Vertebral body replacement

• US 6,375,681 B1
• Filed: 06/22/1999
• Issued: 04/23/2002
• Est. Priority Date: 06/23/1998
• Status: Expired due to Term

• Current Assignee: Zimmer Biomet Spine, Inc. (Zimvie Incorporated)
• Original Assignee: EBI LP (Zimvie Incorporated)
• Inventors: Truscott, James William
• Primary Examiner(s): Smith, Jeffrey A.
• Application Number:
  US09/337,779
• Time in Patent Office: 1,036 Days
• Field of Search: 623/17.11, 623/17.16, 606/61
• US Class Current: 623/17.11
• 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 2/44 for the spine, e.g. vertebrae, spinal discs
• 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 2002/30133 kidney-shaped or bean-shaped
• CPC Class Codes: A61F 2002/30158 trapezoidal
• CPC Class Codes: A61F 2002/30235 tubular, e.g. sleeves
• CPC Class Codes: A61F 2002/3036 Protrusion and recess of kidney-shaped cross-section
• CPC Class Codes: A61F 2002/30451 soldered or brazed or welded
• CPC Class Codes: A61F 2002/30593 hollow
• CPC Class Codes: A61F 2002/30604 modular
• CPC Class Codes: A61F 2002/30777 Oblong apertures
• CPC Class Codes: A61F 2002/30785 parallel
• CPC Class Codes: A61F 2002/30787 inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30892 parallel
• CPC Class Codes: A61F 2002/4631 the prosthesis being specially adapted for being cemented
• 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 2220/0058 soldered or brazed or welded
• CPC Class Codes: A61F 2230/0015 Kidney-shaped, e.g. bean-shaped
• CPC Class Codes: A61F 2230/0026 trapezoidal
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00407 : Coating made of titanium or of Ti-based alloys

Abstract

A spinal prosthesis (1) comprises hollow strut (2) terminated by a pair of end caps (10, 12) which are adapted to engage respective vertebrae. Each end cap (10, 12) may have a flange (20, 22) which is closely received within and supports a respective end (6, 8) of the strut (2). Alternatively, or in addition, each end cap (10, 12) may be substantially kidney shaped and may be provided with a kidney shaped recess (16, 18) which provides access to the interior of the strut (2). Preferably, the end caps (10, 12) are provided with respective shoulders (28, 30) which are adapted to cover the ends of the strut (2) to prevent the strut damaging soft tissue during implantation. A porous titanium plasma coating may be applied to the end caps (10, 12) to enhance bone fixation and to resist anterior translation and rotation of the prosthesis (1).

Claims

1. A prosthesis comprising:

a hollow strut having a first hollow end and a second hollow end with a longitudinal axis that extends from the first hollow end to the second hollow end; and

a pair of end caps which are adapted to be push fit into the first and second hollow ends with each end cap including a flange which is closely received within and supports the first and second ends of the hollow strut, each end cap further including a pair of extensions lying along an axis defined by a coronal plane and being substantially perpendicular to the longitudinal axis, each extension having a distal tip that extends along the axis defined by the coronal plane and into a central opening in each end cap, each extension having a bone engaging pin extending substantially parallel to the longitudinal axis from the distal tip, wherein the bone engaging pins engage adjacent vertebral bodies to improve stability of the prosthesis.

2. The prosthesis as defined in claim 1, in which the leading edge of each flange is chamfered.

3. The prosthesis as defined in claim 1, in which the end caps are substantially kidney shaped.

4. The prosthesis as defined in claim 1, in which each end cap is provided with a shoulder which is adapted to cover the end of the strut.

5. The prosthesis as defined in claim 1, in which a porous titanium plasma coating is applied to the end caps.

6. The prosthesis as defined in claim 1, in which the strut comprises a tube.

7. The prosthesis as defined in claim 6 in which the tube is made from titanium.

8. The prosthesis as defined in claim 7, in which the tube is heat treated.

9. The prosthesis as defined in claim 7, in which the tube is seam welded.

10. The prosthesis as defined in claim 1, in which the strut is provided with a plurality of through holes.

11. The prosthesis as defined in claim 10, in which the through holes are aligned in rows substantially perpendicular to the longitudinal axis of the strut.

12. A prosthesis comprising:

a hollow strut having a first hollow end an a second hollow end with a longitudinal axis extending from the first hollow end and the second hollow end, said strut having a substantially kidney shaped cross-section; and

a pair of end caps which are substantially kidney shaped in a plane substantially perpendicular to the longitudinal axis of the strut, with each having a central substantially kidney shaped opening passing therethrough, each end cap further including a pair of extensions lying along an axis defined by a coronal plane and being substantially perpendicular to the longitudinal axis, each extension having a distal tip that extends along the axis defined by the coronal plane and into the kidney shaped opening in each end cap, each extension having a bone engaging pin extending substantially parallel to the longitudinal axis from the distal tip, wherein the bone engaging pins engage adjacent vertebral bodies to improve stability of the prosthesis.

13. A prosthesis comprising:

a hollow strut having a first hollow end and a second hollow end with a longitudinal axis that extends from the first hollow end to the second hollow end; and

a pair of end caps with each having an end wall which is adapted to engage a respective vertebra, a periphery of each end wall extending further from the strut than a remainder of the end wall, each end wall defining a central opening passing through each end cap and having a pair of extensions lying along an axis defined by a coronal plane and being substantially perpendicular to the longitudinal axis, each extension having a distal tip that extends along the axis defined by the coronal plane and into the central opening, each extension having a bone engaging pin extending substantially parallel to the longitudinal axis from the distal tip, wherein the bone engaging pins engage adjacent vertebral bodies to improve stability of the prosthesis.

14. The prosthesis as defined in claim 13 wherein the central opening is kidney shaped.

15. A vertebral body replacement prosthesis comprising:

a strut terminated at one end by an end cap which is adapted to engage a vertebra, the end cap having an inwardly directed end which is directed towards the strut and an outwardly directed end which, in use, is directed toward the vertebra, the outwardly directed end defining a vertebra engaging surface which is offset from a plane extending perpendicular to the longitudinal axis of the strut, the outwardly directed end defined by a pair of extensions lying along an axis defined by a coronal plane and being substantially perpendicular to the longitudinal axis, each extension having a distal tip that extends along the axis defined by the coronal plane and into a central opening of the end cap with each extension having a bone engaging pin that extends substantially parallel with the longitudinal axis from the distal tip, wherein the bone engaging pins engage adjacent vertebral bodies to improve stability of the prosthesis.

16. The prosthesis as defined in claim 15, in which a further end cap is provided at the other end of the strut.

17. The prosthesis as defined in claim 15, in which the end cap is substantially wedge-shaped.

18. The prosthesis as defined in claim 15, in which the offset is between −

10 to +10°

.

19. The prosthesis as defined in claim 18, in which the offset is between −

5 to +5°

.