Knee prosthesis

Claim 2

A knee joint prosthesis comprising a femoral component having a pair of condylar portions laterally spaced-apart from each other and having outwardly facing surfaces generally matching in shape the anatomical surfaces of the femoral condyles (the condylar surfaces of the femur) and an intercondylar portion interconnecting the femoral condylar portions, the intercondylar portion being generally U-shaped and defining a slot located between the femoral condylar portions and adapted to open toward the tibial plateau; a tibial component in the form of a platelike platform adapted to be positioned on the tibial plateau and having laterally spaced-apart outwardly facing condylar surfaces disposed opposite the femoral condylar portions of the femoral component for support thereof and a post extending upwardly into the slot in the femoral component; and an axle extending transversely across the slot in the femoral component through a hole in the post of the tibial component and into aligned holes in leg portions of the intercondylar portion on either side of the slot in the femoral component and connecting the tibial and femoral components together in hinged relation for relative pivotal movement of the components about a transverse pivot axis to afford flexion of the leg at the joint, each hole into which the axle extends in at least one of the components of the prosthesis having a clearance from the axle in a selected zone, the clearance being shaped, dimensioned and positioned to afford relative rotation between the tibial and femoral components about an axis parallel to the axis of the tibia, i.e., to provide rotational laxity in the joint, the rotational laxity being at a maximum when the prosthesis is in a position corresponding generally to full leg flexion and the outwardly facing surfaces of the condylar portions of the femoral component are in contact with the outwardly facing condylar surfaces of the tibial component, the rotational laxity being at a minimum when the prosthesis is in a position corresponding to full leg extension and said surfaces are in contact.

Claim 3

A knee joint prosthesis according to claim 1 wherein there are clearances between lateral faces of the post of the tibial component and the faces of the intercondylar portion defining the slot in the femoral component.

Claim 4

a very small clearance between the top of the axle and the top of the opening to afford a slight upward displacement of the femoral component in a direction away from the tibial component in conjunction with the relative rotation between the components about an axis parallel to the axis of the tibia;

Claim 5

a very small clearance between the top of the axle and the top of the opening to afford a slight upward displacement of the femoral component in a direction away from the tibial component in conjunction with the relative rotation between the components about an axis parallel to the axis of the tibia;

Claim 6

a clearance between the lower portion of the axle and the lower portion of the opening to enable angular displacement of the femoral component in an anterior-posterior direction relative to the tibial component upon flexion of the joint, i.e., flexural laxity.

Claim 7

a clearance between the lower portion of the axle and the lower portion of the opening to enable angular displacement of the femoral component in an anterior-posterior direction relative to the tibial component upon flexion of the joint, i.e., flexural laxity.

Claim 8

A knee joint prosthesis according to claim 1 and further comprising a tibial pin extending through an opening in the tibial component and positioned in the component to extend through the tibial epiphysis.

Claim 9

A knee joint prosthesis according to claim 1 and further comprising a pin connected to the femoral component and positioned on the component to extend through the femoral epiphysis.

Claim 10

A knee joint prosthesis according to claim 4 wherein the pin of the femoral component is unitary with the intercondylar portion of the femoral component and is an extended curved portion of reduced transverse crOss-section merging smoothly with the intercondylar portion of the femoral component.

Claim 11

A knee joint prosthesis according to claim 1 wherein each of the femoral condylar portions of the femoral component is an elongated doubly curved member shaped and dimensioned to extend from generally the anterior to generally the posterior of the femoral condyle and having (a) a varying curvature in the anterior-posterior direction closely matching the anatomical shape of the femoral condyle and (b) in transverse cross-sections along its length a laterally outwardly located essentially flat zone and a laterally inwardly located curved zone that is externally convex, and wherein each condylar surface of the tibial component has in transverse cross-section a shape matching the cross-sectional shape of the condylar surface of the corresponding femoral condylar portion of the femoral component.

Claim 12

A knee joint prosthesis according to claim 6 wherein each condylar surface of the tibial component is a surface generated by a substantially straight anterior-posterior line line moved along a path conforming substantially to the transverse shape of the corresponding condylar surface of the femoral condylar portions of the femoral component.

Claim 13

A knee joint prosthesis according to claim 1 wherein the axis of the axle is positioned to be spaced posteriorally from the axis of the tibia.

Claim 14

A knee joint prosthesis according to claim 1 wherein the distance between the axis of the axle and an imaginary surface matching the lateral profiles of the femoral condylar surfaces of the femoral component is at or near a maximum at the anterior extremity of such surface and generally diminishes at successive points on such surface moving from the anterior extremity toward the posterior extremity of such surface.

Claim 15

A knee joint prosthesis comprising a femoral component having a pin portion positioned on the femoral component to extend through the femoral epiphysis, a pair of laterally spaced-apart femoral condylar portions in the form of anteriorally-posteriorally elongated, doubly curved plate-like members having a varying curvature in the anterior-posterior direction and having outwardly facing condylar surfaces generally matching the anatomical shapes of the respective condylar surfaces of the femoral condyles and an intercondylar portion connected to the inner edges of the respective femoral condylar portions and to the pin, the intercondylar portion having an outwardly open slot located generally between the femoral condylar portions of the femoral component and adapted to face the tibial plateau; a tibial component in the form of a plate-like platform adapted to be positioned on the tibial plateau and including in each of the laterally outward zones of the surfaces thereof facing the condylar surfaces of the femoral condylar portions of the femoral component a condylar surface positioned in facing relation to the corresponding condylar surface of the femoral component, each condylar surface of the tibial component having a shape closely matching in transverse cross-sections along its length the transverse shape of the corresponding condylar surface of the femoral component and being a surface generated by a generally straight anterior-posterior line moved along a path conforming to said transverse shape of said corresponding condylar surface of the femoral component, the tibial component further including a post projecting upwardly from the upper surface thereof and received in the slot in close clearance relation to the walls of the slot; means adapted for securing the tibial component to the tibia; and an axle coupling the tibial component and femoral component together in hinged relation for relative pivotal movement of the components about a transverse pivot axis to afford flexion of the leg at the joint, the axle extending through aligned transverse openings in the post of the tibial component and the intercondylar portion of the femoral component, each axle opening in at least one of tHe components having, with the leg at or near full extension, the following clearance relationships with the axle;

Claim 16

A knee joint prosthesis comprising a femoral component having a pin portion positioned on the femoral component to extend through the femoral epiphysis, a pair of laterally spaced-apart femoral condylar portions in the form of anteriorally-posteriorally elongated, doubly curved plate-like members having a varying curvature in the anterior-posterior direction and having outwardly facing condylar surfaces generally matching the anatomical shapes of the respective condylar surfaces of the femoral condyles and an intercondylar portion connected to the inner edges of the respective femoral condylar portions and to the pin, the intercondylar portion having an outwardly open slot located generally between the femoral condylar portions of the femoral component and adapted to face the tibial plateau; a tibial component in the form of a plate-like platform adapted to be positioned on the tibial plateau and including in each of the laterally outward zones of the surfaces thereof facing the condylar surfaces of the femoral condylar portions of the femoral component a condylar surface positioned in facing relation to the corresponding condylar surface of the femoral component, each condylar surface of the tibial component having a shape closely matching in transverse cross-sections along its length the transverse shape of the corresponding condylar surface of the femoral component and being a surface generated by a generally straight anterior-posterior line moved along a path conforming to said transverse shape of said corresponding condylar surface of the femoral component, the tibial component further including a post projecting upwardly from the upper surface thereof and received in the slot in close clearance relation to the walls of the slot; means adapted for securing the tibial component to the tibia; and an axle coupling the tibial component and femoral component together in hinged relation for relative pivotal movement of the components about a transverse pivot axis to afford flexion of the leg at the joint, the axle extending through aligned transverse openings in the post of the tibial component and the intercondylar portion of the femoral component, each axle opening in at least one of tHe components having, with the leg at or near full extension, the following clearance relationships with the axle;

Claim 17

A knee joint prosthesis according to claim 10 wherein the axis of the axle is positioned to be spaced posteriorally from the axis of the tibia and the distance between the axis of the axle and an imaginary surface defined by the extremities of the condylar surfaces of the femoral condylar portions of the femoral component is at or near maximum at the anterior extremity of said imaginary surface and generally diminished at successive points moving from the anterior extremity toward the posterior extremity and wherein the axle engages the top of the opening when the leg reaches full extension so that flexion substantially beyond full extension is precluded.

Claim 18

A knee joint prosthesis according to claim 10, wherein there is a clearance of outwardly increasing magnitude between the surfaces defining the slot in the intercondylar portion of the femoral component and the lateral faces of the tibial post, moving along an anterior-posterior axis in at least one direction from the zone of a plane parallel to the axis of the tibia and including the axis of the axle.

Claim 19

A knee prosthesis according to claim 12 wherein the surfaces defining the slot in the femoral component are planar and parallel and are positioned on the femoral component to be oriented substantially anteriorally posteriorally of the femur and wherein portions of the lateral faces of the tibial post on at least one side of said plane converge outwardly.

Claim 20

A knee joint prosthesis according to claim 13 wherein said portions of the lateral faces of the tibial post are planar and the planes thereof intersect at an angle equal to the desired maximum degree of rotational laxity permitted by the prothesis.

Claim 21

A knee joint prosthesis according to claim 14 wherein said angle is on the order of 12*.

Claim 22

A knee joint prosthesis according to claim 10 wherein the axle is affixed to the intercondylar portion of the femoral component and all clearances are between the axle and the opening in the tibial post, the opening in the post, as viewed axially, being defined by a substantially arcuate upper wall in relatively closer clearance with the axle, a substantially arcuate lower wall in relatively larger clearance with the axle, and substantially straight side walls connecting and merging smoothly with the upper and lower walls, whereby the rotational laxity afforded by the prosthesis is at a maximum when the axle resides in the power portion of the opening (its position at full leg flexion) and is at a minimum when the axle resides in the upper portion of the opening (its position at full leg extension).

Claim 23

A knee joint prosthesis according to claim 10 wherein the under surface of the tibial compoNent has at least one slot therein for enhancing the fixation of the tibial component to the tibia against movement out of its position as placed.

Claim 24

A knee joint prosthesis according to claim 10 wherein the tibial component has a recess at the medial anterior portion of the upper surface thereof and where the tibial pin includes an enlarged head portion received in said recess.

Claim 25

A knee joint prosthesis according to claim 10, wherein the under surface of the tibial component has at least one boss projecting therefrom for enhancing the fixation of the tibial component to the tibia against movement out of its position as placed.