Tibial bearing component for a knee prosthesis with improved articular characteristics
An orthopaedic knee prosthesis includes a tibial bearing component with articular features which operate to protect adjacent soft tissues of the natural knee, promote and/or accommodate desired articulation with an abutting femoral component, and facilitate expedient and effective implantation by a surgeon.
1. A tibial bearing component for articulation with a medial femoral condyle and a lateral femoral condyle, the tibial bearing component defining a tibial bearing component coordinate system comprising:
a bearing component transverse plane extending along a medial/lateral direction and an anterior/posterior direction;
a bearing component coronal plane extending along a proximal/distal direction and the medial/lateral direction, said bearing component coronal plane perpendicular to said bearing component transverse plane; and
a bearing component sagittal plane extending along the anterior/posterior direction and the proximal/distal direction, said bearing component sagittal plane perpendicular to said bearing component transverse plane and said bearing component coronal plane,
said tibial bearing component comprising:
an articular surface and an opposing distal surface, said distal surface parallel to the bearing component transverse plane, said articular surface including medial and lateral dished articular compartments sized and shaped for articulation with the medial and lateral femoral condyles respectively, said medial and lateral dished articular compartments separated from one another by the bearing component sagittal plane and extending adjacent an anterior edge of the tibial bearing component to adjacent a posterior edge of the tibial bearing component,
said lateral articular compartment comprising a plurality of coronal cross-sectional profiles defining a lateral set of coronal distal-most points spanning a lateral anterior/posterior extent, said lateral set of coronal distal-most points defining a lateral articular track,
said lateral articular track having an anterior portion and a posterior portion, said anterior portion defining a nominally straight line when projected onto the bearing component transverse plane, said posterior portion defining a curved line when projected onto the bearing component transverse plane.
2. The tibial bearing component of claim 1 , wherein said medial articular compartment comprises a plurality of coronal cross-sectional profiles defining a medial set of coronal distal-most points spanning a medial anterior/posterior extent, said medial set of coronal distal-most points defining a medial articular track, at least a portion of said medial articular track defining a nominally straight line when projected onto the bearing component transverse plane.
3. The tibial bearing component of claim 2 , wherein said nominally straight line defined by said medial articular track is substantially parallel to said nominally straight line defined by said anterior portion of said lateral articular track.
4. The tibial bearing component of claim 2 , wherein said nominally straight line defined by said medial articular track and said nominally straight line defined by said anterior portion of said lateral articular track are substantially parallel to said bearing component sagittal plane.
5. The tibial bearing component of claim 2 , wherein said medial articular track defines a medial posterior portion having an anterior/posterior extent corresponding to said posterior portion of said lateral articular track, said nominally straight line defined by said medial articular track inclusive of said medial posterior portion.
6. The tibial bearing component of claim 2 , wherein said lateral articular track defines a lateral sagittal distal-most point along said lateral anterior/posterior extent and said medial articular track defines a medial sagittal distal-most point along said medial anterior/posterior extent,
said medial and lateral sagittal distal-most points located in a common coronal plane, whereby said medial and lateral articular tracks comprise respective distal-most points at a common anterior/posterior location.
7. The tibial bearing component of claim 2 , in combination with a femoral prosthesis wherein:
said medial condyle comprises a medial prosthetic condyle shaped to articulate with said medial articular compartment through a medial flexion range to define a medial set of contact points, said medial set of contact points corresponding with said medial articular track; and
said lateral condyle comprises a lateral prosthetic condyle shaped to articulate with said lateral articular compartment through a lateral flexion range to define a lateral set of contact points, said lateral set of contact points corresponding with said lateral articular track.
8. The tibial bearing component of claim 1 , wherein said tibial bearing component is implantable at an anteroposterior slope angle as measured in the bearing component sagittal plane, said anteroposterior slope angle formed between the bearing component transverse plane and a transverse reference plane, said transverse reference plane positioned to be normal to an anatomic axis of a tibia when said tibial bearing component is implanted, said anteroposterior slope angle having a positive value when an anterior edge of said tibial bearing component is elevated with respect to a posterior edge thereof,
said lateral articular track defining a lateral sagittal distal-most point defined as a point among said lateral set of coronal distal-most points that is closest to said transverse reference plane when said anteroposterior slope angle is equal to 5 degrees,
said lateral sagittal distal-most point coincident with a posterior terminus of said anterior portion of said lateral articular track.
9. The tibial bearing component of claim 1 , wherein said bearing component is implantable at an anteroposterior slope angle as measured in the bearing component sagittal plane, said anteroposterior slope angle formed between the bearing component transverse plane and a transverse reference plane, said transverse reference plane positioned to be normal to an anatomic axis of a tibia when said tibial bearing component is implanted, said anteroposterior slope angle having a positive value when an anterior edge of said tibial bearing component is elevated with respect to a posterior edge thereof,
said lateral articular track defining a lateral sagittal distal-most point defined as a point among said lateral set of coronal distal-most points that is closest to said transverse reference plane when said anteroposterior slope angle is equal to 5 degrees,
said lateral sagittal distal-most point coincident with an anterior terminus of said posterior portion of said lateral articular track.
10. The tibial bearing component of claim 1 , wherein said curved line of said posterior portion of said lateral articular track defines a radius having a radius center, said radius center spaced medially from said lateral articular track, whereby said curved line arcs inwardly toward said medial articular compartment.
11. The tibial bearing component of claim 10 , wherein said medial articular compartment comprises a plurality of coronal cross-sectional profiles defining a medial set of coronal distal-most points spanning a medial anterior/posterior extent, said medial set of coronal distal-most points defining a medial articular track,
said radius center coincident with a projection of said medial articular track onto the bearing component transverse plane.
12. The tibial bearing component of claim 11 , wherein said tibial bearing component is implantable at an anteroposterior slope angle as measured in the bearing component sagittal plane, said anteroposterior slope angle formed between the bearing component transverse plane and a transverse reference plane, said transverse reference plane positioned to be normal to an anatomic axis of a tibia when said tibial bearing component is implanted, said anteroposterior slope angle having a positive value when an anterior edge of said tibial bearing component is elevated with respect to a posterior edge thereof,
said medial articular track defining a medial sagittal distal-most point defined as a point among said medial set of coronal distal-most points that is closest to said transverse reference plane when said anteroposterior slope angle is equal to 5 degrees,
said radius center coincident with a projection of said medial sagittal distal-most point into the bearing component transverse plane.
13. The tibial bearing component of claim 12 , wherein said lateral articular track defines a lateral sagittal distal-most point along said lateral anterior/posterior extent, said lateral sagittal distal-most point coincident with a transition from said anterior portion to said posterior portion of said lateral articular track.
14. The tibial bearing component of claim 13 , wherein said medial and lateral sagittal distal-most points are located in a common coronal plane, whereby said medial and lateral articular tracks comprise respective distal-most points at a common anterior/posterior location.
15. The tibial bearing component of claim 1 , wherein:
said lateral articular compartment comprises an overall anterior/posterior span, and
said posterior portion of said lateral articular track occupies between 20% and 50% of said overall anterior/posterior span.
16. The tibial bearing component of claim 1 , wherein said nominally straight line is tangent to said curved line.
17. The tibial bearing component of claim 1 , wherein said tibial bearing component comprises a cruciate-retaining design comprising:
a posterior cutout sized and positioned to accommodate a posterior cruciate ligament upon implantation of the tibial bearing component; and
an intercondylar ridge extending anteroposteriorly from said posterior cutout to an anterior relief space proximate an anterior edge of a periphery of said tibial bearing component, said intercondylar ridge disposed between said medial and lateral dished articular compartments.
18. The tibial bearing component of claim 17 , in combination with a femoral prosthesis wherein:
said medial condyle comprises a medial prosthetic condyle shaped to articulate with said medial articular compartment through a medial flexion range,
said lateral condyle comprises a lateral prosthetic condyle shaped to articulate with said lateral articular compartment through a lateral flexion range,
said medial and lateral prosthetic condyles defining an uninterrupted intercondylar space, wherein said femoral prosthesis lacks a femoral cam.
19. The tibial bearing component of claim 1 , wherein said articular surface and said distal surface of said tibial bearing component are bounded by a tibial bearing periphery, said tibial bearing component comprising an ultra-congruent design including a posterior eminence extending proximally from said articular surface,
said lateral articular track defining a lateral sagittal distal-most point along said lateral anterior/posterior extent, said posterior eminence defining an eminence height of between 3.8 mm and 10 min as measured proximally from said lateral sagittal distal-most point,
said posterior eminence extending anteriorly from a posterior edge of said tibial bearing periphery to define an anterior/posterior eminence extent equal to less than 30% of an overall anterior/posterior extent of said tibial bearing component, said posterior eminence disposed between said medial and lateral dished articular compartments.
20. The tibial bearing component of claim 1 , wherein said tibial bearing component comprises a posterior-stabilized design including a spine extending proximally from said articular surface, said spine spaced posteriorly from an anterior edge of a periphery of said tibial bearing component, and said spine disposed between said medial and lateral dished articular compartments.