Implants and Methods of Use

• US 20090228106A1
• Filed: 03/03/2009
• Published: 09/10/2009
• Est. Priority Date: 03/06/2008
• Status: Active Grant

• Current Assignee: Moirai Orthopaedics, LLC
• Original Assignee: Moirai Orthopaedics, LLC
• Inventors: Cook, Stephen D., Strzepa, Peter
• Granted Patent: US 8,177,842 B2
• Time in Patent Office: Days
• US Class Current: 623/14.120
• CPC Class Codes: A61F 2/30756 Cartilage endoprostheses A61F2/3603 takes precedence
• CPC Class Codes: A61F 2/38 for elbows or knees
• CPC Class Codes: A61F 2/3804 for elbows
• CPC Class Codes: A61F 2/40 for shoulders
• CPC Class Codes: A61F 2/4261 for wrists
• CPC Class Codes: A61F 2002/30112 Rounded shapes, e.g. with rounded corners
• CPC Class Codes: A61F 2002/30125 elliptical or oval
• CPC Class Codes: A61F 2002/30299 umbrella-shaped or mushroom-shaped
• CPC Class Codes: A61F 2002/30822 Circumferential grooves
• CPC Class Codes: A61F 2002/30878 with non-sharp protrusions, for instance contacting the bone for anchoring, e.g. keels, pegs, pins, posts, shanks, stems, struts
• CPC Class Codes: A61F 2230/0008 elliptical or oval
• CPC Class Codes: A61F 2230/0093 Umbrella-shaped, e.g. mushroom-shaped
• CPC Class Codes: A61F 2310/00011 Metals or alloys
• CPC Class Codes: A61F 2310/00161 Carbon; Graphite
• CPC Class Codes: A61F 2310/00173 Graphite
• CPC Class Codes: A61F 2310/00179 Ceramics or ceramic-like structures
• CPC Class Codes: A61F 2310/00574 Coating or prosthesis-covering structure made of carbon, e.g. of pyrocarbon
• CPC Class Codes: A61F 2310/00796 Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite
• CPC Class Codes: Y10S 623/908 Bone

Abstract

Implant devices, and method of using the same, are provided. The implant devices have circular, or oblong, articular ends. The articular ends have a convex upper face and a concave lower face, the convex upper face blending to the concave lower face, and the concave lower face having a curvature less than the curvature of the convex upper face. The implant devices further have a stem extending from the concave lower face away from the upper face, the stem having a maximum radius at the convex lower face and tapering to lesser radius along the length of the stem.

Claims

1. ) An implant comprising:

an articular end having a circular perimeter approximately defined by a diameter, a convex upper face, and a concave lower face, the convex upper face having a first spherical radius and the concave lower face having a second spherical radius, wherein the first spherical radius is relatively small if the diameter is relatively large; and

a stem extending from the concave lower face away from the convex upper face along a vertical axis, the stem having a maximum stem circular perimeter at the intersection of the stem and the concave lower face, the maximum stem circular perimeter less than the articular end circular perimeter.

2. ) The implant of claim 1, wherein the stem circular perimeter decreases from a maximum stem circular perimeter to a lesser stem circular perimeter along the vertical axis of the stem.

3. ) The implant of claim 1, wherein the stem has a cylindrical portion extending from the concave lower face away from the convex upper face along the vertical axis, and a conical portion extending from the cylindrical portion away from the convex upper face along the vertical axis.

4. ) The implant of claim 3, wherein the cylindrical portion has a length ranging from about one millimeter to about five millimeters;

and the conical portion has a length ranging from about two millimeters to about fifteen millimeters.

5. ) The implant of claim 1, wherein the diameter ranges from about 17.5 millimeters to about 20 millimeters and the first spherical radius ranges from about 25 millimeters to about 30 millimeters, preferably about 28 millimeters.

6. ) The implant of claim 1, wherein the first spherical radius is relatively large if the diameter is relatively small.

7. ) The implant of claim 6, wherein the diameter ranges from about 10 millimeters to about 15 millimeters and the first spherical radius ranges from about 30 millimeters to about 40 millimeters, preferably about 32 millimeters.

8. ) The implant of claim 1, wherein the first spherical radius is lesser than the second spherical radius if the diameter is relatively large.

9. ) The implant of claim 8, wherein the first spherical radius is about 28 millimeters, the second spherical radius is about 29.5 millimeters and the diameter is greater than about 17 millimeters.

10. ) The implant of claim 1, wherein the first spherical radius is greater than the second spherical radius if the diameter is relatively small.

11. ) The implant of claim 10, wherein the first spherical radius is about 32 millimeters, the second spherical radius is about 29.5 millimeters and the diameter is less than about 17 millimeters.

12. ) The implant of claim 1, wherein the diameter is relatively large, the first spherical radius is about 28 millimeters, the second spherical radius is about 29.5, the convex upper face and the concave lower face are separated by about 2.5 millimeters along a vertical axis of symmetry of the implant, and the center of curvature of the first spherical radius and a center of curvature of the second spherical radius align with the vertical axis of symmetry of the implant.

13. ) The implant of claim 1, wherein the diameter is relatively small, the first spherical radius is about 32 millimeters, the second spherical radius is about 29.5 and the first spherical radius is about concentric with the second spherical radius.

14. ) The implant of claim 3, wherein a portion of the conical portion of the stem is comprised of circumferential grooves.

15. ) The implant of claim 14, wherein the circumferential grooves are defined by a partial torus having a tubular radius of from about 0.25 millimeters to about 1.5 millimeters, and the circumferential grooves are spaced apart at a distance of from about 1 millimeter to about 3 millimeters from each other.

16. ) The implant of claim 1, wherein the articular end and the stem comprise graphite and pyrocarbon.

17. ) The implant of claim 16, wherein the articular end and the stem comprise a graphite core and a pyrocarbon coating, the pyrocarbon coating having an elastic modulus from about 15 GPa to about 22 GPa, the pyrocarbon coating having an average thickness ranging from about 100 to about 1000 microns.

18. ) The implant of claim 17, wherein the pyrocarbon coating has an elastic modulus of about 20 GPa and a strength of at least 400 MPa.

19. ) The implant of claim 16, wherein the upper face and circular perimeter of the articular end are polished, and the lower face and stem are coated with hydroxyapatite.

20. ) An implant comprising:

an articular end having an oval perimeter, a convex upper face, and a concave lower face, the convex upper face having a first circular pitch radius and a first circular roll radius, at least a portion of the concave lower face having a spherical radius, the convex upper face blending into a rim, wherein at least a first and second portion of the rim extends at least a first distance along the vertical axis and a third and fourth portion of the rim tapers inward along the vertical axis, the rim blending into the concave lower face; and

a stem extending from the concave lower face away from the convex upper face, the stem having an oval shaped perimeter in planes perpendicular to the vertical axis.

21. ) The implant of claim 20, wherein the oval articular end has a maximum length, along the horizontal axis of from about 15 millimeters to about 40 millimeters;

the oval articular end has a maximum length, along the depth axis, ranging from about 10 millimeters to about 30 millimeters; and

the implant has a maximum length along the vertical axis ranging from about 10 millimeters to about 35 millimeters.

22. ) The implant of claim 20, wherein the stem has a first portion and a second portion, the first portion extending from the lower concave face a length in the vertical direction away from the upper convex face, the second portion extending from the first portion a length in the vertical direction away from the upper convex face, wherein the first portion tapers inward along its horizontal axis in the vertical direction and has a uniform length along its depth axis in the vertical direction, the second portion tapers inward along its horizontal axis and its depth axis in the vertical direction, the first and second portion blend into each other, the length of the first portion along the vertical is selected from the group consisting of 2 millimeters to about 10 millimeters and from about 2 millimeters to about 8 millimeters, the length of the second portion along the vertical is selected from the group consisting of from about 2 millimeters to about 25 millimeters, from about 5 millimeters to about 20 millimeters, and from about 5 millimeters to about 10 millimeters.

23. ) The implant of claim 22, wherein the second portion of the stem comprises grooves.

24. ) The implant of claim 23, wherein the grooves are defined by a partial, oval, non-planar torus having a tubular radius of from about 0.25 millimeters to about 1.5 millimeters, and the grooves are spaced apart at a distance of from about 1 millimeter to about 3 millimeters from each other.

25. ) The implant of claim 24, wherein the articular end and the stem comprise graphite and pyrocarbon.

26. ) The implant of claim 25, wherein the articular end and the stem comprise a graphite core and a pyrocarbon coating, the pyrocarbon coating having an elastic modulus from about 15 GPa to about 22 GPa, the pyrocarbon coating having an average thickness ranging from about 100 to about 1000 microns.

27. ) The implant of claim 26, wherein the pyrocarbon coating has an elastic modulus of about 20 GPa and a strength of at least 400 MPa.

28. ) The implant of claim 27, wherein the upper face and oval perimeter of the articular end are polished, and the lower face and stem are coated with hydroxyapatite.

29. ) A method of repair of articular cartilage comprising:

locating articular cartilage having a lesion;

utilizing an implant having dimensions compatible with the lesion, wherein the implant comprises;

an articular end having a circular perimeter approximately defined by a diameter, a convex upper face, and a concave lower face, the convex upper face having a first spherical radius and the concave lower face having a second spherical radius, wherein the first spherical radius is relatively small if the diameter is relatively large; and

a stem extending from the concave lower face away from the convex upper face along a vertical axis, the stem having a maximum stem circular perimeter at the intersection of the stem and the concave lower face, the maximum stem circular perimeter less than the articular end circular perimeter

forming a cavity in the cartilage and subchondral bone and cancellous bone; and

engaging the implant with the cavity so that the lower surface abuts against the prepared subchondral bone and the stem abuts against the prepared cancellous bone.

30. ) The method of claim 29, wherein forming the cavity includes placement of autograft, allograft bone, or various bone graft substitute material into the lesion.

31. ) A method of repair of articular cartilage comprising:

locating articular cartilage having a lesion;

utilizing an implant of having dimensions compatible with the lesion, wherein the implant comprises;

an articular end having an oval perimeter, a convex upper face, and a concave lower face, the convex upper face having a first circular pitch radius and a first circular roll radius, at least a portion of the concave lower face having a spherical radius, the convex upper face blending into a rim, wherein at least a first and second portion of the rim extends at least a first distance along the vertical axis and a third and fourth portion of the rim tapers inward along the vertical axis, the rim blending into the concave lower face; and

a stem extending from the concave lower face away from the convex upper face, the stem having an oval shaped perimeter in planes perpendicular to the vertical axis;

forming a cavity in the cartilage and subchondral bone and cancellous bone; and

engaging the implant with the cavity so that the lower surface abuts against the prepared subchondral bone and the stem abuts against the prepared cancellous bone.

32. ) The method of claim 31, wherein forming the cavity includes placement of autograft, allograft bone, or various bone graft substitute material into the lesion.