Tibial prosthesis with asymmetric articular surfaces

• US 7,625,407 B2
• Filed: 02/07/2006
• Issued: 12/01/2009
• Est. Priority Date: 02/07/2006
• Status: Active Grant

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Inventors: Phipps, Michael C., Sichler, Kevin P., Akizuki, Shaw
• Primary Examiner(s): Willse; David H.
• Application Number:
  US11/349,048
• Publication Number:
  US 20070185581A1
• Time in Patent Office: 1,393 Days
• Field of Search: 623/13.12, 623 203- 2034
• US Class Current: 623/20.32
• CPC Class Codes: A61F 2/389 Tibial components A61F2/3868 takes precedence
• CPC Class Codes: A61F 2002/30604 modular
• CPC Class Codes: A61F 2002/30934 Special articulating surfaces

Abstract

A tibial prosthesis has tibial articular surfaces including a medial articular surface in a medial compartment and a lateral articular surface in a lateral compartment. The medial articular surface follows a first arcuate track having a first radius of curvature and a first posterior segment extending along a posterior aspect of the medial compartment to a first superior-interior location. The lateral articular surface follows a second arcuate track having a second radius of curvature and a second posterior segment extending along a posterior aspect of the lateral compartment to a second superior-inferior location. The second posterior segment has a slope extending in an inferior direction along the posterior aspect of the lateral compartment such that the second superior-inferior location is spaced a predetermined distance in an inferior direction from the first superior-inferior location.

Claims

1. In a tibial prosthesis having tibial articular surfaces extending between an anterior edge of the tibial prosthesis and a posterior edge of the tibial prosthesis for enabling relative rotation between the tibial prosthesis and a femoral prosthesis engaged with the tibial prosthesis about a longitudinal axis of rotation during flexion of a prosthetic knee about a transverse axis, the tibial articular surfaces including a medial articular surface in a medial compartment and a lateral articular surface in a lateral compartment, an improvement wherein:

the medial articular surface follows a first arcuate track having a first radius of curvature extending from a corresponding center on a corresponding longitudinal axis and a first posterior segment extending along a posterior aspect of the medial compartment to a first point located adjacent the posterior edge of the tibial prosthesis and placed at a first inferior-superior location;

the lateral articular surface follows a second arcuate track having a second radius of curvature extending from a corresponding center on a corresponding longitudinal axis and a second posterior segment extending along a posterior aspect of the lateral compartment to a second point located adjacent the posterior edge of the tibial prosthesis and placed at a second superior-inferior location;

the second posterior segment follows a slope descending in an inferior direction relative to an anterior-posterior plane normal to a coronal plane and normal to a sagittal plane as the second posterior segment extends in a posterior direction along the posterior aspect of the lateral compartment such that the second superior-inferior location is placed at a predetermined distance in an inferior direction relative to the placement of the first superior-inferior location, thereby enabling the relative rotation between the tibial prosthesis and the femoral prosthesis along the first and second arcuate tracks to mimic corresponding kinematics of a natural knee; and

the first posterior segment and the second posterior segment each extend along corresponding segments of a common helical path having a pitch for establishing the predetermined distance between the placement of the first and second superior-inferior locations.

2. The improvement of claim 1 wherein the first and second radii of curvature are maintained the same along the first and second posterior segments.

3. The improvement of claim 2 wherein the first and second radii extend from a common center.

4. The improvement of claim 3 wherein the common center is located on the longitudinal axis of rotation.

5. The improvement of claim 4 wherein:

the lateral compartment includes a lateral width between laterally spaced apart boundaries;

the lateral articular surface includes a sulcus located in the coronal plane; and

the slope is such that a line from a point located in the coronal plane and placed on the lateral articular surface midway between the laterally spaced apart boundaries makes a prescribed angle of declination with the anterior-posterior plane.

6. The improvement of claim 5 wherein the prescribed angle of declination is up to about 4°

.

7. The improvement of claim 5 wherein the prescribed angle of declination is about 2°

.

8. The improvement of claim 5 wherein the tibial prosthesis comprises a tibial bearing member for affixation to a tibial tray of a tibial component of a knee prosthesis.

9. The improvement of claim 1 wherein:

the lateral compartment includes a lateral width between laterally spaced apart boundaries;

the lateral articular surface includes a sulcus located in the coronal plane; and

the slope is such that a line from a point located in the coronal plane and placed on the lateral articular surface midway between the laterally spaced apart boundaries makes a prescribed angle of declination with the anterior-posterior plane.

10. The improvement of claim 9 wherein the prescribed angle of declination is up to about 4°

.

11. The improvement of claim 9 wherein the prescribed angle of declination is about 2°

.

12. The improvement of claim 1 wherein the tibial prosthesis comprises a tibial bearing member for affixation to a tibial tray of a tibial component of a knee prosthesis.