ORTHOPAEDIC SYSTEM WITH MEDIAL PIVOTING FEMORAL COMPONENT AND INSERT

Abstract

An orthopaedic system includes a tibial insert and a femoral component configured to articulate on the tibial insert. The tibial insert includes an articular surface, and the femoral component includes a femoral articular surface having decreasing radii of curvature posteriorly. The articular surface of the tibial insert includes an increased anterior lip to improve stability of the femoral component.

Claims

1. An orthopaedic system comprising: a tibial insert having a medial articular surface and a lateral articular surface, wherein the medial and lateral articular surfaces are asymmetrically shaped relative to each other; and a femoral component having a medial condyle configured to articulate on the medial articular surface of the tibial insert and a lateral condyle configured to articulate on the lateral articular surface of the tibial insert, wherein the medial condyle of the femoral component includes a femoral articular surface having a first radius of curvature that extends posteriorly to a first degree of flexion of 70 degrees or less and a plurality of decreasing radii of curvature that extend posteriorly from the first degree of flexion to a second degree of flexion greater than the first degree of flexion.

2. The orthopaedic system of claim 1, wherein the femoral articular surface of the femoral component has a second radius of curvature at the second degree of flexion, the second radius of curvature being greater than each of the decreasing radii of curvature.

3. The orthopaedic system of claim 1, wherein the femoral articular surface of the femoral component has a second radius of curvature, posterior of the decreasing radii of curvature, that is greater than the posterior-most radius of the plurality of decreasing radii of curvature.

4. The orthopaedic system of claim 1, wherein the medial articular surface of the tibial insert and the femoral articular surface of the medial condyle of the femoral component are more conforming than the lateral articular surface of the tibial insert and femoral articular surface of the lateral condyle of the femoral component.

5. (canceled)

6. The orthopaedic system of claim 4, wherein the medial articular surface of the tibial insert and the femoral articular surface of the medial condyle have a medial-lateral conformity of at least 93% and wherein the lateral articular surface of the tibial insert and the femoral articular surface of the lateral condyle have a medial-lateral conformity of at least 93%.

7. (canceled)

8. The orthopaedic system of claim 1, wherein the tibial insert includes an anterior medial lip having a first height and an anterior lateral lip having a second height, and wherein the first height of the anterior medial lip is greater than the second height of the anterior lateral lip.

9. (canceled)

10. (canceled)

11. The orthopaedic system of claim 1, wherein the medial articular surface of the tibial insert includes a dwell point and an anterior medial lip, wherein the anterior medial lip has a height, relative to the dwell point, of at least 9 millimeters.

12. The orthopaedic system of claim 1, wherein the medial articular surface of the tibial insert includes a dwell point having an arcuate or oblong shape when viewed in a transverse plane.

13. The orthopaedic system of claim 1, wherein the first radius of curvature has a length that is between 41% to 47% of an anterior-posterior length of the tibial insert.

14. The orthopaedic system of claim 1, wherein the medial articular surface of the tibial insert includes a dwell point and the lateral articular surface provides an arcuate path for pivoting of the femoral component about the dwell point.

15. The orthopaedic system of claim 1, wherein the first radius of curvature extends anteriorly to a hyper-extension degree of flexion of 30 degrees or less.

16. A tibial insert of a knee replacement system, the tibial insert comprising: a lateral articular surface configured to articulate with a lateral condyle of a femoral component; and a medial articular surface configured to articulate with a medial condyle of the femoral component, wherein the medial articular surface is asymmetrically shaped relative to the lateral articular surface and includes a dwell point and an anterior medial lip having a height, relative to the dwell point, of at least nine millimeters.

17. The tibial insert of claim 16, wherein the medial articular surface and the medial condyle of the femoral component are more conforming than the lateral articular surface and the lateral condyle of the femoral component.

18. (canceled)

19. The tibial insert of claim 16, wherein the lateral articular surface includes an anterior lateral lip having a height less than the height of the anterior medial lip.

20. An orthopaedic system comprising: a tibial insert comprising a lateral articular surface and a medial articular surface, and a femoral component comprising a medial condyle configured to articulate on the medial articular surface of the tibial insert, and a lateral condyle configured to articulate on the lateral articular surface of the tibial insert, the medial condyle of the femoral component including a femoral articular surface having a first radius of curvature that extends posteriorly to a first degree of flexion of 70 degrees or less and a plurality of decreasing radii of curvature that extend posteriorly from the first degree of flexion to a second degree of flexion greater than the first degree of flexion, wherein the medial articular surface of the tibial insert is asymmetrically-shaped relative to the lateral articular surface and includes a dwell point having an arcuate or oblong shape when viewed in a transverse plane and an anterior medial lip having a height, relative to the dwell point, of at least nine millimeters.

21. The orthopaedic system of claim 20, wherein the tibial insert includes an anterior lateral lip, and wherein the height of the anterior medial lip is greater than a height of the anterior lateral lip.

22. The orthopaedic system of claim 20, wherein the femoral articular surface of the femoral component has a second radius of curvature at the second degree of flexion, wherein the second radius of curvature is greater than the posterior-most radius of the plurality of decreasing radii of curvature.

23. (canceled)

24. The orthopaedic system of claim 20, wherein the medial articular surface of the tibial insert and the femoral articular surface of the medial condyle of the femoral component are more conforming than the lateral articular surface of the tibial insert and femoral articular surface of the lateral condyle of the femoral component.

25. The orthopaedic system of claim 24, wherein the medial articular surface of the tibial insert and the femoral articular surface of the medial condyle have a medial-lateral conformity of at least 93%.

26. (canceled)

27. The orthopaedic system of claim 20, wherein the first radius of curvature extends anteriorly to a hyper-extension degree of flexion of 30 degrees or less.

28-31. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The detailed description particularly refers to the following figures, in which:

[0020] FIG. 1 is a front perspective view of tibial insert having asymmetric articular surfaces;

[0021] FIG. 2 is a front perspective view of a known tibial insert having symmetric articular surfaces;

[0022] FIG. 3A is a superior view of the known tibial insert of FIG. 2;

[0023] FIG. 3B is a superior view of the orthopaedic insert of FIG. 1;

[0024] FIG. 4 is a side perspective view of an orthopaedic system including a femoral component and the tibial insert of FIGS. 1 and 3B;

[0025] FIG. 5A is a superior view of the tibial insert of FIGS. 1 and 3B;

[0026] FIG. 5B is a rear elevation view of the tibial insert of FIGS. 1 and 3B;

[0027] FIG. 5C is a medial side view of the tibial insert of FIGS. 1 and 3B;

[0028] FIG. 5D is a lateral side of the orthopaedic insert of FIGS. 1 and 3B; and

[0029] FIG. 5E is a front elevation view of the tibial insert of FIGS. 1 and 3B.

DETAILED DESCRIPTION OF THE DRAWINGS

[0030] While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0031] Terms representing anatomical references, such as anterior, posterior, medial, lateral, superior, inferior, etcetera, may be used throughout the specification in reference to the orthopaedic implants and orthopaedic surgical instruments described herein as well as in reference to the patient's natural anatomy. Such terms have well-understood meanings in both the study of anatomy and the field of orthopedics. Use of such anatomical reference terms in the written description and claims is intended to be consistent with their well-understood meanings unless noted otherwise.

[0032] Referring now to the drawings, and more particularly to FIG. 1, an illustrative embodiment of a tibial insert 100 provided in accordance with the present disclosure is illustrated. For comparison, a known tibial insert 200 is illustrated in FIG. 2. Each tibial insert 100, 200 defines a respective anterior-posterior centerline CL1, CL2 and a medial articular surface 102, 104 on one half of the centerline CL1, CL2, respectively, and a lateral articular surface 104, 114 on the other half of the centerline CL1, CL2, respectively. Unlike the known tibial insert 200, the articular surfaces 102, 112 of the tibial insert 100 are asymmetrically-shaped to provide asymmetric pivoting of a femoral component bearing on the tibial insert 100. The medial articular surface 102 of the tibial insert 100 is more conforming to, for example, a condylar portion of a femoral component than the medial articular surface 104 of the tibial insert 200, as will be described further herein. The tibial insert 100 also has a relatively raised anterior surface (anterior medial lip height 122) on a medial side of the tibial insert 100, compared to the tibial insert 200 (anterior medial lip height 144).

[0033] With continued reference to FIG. 1, and referring now to FIG. 3B as well, a lateral side 310 of the tibial insert 100 provides an arcuate path 312, denoted by a curved arrow, for pivoting of the femoral component about a medial pivot point 314 extending through the medial articular surface 102. The arcuate path 312 may be laterally centered on the medial pivot point 314. This pivoting motion differs from the motion path 302, 304 of a femoral component bearing on the tibial insert 200, which is symmetric as shown in FIG. 3A. Thus, the tibial insert 100, unlike the tibial insert 200, provides a medial pivot point for a femoral component bearing on the tibial insert 100.

[0034] Referring now to FIG. 4, an orthopaedic system 400 including a femoral component 410 bearing on the tibial insert 100 illustrated in FIGS. 1 and 3B is illustrated. The femoral component 410 includes a medial femoral condyle 412 configured to articulate on the medial articular surface 102 of the tibial insert 100 and a lateral femoral condyle 414 configured to articulate on the lateral articular surface 112. One or both of the femoral condyles 412, 414 may define a radius of curvature that extends anteriorly between 10 and 30 degrees. One or both of the femoral condyles 412, 414 may define a radius of curvature 418 that extends anteriorly a degree of extension of 30 degrees or less. Additionally, as shown in FIG. 4, the femoral component 410 may define a constant radius of curvature 420 that extends posteriorly to a degree of flexion 422 between 30 and 70 degrees before starting to gradually decrease in radii of curvature that define a remainder of a sagittal shape of the femoral component 410 subsequent to the degree of flexion 422. The femoral component 410 may define a constant radius of curvature that may extend posteriorly to a degree of flexion 422 of 70 degrees or less before starting to gradually decrease in radii of curvature that define a remainder of a sagittal shape of the femoral component.

[0035] For a medial conforming design with a series of radii of curvatures, the choice of conformity is important in defining the ability to resist paradoxical translation. Some embodiments of the femoral component 410 may have the constant radius of curvature 420 extend to a degree of flexion of 30 degrees or less and have subsequently reducing radii of curvature for a range of degrees of flexion thereafter. Some embodiments may have a radius of curvature 420 that can extend to a degree of flexion of 70 degrees or less and then include a few radii of curvature of much smaller size to define the posterior condyle sagittal shape in deep flexion. For a natural medial pivoting motion, some embodiments may have a range of higher conformity on the medial side for stability, plus a series of smaller radii of curvature to restore normal gait in deeper flexion angles. The articular surface of the lateral femoral condyle 414 is generally less conforming sagittally than the articular surface of the medial femoral condyle 412. The lateral tibial surface has an arcuate shape that is generally centered around the lowest position or dwell point/region of the medial conforming surface. In that way, the dwell point acts as the medial pivot point for the femoral component bearing on the tibial insert 100.

[0036] The relationship of the anterior-posterior (AP) length 430 of the tibial insert 100 to the size of the radius of curvature 418 of the femoral component 410 is important. If the radius of curvature of 418 and/or radius of curvature 420 is too large (depending on the particular degree of flexion), a booking or hinge effect can occur in mid flexion. If the radius of curvature 420 is too small, the series of radii of curvature may need to increase at some point to obtain the needed anterior-posterior dimension of the implant. In some embodiments, the radius of curvature 420 may be between 41% and 47% of the anterior-posterior length of the tibial insert 100. A ratio of coronal curvature to sagittal curvature for the radius of curvature defining that section of the femoral component 410 may be between, for example, 41% to 100%.

[0037] Referring now to FIGS. 5A-5E, the geometry of the tibial insert 100 is illustrated. As previously described, the medial articular surface 102 of the tibial insert 100 conforms to the femoral component 410. An anterior-posterior surface conformity of the medial articular surface 102 may be at least 96% of the radius of curvature 420 the femoral component 410 (e.g., at zero degrees of flexion). For example, the anterior-posterior conformity between the medial articular surface 102 and the corresponding femoral articular surface of the femoral component 410 may be 96% or greater (e.g., at zero degrees of flexion). The medial-lateral conformity of the medial and lateral articular surfaces 102, 112 may be at least 93% of a medial-lateral condylar radius of curvature of the femoral component 410. For example, the medial-lateral conformity between the medial and lateral articular surfaces 102, 112 and the corresponding femoral articular surfaces of the femoral component 410 may be 93% or greater.

[0038] For optimal medial stability, it is necessary to extend the extension radius forward by 20-30 degrees. Although a natural knee does not hyperextend to these degrees, the matching conformity on the tibial surface creates a taller medial anterior surface than in most designs. A minimal height of an anterior medial lip 502 (see FIG. 5E) may have a height 504 of at least 9 mm higher than the lowest dwell point 506 (See FIG. 5A) on the medial articular surface 102. This taller surface increases the overall conformity of the medial articular surface 102 and can reduce the likelihood of dislocation if the height of the surface is 9 mm or greater than the lowest articular surface region or dwell point 506. The medial dwell point 506 may be a curved dwell with the shape of an arc or may be oblong with a flat surface of no more than 1 mm between two curved surfaces.

[0039] Another feature of the tibial insert 100 is the location of the dwell point 506 on the medial articular surface 102. If the medial dwell point 506 is too far forward, the artificial knee may not be able to achieve deeper flexion angles without removing the posterior conformity on the tibial surface. If the dwell point 506 on the medial articular surface 102 is too far posterior, the anterior surface of the medial articular surface 102 will have difficulty in obtaining necessary extension of the artificial knee and excessive posterior loading through the tibia may induce some loosening of the tibial insert 100 from the cement. Dwell positions on both the medial and lateral articular surfaces 102, 112 can be in line with respective condylar portions of the femoral component 410.

[0040] Regarding the ratio of conformity of the medial and lateral condylar surfaces of the femoral component 410, the ratio is important in defining a pivoting motion. If the coronal radius is too flat, the ability of the implant or orthopaedic system to rotate and maintain anterior stability is compromised.

[0041] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.