Methods and apparatus for mid-flexion balancing during knee arthroplasty

1. A method of preparing a knee to receive a knee implant, the method comprising:

positioning a knee comprising a distal femur and a proximal tibia at a mid-flexion angle;

performing soft tissue balancing of the knee at the mid-flexion angle;

determining a location of a posterior chamfer cut of the distal femur configured to engage the posterior chamfer angle of a femoral component of a knee implant based at least in part upon the soft tissue balancing of the knee at the mid-flexion angle; and

resecting the distal femur to create the posterior chamfer cut.

2. The method of claim 1 , wherein the mid-flexion angle corresponds approximately to a posterior chamfer angle of the femoral component of the knee implant.

3. The method of claim 1 , wherein the mid-flexion angle is between about 30 degrees of flexion and about 70 degrees of flexion.

4. The method of claim 1 , wherein the mid-flexion angle is between about 30 degrees of flexion and about 60 degrees of flexion.

5. The method of claim 1 , wherein the mid-flexion angle is about 45 degrees of flexion.

6. The method of claim 1 , further comprising

performing soft tissue balancing of the knee relative to the posterior chamfer cut;

determining a location of a tibial plateau cut configured to engage a tibial component of the knee implant based at least in part upon the soft tissue balancing of the knee relative to the posterior chamfer cut; and

resecting the proximal tibia to create the tibial plateau cut.

7. The method of claim 6 , further comprising

positioning the knee at full extension;

performing soft tissue balancing of the knee relative to the tibial plateau cut;

determining a location of a femoral extension cut configured to engage the femoral component of the knee implant based at least in part upon the soft tissue balancing of the knee relative to the tibial plateau cut; and

resecting the distal femur to create the femoral extension cut.

8. The method of claim 7 , further comprising

positioning the knee at about 90 degrees of flexion;

performing soft tissue balancing of the knee relative to the tibial plateau cut;

determining a location of a femoral flexion cut configured to engage the femoral component of the knee implant based at least in part upon the soft tissue balancing of the knee relative to the tibial plateau cut; and

resecting the distal femur to create the femoral flexion cut.

9. The method of claim 8 , further comprising

determining a location of a femoral flexion cut configured to engage the femoral component of the knee implant based at least in part upon a femoral component size determined using an anterior reference guide; and

resecting the distal femur to create the femoral flexion cut.

10. The method of claim 9 ,

wherein using the anterior reference guide comprises

placing a movable stylus of the anterior reference guide on an anterior aspect of the distal femur; and

translating a posterior indicator of the anterior reference guide using the movable stylus.

11. The method of claim 9 ,

wherein the anterior reference guide comprises a posterior chamfer cut contact surface; and

wherein using the anterior reference guide comprises positioning the posterior chamfer cut contact surface on the posterior chamfer cut.

12. The method of claim 1 , wherein performing soft tissue balancing of the knee at the mid-flexion angle comprises performing soft tissue balancing of the knee at the mid-flexion angle relative to a tibial plateau cut of the proximal tibia.

13. The method of claim 12 , further comprising, before performing soft tissue balancing of the knee at the mid-flexion angle relative to the tibial plateau cut of the proximal tibia, resecting the proximal tibia to create the tibial plateau cut.

14. The method of claim 1 , wherein performing soft tissue balancing of the knee at the mid-flexion angle comprises applying a linear separating force to bones comprising the knee using a gap tensioner.

15. The method of claim 14 , wherein applying the linear separating force to bones of the knee using the gap tensioner comprises

inserting a first paddle and a second paddle into a gap between the bones of the knee; and

applying the linear separating force to the bones of the knee using the first paddle and the second paddle.

16. The method of claim 15 , wherein applying the linear separating force to the bones of the knee using the first paddle and the second paddle comprises applying a torsional force to the gap tensioner, the gap tensioner converting the torsional force to the linear separating force.

17. The method of claim 16 , wherein applying the torsional force to the gap tensioner comprises applying a torsional force to an actuating shaft of the gap tensioner using a torque wrench.