Apparatus and method for joint characterization and treatment

1. A method of evaluating a human knee joint which includes a femur bone, a tibia bone, a patella bone, a patellar tendon, and ligaments, wherein the ligaments and patellar tendon are anatomically located to connect the femur and tibia together, creating a load-bearing articulating joint, the method comprising:

making a tibial cut along a first cutting plane to cut away a proximal portion of the tibia;

providing a gap tensioner operable to move between retracted and extended positions for distracting the knee joint while permitting varus/valgus angulation;

inserting the gap tensioner between the tibia and the femur, with the gap tensioner in the retracted position;

moving the gap tensioner towards the extended position, so as to urge the tibia and the femur apart and apply tension to medial and lateral collateral ligaments of the knee joint;

associating at least two tracking markers with the knee joint;

providing an electronic receiving device, wherein the receiving device is operable in combination with the tracking markers to determine a position and orientation of each of the tracking markers relative to the electronic receiving device;

moving the knee joint through at least a portion of its range of motion;

while moving the knee joint, using the electronic receiving device to collect position data from the tracking markers;

processing the collected position data to produce a geometric model of at least a portion of the knee joint;

computing one or more tool paths passing through the knee joint; and

moving a tool along the one or more tool paths so as to remove bone from the knee joint, thereby forming a machined feature in the knee joint, wherein the step of moving the tool includes:

receiving data representing an actual position and orientation of the tool relative to one of the at least two tracking markers;

determining a difference between the actual position and orientation of the tool and a position and orientation lying on the computed one or more tool paths; and

using at least one actuator coupled to the tool, moving the tool in a direction so as to reduce the difference.

2. The method of claim 1 further comprising

displaying on a display an image representing the actual position and orientation of the tool relative to the computed one or more tool paths.

3. The method of claim 1 wherein the tool is a machining tool and the machined feature is a surface resulting from moving the machining tool along a shaped cutting surface.

4. The method of claim 3 wherein the machined feature is at least one of a distal femoral cut and a posterior femoral cut formed in the femur.

5. The method of claim 1 wherein the tool is a drilling tool and the machined feature is a channel passing through at least one of the tibia and the femur.

6. The method of claim 5 further comprising implanting an end of a tensile member in the channel.

7. The method of claim 1 wherein one of the tracking markers is contained in the gap tensioner.

8. The method of claim 1 wherein one of the tracking markers is contained in an actuating instrument coupled to the gap tensioner.

9. The method of claim 1 wherein the electronic receiving device is contained in the gap tensioner.

10. The method of claim 1 wherein the steps of: processing the collected position data to produce a geometric model of at least a portion of the knee joint and computing a tool path passing through the knee joint are performed using one or more processors contained in the gap tensioner.

11. The method of claim 1 further comprising, prior to the step of inserting the gap tensioner between the tibia and the femur:

making a distal femoral cut along a second cutting plane to cut away a distal portion of the femur, such that an extension gap is defined between the first and second cutting planes.

12. The method of claim 1 further comprising measuring a relative position of the tracking markers to measure a varus/valgus angle of the knee joint.

13. The method of claim 12 further comprising changing the measured varus/valgus angle.

14. The method of claim 13 further comprising:

moving a cutting tool along the one or more tool paths to form at least one of a distal femoral cut and a posterior femoral cut in the femur, wherein the cut is positioned and oriented so as to change the measured varus/valgus angle.

15. The method of claim 14 further comprising implanting a prosthetic device between the femur and the tibia.

16. The method of claim 13 further comprising:

moving a drilling tool along the one or more tool paths to form a channel passing through at least one of the tibia and the femur, wherein the channel is positioned and oriented so as to change the measured varus/valgus angle.

17. The method of claim 16 further comprising implanting an end of a tensile member in the channel.