High performance knee prostheses
Knee prostheses featuring components that more faithfully replicate the structure and function of the human knee joint in order to provide, among other benefits: greater flexion of the knee in a more natural way by promoting or at least accommodating internal tibial rotation in a controlled way, replication of the natural screw home mechanism, and controlled articulation of the tibia and femur respective to each other in a more natural way. In a preferred embodiment, such prostheses include an insert component disposed between a femoral component and a tibial component, the insert component preferably featuring among other things a reversely contoured posterolateral bearing surface that helps impart internal rotation to the tibia as the knee flexes. Other surfaces can also be specially shaped to achieve similar results, preferably using iterative automated techniques that allow testing and iterative design taking into account a manageable set of major forces acting on the knee during normal functioning, together with information that is known about natural knee joint kinetics and kinematics.
1. A tibial articular component of a knee prosthesis comprising:
(a) a medial bearing surface comprising a medial anterior half and a medial posterior half, wherein the medial posterior half comprises a first outermost bearing surface posterior edge; and
(b) a lateral bearing surface comprising a lateral anterior half and a lateral posterior half, wherein the lateral posterior half comprises a second outermost bearing surface posterior edge;
wherein the medial bearing surface has a minimum thickness that is thicker in a superior inferior direction at the first outermost bearing surface posterior edge than a minimum thickness of the lateral bearing surface at the second outermost bearing surface posterior edge.
2. The tibial articular component of claim 1 , further comprising a central post positioned between the medial bearing surface and the lateral bearing surface.
3. The tibial articular component of claim 1 , wherein the thicker posterior half of the medial bearing surface at the first outermost bearing surface posterior edge increases internal rotation of the tibial articular component relative to a femur during flexion.
4. A knee prosthesis, comprising:
a tibial component comprising a superior side and an inferior side, wherein the superior side comprises a medial articular portion and a lateral articular portion, the medial articular portion extending between an anterior end of the medial articular portion and a posterior end of the medial articular portion, the lateral articular portion extending between an anterior end of the lateral articular portion and a posterior end of the lateral articular portion, the posterior end of the medial articular portion curving away from the inferior side such that an inferior-most portion of the superior side of the posterior end of the medial articular portion is superior to an inferior-most portion of the superior side of the posterior end of the lateral articular portion, the anterior end of the lateral articular portion extending upwardly from the inferior side.
5. The knee prosthesis of claim 4 , wherein a superior-most portion of the anterior end of the lateral articular portion is superior to a superior-most portion of the posterior end of the lateral articular portion.
6. The knee prosthesis of claim 5 , wherein the posterior end of the lateral articular portion comprises a relatively flat portion relative to the anterior end of the lateral articular portion.
7. The knee prosthesis of claim 5 , wherein the posterior end of the lateral articular portion is closer to the inferior side than the posterior end of the medial articular portion.
8. The knee prosthesis of claim 5 , further comprising a femoral component comprising a medial condyle configured to articulate on the medial articular portion and a lateral condyle configured to articular on the lateral articular portion.
9. The knee prosthesis of claim 8 , wherein the posterior end of the lateral articular portion is configured to facilitate inward rotation of the tibial component relative to the femoral component during flexion of the femoral component relative to the tibial component.
10. The knee prosthesis of claim 9 , wherein the posterior end of the lateral articular portion slopes towards the inferior side of the tibial component.
11. The knee prosthesis of claim 8 , wherein
the femoral component further comprises a posterior cam, the posterior cam comprising an anterior facing cam surface; and
the tibial component further comprises a post extending in a superior direction between the medial and lateral articular portions, the post comprising a posterior facing cam surface.
12. The knee prosthesis of claim 11 , wherein the posterior facing cam surface of the post is configured in shape to facilitate inward rotation of the tibial component relative to the femoral component during flexion of the femoral component relative to the tibial component.
13. The knee prosthesis of claim 5 , wherein the tibial component further comprises a chamfered surface extending towards the inferior side of the tibial component from at least one of the posterior end of the lateral articular portion and the posterior end of the medial articular portion.
14. The knee prosthesis of claim 5 , wherein the tibial component comprises an articular insert and a tibial tray.