Prosthetic spinal disc nucleus

• US 5,674,295 A
• Filed: 04/26/1996
• Issued: 10/07/1997
• Est. Priority Date: 10/17/1994
• Status: Expired due to Fees

• Current Assignee: Raymedica, Inc.
• Original Assignee: Raymedica, Inc.
• Inventors: Frutiger, Beth A., Ledoux, Philip J., Dickhudt, Eugene A., Ray, Charles D.
• Primary Examiner(s): Milano, Michael J.
• Application Number:
  US08/638,306
• Time in Patent Office: 529 Days
• Field of Search: 623/8, 623/17, 606/61, 606/71
• US Class Current: 623/17.12
• CPC Class Codes: A61F 2/3094 Designing or manufacturing processes
• CPC Class Codes: A61F 2/441 made of inflatable pockets or chambers filled with fluid, e.g. with hydrogel
• 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 2002/3008 radio-opaque, e.g. radio-opaque markers
• CPC Class Codes: A61F 2002/30156 triangular
• CPC Class Codes: A61F 2002/30235 tubular, e.g. sleeves
• CPC Class Codes: A61F 2002/30291 spirally-coiled, i.e. having a 2D spiral cross-section
• CPC Class Codes: A61F 2002/30461 sutured, ligatured or stitched
• CPC Class Codes: A61F 2002/30579 with mechanically expandable devices, e.g. fixation devices
• CPC Class Codes: A61F 2002/30581 having a pocket filled with fluid, e.g. liquid
• CPC Class Codes: A61F 2002/30617 Visible markings for adjusting, locating or measuring
• CPC Class Codes: A61F 2002/30841 Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2002/30878 with non-sharp protrusions, for instance contacting the bone for anchoring, e.g. keels, pegs, pins, posts, shanks, stems, struts
• CPC Class Codes: A61F 2002/444 for replacing the nucleus pulposus
• 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 2002/4495 having a fabric structure, e.g. made from wires or fibres
• 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 2230/0023 triangular
• CPC Class Codes: A61F 2230/0069 cylindrical
• CPC Class Codes: A61F 2230/0091 helically-coiled or spirally-coiled, i.e. having a 2-D spiral cross-section
• CPC Class Codes: A61F 2250/0097 : Visible markings, e.g. indicia
• CPC Class Codes: A61F 2250/0098 : radio-opaque, e.g. radio-opaque markers

Abstract

An elongated, pillow shaped prosthetic spinal disc nucleus body for implantation into a human intervertebral spinal disc, made of a hydrogel core and a flexible constraining jacket surrounding the hydrogel material core that permits the hydrogel core to expand and contract. The hydrogel core has a length approximating the sagittal diameter of a nucleus of the human disc, a width less than the length, and a height less than the length or width. The hydrogel core will expand and contract in a desired fashion as it imbibes and expels fluids in response to various loads placed upon the spinal tract. The constraining jacket is porous to allow fluids to pass through to the hydrogel core, but prevents the hydrogel from escaping, thus fostering the natural physiology of the human intervertebral disc. By implanting two prosthetic spinal disc nucleus bodies side-by-side into a damaged disc of a human spine, both height and motion can be maintained.

Claims

1. A prosthetic disc nucleus for implantation into a human spinal disc having a nucleus area defined generally in a horizontal plane by an anulus and generally in a vertical plane by two vertebral end plates, the nucleus area having a sagittal diameter and a traverse diameter, the prosthetic disc nucleus comprising:

a hydrogel core having a length approximating the sagittal diameter of the nucleus area and a width less than half of the transverse diameter of the nucleus area, wherein the hydrogel core is configured such that it will consistently return to a predetermined shape following removal of a load; and

a jacket surrounding the hydrogel core, wherein the jacket is configured to have a horizontal limit in the horizontal plane of the nucleus area such that the jacket directs expansion of the hydrogel core to only the vertical plane of the nucleus area after expansion of the hydrogel core reaches the horizontal limit of the jacket.

2. The prosthetic disc nucleus of claim 1 wherein the predetermined shape is an oval frontal cross-section.

3. The prosthetic disc nucleus of claim 1 wherein the hydrogel core is subjected to a plurality of compressive forces prior to implant to render the hydrogel core to the predetermined shape.

4. The prosthetic disc nucleus of claim 1 wherein the hydrogel core is dehydrated prior to implantation and hydrated after implantation, and further wherein the hydrogel core constrained by the jacket is configured to expand predominately in height upon hydration.

5. The prosthetic disc nucleus of claim 1 wherein the hydrogel core is dehydrated prior to implantation and hydrated after implantation, and further wherein the jacket is configured to direct the hydrogel core to expand in the vertical plane upon hydration.

6. The prosthetic disc nucleus of claim 5 wherein the jacket is substantially inelastic for directing the hydrogel core to expand in the vertical plane upon hydration.

7. The prosthetic disc nucleus of claim 1 wherein the hydrogel core has a water content of 25-65% when fully hydrated.

8. The prosthetic disc nucleus of claim 1 wherein the jacket is a woven tube.

9. The prosthetic disc nucleus of claim 1 wherein the jacket has openings which permit fluids to pass through the jacket to the hydrogel core while blocking passage of the hydrogel core out of the jacket.

10. The prosthetic disc nucleus of claim 1 wherein the jacket is made of a high molecular weight, high tenacity material.

11. The prosthetic disc nucleus of claim 1 wherein the jacket is woven tube having two ends and wherein at least one end has a closure.

12. The prosthetic disc nucleus of claim 1, further including:

radiopaque material within the jacket.

13. The prosthetic disc nucleus of claim 1, further including:

means for maintaining the prosthetic disc nucleus within the disc area following implant, wherein the means for maintaining is attached to the jacket.

17. The prosthetic disc nucleus of claim 1 wherein the hydrogel core swells from the dehydrated state to the fully hydrated state, and further wherein the hydrogel core is configured to swell with enough to force to restore natural disc height.

14. A prosthetic disc nucleus for implantation into a human spinal disc having a nucleus area defined by an anulus, the nucleus area having a sagittal diameter and a transverse diameter, the prosthetic disc nucleus comprising:

a hydrogel core having a cylindrical body and a frontal cross-section which is a flattened oval, wherein the flattened oval cross-section defines a major axis and a minor axis; and

a jacket surrounding the hydrogel core, wherein the jacket is configured to have a horizontal limit in a plane defined by the major axis of the hydrogel core such that the jacket directs expansion of the hydrogel core to only the minor axis of the hydrogel core after expansion of the hydrogel core reaches the horizontal limit of the jacket.

15. The prosthetic disc nucleus of claim 14 wherein the frontal cross-section of the hydrogel core has a height which is less than a height of the anulus.

16. The prosthetic disc nucleus of claim 14 wherein the hydrogel core is in a dehydrated state prior to implantation and is in a fully hydrated state after implantation, and further wherein the fully hydrated hydrogel core constrained by the jacket is configured to provide a natural disc space height.

18. A prosthetic disc nucleus for implantation into a human spinal disc having a nucleus area with a generally horizontal plane, a sagittal diameter and a transverse diameter defined by an anulus, and a generally vertical plane defined by two vertebral end plates, the prosthetic disc nucleus comprising:

a hydrogel core having a length approximating the sagittal diameter of the nucleus area and a width less than half of the transverse diameter of the nucleus area, wherein the hydrogel core is dehydrated prior to implantation and hydrated after implantation and the hydrogel core is configured such that it will maintain a predetermined shape after hydration; and

a jacket surrounding the hydrogel core, wherein the jacket is configured to have a horizontal limit in the horizontal plane of the nucleus area such that the jacket directs expansion of the hydrogel core to only the vertical plane of the nucleus area after expansion of the hydrogel core, reaches the horizontal limit of the jacket.

19. A prosthetic disc nucleus for implantation into a human spinal disc having a nucleus area defined by an anulus, the nucleus area having a sagittal diameter and a transverse diameter, the prosthetic disc nucleus comprising:

a hydrogel core having a length approximating the sagittal diameter of the nucleus area, a width less than half of the transverse diameter and a frontal cross-section which is a flattened oval having a major axis and a minor axis, wherein the hydrogel core has a water content of 25-65% when fully hydrated and is subjected to a plurality of compressive cycles prior to implantation so that the hydrogel core is configured such that it will consistently return to a predetermined shape following removal of a load; and

a substantially inelastic woven tube surrounding the hydrogel core, wherein the woven tube is configured to have a horizontal limit in a plane defined by the major axis of the hydrogel core such that the jacket directs expansion of the hydrogel core to only the minor axis of the hydrogel core after expansion of the hydrogel core reaches the horizontal limit of the jacket.

20. A method of manufacturing a prosthetic disc nucleus for implantation into a human disc having a nucleus area defined by an anulus, the nucleus area having a sagittal diameter and a transverse diameter, the method including:

forming a cylindrical hydrogel core having a flattened oval-shaped frontal cross-section which defines a major axis and a minor axis;

forming a woven jacket having a limit in a plane defined by the major axis of the hydrogel core, wherein the jacket is configured to direct expansion of the hydrogel core only to a direction defined by the minor axis once expansion of the hydrogel core reaches the limit of the jacket;

inserting the hydrogel core into an open end of the woven jacket; and

closing the open end of the woven jacket to surround the hydrogel core.

21. The method of manufacturing of claim 20, further including:

hydrating the hydrogel core after insertion into the woven jacket.

22. The method of manufacturing of claim 20, further including:

subjecting the hydrogel core to a plurality of compressive loads prior to implant.

23. The method of manufacturing of claim 20 wherein the hydrogel core has a length approximating the sagittal diameter and a width which is less than half of the transverse diameter.