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1. US20110125279 - Constrained condylar knee device

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[ EN ]

Claims

1. A knee joint prosthesis comprising:
a femoral component having a first condylar bearing surface and a second condylar bearing surface, wherein each of the first and second condylar bearing surfaces has a convex shape and has a cross-section in a coronal plane that exhibits at least two different radii that define the convex shape of the bearing surface;
a tibial component; and
an insert component associated with the tibial component and having bearing surfaces that are complementary to the first and second condylar bearing surfaces, wherein a contact point is established between the bearing surfaces of the insert component and the first and second condylar bearing surfaces;
wherein varus and valgus rotation of the femoral component relative to the insert component causes the contact point to move laterally when the tibial component is in near full extension relative to the femoral component.
2. The knee joint prosthesis of claim 1, wherein a medial radius of each of the first and second condylar bearing surfaces is less than a lateral radius thereof, the medial radius and lateral radius being two tangent radii.
3. The knee joint prosthesis of claim 1, wherein the insert component includes first and second laterally spaced-apart, oblong concavities formed along an upper surface for receiving the first and second condylar bearing surfaces of the femoral component to provide a nested configuration between the femoral component and the insert component, the oblong concavities defining the bearing surfaces of the insert component.
4. The knee joint prosthesis of claim 3, wherein each bearing surface of the insert component includes a lateral portion and a medial portion, with a radius of the medial portion being less than a radius of the lateral portion.
5. The knee joint prosthesis of claim 1, wherein the femoral component includes an intercondylar box and the insert component includes a constraint post for reception within the intercondylar box.
6. The knee joint prosthesis of claim 5, wherein the constraint post has a medial face and a lateral face, each of the medial and lateral faces having a curved shape.
7. The knee joint prosthesis of claim 6, wherein the constraint post further includes a recessed section formed along a lower portion thereof to reduce contact between an inside edge of the femoral component and the constraint post.
8. The knee joint prosthesis of claim 5, wherein the intercondylar box includes a first inner wall and an opposing second inner wall, each of the first and second inner walls having a stepped construction in that an anterior portion of the intercondylar box is wider relative to a posterior portion of the intercondylar box as measured between the first and second inner walls.
9. The knee joint prosthesis of claim 8, wherein the knee is in extension and rotated in a varus or valgus direction, contact between the constraint post and the femoral component occurs at the wider anterior portion of the intercondylar box.
10. The knee joint prosthesis of claim 5, wherein the intercondylar box includes a first inner wall and an opposing second inner wall that are inwardly tapered relative to one another in a direction toward a posterior portion of the intercondylar box.
11. The knee joint prosthesis of claim 1, wherein a clearance exists between the lateral condylar bearing surface and a lateral bearing surface of the insert component when the knee is in 0 degrees of rotation in a varus/valgus direction.
12. A tibial component for a knee joint prosthesis comprising: a platform having an upper surface that includes first and second laterally spaced concavities, each concavity being adapted for receiving one condylar portion of the femoral component and a constraint post for reception in an intercondylar recess of the femoral component, wherein each of the first and second laterally spaced concavities includes a bearing surface that is defined by at least two different radii in a coronal plane, wherein medial and lateral faces of the constraint post further includes a recessed section formed along a lower portion thereof to reduce contact between an inside edge of the femoral component and the constraint post.
13. The tibial component of claim 12, wherein each bearing surface includes a lateral portion and a medial portion, with a radius of the medial portion being less than a radius of the lateral portion.
14. The tibial component of claim 12, wherein the constraint post has a medial face and a lateral face, each of the medial and lateral faces having a curved shape.
15. A knee joint prosthesis comprising: a femoral component having a first condylar bearing surface and a second condylar bearing surface and an intercondytar box; a tibial component; and an insert component associated with the tibial component and having bearing surfaces that are complementary to the first and second condylar bearing surfaces, the insert component including a constraint post for reception within the intercondylar box, wherein the constraint post has a medial face and a lateral face, each of the medial and lateral faces having a curved shape in a coronal plane extending through the constraint post, wherein the curved shape extends superiorly through the constraint post and a portion of each of the medial and lateral faces of the constraint post that is defined by the curved shape contacts walls of the intercondylar box in a varus/valgus rotation, wherein the curvature of each of the medial and lateral faces extends to and terminates at a top of the constraint post, wherein the medial and lateral faces of the constraint post further includes a recessed section formed along a lower portion thereof to reduce contact between an inside edge of the femoral component and the constraint post.
16. The prosthesis of claim 15, wherein each of the first and second condylar bearing surfaces has a convex shape and has a cross-section in a coronal plane that exhibits at least two different radii that define the convex shape of the bearing surface.
17. The prosthesis of claim 15, wherein the medial and lateral faces taper inwardly in a direction toward the top of the constraint post.