Surgically implanting threaded fusion cages between adjacent low-back vertebrae by an anterior approach

• US 5,055,104 A
• Filed: 11/06/1989
• Issued: 10/08/1991
• Est. Priority Date: 11/06/1989
• Status: Expired due to Term

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: Surgical Dynamics Incorporated (Medtronic Plc)
• Inventors: Ray, Charles D.
• Primary Examiner(s): Yu, Mickey
• Assistant Examiner(s): BROWN, MICHAEL A
• Application Number:
  US07/432,087
• Time in Patent Office: 701 Days
• Field of Search: 606/53, 606/60, 606/61, 606/72, 606/73, 623/16, 623/17, 128/69, 267/162, 267/166, 267/168, 267/289, 267/290
• US Class Current: 606/247
• CPC Class Codes: A61B 17/1757 for the spine
• 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 2/446 having a circular or elliptical cross-section substantially parallel to the axis of the spine, e.g. cylinders or frustocones
• 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 2002/30062 (bio)absorbable, biodegradable, bioerodable, (bio)resorbable, resorptive
• CPC Class Codes: A61F 2002/3013 figure-"8"- or hourglass-shaped
• CPC Class Codes: A61F 2002/30131 horseshoe- or crescent- or C-shaped or U-shaped
• CPC Class Codes: A61F 2002/302 toroidal, e.g. rings
• CPC Class Codes: A61F 2002/30225 Flat cylinders, i.e. discs
• CPC Class Codes: A61F 2002/30289 helically-coiled
• CPC Class Codes: A61F 2002/30329 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2002/30405 made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/30451 soldered or brazed or welded
• CPC Class Codes: A61F 2002/305 Snap connection
• CPC Class Codes: A61F 2002/30565 having spring elements
• CPC Class Codes: A61F 2002/30566 Helical springs
• CPC Class Codes: A61F 2002/30568 Multiple spring systems including two or more helical springs
• CPC Class Codes: A61F 2002/30593 : hollow
• CPC Class Codes: A61F 2002/30841 : Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2002/3085 : with a threaded, e.g. self-tapping, bone-engaging surface, e.g. external surface
• 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 2210/0004 : bioabsorbable
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0058 : soldered or brazed or welded
• CPC Class Codes: A61F 2230/001 : Figure-8-shaped, e.g. hourglass-shaped
• CPC Class Codes: A61F 2230/0013 : Horseshoe-shaped, e.g. crescent-shaped, C-shaped, U-shaped
• CPC Class Codes: A61F 2230/0065 : toroidal, e.g. ring-shaped, doughnut-shaped
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2230/0091 : helically-coiled or spirally-coiled, i.e. having a 2-D spiral cross-section
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys

Abstract

When an intervertebral fusion is required, and the disc space is unusualy large, that disc space can be preserved by surgically implanting a pair of relatively large male-thread fusion cages 20, 20A with their threads 13 overlapping. Because of their large size, such fusion cages 20, 20A should be implanted by an anterior approach to the lower back. When each of the cages is made of a shape-retaining helix 22 of wire that is hollow within the helix 22 and has openings 23 between adjacent turns, the cages 20, 20A can be removed after the adjacent vertebrae have become fused together and without disrupting that fusion, thus guarding against possible rejection of the cages 20, 20A by the patient'"'"'s body. The anterior approach and scaled-down fusion cages 20, 20A may be used in cervical spine fusions.

Claims

1. A fusion cage system for being implanted in and promoting fusion with respect to one of more bone structures, said fusion cage system for containing bone-growth-inducing substance packed therein for accelerating bone fusion, said fusion cage system comprising:

a first fusion cage which has a first outside dimension and a first internal cavity means for being packed with the bone-growth-induction substance;

a second fusion cage which has a second outside dimension and a second internal cavity means for being packed with the bone-growth-inducing substance;

at least one of the first fusion cage and the second fusion cage including means for allowing said first and second fusion cages to be positioned adjacent each other such that an outside dimension of the combination of the first fusion cage positioned adjacent the second fusion cage is less than the sum of the first outside dimension and the second outside dimension.

2. The fusion cage system of claim 1 wherein:

said first fusion cage and said second fusion cage include first and second means respectively for allowing immediate contact between the one or more bone structures and the bone-growth-inducing substance.

3. The fusion cage system of claim 1 wherein said allowing means includes means for intermeshing the first fusion cage with the second fusion cage.

4. The fusion cage system of claim 1 wherein said allowing means includes means for allowing the first fusion cage to be rotatably implanted and the second fusion cage to be rotatably implanted adjacent the first fusion cage.

5. The fusion cage system of claim 1 including means for blocking a portion of said first fusion cage and a portion of said second fusion cage to prevent tissue ingrowth where blocking occurs.

6. The fusion cage system of claim 1 wherein said allowing means includes a first helical structure formed by the first fusion cage and a second helical structure formed by the second fusion cage.

7. The fusion cage system of claim 6 wherein said first helical structure includes means for intermeshing with the second helical structure.

8. The fusion cage system of claim 1 wherein said first fusion cage includes a first cylindrical body and said allowing means includes a first wall formed along a chord of the first cylindrical body.

9. The fusion cage system of claim 1 wherein said first fusion cage includes a "C"-shaped cylindrical body and said allowing means includes an opening in said "C"-shaped cylindrical body that communicates with said first internal cavity means.

10. A fusion cage system for being implanted in and promoting fusion with respect to one or more bone structures, said fusion cage system for containing bone-growth-inducing substance packed therein for accelerating bone fusion, said fusion cage system comprising:

a first fusion cage which is substantially cylindrical in shape and which has a first outside diameter and a first internal cavity means for being packed with the bone-growth-inducing substance;

a second fusion cage which is substantially cylindrical in shape and which has a second outside diameter and a second internal cavity means for being packed with the bone-growth-inducing substance; and

said second fusion cage including means for allowing said first fusion cage to be rotatably positioned with respect to the one or more bone structures and with respect to the second fusion cage such that the outside dimension of the combination of the first fusion cage positioned adjacent the second fusion cage is less than the sum of the first outside diameter and the second outside diameter.

11. The fusion cage system of claim 10 wherein:

said first fusion cage and said second fusion cage include first and second means respectively for allowing immediate contact between the one or more bone structures and the bone-growth-inducing substance.

12. A fusion cage system for being implanted in and promoting fusion with respect to one or more bone structures, said fusion cage system for containing bone-growth-inducing substance packed therein for accelerating bone fusion, said fusion cage system comprising:

a first fusion cage which is substantially cylindrical in shape and which has a first outside diameter and a first internal cavity means for being packed with the bone-growth-inducing substance;

a second fusion cage which is substantially cylindrical in shape and which has a second outside diameter and a second internal cavity means for being packed with the bone-growth-inducing substance;

said first fusion cage including first means for allowing the intermeshing of the first fusion cage with the second fusion cage as the second fusion cage is rotatably positioned with respect to the one or more bone structures and with respect to the first fusion cage previously implanted with respect to one or more bone structures; and

said second fusion cage including second means for allowing the intermeshing of the second fusion cage with the first fusion cage as the second fusion cage is rotatably positioned with respect to the one or more bone structures and with respect to the first fusion cage previously implanted with respect to the one or more bone structures.

13. The fusion cage system of claim 12 wherein:

said first fusion cage and said second fusion cage include first and second means respectively for allowing immediate contact between the one or more bone structures and the bone-growth-inducing substances.

14. A fusion cage system for being implanted in and promote fusion with respect to one or more bone structures, said fusion cage system for containing bone-growth-inducing substance packed therein for accelerating bone fusion, said fusion cage system comprising:

a first fusion cage which is comprised of a first helical structure having a first inner surface which defines a first internal cavity, which first helical structure including a plurality of spaced apart first turns, said first helical structure having a first outer diameter;

a second fusion cage which is comprised of a second helical structure having a second inner surface which defines a second internal cavity, said second helical structure including a plurality of spaced apart second turns, said second helical structure having a second outer diameter;

wherein the spacing of the first turns and the spacing of the second turns is such that the first turns can intermesh with the second turns when the first fusion cage is implanted beside the second fusion cage with respect to the one or more bone structures, with the overall dimension of the first fusion cage intermeshed with the second fusion cage being less than the sum of the first outer diameter and the second outer diameter.

15. The fusion cage system of claim 14 wherein:

with the first and second fusion cages implanted in the one or more bone structures the spaces between the first turns and the second turns are so configured so that there is immediate contact between the one or more bone structures and the bone-growth-inducing substance packed into the first and second internal cavity.

16. The fusion cage system of claim 14 wherein:

said first turns have first substantially v-shaped outer surfaces pointing in a direction away from the first internal cavity; and

wherein said second turns have second substantially v-shaped outer surfaces pointing in a direction away from the second internal cavity, such that the first and second turns can intermesh in a side-by-side relative to each other, with the first v-shaped outer surfaces of the first turns pointing in opposite directions from the second v-shaped outer surfaces of the second turns at the location of side-by-side intermeshing.

17. The fusion cage system of claim 14 including:

first means for blocking a portion of the space between the first turns at a first location diametrically opposite from where the first turns intermesh with the second turns; and

second means for blocking a portion of the space between the second turns at a second location diametrically opposite from where the second turns intersect with the first turns so as to prevent tissue ingrowth where blocking occurs.

18. The fusion cage system of claim 17 wherein said first blocking means includes means for snapping into the space between the first turns, and the second blocking means includes means for snapping into the space between the second turns.

19. The fusion cage system of claim 14 including means for securing the first helical structure to the second helical structure.

20. The fusion cage system of claim 14 wherein said first fusion cage has a first axis about which said first helical structure is symmetrical and said second fusion cage has a second axis about which said second helical structure is symmetrical, such that with the first turns intermeshed with the second turns and with the first axis and the second axis separated by a distance, the distance is less than the first outer diameter or the second outer diameter.