# US 8,784,496 B2 · Orthopaedic knee prosthesis having controlled condylar curvature

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- Number: US 8,784,496 B2
- Document ID: US8784496B2
- Status: Granted
- Kind: B2
- Application number: 13/487,990
- Filed: 2012-06-04
- Published: 2012-09-20
- Granted: 2014-07-22
- Earliest claimed: 2008-06-30
- Assignees: Depuy (Ireland)
- Applicants: Christel M. Wagner; Dimitri Sokolov; Jordan S. Lee; John L. Williams; Said T. Gomaa; John M. Armacost
- Inventors: Christel M. Wagner; Dimitri Sokolov; Jordan S. Lee; John L. Williams; Said T. Gomaa; John M. Armacost
- Web page: https://patentgrep.com/patent/US8784496B2

## CPC

- A61F 2/3836: {Special connection between upper and lower leg, e.g. constrained}
- A61F 2/38: for elbows or knees
- A61F 2/3868: {with sliding tibial bearing}
- A61F 2/3859: {Femoral components}
- A61F 2/3886: {for stabilising knees against anterior or lateral dislocations}
- A61F 2002/30116: {partial circles, i.e. circular segments}
- A61F 2002/30332: {Conically- or frustoconically-shaped protrusion and recess}
- A61F 2220/0033: made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit
- A61F 2230/0006: circular
- A61F 2310/00179: Ceramics or ceramic-like structures
- A61F: FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS (dental prosthetics A61C)

## Abstract

An orthopaedic knee prosthesis includes a tibial bearing and a femoral component configured to articulate with the tibial bearing. The femoral component includes a condyle surface curved in the sagittal plane. The radius of curvature of the condyle surface decreases gradually between early-flexion and mid-flexion. Additionally, in some embodiments, the radius of curvature may be increased during mid-flexion.

## Claims

### Claim 1

An orthopaedic knee prosthesis comprising:
a femoral component having a condyle surface curved in the sagittal plane; and
a tibial bearing having a bearing surface configured to articulate with the condyle surface of the femoral component,
wherein the condyle surface (i) contacts the bearing surface at a first contact point on the condyle surface at a first degree of flexion, the first degree of flexion being less than about 30 degrees, (ii) contacts the bearing surface at a second contact point on the condyle surface at a second degree of flexion, the second degree of flexion being in the range of 45 degrees to 90 degrees, and (iii) contacts the bearing surface at a third contact point on the condyle surface at a third degree of flexion greater than the second degree of flexion,
wherein (i) the condyle surface in the sagittal plane has a first radius of curvature at the first contact point, (ii) the condyle surface in the sagittal plane has a second radius of curvature at the second contact point, (iii) the condyle surface in the sagittal plane has a third radius of curvature at the third contact point, (iv) the ratio of the first radius of curvature to the second radius of curvature is in the range of 1.10 to 1.45, and (v) the third radius of curvature being greater than the second radius of curvature by at least 0.5 millimeters,
wherein the condyle surface in the sagittal plane includes a first curved surface section defined between the first contact point and the second contact point, the first curved surface section having a non-constant radius of curvature.

### Claim 2 (depends on 1)

The orthopaedic knee prosthesis of claim 1, wherein ratio of the first radius of curvature to the second radius of curvature is about 1.35.

### Claim 3 (depends on 1)

The orthopaedic knee prosthesis of claim 1, wherein the first degree of flexion is in the range of 0 degrees to 10 degrees and the second degree of flexion is in the range of 60 degrees to 70 degrees.

### Claim 4 (depends on 3)

The orthopaedic knee prosthesis of claim 3, wherein the first degree of flexion is about 5 degrees and the second degree of flexion is about 65 degrees.

### Claim 5 (depends on 1)

The orthopaedic knee prosthesis of claim 1, wherein the ratio of the first radius of curvature to the third radius of curvature is in the range of 1.10 to 1.45.

### Claim 6 (depends on 5)

The orthopaedic knee prosthesis of claim 5, wherein the ratio of the first radius of curvature to the third radius of curvature is about 1.28.

### Claim 7 (depends on 1)

The orthopaedic knee prosthesis of claim 1, wherein the third degree of flexion is in the range of 80 degrees to 110 degrees.

### Claim 8 (depends on 7)

The orthopaedic knee prosthesis of claim 7, wherein the third degree of flexion is about 90 degrees.

### Claim 9 (depends on 1)

The orthopaedic knee prosthesis of claim 1, wherein:
(i) the condyle surface contacts the bearing surface at a fourth contact point on the condyle surface at a fourth degree of flexion, the fourth degree of flexion being greater than the third degree of flexion, and
(ii) the condyle surface in the sagittal plane has a fourth radius of curvature at the fourth contact point, the fourth radius of curvature being less than the third radius of curvature.

### Claim 10 (depends on 9)

The orthopaedic knee prosthesis of claim 9, wherein the ratio of the first radius of curvature to the fourth radius of curvature is in the range of 1.10 to 1.45.

### Claim 11 (depends on 10)

The orthopaedic knee prosthesis of claim 10, wherein the ratio of the first radius of curvature to the fourth radius of curvature is about 1.305.

### Claim 12 (depends on 9)

The orthopaedic knee prosthesis of claim 9, wherein the fourth degree of flexion is in the range of 90 degrees to 120 degrees.

### Claim 13 (depends on 12)

The orthopaedic knee prosthesis of claim 12, wherein the third degree of flexion is about 105 degrees.

### Claim 14 (depends on 9)

The orthopaedic knee prosthesis of claim 9, wherein the ratio of the first radius of curvature to the second radius of curvature is about 1.35, the ratio of the first radius of curvature to the third radius of curvature is about 1.28, and the ratio of the first radius of curvature to the third radius of curvature is about 1.305.

### Claim 15 (depends on 9)

The orthopaedic knee prosthesis of claim 9, wherein:
the condyle surface of the femoral component in the sagittal plane includes (i) a second curved surface section defined between the second contact point and the third contact point and (ii) a third curved surface section defined between the third contact point and the fourth contact point,
the second curved surface section having a substantially constant radius of curvature substantially equal to the third radius of curvature, and
the third curved surface section having a substantially constant radius of curvature substantially equal to the fourth radius of curvature.

### Claim 16 (depends on 1)

The orthopaedic knee prosthesis of claim 1, wherein:
the condyle surface contacts the bearing surface at a plurality of contact points between the first contact point and the second contact point when the femoral component is moved from the first degree of flexion to the second degree of flexion, and
each contact point of the plurality of contact points is defined by a ray extending from a common origin to the respective contact point of the plurality of contact points, each ray having a length defined by the following polynomial equation:
rθ=(a+(b*θ)+(c*θ2)+(d*θ3)),
wherein rθ is the length of the ray defining a contact point at θ degrees of flexion, a is a coefficient value between 20 and 50, and b is a coefficient value in a range selected from the group consisting of: −0.30<b<0.00, 0.00<b<0.30, and b=0,
wherein when b is in the range of −0.30<b<0.00, (i) c is a coefficient value between 0.00 and 0.012 and (ii) d is a coefficient value between −0.00015 and 0.00,
wherein when b is in the range of 0<b<0.30, (i) c is a coefficient value between −0.010 and 0.00 and (ii) d is a coefficient value between −0.00015 and 0.00, and
wherein when b is equal to 0, (i) c is a coefficient value in a range selected from the group consisting of: −0.0020<c<0.00 and 0.00<c<0.0025 and (ii) d is a coefficient value between −0.00015 and 0.00.

### Claim 17 (depends on 16)

The orthopaedic knee prosthesis of claim 16, wherein:
the first radius of curvature has an origin, and
the distance between the origin of the first radius of curvature and the common origin of the rays is in the range of 0 and 10 millimeters.

### Claim 18 (depends on 1)

The orthopaedic knee prosthesis of claim 1, wherein the femoral component is a posterior cruciate-retaining femoral component.

### Claim 19

An orthopaedic knee prosthesis comprising:
a femoral component having a condyle surface curved in the sagittal plane; and
wherein the condyle surface (i) contacts a bearing surface of a tibial bearing at a first contact point on the condyle surface at a first degree of flexion, the first degree of flexion being less than about 30 degrees, (ii) contacts the bearing surface at a second contact point on the condyle surface at a second degree of flexion, the second degree of flexion being in the range of 45 degrees to 90 degrees, and (iii) contacts the bearing surface at a plurality of contact points between the first contact point and the second contact point when the femoral component is moved from the first degree of flexion to the second degree of flexion,
wherein each contact point of the plurality of contact points is defined by a ray extending from a common origin to the respective contact point of the plurality of contact points, each ray having a length defined by the following polynomial equation:
i rθ=(a+(b*θ)+(c*θ2)+(d*θ3))
wherein rθ is the length of the ray defining a contact point at θ degrees of flexion, a is a coefficient value between 20 and 50, and b is a coefficient value in a range selected from the group consisting of: −0.30<b<0.00, 0.00<b<0.30, and b=0,
wherein when b is in the range of −0.30<b<0.00, (i) c is a coefficient value between 0.00 and 0.012 and (ii) d is a coefficient value between −0.00015 and 0.00,
wherein when b is in the range of 0<b<0.30, (i) c is a coefficient value between −0.010 and 0.00 and (ii) d is a coefficient value between −0.00015 and 0.00, and
wherein when b is equal to 0, (i) c is a coefficient value in a range selected from the group consisting of: −0.0020<c<0.00 and 0.00<c<0.0025 and (ii) d is a coefficient value between −0.00015 and 0.00.