Self-aligning knee prosthesis
A prosthesis for repairing a knee is made with an insert sandwiched between a femoral component and a tibial tray. The parts are shaped so that both the femoral component and the tibial tray will slidingly interface with the insert during motion of the knee. At regions where the femoral component interfaces with the insert during extension and during an initial range of flexion of the knee, the femoral component's radius of curvature (R 1 ) for flexion rotation is larger than its radius of curvature (R 3 ) for varus/valgus rotation. In a preferred embodiment, the surface of the tibial tray is convex and spherically curved, and the insert is free to move in both the posterior-anterior direction and the medial-lateral direction with respect to the tibial tray.
1. A knee joint prosthesis comprising:
a femoral component having a fixation surface configured for attaching to a femur and a sliding surface;
a tibial tray having a fixation surface configured for attaching to a tibial and a sliding surface; and
an insert that fits between the femoral component and the tibial tray when the prosthesis is installed in a subject, the insert having a femoral side and a tibial side, wherein the femoral side is shaped to slidingly interface with the sliding surface of the femoral component during flexion of the knee and the tibial side is shaped to slidingly interface with the sliding surface of the tibial tray,
wherein, at regions where the sliding surface of the femoral component interfaces with the insert during extension and an initial range of flexion of the knee, a radius of curvature (R 1 ) of the sliding surface of the femoral component for flexion rotation is larger than a radius of curvature (R 3 ) of the sliding surface of the femoral component for varus/valgus rotation, and
wherein the sliding surface of the tibial tray is spherically or toroidally curved.
2. The prosthesis of claim 1 , wherein the sliding surface of the tibial tray is convex and the tibial side of the insert is concave.
3. The prosthesis of claim 1 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 .
4. The prosthesis of claim 1 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is less than R 1 .
5. The prosthesis of claim 1 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is larger than or equal to R 3 , and wherein R 2 is less than R 1 .
6. The prosthesis of claim 5 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 , R 2 is between about 1 and 1.2 times as large as R 3 , and the transition between R 1 and R 2 occurs at between about 280° and about 55° with respect to a proximal-distal axis.
7. The prosthesis of claim 6 , wherein the sliding surface of the tibial tray is convex and the tibial side of the insert is concave.
8. A knee joint prosthesis comprising:
a femoral component having a fixation surface configured for attaching to a femur and a sliding surface;
a tibial tray having a fixation surface configured for attaching to a tibial and a sliding surface; and
an insert that fits between the femoral component and the tibial tray when the prosthesis is installed in a subject, the insert having a femoral side and a tibial side, wherein the femoral side is shaped to slidingly interface with the sliding surface of the femoral component during flexion of the knee and the tibial side is shaped to slidingly interface with the sliding surface of the tibial tray,
wherein, at regions where the sliding surface of the femoral component interfaces with the insert during extension and an initial range of flexion of the knee, a radius of curvature (R 1 ) of the sliding surface of the femoral component for flexion rotation is larger than a radius of curvature (R 3 ) of the sliding surface of the femoral component for varus/valgus rotation, and
wherein the insert is free to move in both the posterior-anterior direction and the medial-lateral direction with respect to the tibial tray.
9. The prosthesis of claim 8 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 .
10. The prosthesis of claim 8 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is less than R 1 .
11. The prosthesis of claim 8 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is larger than or equal to R 3 , end wherein R 2 is less than R 1 .
12. The prosthesis of claim 11 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 , R 2 is between about 1 and 1.2 times as large as R 3 , and the transition between R 1 and R 2 occurs at between about 28° and about 55° with respect to a proximal-distal axis.
13. A knee joint prosthesis comprising:
a femoral component having a fixation surface configured for attaching to a femur and a sliding surface;
a tibial tray having a fixation surface configured for attaching to a tibial and a sliding surface; and
an insert that fits between the femoral component and the tibial tray when the prosthesis is installed in a subject, the insert having a femoral side and a tibial side, wherein the femoral side is shaped to slidingly interface with the sliding surface of the femoral component during flexion of the knee and the tibial side is shaped to slidingly interface with the sliding surface of the tibial tray,
wherein, at regions where the sliding surface of the femoral component interfaces with the insert during extension and an initial range of flexion of the knee, a radius of curvature (R 1 ) of the sliding surface of the femoral component for flexion rotation is larger than a radius of curvature (R 3 ) of the sliding surface of the femoral component for varus/valgus rotation,
wherein the sliding surface of the tibial tray is spherically curved and convex, and the tibial side of the insert is concave, and
wherein the insert is free to move in both the posterior-anterior direction and the medial-lateral direction with respect to the tibial tray.
14. The prosthesis of claim 13 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 .
15. The prosthesis of claim 13 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is less than R 1 .
16. The prosthesis of claim 13 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is larger than or equal to R 3 , and wherein R 2 is less than R 1 .
17. The prosthesis of claim 16 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 , R 2 is between about 1 and 1.2 times as large as R 3 , and the transition between R 1 and R 2 occurs at between about 28° and about 55° with respect to a proximal-distal axis.
18. A joint prosthesis comprising:
a first component having a fixation surface configured for attaching to a first bone and a sliding surface;
a second component having a fixation surface configured for attaching to a second bone and a sliding surface; and
an insert that fits between the first component and the second component when the prosthesis is installed in a subject, the insert having a first side and a second side, wherein the first side is shaped to slidingly interface with the sliding surface of the first component during flexion of the joint and the second side is shaped to slidingly interface with the sliding surface of the second component,
wherein, at regions where the sliding surface of the first component interfaces with the insert during extension and an initial range of flexion of the joint, a radius of curvature (R 1 ) of the sliding surface of the first component for flexion rotation is larger than a radius of curvature (R 3 ) of the sliding surface of the first component for rotation about an axis that is perpendicular to the coronal plane of the subject, and
wherein the sliding surface of the second component is spherically or toroidally curved.
19. A joint prosthesis comprising:
a first component having a fixation surface configured for attaching to a first bone and a sliding surface;
a second component having a fixation surface configured for attaching to a second bone and a sliding surface; and
an insert that fits between the first component and the second component when the prosthesis is installed in a subject, the insert having a first side and a second side, wherein the first side is shaped to slidingly interface with the sliding surface of the first component during flexion of the joint and the second side is shaped to slidingly interface with the sliding surface of the second component,
wherein, at regions where the sliding surface of the first component interfaces with the insert during extension and an initial range of flexion of the joint, a radius of curvature (R 1 ) of the sliding surface of the first component for flexion rotation is larger than a radius of curvature (R 3 ) of the sliding surface of the first component for rotation about an axis that is perpendicular to the coronal plane of the subject, and
wherein the insert is free to move in both the posterior-anterior direction and the medial-lateral direction with respect to the second component.
20. The prosthesis of claim 1 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly.
21. The prosthesis of claim 1 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly by about 5°.
22. The prosthesis of claim 1 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is less than 90°.
23. The prosthesis of claim 1 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is about 80°.
24. The prosthesis of claim 8 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly.
25. The prosthesis of claim 8 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly by about 5°.
26. The prosthesis of claim 8 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is less than 90°.
27. The prosthesis of claim 8 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is about 80°.
28. The prosthesis of claim 13 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly.
29. The prosthesis of claim 13 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly by about 5°.
30. The prosthesis of claim 13 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is less than 90°.
31. The prosthesis of claim 13 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is about 80°.
32. A knee joint prosthesis comprising:
a unicondylar femoral component having a fixation surface configured for attaching to a femur and a sliding surface;
a unicondylar tibial tray having a fixation surface configured for attaching to a tibial and a sliding surface; and
a unicondylar insert that fits between the femoral component and the tibial tray when the prosthesis is installed in a subject, the insert having a femoral side and a tibial side, wherein the femoral side is shaped to slidingly interface with the sliding surface of the femoral component during flexion of the knee and the tibial side is shaped to slidingly interface with the sliding surface of the tibial tray,
wherein, at regions where the sliding surface of the femoral component interfaces with the insert during extension and an initial range of flexion of the knee, a radius of curvature (R 1 ) of the sliding surface of the femoral component for flexion rotation is larger than a radius of curvature (R 3 ) of the sliding surface of the femoral component for varus/valgus rotation, and
wherein the sliding surface of the tibial tray is spherically or toroidally curved.
33. The prosthesis of claim 32 , wherein the sliding surface of the tibial tray is convex and the tibial side of the insert is concave.
34. The prosthesis of claim 32 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 .
35. The prosthesis of claim 32 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component far flexion rotation is less than R 1 .
36. The prosthesis of claim 32 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is larger than or equal to R 3 , and wherein R 2 is less than R 1 .
37. The prosthesis of claim 36 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 , R 2 is between about 1 and 1.2 times as large as R 3 , and the transition between R 1 and R 2 occurs at between about 28° and about 55° with respect to a proximal-distal axis.
38. The prosthesis of claim 37 , wherein the sliding surface of the tibial tray is convex and the tibial side of the insert is concave.
39. The prosthesis of claim 32 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly.
40. The prosthesis of claim 32 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly by about 5°.
41. The prosthesis of claim 32 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is less than 90°.
42. The prosthesis of claim 32 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is about 80°.
43. A knee joint prosthesis comprising:
a unicondylar femoral component having a fixation surface configured for attaching to a femur and a sliding surface;
a unicondylar tibial tray having a fixation surface configured for attaching to a tibial and a sliding surface; and
a unicondylar insert that fits between the femoral component and the tibial way when the prosthesis is installed in a subject, the insert having a femoral side and a tibial side, wherein the femoral side is shaped to slidingly interface with the sliding surface of the femoral component during flexion of the knee and the tibial side is shaped to slidingly interface with the sliding surface of the tibial tray,
wherein, at regions where the sliding surface of the femoral component interfaces with the insert during extension and an initial range of flexion of the knee, a radius of curvature (R 1 ) of the sliding surface of the femoral component for flexion rotation is larger than a radius of curvature (R 3 ) of the sliding surface of the femoral component for varus/valgus rotation, and
wherein the insert is free to move in both the posterior-anterior direction and the medial-lateral direction with respect to the tibial tray.
44. The prosthesis of claim 43 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 .
45. The prosthesis of claim 43 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is less than R 1 .
46. The prosthesis of claim 43 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is larger than or equal to R 3 , and wherein R 2 is less than R 1 .
47. The prosthesis of claim 46 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 , R 2 is between about 1 and 1.2 times as large as R 3 , and the transition between R 1 and R 2 occurs at between about 28° and about 55° with respect to a proximal-distal axis.
48. The prosthesis of claim 43 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly.
49. The prosthesis of claim 43 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly by about 5°.
50. The prosthesis of claim 43 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is less than 90°.
51. The prosthesis of claim 43 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is about 80°.
52. A knee joint prosthesis comprising:
a unicondylar femoral component having a fixation surface configured for attaching to a femur and a sliding surface;
a unicondylar tibial tray having a fixation surface configured for attaching to a tibial and a sliding surface; and
a unicondylar insert that fits between the femoral component and the tibial tray when the prosthesis is installed in a subject, the insert having a femoral side and a tibial side, wherein the femoral side is shaped to slidingly interface with the sliding surface of the femoral component during flexion of the knee and the tibial side is shaped to slidingly interface with the sliding surface of the tibial tray,
wherein, at regions where the sliding surface of the femoral component interfaces with the insert during extension and an initial range of flexion of the knee, a radius of curvature (R 1 ) of the sliding surface of the femoral component for flexion rotation is larger than a radius of curvature (R 3 ) of the sliding surface of the femoral component for varus/valgus rotation,
wherein the sliding surface of the tibial tray is spherically curved and convex, and the tibial side of the insert is concave, and
wherein the insert is free to move in both the posterior-anterior direction and the medial-lateral direction with respect to the tibial tray.
53. The prosthesis of claim 52 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 .
54. The prosthesis of claim 52 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is less than R 1 .
55. The prosthesis of claim 52 , wherein, at regions where the sliding surface of the femoral component interfaces with the insert when flexion of the knee exceeds the initial range, a radius of curvature (R 2 ) of the sliding surface of the femoral component for flexion rotation is larger than or equal to R 3 , and wherein R 2 is less than R 1 .
56. The prosthesis of claim 55 , wherein R 1 is between about 1.5 and 1.9 times as large as R 3 , R 2 is between about 1 and 1.2 times as large R 3 , and the transition between R 1 and R 2 occurs at between about 28° and about 55° with respect to a proximal-distal axis.
57. The prosthesis of claim 52 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly.
58. The prosthesis of claim 52 , wherein the femoral component is tapered so that it is wider posteriorly than anteriorly by about 5°.
59. The prosthesis of claim 52 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is less than 90°.
60. The prosthesis of claim 52 , wherein an angle between the posterior cut surface and the distal cut surface of the femoral component is about 80°.