Posterior-stabilized total knee prosthesis

Patent metadata

Field	Value
Publication number	US-9615929-B2
Application number	US-69237110-A
Country	US
Kind code	B2
Filing date	Jan 22, 2010
Priority date	Jan 23, 2009
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

In an orthopaedic knee joint prosthesis, an intercondylar fossa of a femoral component cooperates with a spine formed in a tibial component to reproduce the screw home mechanism of a natural knee. When the femoral component and tibial component are positioned to correspond with slight flexion of the knee, the components are mutually rotationally locked against internal or external rotation. At higher degrees of flexion, such as greater than about 10-20 degrees of flexion, internal/external rotation of the tibia is permitted. The tibia is in an externally rotated position when locked, thereby reproducing the screw home mechanism and providing high stability.

First claim

What is claimed is:

1. A knee joint prosthesis moveable between an extension orientation and a flexion orientation, the prosthesis comprising:
a femoral component comprising:
a lateral condyle having a lateral condylar inner wall;
a medial condyle having a medial condylar inner wall; and
an intercondylar fossa bounded on two sides by said lateral condylar inner wall and said medial condylar inner wall; and

a tibial component comprising:
a tibial articulating surface;
a spine extending proximally from said tibial articulating surface at a first junction, said spine including a base adjacent said tibial articulating surface, said base having a lateral base wall and an opposed medial base wall with a base width defined between said lateral base wall and medial base wall, each of said lateral base wall and said medial base wall is parallel to a sagittal plane, said spine including a peak disposed proximally of said base and having a lateral peak surface and an opposed medial peak surface, a peak width defined between said lateral peak surface and medial peak surface, said peak width less than said base width;

said lateral condylar inner wall engaging with said lateral base wall and said medial condylar inner wall engaging with said medial base wall, to prevent internal rotation and external rotation of said tibial component when the knee joint prosthesis is in the extension orientation; and
said lateral condylar inner wall cooperating with said lateral peak surface and said medial condylar inner wall cooperating with said medial peak surface, to permit at least one of internal rotation and external rotation of said tibial component when the knee joint prosthesis is in the flexion orientation.

2. The knee joint prosthesis of claim 1 , wherein said peak width tapers from equal to said base width at said first junction and a second junction between said peak and said base approximately midway along the spine to substantially less than said base width at a proximal summit of said peak, said second junction between said peak and said base defining an inflection point along said spine.

3. The knee joint prosthesis of claim 2 , wherein said spine of said tibial component remains engaged with said intercondylar fossa over a range from said first junction to said inflection point and disengages said intercondylar fossa of said femoral component over a range from said inflection point to said summit, said inflection point being located at an orientation of the knee prosthesis corresponding to about 10 degrees to about 45 degrees flexion.

4. The knee joint prosthesis of claim 1 , wherein the flexion orientation of the knee prosthesis corresponds to an orientation of at least 20 degrees flexion.

5. The knee joint prosthesis of claim 1 , wherein the flexion orientation of the knee prosthesis corresponds to an orientation of at least 15 degrees flexion.

6. The knee joint prosthesis of claim 1 , wherein the flexion orientation of the knee prosthesis corresponds to an orientation of at least 10 degrees flexion.

7. The knee joint prosthesis of claim 1 , wherein said peak and said base extend along approximately equal lengths of an anterior surface of said spine.

8. The knee joint prosthesis of claim 1 , wherein said spine is stepped between said base and said peak.

9. The knee joint prosthesis of claim 1 wherein said peak is tapered, and wherein said tapered peak produces a screw-home mechanism of the femoral component in the range of about forty-five degrees to about twenty degrees of flexion and said base locks said femoral component from rotation from about twenty degrees of flexion to zero degrees of flexion.

10. A knee joint prosthesis moveable between an extension orientation and a flexion orientation, the prosthesis comprising:
a femoral component comprising:
a lateral condyle having a lateral condylar inner wall;
a medial condyle having a medial condylar inner wall; and
an intercondylar fossa bounded on two sides by said lateral condylar inner wall and said medial condylar inner wall; and

a tibial component comprising:
a tibial articulating surface; and
a spine extending proximally from said tibial articulating surface, said spine including a lateral spine wall and an opposed medial spine wall, each of said lateral spine wall and said medial spine wall is parallel to a sagittal plane at a base, said lateral spine wall and said medial spine wall tapering to a summit at a peak so that portions of said lateral and medial spine walls defining said peak are disposed at a different angle relative to said sagittal plane than portions of said lateral and medial spine walls defining said base;

said lateral condylar inner wall engaging with said lateral spine wall and said medial condylar inner wall engaging with said medial spine wall, to prevent internal rotation and external rotation of said tibial component when the knee joint prosthesis is in the extension orientation and the femoral component engages the base of the spine, and to permit at least one of internal rotation and external rotation of said tibial component when the knee joint prosthesis is in the flexion orientation by disengaging from the base to cooperate with the peak at an orientation of the knee prosthesis corresponding to less than about 45 degrees of flexion.

11. The knee joint prosthesis of claim 10 , wherein the flexion orientation of the knee prosthesis corresponds to an orientation of at least 20 degrees flexion.

12. The knee joint prosthesis of claim 10 , wherein the flexion orientation of the knee prosthesis corresponds to an orientation of at least 15 degrees flexion.

13. The knee joint prosthesis of claim 10 , wherein the flexion orientation of the knee prosthesis corresponds to an orientation of at least 10 degrees flexion.

14. The knee joint prosthesis of claim 10 , wherein said lateral and medial spine walls first disengage from said lateral and medial condylar inner walls, respectively, as the knee joint prosthesis transitions from the extension orientation to the flexion orientation at about 10 degrees to about 45 degrees flexion.

15. The knee joint prosthesis of claim 10 , wherein said peak having a peak width less than a width between said lateral and medial spine walls such that said peak permits internal/external rotation of said tibial component when the knee joint prosthesis is in the flexion orientation.

Assignees

• Sanford Adam H
• Zimmer Inc

Inventors

• Sanford Adam H

Classifications

• A61F2230/0095

  Saddle-shaped · CPC title

• A61F2002/30301

  saddle-shaped · CPC title

• A61F2/389

  Tibial components (A61F2/3868 takes precedence) · CPC title

• A61F2/3859

  Femoral components · CPC title

• A61F2/3836

  Special connection between upper and lower leg, e.g. constrained · CPC title