Method and apparatus for generating a tool path for a robotic orthopedic surgical procedure

1. A method for generating an improved tool path for cutting a bone so as to minimize soft tissue trauma, wherein the method comprises:

accessing an image of the bone which is to be cut;

accessing an image of a pre-determined cutting pattern;

superimposing the image of the pre-determined cutting pattern against the image of the bone;

calculating the intersection of the pre-determined cutting pattern and the bone using the superimposed images of the pre-determined cutting pattern and the bone; and

generating a tool path based upon the intersection of the pre-determined cutting pattern and the bone so as to minimize soft tissue trauma by leaving a thin perimeter of bone at the boundary of the bone cut when the boundary of the bone cut is adjacent to a bone surface;

wherein the tool path is generated to provide for tool access which complies with the surgical access which is defined by user input during the surgery; and

wherein sizing of a surgical opening is reduced according to the following algorithm:

(1) Define a position, P 0 , which is the center of the surgical opening:

(2) For a given tool position at a time t, let the tool center position be P(t) and let the directional vector of the long axis of the tool be V(t), then calculate distance d(t) as follows:

d ( t )=| P 0 −P ( t )−( P 0 −P ( t ))· V ( t )/| V ( t )| |

where the · means vector dot and | | means vector norm:

(3) The optimized tool path is that which minimizes the maximum d(t) over the entire time.

2. A method according to claim 1 wherein the pre-determined cutting pattern is associated with an implant which is to be placed into the bone.

3. A method according to claim 1 wherein the tool path is generated to leave a thin perimeter of bone except where required for tool access.

4. A method according to claim 1 wherein the image of the bone is provided via a virtual model of the bone.

5. A method according to claim 4 wherein the virtual model of the bone is generated from CT data.

6. A method according to claim 1 wherein the image of the pre-determined cutting pattern is provided by a virtual model of the pre-determined cutting pattern.

7. A method according to claim 1 wherein the tool path takes into account an angle of approach specified by the surgeon.

8. A method according to claim 1 wherein the tool path takes into account surgeon-specified boundaries beyond which the bone is not to be cut.

9. A method for cutting bone, the method comprising:

accessing an image of the bone which is to be cut;

accessing an image of a pre-determined cutting pattern;

superimposing the image of the pre-determined cutting pattern against the image of the bone;

calculating the intersection of the pre-determined cutting pattern and the bone using the superimposed images of the pre-determined cutting pattern and the bone;

identifying a preferred surgical access prior to or during the surgery; and

generating a tool path based upon the intersection of the pre-determined cutting pattern and the bone which accesses the bone through the preferred surgical access and leaves a thin perimeter of bone at the boundary of the bone cut is adjacent to a bone surface, except for where the tool needs to approach and cut the bone from the preferred surgical access;

wherein the tool path is generated to provide for tool access which complies with the surgical access which is defined by user input during the surgery; and

wherein sizing of a surgical opening is reduced according to the following algorithm:

(1) Define a position, P 0 , which is the center of the surgical opening:

(2) For a given tool position at a time t, let the tool center position be P(t) and let the directional vector of the long axis of the tool be V(t), then calculate distance d(t) as follows:

d ( t )=| P 0 −P ( t )−( P 0 −P ( t ))· V ( t )/| V ( t )| |

where the · means vector dot and | | means vector norm:

(3) The optimized tool path is that which minimizes the maximum d(t) over the entire time.

10. A method according to claim 9 further comprising cutting the bone according to the tool path generated.

11. A method according to claim 10 wherein the bone is cut by a surgical robot using the generated tool path.

12. A method according to claim 9 wherein the pre-determined cutting pattern is associated with an implant to be placed into the bone.

13. Apparatus for generating an improved tool path for cutting a bone so as to minimize soft tissue trauma, wherein the method comprises:

means for accessing an image of the bone which is to be cut;

means for accessing an image of a pre-determined cutting pattern;

means for superimposing the image of the pre-determined cutting pattern against the image of the bone;

means for calculating the intersection of the pre-determined cutting pattern and the bone using the superimposed images of the pre-determined cutting pattern and the bone;

means for generating a tool path based upon the intersection of the pre-determined cutting pattern and the bone so as to minimize soft tissue trauma by leaving a thin perimeter of bone at the boundary of the bone cut when the boundary of the bone cut is adjacent to a bone surface;

wherein the tool path is generated to provide for tool access which complies with the surgical access which is defined by user input during the surgery; and

wherein sizing of a surgical opening is reduced according to the following algorithm:

(1) Define a position, P 0 , which is the center of the surgical opening:

(2) For a given tool position at a time t, let the tool center position be P(t) and let the directional vector of the long axis of the tool be V(t), then calculate distance d(t) as follows:

d ( t )=| P 0 −P ( t )−( P 0 −P ( t ))· V ( t )/| V ( t )| |

where the · means vector dot and | | means vector norm:

(3) The optimized tool path is that which minimizes the maximum d(t) over the entire time.

14. Apparatus according to claim 13 wherein the pre-determined cutting pattern is associated with an implant which is to be placed into the bone.

15. Apparatus for cutting bone, the apparatus comprising:

means for accessing an image of the bone which is to be cut;

means for accessing an image of a pre-determined cutting pattern;

means for superimposing the image of the pre-determined cutting pattern against the image of the bone;

means for calculating the intersection of the pre-determined cutting pattern and the bone using the superimposed images of the pre-determined cutting pattern and the bone;

means for identifying a preferred surgical access prior to or during the surgery; and

means for generating a tool path based upon the intersection of the pre-determined cutting pattern and the bone which accesses the bone through the preferred surgical access and leaves a thin perimeter of bone at the boundary of the bone cut is adjacent to a bone surface, except for where the tool needs to approach and cut the bone from the preferred surgical access;

wherein the tool path is generated to provide for tool access which complies with the surgical access which is defined by user input during the surgery; and

wherein sizing of a surgical opening is reduced according to the following algorithm:

(1) Define a position, P 0 , which is the center of the surgical opening:

(2) For a given tool position at a time t, let the tool center position be P(t) and let the directional vector of the long axis of the tool be V(t), then calculate distance d(t) as follows:

d ( t )=| P 0 −P ( t )−( P 0 −P ( t ))· V ( t )/| V ( t )| |

where the · means vector dot and | | means vector norm:

(3) The optimized tool path is that which minimizes the maximum d(t) over the entire time.

16. Apparatus according to claim 15 further comprising means for cutting the bone according to the tool path generated.

17. Apparatus according to claim 16 wherein the bone is cut by a surgical robot using the generated tool path.

18. Apparatus according to claim 15 wherein the cutting pattern is associated with an implant to be placed into the bone.