Artificial intervertebral disc assembly

• US 20050273169A1
• Filed: 02/22/2005
• Published: 12/08/2005
• Est. Priority Date: 02/23/2004
• Status: Active Grant

• Current Assignee: Alphatec Spine Incorporated (Alphatec Holdings Incorporated)
• Original Assignee: Alphatec Spine Incorporated (Alphatec Holdings Incorporated)
• Inventors: Purcell, Thomas
• Granted Patent: US 7,485,145 B2
• Time in Patent Office: Days
• US Class Current: 623/17.120
• 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 2/441 made of inflatable pockets or chambers filled with fluid, e.g. with hydrogel
• CPC Class Codes: A61F 2/4425 made of articulated components
• CPC Class Codes: A61F 2002/30354 Cylindrically-shaped protrusion and recess, e.g. cylinder of circular basis
• CPC Class Codes: A61F 2002/30364 Rotation about the common longitudinal axis
• CPC Class Codes: A61F 2002/3037 Translation along the common longitudinal axis, e.g. piston
• CPC Class Codes: A61F 2002/30383 made by laterally inserting a protrusion, e.g. a rib into a complementarily-shaped groove
• CPC Class Codes: A61F 2002/30448 using adhesives
• CPC Class Codes: A61F 2002/30649 Ball-and-socket joints
• CPC Class Codes: A61F 2002/30769 madreporic
• 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 2002/30892 parallel
• CPC Class Codes: A61F 2002/443 having two transversal endplates and at least one intermediate component
• 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 2220/005 using adhesives
• 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: A61F 2310/00796 Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite

Abstract

An artificial intervertebral disc assembly including upper and lower end plates, an expandable bladder carried by the end plates and circumscribing a containment area therebetween. A biocompatible fluid is disposed within the containment area. A cylinder having a plurality of apertures therein projects from the lower plate into the containment area. A piston having a curvilinear upper surface is reciprocally moveable within the cylinder and projects from the open end thereof. A cylindrical projection depending from the upper plate bears against and mates with the upper surface of the piston so as to allow relative rotational movement of the end plates into and out of parallel alignment. By varying the size of the apertures in the cylinder and the elasticity of the bladder, the amount of axial load necessary to effect inward movement of the end plates can be varied.

Claims

1. An artificial intervertebral disc assembly adapted to be implanted adjacent the end plates of the vertebral body following the removal of a diseased or damaged intervertebral disc, said assembly comprising:

an upper end plate;

a lower end plate, said plates each defining an inner surface and an outer vertebral body engaging surface;

an expandable bladder carried by said plates and circumscribing a fluid containment area therebetween;

a biocompatible fluid disposed within said containment area between said end plates;

a cylinder projecting from said inner surface of said lower plate into said containment area and having an open upper end;

a piston reciprocally moveable within said cylinder and projecting from said open end thereof, said piston defining a curvilinear upper surface;

a projection depending from said inner surface of said upper end plate into said containment area, said projection defining a curvilinear lower surface for mating with said upper surface of said piston so as to allow relative rotational movement of said end plates and into and out of parallel alignment and a plurality of fluid flow apertures disposed in said cylinder below said piston.

2. The assembly of claim 1 wherein said end plates are oval-shaped.

3. The assembly of claim 1 wherein said outer surfaces on said discs define a plurality of spikes, ribs or ridges thereon for engaging the end plates of the vertebral body and preventing migration of said assembly.

4. The assembly of claim 1 wherein said outer surfaces of said discs define dove-tailed projections thereon for engaging mating surfaces formed in the end plates of the vertebral body and preventing migration of said assembly.

5. The assembly of claim 1 wherein said expandable bladder is formed of a flexible polymer material having a predetermined measure of elasticity and wherein said apertures in said cylinder collectively define a fluid flow area of predetermined size, said area cooperating with said measure of elasticity to define the desired axial force necessary to effect relative inward movement of said end plates.

6. The assembly of claim 3 wherein said discs are oval-shaped.

7. The assembly of claim 4 wherein said discs are oval-shaped.

8. The assembly of claim 5 wherein said discs are oval-shaped.

9. The assembly of claim 5 wherein said outer surfaces on said discs define a plurality of spikes, ribs or ridges thereon for engaging the end plates of the vertebral body and preventing migration of said assembly.

10. The assembly of claim 5 wherein said outer surfaces of said discs define dove-tailed projections thereon for engaging mating surfaces formed in the end plates of the vertebral body and preventing migration of said assembly.

11. An artificial intervertebral disc assembly adapted to be implanted adjacent the end plates of the vertebral body following the removal of a diseased or damaged intervertebral disc, said assembly comprising:

an upper end plate;

a lower end plate, said plates each defining an inner surface and an outer vertebral body engaging surface;

an expandable bladder having a predetermined measure of elasticity carried by said plates and circumscribing a fluid containment area therebetween;

a biocompatible fluid disposed within said containment area between said end plates;

a cylinder projecting from said inner surface of said lower plate into said containment area and having an open upper end;

a piston reciprocally moveable within said cylinder and projecting from said open end thereof, said piston defining a curvilinear upper surface;

a projection depending from said inner surface of said upper end plate into said containment area, said projection defining a curvilinear lower surface for mating with said upper surface of said piston so as to allow relative rotational movement of said end plates and into and out of parallel alignment and a plurality of fluid flow apertures of predetermined size disposed in said cylinder below said piston whereby inward movement of said end plates will cause fluid in said cylinder to pass outwardly through said apertures therein and expand said bladder such that variations in the collective area defined by said apertures and the elasticity of said bladder will vary the amount of axial load necessary to effect such inward movement of said end plates.

12. The assembly of claim 11 wherein said end plates are oval-shaped.

13. The assembly of claim 11 wherein said outer surfaces on said discs define a plurality of spikes, ribs or ridges thereon for engaging the end plates of the vertebral body and preventing migration of said assembly.

14. The assembly of claim 11 wherein said outer surfaces of said discs define dove-tailed projections thereon for engaging mating surfaces formed in the end plates of the vertebral body and preventing migration of said assembly.

15. An artificial intervertebral disc assembly adapted to be implanted adjacent the end plates of the vertebral body following the removal of a diseased or damaged intervertebral disc, said assembly comprising:

an upper end plate;

a lower end plate, said plates each defining an inner surface and an outer vertebral body engaging surface;

an expandable bladder carried by said plates and circumscribing a fluid containment area therebetween;

a biocompatible fluid disposed within said containment area between said end plates;

a fluid flow path disposed between said end plates within said fluid containment area such that relative inward movement of said end plates effects fluid flow through said path so as to urge said bladder to expand outwardly such that variations in the size of said fluid flow path and the elasticity of said bladder will vary the amount of axial load necessary to effect such inward movement of said end plates.

16. The assembly of claim 15 wherein said end plates are oval-shaped.

17. The assembly of claim 15 wherein said outer surfaces on said discs define a plurality of spikes, ribs or ridges thereon for engaging the end plates of the vertebral body and preventing migration of said assembly.

18. The assembly of claim 15 wherein said outer surfaces of said discs define dove-tailed projections thereon for engaging mating surfaces formed in the end plates of the vertebral body and preventing migration of said assembly.

19. A method for varying the axial force necessary to effect relative movement of the end plates in an artificial disc assembly to accommodate patients of varying size, said method comprising the steps of providing a fluid flow path of predetermined size between the end plates of the assembly such that relative inward movement of said end plates effects fluid flow through said path and circumscribing an area between said end plates and about said fluid flow path with a flexible bladder having a predetermined measure of elasticity.