

means for tracking the position of the first bone relative to the second bone;

means for planning a position of at least one virtual implant relative to the first tracked bone and at least one virtual implant relative to the second tracked bone; and

means for controlling the relative position of the first and second tracked bones in at least one direction and with a controllable device that is physically coupled to the second bone and is operated such that relative positions of the bones behave in the manner as if an actual implant corresponding to the first and second virtual implants were installed according to the planned implant position, wherein the controllable device is a different structure relative to the actual implant and temporarily occupies a location which subsequently receives the actual implant.

2. A computer assisted orthopaedic surgery system for performing joint replacement of a joint that is defined by a first bone and a second bone comprising:

a first device that is physically coupled to the second bone for moving the second bone in relation to the first bone, wherein the first device comprises a distraction device that is disposed between the first and second bones and is configured to engage and support the first bone; and

a computer that permits an operator to plan a position of an implant by evaluating positions of first and second virtual implant components relative to the first and second bones, respectively; and a controller for controlling the position and movement of the first device coupled to the second bone such that actual positions of the first and second bones and theoretical contact positions for the first and second virtual implant components converge and contact is simulated between the first and second virtual implant components over a range of motion, wherein the controller is operatively connected to the distraction device and automatically adjusts a height of the distraction device such that contact is simulated between the first and second virtual implant components over the range of motion.

3. The system of claim 2 , wherein the first bone is a femur and the second bone is a tibia and the first device is one of a distraction device and a robotic device that grips the second bone.

4. The system of claim 2 , further including: a display operatively connected to the controller, wherein the controller generates three-dimensional images of the first and second bones and the first and second virtual components, the three-dimensional images being displayed on the display.

5. A computer assisted orthopaedic surgery system for performing joint replacement or resurfacing surgeries comprising:

a computer that contains software that is adapted to measure and track a relationship between a first virtual implant component to be associated with a first bone and a second virtual implant component to be associated with a second bone and simulate the relationship of the two virtual implant components over a desired range of motion such that the two virtual implant components remain in contact with one another along outer surfaces thereof over the range of motion, the software receiving positional information for the two virtual implant components over the range of motion and then calculates the optimal locations for bone cuts so as to position the two virtual implants in the desired relationship where the outer surfaces are in contact with one another over the range of motion; and

a distraction device that is coupled to the second bone and is disposed between the first and second bones and is configured to physically engage and support the first bone, wherein the system measures the position of the first bone relative to the second bone; and a controller that adjusts a height of the distraction device such that the first and second virtual implant components are positioned in locations where they are in contact with one another over the range of motion;

wherein the distraction device has a pair of separate support members that each includes a bottom base plate, the bottom base plates being movably attached to one another to permit a distance between the separate support members to be varied, the support members being detached from one another along upper surfaces thereof.

6. The system of claim 5 , wherein the first bone is a femur and the second bone is a tibia.

7. The system of claim 5 , wherein the distraction device comprises a medical instrument, in the form of one of the support members, that includes a base; an upper member; and a linkage mechanism coupled to the base and the upper member and being operable to maintain the upper member in a variable fixed position that is substantially parallel to the base and spaced a predetermined, variable distance therefrom, wherein the linkage mechanism includes at least three linkage elements that are arranged at angles relative to one another such that when one link element opens, the other link elements open with at an equal angle resulting in the upper member being constrained to remain parallel to the base.

8. The system of claim 5 , further including: a display operatively connected to the computer, wherein the computer generates three-dimensional images of the first and second bones and the first and second virtual components, the three-dimensional images being displayed on the display.

9. The system of claim 8 , wherein the images of the first and second virtual implants are visually distinguished on the screen by either being displayed in a different color from the color of the images of the first and second bones or by displaying an outline of each of the virtual implants with broken lines.

10. The system of claim 5 , further including: a robotic device that is movable in at least one direction and is coupled to the second bone for moving the second bone in at least one direction to permit tracking of the second bone relative to the first bone which is fixed in location, wherein the robotic device controls the relative positions of the tracked first and second bones such that kinematics of the joint behave as if an actual implant corresponding to the first and second virtual implant components was installed according to a planned implant position.

11. A computer assisted orthopaedic surgery system for performing implant surgery on a joint that is defined by a first bone and a second bone comprising:

a computer configured to plan the position and/or orientation of at least one first virtual implant with respect to the first bone and at least one second implant with respect to the second bone,

a three-dimensional position measuring device in communication with the computer, configured to measure the relative positions of the first and second bones; and

a first device selected from the group consisting of a distraction and a robotic device, each of which has at least one degree of freedom that is in communication with and is controlled by the computer, and is configured to limit the relative positions of the first and second bone so that the first virtual implant is prevented from overlapping the second virtual implant, wherein the computer is configured to communicate with the first device to automatically adjust a height of the first device to simulate movement between the first and second virtual implants over a range of motion in a manner in which the first virtual implant is prevented from overlapping the second virtual implant, wherein the first device is removable from its location between the first and second bones to permit insertion of an actual implant that has a first component for coupling to the first bone and a second component for coupling to the second bone.

12. The system of claim 11 , wherein the first device is configured to measure the forces acting on it, wherein the measured forces are displayed on a screen of the computer.

13. The system of claim 11 , wherein the computer can measure the relative displacements of the first and second bones at predefined points, and display the distances while the joint is manipulated.

14. The system of claim 13 wherein the displacements represent lift-off values and/or laxity values.

15. The system of claim 11 , wherein the first device is a robotic device having a haptic arm of having at least 6 degrees of freedom.

16. The system of claim 1 , wherein the first device has a pair of separate support members that are adjustably attached to one another but detached from one another along upper surfaces thereof to allow one support member to seat against one condyle and the other support member to seat against the other condyle.

17. The system of claim 16 , wherein the first device has a planar lower surface and rests on a plateau cut made in the second bone.

18. The system of claim 17 , wherein a pivotal connection between the separate support members is disposed above and out of a common plane that contains the lower surfaces of the pair of support members.

19. A computer assisted orthopaedic surgery system for performing joint replacement of a joint that is defined by a first bone and a second bone comprising:

means for tracking the position of the first bone relative to the second bone;

means for planning a position of at least one virtual implant relative to at least one of the first and second tracked bones; and

means for controlling the relative position of the first and second tracked bones in at least one direction and with a controllable device that is physically coupled to the second bone and is operated such that relative positions of the bones are spaced apart as if an actual implant corresponding to the virtual implant was installed according to the planned implant position, wherein the controllable device is a different structure relative to the actual implant and temporarily occupies a location which subsequently receives the actual implant.

20. A computer assisted orthopaedic surgery system for performing joint replacement of a knee joint that is defined by a femur bone and a tibia bone comprising:

means for tracking the position of the femur relative to the tibia;

means for planning on the computer a position of a virtual femoral implant on a model of the femur; and

means for automatically controlling via the computer and a controller the height of a distraction device placed in between the tibia and the femur, wherein the automatic controlling means is based at least partially on the difference in the distance between the surfaces of the virtual femoral implant and the model of the femur as determined at any particular degree of flexion.

21. The system of claim 20 wherein the distance is calculated in the direction normal to a cut made in the tibial to accommodate the distraction device.

22. The system of claim 20 wherein the model of the femur is a surface model.

23. The system of claim 20 wherein the model of the femur is based on at least one of the following data: point data, bone morphing data, medical image data.

24. The system of claim 20 wherein the computer also comprises means for planning a virtual tibial implant on a model of the tibia.

25. The system of claim 24 wherein the controlling means is also partially based on a fixed height of the planned tibial implant.

26. The system of claim 20 wherein the calculation is performed statically for different positions of knee flexion.

27. The system of claim 20 wherein the calculation is performed dynamically in real time for different positions of knee flexion, as measured by the tracking means.

28. The system of claim 20 , wherein the controllable device is a different structure relative to the actual implant and temporarily occupies a location which subsequently receives the actual implant.

29. A computer assisted orthopaedic surgery system for performing joint replacement of a knee joint that is defined by a femur bone and a tibia bone comprising:

means for tracking the position of the femur relative to the tibia;

means for planning on a computer a position of a virtual femoral implant on a model of the femur; and

means for automatically controlling via the computer and a controller the height of a distraction device that is intended to be placed in between the tibia and the femur, wherein the automatic means for controlling the distraction device height is based at least partially on the distance between the surfaces of the virtual femoral implant and the virtual tibial implant, such that contact between the surfaces of the virtual femoral implant and the virtual tibial implant is obtained for at least a portion of the virtual implants.

30. The system of claim 29 , wherein the distance between the surfaces of the virtual femoral implant and the virtual tibial implant is determined by the tracked position of the femur relative to the tibia.

31. The system of claim 29 , wherein the distance between the surfaces of the virtual femoral implant and the virtual tibial implant is based on a most distal point on the virtual femur and fixed height value associated with the virtual tibial implant.

32. The system of claim 29 wherein the distraction device has one of flat and convex shaped upper plateau surfaces.

33. The system of claim 20 wherein, the difference in the distance between the surfaces of the virtual femoral implant and the model of the femur are determined with the knee in an extended position.

34. The system of claim 20 wherein, the difference in the distance between the surfaces of the virtual femoral implant and the model of the femur are determined with the knee in a flexed position.