Facet joint prosthesis

• US 20070149983A1
• Filed: 12/12/2006
• Published: 06/28/2007
• Est. Priority Date: 12/13/2005
• Status: Active Grant

• Current Assignee: Facet-Link Inc.
• Original Assignee: DERU GmbH
• Inventors: Link, Helmut
• Granted Patent: US 7,896,903 B2
• Time in Patent Office: Days
• US Class Current: 606/99
• CPC Class Codes: A61F 2/4405 for apophyseal or facet joints, i.e. between adjacent spinous or transverse processes devices implanted between spinous or transverse processes A61B17/7062
• CPC Class Codes: A61F 2002/30125 elliptical or oval
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30331 made by longitudinally pushing a protrusion into a complementarily-shaped recess, e.g. held by friction fit
• CPC Class Codes: A61F 2002/30364 Rotation about the common longitudinal axis
• CPC Class Codes: A61F 2002/30405 made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/30471 connected by a hinged linkage mechanism, e.g. of the single-bar or multi-bar linkage type
• CPC Class Codes: A61F 2002/30476 locked by an additional locking mechanism
• CPC Class Codes: A61F 2002/3052 unrestrained in only one direction, e.g. moving unidirectionally
• CPC Class Codes: A61F 2002/30538 for adjusting angular orientation
• CPC Class Codes: A61F 2002/3055 for adjusting length
• CPC Class Codes: A61F 2002/30578 having apertures, e.g. for receiving fixation screws
• CPC Class Codes: A61F 2002/30601 telescopic
• CPC Class Codes: A61F 2002/30604 modular
• CPC Class Codes: A61F 2002/30635 Cardan or gimbal joints
• CPC Class Codes: A61F 2002/30649 Ball-and-socket joints
• CPC Class Codes: A61F 2002/30841 Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2002/30883 dovetail-shaped
• CPC Class Codes: A61F 2002/30904 serrated profile, i.e. saw-toothed
• CPC Class Codes: A61F 2002/449 comprising multiple spinal implants located in different intervertebral spaces or in different vertebrae
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0033 : made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit
• CPC Class Codes: A61F 2220/0091 : connected by a hinged linkage mechanism, e.g. of the single-bar or multi-bar linkage type
• CPC Class Codes: A61F 2230/0008 : elliptical or oval
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2250/0006 : for adjusting angular orientation
• CPC Class Codes: A61F 2250/0007 : for adjusting length
• CPC Class Codes: A61F 2310/00029 : Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium
• CPC Class Codes: A61F 2310/00796 : Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite

Abstract

The invention relates to a prosthesis for facet joints (12) of the spinal column, with a bearing piece (23) and a guide rod (21). The bearing piece (23) comprises a pressure plate (24) for resting on an articular surface (13, 14) of the vertebra (1) and, on the opposite side, a bearing insert (27) which has an articular surface for interacting with an articular surface (13, 14) of an adjacent vertebra (1′). The guide rod (21) is secured on the bearing piece (23) by means of a pivot joint. The bearing forces are transmitted to the vertebra (1) via the pressure plate (24). In this way, the guide rod (21) can have a narrow configuration, such that the slit (18) for receiving the guide rod on the vertebra (1) can also be made narrow. This permits a simple and reliable implantation technique which at the same time is gentle on bone substance.

Claims

1. A prosthesis for facet joints of the spinal column, with a bearing piece (23) and a retaining piece with a guide rod (21), the bearing piece (23, 33) comprising a pressure plate (24) for resting on the vertebra (1) and, on the opposite side, a bearing shell (27, 37) which has an articular surface for interacting with an articular surface of an adjacent vertebra (1′

) wherein a pivot joint (22) is provided for securing the guide rod (21) on the bearing piece (23).

2. The prosthesis as claimed in claim 1, wherein the pivot joint is a cardan joint (32).

3. The prosthesis as claimed in one of the preceding claims, wherein a second bearing piece (33) with pressure plate (34) and bearing insert (37) is arranged at the other end of the guide rod (21).

4. The prosthesis as claimed in claim 3, wherein an inner guide rod (31) is provided which engages in a telescopic manner in the guide rod (21).

5. The prosthesis as claimed in claim 4, wherein locking means (39) are provided for securing the guide rods (21, 31) against moving apart.

6. The prosthesis as claimed in one of claims 3 through 5, wherein the bearing piece (23) at the upper end of the guide rod (21, 31) has a contour with an oval envelope, and the bearing piece (33) at the lower end has a contour with a rectangular envelope.

7. The prosthesis as claimed in one of the preceding claims, wherein at least one of the bearing pieces (23, 33) has a screw opening (38) in its articular surface and is connected in a rotationally fixed manner to the inner guide rod (31).

8. The prosthesis as claimed in one of the preceding claims, wherein the bearing piece (23) with pressure plate (24) and bearing insert (27) is designed in one piece.

9. The prosthesis as claimed in claim 1 or 2, wherein a thickened part (29) is formed at the other end of the guide rod (21).

10. The prosthesis as claimed in claim 9, wherein the thickened part (29) has a curvature on its side directed toward the bearing piece (23).

11. The prosthesis as claimed in claim 10, wherein the curvature has a rotationally symmetrical design.

12. The prosthesis as claimed in one of claims 9 through 11, wherein the thickened part (29) has a spheroid design.

13. The prosthesis as claimed in one of the preceding claims, wherein the guide rod (21) is designed for insertion into a slit (18) between articular surfaces (13, 14) of a vertebra (1).

14. The prosthesis as claimed in one of the preceding claims, wherein the guide rod (21) has a non-circular, preferably rectangular or oval cross section (21) whose greatest width is greater than the width of the slit (18).

15. The prosthesis as claimed in one of the preceding claims, wherein a radially protruding serration (28) is provided along the guide rod (21).

16. The prosthesis as claimed in one of the preceding claims, wherein a toothing arrangement (25) engaging in the vertebra (1) is provided on the pressure plate (24).

17. The prosthesis as claimed in one of the preceding claims, wherein the pressure plate (24, 34) is provided with a coating that promotes bone growth, in particular a coating of hydroxyapatite.

18. The prosthesis as claimed in one of the preceding claims, wherein the bearing shell (27, 37) has an articular surface with a convex curvature.

19. The prosthesis as claimed in claim 14, wherein the interacting articular surface on the adjacent vertebra (1′

) has a complementary curvature.

20. A prosthesis set comprising at least one prosthesis as claimed in one of the preceding claims, wherein at least one prosthesis (3) with two bearing pieces (23, 33) and at least one prosthesis (2) with one bearing piece (23) are provided.

21. A method for implanting a prosthesis, comprising a bearing piece (23, 33) and a guide rod (21) arranged at an angle thereon, as claimed in one of the preceding claims, in which method a slit (18, 18′

) is excavated on a vertebra (1) so as to extend from an articular surface (13) of the vertebra (1) in the direction of the other articular surface (14) of the vertebra (1), and the guide rod (21) is inserted into the slit (18, 18′

), with the bearing piece (23, 33) coming to rest with a pressure plate (24, 34) on the articular surface (13, 14).

22. The method as claimed in claim 21, in which method the slit (18, 18′

) is excavated in the dorso-lateral direction on the articular process (15) of the vertebra (1).

23. The method as claimed in claim 21 or 22, in which method the slit (18′

) is excavated as far as the other articular surface of the vertebra (1).

24. The method as claimed in claim 22 or 23, wherein a transverse bore (19) is formed opening into the slit (18).