Spinal fusion cage with lordosis correction

• US 6,491,724 B1
• Filed: 12/03/1999
• Issued: 12/10/2002
• Est. Priority Date: 08/13/1999
• Status: Expired due to Fees

• Current Assignee: Anova Corp.
• Original Assignee: Bret Ferree
• Inventors: Ferree, Bret
• Primary Examiner(s): Willse, David H.
• Assistant Examiner(s): GHERBI, SUZETTE JAIME J
• Application Number:
  US09/454,908
• Time in Patent Office: 1,103 Days
• Field of Search: 623/17-1-
• US Class Current: 623/17.11
• CPC Class Codes: A61B 2017/0256 for the spine
• CPC Class Codes: A61F 2/2846 Support means for bone substitute or for bone graft implants, e.g. membranes or plates for covering bone defects nets or sleeves applied to surface of endoprostheses A61F2/30907; bone plates A61B17/80; bone regeneration in dental surgery A61C8/0006
• CPC Class Codes: A61F 2/30742 Bellows or hose-like seals; Sealing membranes A61B17/8808 takes precedence; sealing membranes for retaining bone substitute A61F2/2846
• CPC Class Codes: A61F 2/30744 End caps, e.g. for closing an endoprosthetic cavity
• CPC Class Codes: A61F 2/30965 Reinforcing the prosthesis by embedding particles or fibres during moulding or dipping
• 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 2/4455 for the fusion of spinal bodies, e.g. intervertebral fusion of adjacent spinal bodies, e.g. fusion cages intervertebral discs A61F2/442
• CPC Class Codes: A61F 2/4465 having a circular or kidney shaped cross-section substantially perpendicular to the axis of the spine
• CPC Class Codes: A61F 2/447 substantially parallelepipedal, e.g. having a rectangular or trapezoidal cross-section
• CPC Class Codes: A61F 2/4601 for introducing bone substitute, for implanting bone graft implants or for compacting them in the bone cavity
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• 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 2002/30092 using shape memory or superelastic materials, e.g. nitinol
• CPC Class Codes: A61F 2002/30131 horseshoe- or crescent- or C-shaped or U-shaped
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/302 toroidal, e.g. rings
• CPC Class Codes: A61F 2002/30235 tubular, e.g. sleeves
• CPC Class Codes: A61F 2002/30261 parallelepipedal
• CPC Class Codes: A61F 2002/3028 polyhedral different from parallelepipedal and pyramidal
• CPC Class Codes: A61F 2002/30329 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2002/30433 : using additional screws, bolts, dowels, rivets or washers e.g. connecting screws
• CPC Class Codes: A61F 2002/30461 : sutured, ligatured or stitched
• 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 2002/30556 : for adjusting thickness
• CPC Class Codes: A61F 2002/30565 : having spring elements
• CPC Class Codes: A61F 2002/30579 : with mechanically expandable devices, e.g. fixation devices
• CPC Class Codes: A61F 2002/30593 : hollow
• CPC Class Codes: A61F 2002/30624 : Hinged joint, e.g. with transverse axle restricting the movement
• CPC Class Codes: A61F 2002/30677 : Means for introducing or releasing pharmaceutical products, e.g. antibiotics, into the body
• CPC Class Codes: A61F 2002/30774 : internally-threaded
• CPC Class Codes: A61F 2002/30777 : Oblong apertures
• CPC Class Codes: A61F 2002/30784 : Plurality of holes
• CPC Class Codes: A61F 2002/30787 : inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30828 : parallel
• CPC Class Codes: A61F 2002/30909 : Nets
• CPC Class Codes: A61F 2002/30975 : made of two halves
• CPC Class Codes: A61F 2002/4435 : Support means or repair of the natural disc wall, i.e. annulus, e.g. using plates, membranes or meshes
• CPC Class Codes: A61F 2002/444 : for replacing the nucleus pulposus
• CPC Class Codes: A61F 2002/4445 : Means for culturing intervertebral disc tissue
• CPC Class Codes: A61F 2002/445 : Intervertebral disc tissue harvest sites
• CPC Class Codes: A61F 2002/448 : comprising multiple adjacent spinal implants within the same intervertebral space or within the same vertebra, e.g. comprising two adjacent spinal implants
• CPC Class Codes: A61F 2002/4627 : with linear motion along or rotating motion about the instrument axis or the implantation direction, e.g. telescopic, along a guiding rod, screwing inside the instrument
• CPC Class Codes: A61F 2210/0019 : operated at only one temperature whilst inside or touching the human body, e.g. constrained in a non-operative shape during surgery, another temperature only occurring before the operation
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0041 : using additional screws, bolts, dowels or rivets, e.g. connecting screws
• CPC Class Codes: A61F 2220/0075 : sutured, ligatured or stitched, retained or tied with a rope, string, thread, wire or cable
• CPC Class Codes: A61F 2230/0013 : Horseshoe-shaped, e.g. crescent-shaped, C-shaped, U-shaped
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2230/0063 : Three-dimensional shapes
• CPC Class Codes: A61F 2230/0065 : toroidal, e.g. ring-shaped, doughnut-shaped
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2230/0082 : parallelepipedal
• CPC Class Codes: A61F 2250/0006 : for adjusting angular orientation
• CPC Class Codes: A61F 2250/0009 : for adjusting thickness
• 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: A61L 2400/16 : Materials with shape-memory or superelastic properties
• CPC Class Codes: A61L 2430/38 : for reconstruction of the spine, vertebrae or intervertebral discs
• CPC Class Codes: A61L 27/38 : containing added animal cells organs or tissue containing native cells A61L27/36

Abstract

Intervertebral cages, and methods of introducing the same, require few, if any, structural components within the cage itself, thereby providing a maximum volume for bone-graft filler. Cages according to the invention may passively expand to fill a volume within the disk space, or active expansion means may be provided. In terms of a passive expansion, at least a portion of the frame may be composed of a shape-memory material, causing the cage to naturally expand from the compressed to the expanded state once the cage is positioned within the intervertebral space. In either case, locking means are provided to maintain the shape of the cage once in position. An alternative embodiment includes first and second components, each having a compressed state which consumes a compressed volume associated with insertion of the component into an intervertebral space, and an expanded state which consumes a greater volume when the component is positioned within the intervertebral space. In terms of an active expansion, an externally accessible mechanism may be used to increase the anterior height once the cage is positioned within the intervertebral space. In all embodiments, connection means may be provided for interconnecting a plurality of cages together within the same intervertebral space.

Claims

1. An intervertebral cage, comprising:

a rigid frame having anterior and posterior portions, superior and inferior surfaces, and two opposing sides;

the thickness of the frame between the superior and inferior surfaces in the anterior portion defining an anterior height, and the thickness of the frame between the superior and inferior surfaces in the posterior portion defining a posterior height;

a connector associated with the posterior portion facilitating insertion of the frame into an intervertebral space using a posterior approach;

the frame having a compressed state associated with insertion of the frame into an intervertebral space, wherein the anterior height is less than or equal to the posterior height, and an expanded state, wherein the anterior height is greater than the posterior height to account for lordosis; and

a mechanism for locking the cage into the expanded state once the frame is positioned within intervertebral space.

2. The intervertebral cage of claim 1, wherein the means for locking the frame into the expanded state includes a ratchet mechanism associated with the anterior portion.

3. The Intervertebral cage of claim 1, wherein the interior volume of the frame is substantially unoccupied to receive bone graft material.

4. The intervertebral cage of claim 1, wherein at least a portion of the frame is composed of a shape-memory material causing the frame to naturally expand from the compressed to the expanded state once the frame is positioned within the intervertebral space.

5. The intervertebral cage of claim 1, wherein the superior and inferior surfaces are attached to the posterior portion so as to form a spring which causes the cage to naturally expand from the compressed to the expanded state once the cage is positioned within the intervertebral space.

6. The intervertebral cage of claim 1, wherein the superior and inferior surfaces include protrusions for frictionally engaging with vertebral endplates defining the disk space.

7. The intervertebral cage of claim 1, wherein one or both of the superior and inferior surfaces are convex.

8. The intervertebral cage of claim 1, wherein one or both of the superior and inferior surfaces are hinged to the posterior portion.

9. The intervertebral cage of claim 1, wherein the mechanism for locking the cage into the expanded state includes one or two anterior members hinged to one or both of the superior and inferior surfaces, respectively.

10. The intervertebral cage of claim 1, further including a posteriorly accessible mechanism operative to increase the anterior height once the cage is positioned within the intervertebral space.

11. The intervertebral cage of claim 10, wherein the posteriorly accessible mechanism includes a slug positioned on a threaded rod which moves back and forth posterior to anterior when the rod is rotated.

12. The intervertebral cage of claim 1, further including a radiolucent screen covering at least the open sides of the cage.

13. The intervertebral cage of claim 1, further including a connector associated with the posterior portion for interconnecting a plurality of the frames together within the same intervertebral space.