Articulating spinal implant

• US 6,179,874 B1
• Filed: 04/23/1999
• Issued: 01/30/2001
• Est. Priority Date: 04/23/1998
• Status: Expired due to Fees

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: Cauthen Research Group, Inc.
• Inventors: Cauthen, Joseph C.
• Primary Examiner(s): Willse, David H.
• Application Number:
  US09/298,524
• Time in Patent Office: 648 Days
• Field of Search: 623/17
• US Class Current: 623/17.14
• CPC Class Codes: A61B 17/1604 Chisels; Rongeurs; Punches; Stamps
• CPC Class Codes: A61B 17/1671 for the spine
• CPC Class Codes: A61F 2/30724 Spacers for centering an implant in a bone cavity, e.g. in a cement-receiving cavity
• CPC Class Codes: A61F 2/30744 End caps, e.g. for closing an endoprosthetic cavity
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2/4425 made of articulated components
• CPC Class Codes: A61F 2/446 having a circular or elliptical cross-section substantially parallel to the axis of the spine, e.g. cylinders or frustocones
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/2817 Bone stimulation by chemical reactions or by osteogenic or biological products for enhancing ossification, e.g. by bone morphogenetic or morphogenic proteins [BMP] or by transforming growth factors [TGF]
• CPC Class Codes: A61F 2002/2821 Bone stimulation by electromagnetic fields or electric current for enhancing ossification
• CPC Class Codes: A61F 2002/2835 Bone graft implants for filling a bony defect or an endoprosthesis cavity, e.g. by synthetic material or biological material
• CPC Class Codes: A61F 2002/30062 (bio)absorbable, biodegradable, bioerodable, (bio)resorbable, resorptive
• CPC Class Codes: A61F 2002/30232 Half-cylinders
• CPC Class Codes: A61F 2002/30329 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2002/30385 the rib and groove having non-parallel, e.g. conically-tapered, cooperating sides, e.g. having a trapezoidal front cross-section
• CPC Class Codes: A61F 2002/30387 Dovetail connection
• CPC Class Codes: A61F 2002/3039 with possibility of relative movement of the rib within the groove
• CPC Class Codes: A61F 2002/30393 with additional means for limiting said rotation
• CPC Class Codes: A61F 2002/30397 Limited lateral translation of the rib within a larger groove
• CPC Class Codes: A61F 2002/30515 : using a locking wedge or block
• CPC Class Codes: A61F 2002/30593 : hollow
• CPC Class Codes: A61F 2002/30649 : Ball-and-socket joints
• CPC Class Codes: A61F 2002/30662 : with rotation-limiting means
• CPC Class Codes: A61F 2002/30663 : multiaxial, e.g. biaxial; multipolar, e.g. bipolar or having an intermediate shell articulating between the ball and the socket
• CPC Class Codes: A61F 2002/30672 : temporary
• CPC Class Codes: A61F 2002/30785 : parallel
• CPC Class Codes: A61F 2002/30787 : inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/3081 : inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30827 : Plurality of grooves
• CPC Class Codes: A61F 2002/3085 : with a threaded, e.g. self-tapping, bone-engaging surface, e.g. external surface
• CPC Class Codes: A61F 2002/30879 : Ribs
• CPC Class Codes: A61F 2002/30934 : Special articulating surfaces
• CPC Class Codes: A61F 2002/30975 : made of two halves
• CPC Class Codes: A61F 2002/443 : having two transversal endplates and at least one intermediate component
• CPC Class Codes: A61F 2210/0004 : bioabsorbable
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2310/00017 : Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00029 : Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium
• CPC Class Codes: A61F 2310/00059 : Chromium or Cr-based alloys
• CPC Class Codes: A61F 2310/00239 : containing zirconia or zirconium oxide ZrO2
• CPC Class Codes: A61F 2310/00293 : containing a phosphorus-containing compound, e.g. apatite
• CPC Class Codes: A61F 2310/00401 : Coating made of iron, of stainless steel or of other Fe-based alloys
• CPC Class Codes: A61F 2310/00407 : Coating made of titanium or of Ti-based alloys
• CPC Class Codes: A61F 2310/00413 : Coating made of cobalt or of Co-based alloys
• CPC Class Codes: A61F 2310/00449 : Coating made of chromium or Cr-based alloys
• CPC Class Codes: A61F 2310/00634 : Coating made of zirconium oxide or hydroxides

Abstract

A spinal implant for intervertebral disc replacement. The implant is formed from two hemicylindrical elements, each engaging one of an adjacent pair of vertebrae. An articulating ball-and-socket joint between the two elements resists compression and lateral movement between the vertebra, but allows pivotal movement, thereby preserving mobility. Fusion chambers are provided for allowing bone ingrowth to fuse the elements to the vertebrae. Biocompatible, bioreabsorbable struts, shims, fillers and/or end caps are provided for temporary stabilization of the first and second hemicylindrical elements. Bone chips removed from the vertebrae during implantation or bone growth stimulators can be inserted into the fusion chamber or otherwise applied to the implant to enhance bone ingrowth.

Claims

1. A spinal implant comprising:

(a) a first element comprising a first articulation surface, a first outer surface, and a first connection means for engaging a first vertebra, wherein said first outer surface comprises a first radiused outer wall;

(b) a second element comprising a second articulation surface, a second outer surface, and a second connection means for engaging a second vertebra, wherein said second outer surface comprises a second radiused outer wall, wherein at least one of said connection means comprises a fusion chamber located between said articulation surface and said outer surface, and said outer surface comprises at least one opening for facilitating bone ingrowth into said fusion chamber;

(c) a tail wall and a leading wall; and

(d) an articulation means, coupling said first articulation surface to said second articulation surface, for allowing relative movement between said first element and said second element, wherein said articulation means resist axial compression in the direction of a support axis, wherein said first articulation surface abuts said second articulation surface to form said articulation means, said articulation means comprising a channel along said second element and a rocker along said first element, and wherein at least a portion of said rocker is engaged within said channel.

2. The spinal implant of claim 1, wherein said channel along said second element has a width at a top and a bottom of said channel which is greater than the width at a point, between said top and said bottom.

3. The spinal implant of claim 1, wherein said channel along said second element has a channel width at a first end and a second end which is greater then the channel width at a point between said first end and said second end.

4. The spinal implant of claim 1, wherein said second connection means comprises a second fusion chamber located between said second articulation surface and said second outer surface, and said second outer surface comprises at least one opening for facilitating bone ingrowth into said second fusion chamber.

5. The spinal implant of claim 1, wherein said first radiused outer Wall ain said second radiused outer wall comprise a securing means for securing said spinal implant within a cavity between said first vertebra and said second vertebra.

6. The spinal implant of claim 5, wherein said securing means comprises a threaded walls on said first and second radiused outer surface.

7. The spinal implant of claim 1, wherein said first radiused outer wall and said second radiused outer wall comprise a hemicylindrical outer surface.

8. The spinal implant of claim 1, wherein said first radiused outer wall and said second radiused outer wall comprise a hemielliptical outer surface.

9. The spinal implant of claim 1, wherein a first vertical radius of said tail wall is greater than a second vertical radius of said leading wall.

10. The spinal implant of claim 1, further comprising a stabilizing means for temporarily rigidly coupling said first element to said second element.

11. The spinal implant of claim 10 wherein said stabilizing means comprises an endcap adapted to releasably engage a portion of said first element and a portion of said second element.

12. The spinal implant of claim 10, wherein said stabilizing means comprises at least one bioreabsorbable element adapted to be absorbed after implantation.

13. The spinal implant of claim 1, wherein an intermediate articulation element is positioned between said first and second articulation surfaces.

14. The spinal implant of claim 13, wherein said first articulation surface comprises a concave surface, and said second articulation surface comprises a convex surface, and said intermediate articulation element comprises a generally hemispherical cap.

15. A method of maintaining an intervertebral space between a first vertebra and a second vertebra, said method comprising the steps of

(a) removing a section of the first vertebra and the second vertebra to form a cavity therein;

(b) mounting a first clement of a spinal implant within the cavity formed in the first vertebra, said first element comprising a first articulation surface, a first outer surface, and a first connection means for engaging the first vertebra, wherein said first outer surface comprises a first radiused outer wall, and said first connection means comprises a first fusion chamber located between said first articulation surface and said first outer surface, and said first outer surface comprises at least one opening for facilitating bone ingrowth into said first fusion chamber;

(c) mounting a second element of the spinal implant within the cavity formed in the second vertebra, said second element comprising a second articulation surface, a second outer surface, and a second connection means for engaging the second vertebra, wherein said second outer surface comprises a second radiused outer wall, and said first and second articulation surfaces adjoin to form a joint allowing relative pivotal movement between said first and second elements but preventing relative compression between said first and second elements; and

(d) temporarily rigidly coupling said first element to said second element with at least one biorcabsorbable stabilizing means prior to mounting said first clement within said cavity in said first vertebra.

16. The method of claim 15, further comprising inserting at least a portion of said removed section of said first vertebra into said first fusion chamber.

17. The method of claim 16, wherein said second connection means comprises a second fusion chamber located between said second articulation surface and said second outer surface, and said second outer surface comprises at least one opening for facilitating bone ingrowth into said second fusion chamber.

18. The method of claim 17, further comprising applying means for stimulating bone growth to each of said first and second fusion chambers.

19. A spinal implant comprising:

(a) a first element comprising a first articulation surface, a first outer surface, and a first connection means for engaging a first vertebra, wherein said first outer surface comprises a first radiused outer wall, and said first connection means comprises a first fusion chamber located between said first articulation surface and said first outer surface, and said first outer surface comprises at least one opening for facilitating bone ingrowth into said first fusion chamber;

(b) a second element comprising a second articulation surface, a second outer surface, and a second connection means for engaging a second vertebra, wherein said second outer surface comprises a second radiused outer wall, wherein said first radiused outer wall and said second radiused outer wall comprise a hemielliptical outer surface;

(c) a tail wall and a leading wall; and

(d) an articulation means, coupling said first articulation surface to said second articulation surface, for allowing relative movement between said first element and said second element, wherein said articulation means resist axial compression in the direction of a support axis.

20. The spinal implant of claim 19, wherein said first articulation surface abuts said second articulation surface to form said articulation means.

21. The spinal implant of claim 20, wherein said articulation means comprises a concave surface in said first element and a convex surface from said second element, wherein at least a portion of said convex surface is engaged within said concave surface.

22. The spinal implant of claim 19, wherein said second connection means comprises a second fusion chamber located between said second articulation surface and said second outer surface, and said second outer surface comprises at least one opening for facilitating bone ingrowth into said second fusion chamber.

23. The spinal implant of claim 19, wherein said first radiused outer wall and said second radiused outer wall comprise a securing means for securing said spinal implant within a cavity between said first vertebra and said second vertebra.

24. The spinal implant of claim 19, wherein a first vertical radius of said tail wall is greater than a second vertical radius of said leading wall.

25. The spinal implant of claim 19, further comprising a stabilizing means for temporarily rigidly coupling said first element to said second element.

26. The spinal implant of claim 25, wherein said stabilizing means comprises an endcap adapted to releasably engage a portion of said first element and a portion of said second element.

27. The spinal implant of claim 25, wherein said stabilizing means comprises at least one bioreabsorbable element adapted to be absorbed after implantation.

28. The spinal implant of claim 19, wherein an intermediate articulation element is positioned between said first and second articulation surfaces.

29. The spinal implant of claim 28, wherein said first articulation surface comprises a concave surface, and said second articulation surface comprises a convex surface, and said intermediate articulation clement comprises a generally hemispherical cap.