Robotic total/partial knee arthroplastics

• US 20070100258A1
• Filed: 05/16/2004
• Published: 05/03/2007
• Est. Priority Date: 05/16/2003
• Status: Active Grant

• Current Assignee: Mazor Robotics, Ltd (Medtronic Plc)
• Original Assignee: Mazor Robotics, Ltd (Medtronic Plc)
• Inventors: Shoham, Moshe, Burman, Michael
• Granted Patent: US 8,518,051 B2
• Time in Patent Office: Days
• US Class Current: 600/587
• CPC Class Codes: A61B 17/155 Cutting femur
• CPC Class Codes: A61B 17/157 Cutting tibia
• CPC Class Codes: A61B 17/1703 using imaging means, e.g. by X-rays
• CPC Class Codes: A61B 17/1725 for applying transverse screws or pins through intramedullary nails or pins
• CPC Class Codes: A61B 17/1764 for the knee
• CPC Class Codes: A61B 2034/304 including a freely orientable platform, e.g. so called 'Stewart platforms'
• CPC Class Codes: A61B 2090/376 using X-rays, e.g. fluoroscopy
• CPC Class Codes: A61B 34/30 Surgical robots
• CPC Class Codes: A61B 6/0421 with immobilising means

Abstract

A system and method for knee arthroplasty procedures, using a novel leg rotation fixture to enable the leg mechanical axis, the tibia and the femur to be mutually disposed such that the load bearing, mechanical axis of the leg runs through the center of the knee joint. A measurement gauge is provided for mounting on the tibia and for aligning a baseplate in a known position on the tibia. This baseplate supports an X-ray target plate in a known position relative to the tibia, used in determining the mechanical axis, and an optional surgical robot, used to perform tibial and femoral cuts. The position of the femur relative to the robot may be determined from X-ray imaging of the pelvic region after attachment to the baseplate of an additional target extending to the pelvic region. The system enables improvement in the accuracy of knee arthroplasty procedures.

Claims

1. A system for determining the mechanical axis of a leg of a subject, comprising a support ring, said support ring being adapted to rotate at least about an axis perpendicular to its plane, said support ring having an adjustable clamping device adapted to hold said leg within said support ring in such a position that rotation of said support ring about its axis rotates said leg about its mechanical axis.

2. A system according to claim 1 and also comprising a base element to which said ring is attached by means of a bearing, said bearing allowing said ring to rotate, but fixing its spatial position relative to said base element.

3. A system according to claim 1 and also comprising a pointer attached to said support ring, said pointer being aimed at said axis of rotation of said support ring.

4. A system according to claim 3 and wherein said leg is positioned such that said pointer points to the center of the ankle of the subject.

5. A system according to claim 1 and also comprising an X-ray identifiable target plate adapted to be fixed to a bone of said leg, such that at least the orientation of said leg can be determined by X-ray imaging of said bone.

6. A system according to claim 5 and wherein said X-ray imaging is performed at two angles of rotation of said leg about its mechanical axis.

7. A system according to claim 6 and wherein said X-ray imaging is performed by means of an X-ray imaging system having a coordinate system, and said mechanical axis of said leg is defined in said coordinate system.

8. A system according to claim 5 and also comprising a cutting tool whose alignment is known relative to said bone, such that said cutting tool can cut said bone at a predetermined plane relative to said mechanical axis of said leg.

9. A system according to claim 8 and wherein said alignment of said cutting tool relative to said bone is known by means of attachment to said bone of a cutting jig for said cutting tool.

10. A system according to claim 8 and wherein said alignment of said cutting tool relative to said bone is accomplished by a robot mounted in a known position relative to said bone, such that said predetermined plane can be adjusted at least by means of programmed motion of said robot.

11. A system for performing a cut on a bone of a subject at a predetermined plane on said bone, comprising:

a baseplate adapted to be fixed to said bone, such that the location and orientation of said baseplate is fixed relative to said bone;

an X-ray identifiable target plate adapted to be fixed to said baseplate, such that a first set of information regarding the location and rotational orientation of said bone can be determined by X-ray imaging of said bone;

an X-ray identifiable feature at least two points along the length of said bone, such that a second set of information about the axis of said bone is determined by X-ray imaging of said bone; and

a cutting guide disposed at a predetermined location relative to said baseplate, said location being determined from at least one of said first and second sets of information, such that said cut is made on said bone at said predetermined plane.

12. A system according to claim 11, and wherein said X-ray identifiable feature is a guide rod aligned along the length of said bone generally parallel to the axis of said bone.

13. A system according to claim 11, and wherein said X-ray identifiable feature is the image of said bone itself, such that said axis of said bone is discerned.

14. A system according to claim 11 and also comprising a gauge element having at least one reference point in contact with at least one feature of said bone, such that the position of said baseplate can be fixed relative to said at least one feature of said bone.

15. A system according to claim 14 and wherein said gauge element also comprises a shaft section such that said gauge can be aligned along the length of said bone.

16. A system according to claim 11 and also comprising a robot attached to said baseplate, such that the position of said robot is known relative to said bone.

17. A system according to claim 16 and wherein said cutting guide is mounted on said robot, such that said predetermined plane on said bone can be reached by at least one programmed position of said robot.

18. A system according to claim 11 and wherein said bone is a tibia.

19. A system for determining the mechanical axis of a femur, comprising:

an X-ray identifiable target adapted to be fixed in a predefined position close to the knee joint region of said femur, said target extending to the head of said femur in the pelvic region of said leg;

an X-ray imager generating at least one image of said pelvic region, such that said target in the pelvic region is defined in the coordinate system of said X-ray imager, and at least one image of said knee region showing said target, such that said head of said femur and said knee region are both correlated to said coordinate system of said X-ray imager; and

an image processor for determining the center of said femoral head from at least one X-ray image of said pelvic region, such that said mechanical axis of said femur is determined between said center of said femoral head and the center of said knee joint.

20. A system for determining the mechanical axis of a femur of a subject on an operating table, comprising:

a leg holding fixture, having a plane of translation in the plane of said operating table such that said leg rotates about its femoral head center in said plane of said operating table; and

an X-ray imager generating (i) at least two images of said femoral head center at different rotational positions of said leg such that said femoral head center coordinates are determined at the center of rotation of said leg, and (ii) at least one image of the knee joint of said subject such that the center of said knee joint is determined;

wherein said mechanical axis of said femur is determined by the space line between said center of said femoral head and said center of said knee joint.

21. A system for preparing a knee joint of a leg of a subject for implant insertion, said leg comprising tibia and femur bones, comprising:

an X-ray imager for imaging said leg, said X-ray imager having a coordinate system;

a leg rotational fixture for determining the mechanical axis of said leg in said coordinate system of said X-ray imager;

a baseplate adapted to be fixed to said tibia in the region of said knee joint such that said baseplate is defined in said coordinate system of said X-ray imager;

an X-ray identifiable target plate adapted to be fixed to said baseplate, and an X-ray identifiable feature at least two points along the length of said tibia, such that the axis of said tibia is defined in said coordinate system of said X-ray imager;

a femur mechanical axis determiner, utilizing at least one X-ray image of the head of said femur, and at least one X-ray image of said region of said knee joint to determine said femur mechanical axis in said coordinate system of said X-ray imager;

a controller for calculating desired cutting planes of said tibia and said femur such that when said knee joint is assembled, said tibia axis, said femur mechanical axis and said leg mechanical axis are aligned in a predetermined manner; and

a cutting tool disposed relative to said baseplate such that the cutting plane of said cutting tool is defined in said coordinate system of said X-ray imager;

such that the ends of said tibia and said femur are cut in said desired planes.

22. A system according to claim 21 and wherein said femur mechanical axis determiner comprises an X-ray identifiable target adapted to be fixed in a predefined position close to the knee joint region of said femur, said target extending to the head of said femur in the pelvic region of said leg, such that said at least one image of said pelvic region and said at least one image of said knee region both show said target correlated to said coordinate system of said X-ray imager, and an image processor for determining the center of said femoral head from said at least one X-ray image of said pelvic region, such that said mechanical axis of said femur is determined between said center of said femoral head and the center of said knee joint.

23. A system according to claim 21 and wherein said subject is disposed on an operating table, and wherein said femur mechanical axis determiner comprises a leg holding fixture, having a plane of translation in the plane of said operating table such that said leg rotates about its femoral head center in said plane of said operating table, such that said at least one image of said pelvic region comprises at least two images of said femoral head center at different rotational positions of said leg such that said femoral head center coordinates are determined at the center of rotation of said leg, such that said mechanical axis of said femur is determined by the space line between said center of said femoral head and said center of said knee joint.

24. A method of preparing for implant insertion in a knee joint of a leg of a subject, said leg comprising tibia and femur bones, comprising the steps of:

providing an X-ray imager for imaging said leg, said X-ray imager having a coordinate system;

defining the mechanical axis of said leg in said coordinate system of said X-ray imager;

defining the tibia axis in said coordinate system of said X-ray imager;

defining the femur mechanical axis in said coordinate system of said X-ray imager;

disposing a baseplate on said tibia in the region of said knee joint such that said baseplate is defined in said coordinate system of said X-ray imager;

calculating desired cutting planes of said tibia and said femur such that when said knee joint is assembled, said tibia axis, said femur mechanical axis and said leg mechanical axis are aligned in a predetermined manner;

disposing a cutting tool relative to said baseplate such that the cutting plane of said cutting tool is defined in said coordinate system of said X-ray imager; and

cutting the ends of said tibia and said femur in said desired planes.

25. The method of claim 24 and wherein said predetermined manner is such that said femur mechanical axis and said leg mechanical axis are essentially collinear.

26. The method of claim 25 and wherein said step of aligning said femur mechanical axis and said leg mechanical axis essentially collinear is achieved by laterally cutting an end of said femur at essentially the valgus angle to a plane perpendicular to the anatomical axis of said femur.

27. The method of claim 26 and wherein said step of cutting is such that said leg mechanical axis and said anatomical axis of said femur are aligned at essentially said valgus angle when said knee joint is assembled.

28. The method of claim 24 and wherein said step of defining the tibia axis is performed by means of an X-ray identifiable guide line aligned along said tibia.

29. The method of claim 24 and wherein said step of defining the mechanical axis of said leg is performed by inserting said leg when straightened into a leg rotational fixture and X-ray imaging at least two rotational orientations of said leg.

30. The method of claim 24 and wherein said step of defining said femur mechanical axis is performed by the steps of:

translating said leg rotational fixture in the plane of the operating table such that said leg rotates about its femoral head center in said plane of said operating table;

determining the femoral head center coordinates at the center of rotation of said leg, by means of X-ray imaging of said pelvic region of at least two different rotational positions of said leg;

determining the coordinates of the center of said knee joint by X-ray imaging of said knee joint; and

defining said femur mechanical axis between said center of said femoral head and said center of said knee joint.

31. The method of claim 24 and wherein said step of defining said femur mechanical axis is performed by the steps of:

attaching a known target in a predefined position to said base, said target extending to the head of said femur in the pelvic region of said leg;

X-ray imaging said pelvic region, such that said target in the pelvic region is defined in said coordinate system of said X-ray imager;

correlating said X-ray imaging of said pelvic region with said X-ray imaging of said base, such that said head of said femur and said base are correlated to the same coordinate system of said X-ray imager;

determining the center of the femoral head by image processing of an X-ray of said pelvic region; and

determining the center of said knee joint by X-ray imaging of said knee joint; and

defining said femur mechanical axis between said center of said femoral head and said center of said knee joint.

32. The method of claim 24 and wherein said step of defining said femur mechanical axis is performed by extracting data on the anatomical location of parts of said femur by inspection of X-ray images of said leg.

33. The method of claim 24 and also comprising the step of mounting a surgical robot onto said base, such that said robot position is known in said coordinate system of said X-ray imager, and wherein said step of cutting the ends of said tibia and said femur is performed by means of a cutting tool operating in a cutting jig mounted on said robot.

34. The method of claim 33, and wherein said robot is moved such that said cutting is performed in said desired planes by means of at least one programmed step, determined in said step of calculating said desired cutting planes.

35. The method of claim 33, and wherein said robot is moved such that said cutting is performed in said desired planes, by means of at least one manual input by the surgeon to desired cutting planes determined by the surgeon from information provided by said X-ray imager.