DISTRACTOR SYSTEM

Abstract

According to one aspect of the present invention, a computer assisted orthopaedic surgery system for performing joint replacement or resurfacing surgeries includes a computer that contains software that is adapted to permit an operator of the system to physically evaluate post-operative laxity and stiffness of a joint based on planned implant placement, prior to all cuts being made for at least one side of the joint to accommodate the implant and before components of the implant are installed in the joint, wherein the planned implant placement is measured in terms of a position of at least one virtual implant.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The foregoing and other features of the present invention will be more readily apparent from the following detailed description and drawings figures of illustrative embodiments of the invention in which:

FIG. 1 is a perspective view of a computer-assisted orthopedic surgery system and a view of a knee joint defined by a femur bone and a tibia bone;

FIG. 2 is a perspective view a distraction device according to one embodiment relative to the femur bone;

FIG. 3 is a side perspective view of the distraction device of FIG. 2;

FIG. 4 is a perspective view of one exemplary spacer means for changing the position of the distraction device of FIG. 2;

FIG. 5 is a schematic of one exemplary control system for controlling the movement of the distraction device of FIG. 2;

FIG. 6 is a perspective view of a calibration tool for calibrating the distraction device of FIG. 2;

FIG. 7 is a side view of a knee joint showing the planned position of a virtual femoral implant, a virtual tibial implant, the femur, the tibia and the distraction device;

FIG. 8 a is side view of the knee in flexion and illustrates a method of calculating a distraction height;

FIG. 8 b is a side view of the knee in flexion with the virtual femoral implant in contact with and abutting against a virtual flat tibial plateau;

FIGS. 9 a-c are side views of the knee in flexion and being moved in anterior to posterior direction; and

FIG. 10 is a schematic view illustrating a geometrical implant file for a femoral implant.

Claims

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 at least one of the first and second tracked bones; andmeans for controlling the relative position of the first and second tracked bones in at least one direction and with a controllable device that is coupled to the second bone and is operated such that kinematics of the joint behave in the manner as if an actual implant corresponding to the virtual implant was installed according to the planned implant position.

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 coupled to the second bone for moving the second bone in relation to the first bone; anda controller that permits an operator to plan a position of an implant device prior to making cuts in at least one of the first and second bones to accommodate the implant device, wherein the controller calculates the planned implant placement by computing theoretical contact positions of first and second virtual implant components that define the implant device based on spatial information and relative positions of the first and second virtual implant components, the controller 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 the theoretical contact positions for the first and second virtual components converge and contact is simulated between the first and second virtual implant components over a 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.

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, further including: a distraction device that is coupled to the second bone and is disposed between the first and second bones and is configured to engage and support the first bone, wherein the system measures the position of the first bone relative to the second bone; anda controller that 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.

8. The system of claim 7, wherein the distraction device comprises a medical instrument including 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.

9. 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.

10. The system of claim 9, 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.

11. 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.

12. A method for physically evaluating post-operative laxity and stiffness of a joint based on a planned implant placement, prior to cuts being made for at least one side of the joint to accommodate the implant and before components of the implant are installed in the joint comprising the steps of: selecting a first implant component that is to be associated with a first bone;selecting a second implant component that is to be associated with a second bone;generating a first virtual implant based in part on the selected first implant component and which is representative of the first implant component;generating a second virtual implant based in part on the selected second implant component and which is representative of the second implant component;displaying images of the first and second bones on a screen;displaying the first virtual implant on the screen by superimposing it on the first bone;displaying the second virtual implant on the screen by superimposing it on the second bone; andmoving the first bone relative to the second bone over a range of motion by means of manipulating an actuator that is coupled to the second bone, while measuring positions of the first and second bones that results in outer surfaces of the first and second virtual implants being in contact with one another over the range of motion resulting in the joint substantially behaving as through the first and second virtual implants are installed in planned implant positions.

13. The method of claim 12, wherein the first bone is a femur, the second bone is a tibia, the first implant component is a femoral implant component and the second implant component is a tibial implant component.

14. The method of claim 12, wherein each of the steps of displaying the first and second bones and displaying the first and second virtual implants includes creating a three-dimensional model for the respective object and displaying it on the screen.

15. The method of claim 12, wherein the step of moving the first bone relative to the second bone includes the steps of: making a first cut in the second bone;inserting and coupling a distraction device to the second bone such that the distraction device is between the first and second bones and can engage and support the first bone;measuring the position of the first bone relative to the second bone; andadjusting a height of the distraction device in real time such that contact is simulated between the first and second virtual implants over the range of motion.

16. The method of claim 15, wherein the distraction device comprises a medical instrument including 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.

17. The method of claim 12, wherein the steps of displaying the first and second virtual implants include the step of visually distinguishing the images of the first and second virtual implants from the images of the first and second bones.

18. The method of claim 17, 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.

19. The method of claim 12, further including the steps of: measuring and displaying a value of any gap distance between the first and second virtual implants; anddisplaying laxity values that are determined by measuring and storing the gap distance values between the first and second virtual implants as the joint is manipulated over the range of motion.

20. The method of claim 12, further including the step of: detecting when the first virtual implant lifts off the and separates from contact with the second virtual implant and when this occurs, the distraction device is prevented from increasing its height;estimating by means of a collision detection module in which area contact between the two virtual implants is likely and then calculating the area of contact as the first virtual implant moves closer to the second virtual implant.

21. The method of claim 12, wherein the step of moving the first bone relative to the second bone includes the steps of: providing a device that is capable of controlling or limiting the contact between the first and second bones, wherein the device is contained substantially outside of a joint space; andmanipulating the first and second bones relative to one another in order to track and observe the relative positions of the first and second virtual implants.

22. The method of claim 21, wherein the device is a robotic device that is configured to guide the motion of the second bone with respect to the first bone such that the first and second virtual implants are permitted to come into contact with one another but do not significantly overlap one another.

23. A method for performing computer assisted orthopaedic surgery to replace a joint that is defined by a first bone and a second bone comprising the steps of: tracking the position of a first bone relative to an one other second bone;planning a position of at least one virtual implant relative to at least one of the tracked bones; andcontrolling the relative positions of the tracked first and second bones in at least one direction using a first device that is coupled to at least the second bone to permit movement of the second bone relative to the first bone over a range of motion such that the joint connecting the first and second bones functions, over a range of motion, as through the at least one virtual implant was installed in the planned position.

24. The method of claim 23, wherein the step of controlling the relative positions of the tracked first and second bones comprises the step of: positioning a distraction device between the first and second bones, the distraction device supporting the first bone and being coupled to the second bone and compensating for pressure to position the height of the distraction device;manipulating the distraction device so that the second bone is moved relative to the first bone over a range of motion; andmeasuring positions of the first and second bones that results in outer surfaces of the first and second virtual implants being in contact with one another over the range of motion resulting in the joint substantially behaving as through the first and second virtual implants are installed in planned implant positions.

25. The method of claim 23, wherein the step of controlling the relative positions of the tracked first and second bones comprises the step of: coupling a robotic device to the second bone;manipulating the robotic device so that the second bone is moved relative to the first bone over a range of motion; andmeasuring positions of the first and second bones that results in outer surfaces of the first and second virtual implants being in contact with one another over the range of motion resulting in the joint substantially behaving as through the first and second virtual implants are installed in planned implant positions.

26. A method for performing computer assisted orthopaedic surgery to replace a joint that is defined by a first bone and a second bone comprising the steps of: selecting a first implant component that is to be associated with a first bone;selecting a second implant component that is to be associated with a second bone;generating a first virtual implant based in part on the selected first implant component and which is representative of the first implant component;generating a second virtual implant based in part on the selected second implant component and which is representative of the second implant component;displaying images of the first and second bones on a screen;displaying the first virtual implant on the screen by superimposing it on the first bone;displaying the second virtual implant on the screen by superimposing it on the second bone;positioning a distraction device between the first and second bones, the distraction device supporting the first bone and being coupled to the second bone; andadjusting and controlling a height of the distraction device such that a height of the distraction device is calculated based on a difference in geometry between the first virtual implant and the first bone at a chosen knee flexion orientation.

27. The method of claim 26, wherein the height of the distraction device (hd)=ht−hpd, where ht is a height of a second implant surface and hpd is a distance between a selected point on the first bone and a selected point on the first virtual implant.

28. The method of claim 27, in which the distance hpd is calculated in a predefined direction.

29. The method of claim 27, further including the step of: recalculating corresponding closest normal distances to the first bone and virtual prosthesis surfaces dp*−db*; and adjusting the height hd of the distraction device for different knee flexion orientations based on the recalculated distances.

30. 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; anda 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.

31. The system of claim 30, 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.

32. The system of claim 30, 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.

33. The system of claim 32 wherein the displacements represent lift-off values and/or laxity values.

34. The system of claim 30, wherein the first device is a robotic device having a haptic arm of having at least 6 degrees of freedom.