Reinforced expandable cage and method of deploying

• US 6,488,710 B2
• Filed: 03/02/2001
• Issued: 12/03/2002
• Est. Priority Date: 07/02/1999
• Status: Expired due to Fees

• Current Assignee: Petrus Besselink
• Original Assignee: Petrus Besselink
• Inventors: Besselink, Petrus
• Primary Examiner(s): Lucchesi, Nicholas D.
• Assistant Examiner(s): Priddy, Michael B.
• Application Number:
  US09/797,927
• Publication Number:
  US 20010032020A1
• Time in Patent Office: 641 Days
• Field of Search: 623/17.11, 623/17.15, 623/17.16, 623/17.13, 606/61
• US Class Current: 623/17.15
• 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 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/30092 using shape memory or superelastic materials, e.g. nitinol
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30179 X-shaped
• CPC Class Codes: A61F 2002/30261 parallelepipedal
• CPC Class Codes: A61F 2002/3028 polyhedral different from parallelepipedal and pyramidal
• CPC Class Codes: A61F 2002/30293 Cylindrical body made by spirally rolling up a sheet or a strip around itself
• CPC Class Codes: A61F 2002/30476 locked by an additional locking mechanism
• 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 2002/30594 slotted, e.g. radial or meridian slot ending in a polar aperture, non-polar slots, horizontal or arcuate slots
• CPC Class Codes: A61F 2002/30624 Hinged joint, e.g. with transverse axle restricting the movement
• CPC Class Codes: A61F 2002/30975 made of two halves
• CPC Class Codes: A61F 2002/444 for replacing the nucleus pulposus
• 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 2002/4635 using minimally invasive surgery
• 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 2210/0033 electrically, e.g. heated by resistor
• CPC Class Codes: A61F 2210/0038 : electromagnetically
• CPC Class Codes: A61F 2210/0042 : using a fluid, e.g. circulating
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2230/0058 : X-shaped
• CPC Class Codes: A61F 2230/0063 : Three-dimensional shapes
• CPC Class Codes: A61F 2230/0082 : parallelepipedal
• CPC Class Codes: A61F 2230/0091 : helically-coiled or spirally-coiled, i.e. having a 2-D spiral cross-section
• CPC Class Codes: A61F 2310/00011 : Metals or alloys

Abstract

An expandable inter-vertebral prosthesis. The prosthesis takes over the supporting function of the inter-vertebra disc between two adjacent vertebra bodies, and includes one or more cages and a reinforcing element. Upon cage expansion, a hollow central portion of the cage can accommodate the reinforcing element. The reinforcing element, upon expansion, assumes a spiral shape, and substantially fills up the hollow central portion of the cage to provide enhanced load-bearing capability in a substantially longitudinal spinal direction. Hinges in the cage permit expansion and, once the cage has expanded, prevent it from collapsing. Delivery of the cage in an unexpanded condition into an inter-vertebral space is ensured with a restraining tool that engages the hinge members. The cage, reinforcing element and restraining tool are inserted with the aid of a conventional delivery tube.

Claims

1. An expandable intervertebral prosthesis for replacement of the nucleus of an intervertebral disc, said prosthesis comprising:

at least one cage made from a relatively thin walled material; and

a reinforcing element that rolls up from an oblong geometry into at least one substantially planar spiral geometry in a force-free state that at least partly fills a substantially hollow central region within said at least one cage in such a way that stability along a substantially longitudinal axis of said at least one cage is increased, thereby enabling a permanent spinal fusion.

2. The prosthesis according to claim 1, wherein said at least one cage is configured so that it to can be brought into an intervertebral space in an unexpanded state, and then caused to change shape to at least a final, expanded state.

3. The prosthesis according to claim 2, further comprising at least one aperture disposed within at least one surface of said cage.

4. The prosthesis according to claim 3, further comprising an elongate instrument adapted to facilitate insertion of said at least one cage into said intervertebral space, said elongate instrument comprising:

an outer tube with a proximal and distal end;

a tension wire disposed within said outer tube, said tension wire moveable relative to said outer tube; and

a restraining element disposed on said tension wire, said restraining element adapted to selectively engage said at least one aperture disposed within at least one surface of said cage.

5. The prosthesis according to claim 4, wherein said unexpanded state of said at least one cage is configured so that it can be introduced into said intervertebral space by pushing it through a delivery tube with said elongate instrument.

6. The prosthesis according to claim 5, wherein said restraining element can hold said at least one cage in said unexpanded state at least until said at least one cage is removed from said delivery tube and placed into said intervertebral space.

7. The prosthesis according to claim 6, wherein relative movement between said tension wire and said outer tube permits the release of said at least one cage from said unexpanded state to said expanded state.

8. The prosthesis according to claim 1, wherein said substantially hollow central region is made up of a plurality of cages.

9. The prosthesis according to claim 1, further comprising a plurality of preferential bending spots, said plurality of preferential bending spots configured to act as hinges.

10. The prosthesis according to claim 9, wherein said preferential bending spots are created by either locally cutting, grinding or heat treating the material of said at least one cage, or by the use of an additional hinge pin.

11. The prosthesis according to claim 9, wherein at least some of said preferential bending spots further include an end position to act as a mechanical stop, thereby locking said at least one cage into a stable configuration after expansion.

12. The prosthesis according to claim 1, wherein said at least one cage is expandable in both said longitudinal direction and in a direction perpendicular to said longitudinal direction.

13. The prosthesis according to claim 1, wherein said reinforcing element has the shape of an elongated strip with a flat or slightly curved cross section.

14. The prosthesis according to claim 13, wherein said reinforcing element is selected from a material consisting of a polymer, composite, metal, shape memory material with superelastic behavior, shape memory material with shape memory behavior, and combinations thereof.

15. The prosthesis according to claim 13, wherein said reinforcing element has the tendency to roll up from said oblong geometry to said substantially planar spiral geometry, said tendency caused by elastic energy inherent in said reinforcing element.

16. The prosthesis according to claim 13, wherein said reinforcing element has the tendency to roll up from said oblong geometry to said substantially planar spiral geometry, said tendency caused by a stored shape memory effect that is triggered by a change in temperature that said reinforcing element is exposed to.

17. The prosthesis according to claim 16, wherein said temperature change is caused by resistance heating, radiation, conductive contact with an elevated temperature fluid, a Peltier element, or combinations thereof.

18. The prosthesis according to claim 1, said at least one cage made from a material selected from the group consisting of a polymer, metal, shape memory material with superelastic behavior, shape memory material with shape memory behavior, and combinations thereof.

19. The prosthesis according to claim 1, wherein deformation of said at least one cage or said reinforcing element is selected from the group of deformations consisting of plastic deformation, elastic deformation, superelastic deformation, deformation by shape memory behavior, and combinations thereof.

20. An expandable intervertebral prosthesis with increased axial stability in a direction substantially parallel with a longitudinal spinal axis, said prosthesis comprising:

a first cage in an unexpanded state, said first cage adapted to be placed in an intervertebral position within a spine, and then caused to expand to an expanded state;

a second cage placed inside said first cage in said expanded state such that when both said first cage is in said expanded state and said second cage is in an expanded state, they together form an assembled cage, said assembled cage defining a substantially hollow central region; and

a reinforcing element that rolls up from an oblong geometry into at least one substantially planar spiral geometry in a force-free state to at least partly fill said substantially hollow central region in said assembled cage, thereby forming a reinforced cage.

21. The prosthesis according to claim 20, wherein said reinforcing element forms a form-fitted spiral without intervening spaces in said force-free state.

22. The prosthesis according to claim 20, wherein said spiral has axial surfaces in substantial contact with corresponding inner surfaces of said cage assembly to enable said cage assembly to take up high axial loads.

23. The prosthesis according to claim 20, wherein said reinforced cage further comprises sterilizable material with deformation properties corresponding essentially to those of an intervertebral disc to be replaced.

24. An expandable prosthesis for replacement of an intervertebral disc to promote spinal fusion, said prosthesis comprising:

at least one cage made from a relatively thin walled material, said at least one cage comprising;

a first, unexpanded state prior to deployment into an intervertebral space; and

a second state wherein after deployment in said intervertebral space, said at least one cage is expanded, thereby defining a substantially hollow central region; and

a reinforcing element disposed within said substantially hollow central region, said reinforcing element comprising;

a first, oblong state prior to deployment into said substantially hollow central region; and

a second state wherein said reinforcing element assumes a substantially planar spiral configuration upon deployment in said substantially hollow central region, said substantially planar spiral configuration to at least partly fill said substantially hollow central region in such a way as to improve the stability of said expanded at least one cage in a direction substantially parallel to a longitudinal axis of said intervertebral space.

25. A prosthesis expandable in a plurality of dimensions to promote intervertebral fusion, said prosthesis comprising:

a cage comprising;

a first, unexpanded state prior to deployment into an intervertebral space; and

a second, expanded state wherein said second, expanded state comprises at least;

a first expansion in a direction substantially parallel to a longitudinal axis of said intervertebral space thereby defining a substantially hollow central region; and

a second expansion in a plane normal to said first expansion such that a space formed by said first and second expansions defines a substantially hollow central region; and

a reinforcing element adapted to be disposed within said substantially hollow central region, said reinforcing element comprising;

a first, oblong state prior to deployment into said substantially hollow central region; and

a second state wherein said reinforcing element assumes a substantially planar spiral configuration upon deployment in said substantially hollow central region, said substantially planar spiral configuration to at least partly fill said substantially hollow central region in such a way as to improve the stability of said expanded cage in a direction substantially parallel to a longitudinal axis of said intervertebral space.

26. A prosthesis according to claim 25, further comprising a plurality of hinges, at least some of which are designed to pivot around an axis substantially parallel to a longitudinal axis of said intervertebral space.

27. A method of deploying an intervertebral prosthesis, said method comprising the steps of:

providing a prosthesis, wherein said prosthesis comprises;

at least one expandable cage that defines a substantially hollow central region upon expansion; and

a reinforcing element adapted to be disposed within said substantially hollow central region; and

an elongate instrument adapted to control said expansion of said at least one expandable cage, said elongate instrument comprising;

an outer tube;

a tension wire disposed within and relatively movable to said outer tube; and

a restraining element disposed on said tension wire, said restraining element adapted to engage at least a portion of said at least one expandable cage;

spreading apart adjacent vertebrae such that an intervertebral space is defined thereby;

placing said prosthesis in a delivery tube;

inserting said delivery tube into said intervertebral space;

controlling the expansion of said at least one expandable cage through limiting the relative movement between said outer tube and said tension wire;

using said elongate instrument to remove said at least one expandable cage from said delivery tube;

placing said at least one expandable cage in said intervertebral space;

expanding said at least one expandable cage; and

inserting said reinforcing element into said substantially hollow central region such that said reinforcing element rolls up from an oblong geometry into at least one substantially planar spiral geometry in a force-free state that at least partly fills said substantially hollow central region.