Anterior expandable spinal fusion cage system

• US 20020138146A1
• Filed: 05/13/2002
• Published: 09/26/2002
• Est. Priority Date: 04/18/2000
• Status: Active Grant

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: Roger P. Jackson
• Inventors: Jackson, Roger P.
• Granted Patent: US 6,835,206 B2
• Time in Patent Office: Days
• US Class Current: 623/17.15
• 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 2/446 having a circular or elliptical cross-section substantially parallel to the axis of the spine, e.g. cylinders or frustocones
• CPC Class Codes: A61F 2/447 substantially parallelepipedal, e.g. having a rectangular or trapezoidal cross-section
• 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 2002/30131 horseshoe- or crescent- or C-shaped or U-shaped
• CPC Class Codes: A61F 2002/30143 hexagonal
• CPC Class Codes: A61F 2002/30507 using a threaded locking member, e.g. a locking screw or a set screw
• CPC Class Codes: A61F 2002/30515 using a locking wedge or block
• CPC Class Codes: A61F 2002/30517 using a locking plate
• CPC Class Codes: A61F 2002/30538 for adjusting angular orientation
• CPC Class Codes: A61F 2002/30556 for adjusting thickness
• 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 2002/30604 modular
• CPC Class Codes: A61F 2002/30616 Sets comprising a plurality of prosthetic parts of different sizes or orientations
• CPC Class Codes: A61F 2002/30774 internally-threaded
• CPC Class Codes: A61F 2002/30779 : arcuate
• CPC Class Codes: A61F 2002/30785 : parallel
• CPC Class Codes: A61F 2002/30787 : inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/3079 : Stepped or enlarged apertures, e.g. having discrete diameter changes
• CPC Class Codes: A61F 2002/3085 : with a threaded, e.g. self-tapping, bone-engaging surface, e.g. external surface
• CPC Class Codes: A61F 2002/30904 : serrated profile, i.e. saw-toothed
• 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 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2230/0013 : Horseshoe-shaped, e.g. crescent-shaped, C-shaped, U-shaped
• CPC Class Codes: A61F 2230/0017 : Angular shapes
• 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 2310/00131 : Tantalum or Ta-based alloys
• CPC Class Codes: Y10S 623/908 : Bone

Abstract

An apparatus and method for implanting an intervertebral cage containing a bone graft and fusing adjacent vertebrae together while maintaining or correcting the angular alignment and balance of the spine. The invention provides a greatly improved method for anterior interbody fusion to form a fused bone segment having a predetermined fixed angular orientation. The apparatus has a cage unit adjustably coupled to an expansion cap, and has a wedge which may be adjusted to support the adjacent vertebrae with facing surfaces at a predetermined angle relative to each other. The cage unit is fenestrated and hollow, to receive a packed, harvested bone graft. A connecting bolt may be threaded or fixed to the rear of the cage unit. In certain embodiments, the cage unit and expansion cap are interlocking. Also in certain embodiments, especially utilizing round cages, the expansion cap may also include upper and lower horizontal bone-supporting surfaces and an anterior recess for receiving fasteners. A pair of independently adjustable cage units is fixedly intercoupled by a link.

Claims

1. An implant apparatus for positioning between adjacent vertebrae and comprising:

a) an anterior inserted fusion cage having a pair of legs interconnected at one end each by a posterior wall having a threaded bore, said legs having free ends opposite said wall, said cage being adapted for implanting between said adjacent vertebrae with outer surfaces of said legs engaging said vertebrae respectively;

b) an anterior expansion cap having a wedge member positioned between said free ends of said legs in such a manner that movement of said wedge member toward said wall urges said leg free ends apart; and

c) a fastener engaging said wedge member and extending between said wedge member and said wall;

said fastener having a shank that is posteriorly threaded so as to be threadedly received in a threaded bore in said wall;

said fastener being rotatable so as to advance in said bore to selectively urge said wedge member toward said wall.

2. The apparatus according to claim 1 wherein:

a) said expansion wedge member is selected from a set of a plurality of interchangeable wedge members; and

b) each wedge member being sized to form said legs into a different predetermined angle relative to each other.

3. The apparatus according to claim 1 wherein:

a) said cage member includes an interior chamber for receiving bone fragments; and

b) a plurality of radially positioned apertures for permitting bone fragments in said chamber to join and fuse with bone in the adjacent vertebrae.

4. An apparatus for positionally stabilizing adjacent vertebrae of a spine by promotion of bone fusion between the adjacent vertebrae, said apparatus comprising:

a) an implant for anteriorly implanting between a pair of adjacent vertebrae, said implant adapted to promote bone growth between the adjacent vertebrae and having a posterior wall;

b) an expansion cap coupled with an anterior end of said implant for expanding an anterior portion of said implant for forming upper and lower surfaces of said implant into a predetermined angle relative to each other so as to be adapted to produce a desired alignment of the adjacent vertebrae; and

c) a fastener mechanism operably mating with said expansion cap at an anterior end of said fastener mechanism and being threadedly received at a posterior end of said fastener mechanism in a bore in said wall;

said fastener mechanism operably securing said expansion cap to said implant during use.

5. The apparatus according to claim 4 wherein:

a) said expansion cap is selected from a set including a plurality of different expansion caps; and

b) each cap of said set being sized to form said implant upper and lower surfaces into a different predetermined angle relative to each other.

6. The apparatus according to claim 4 wherein:

a) said implant includes an interior chamber for receiving bone fragments; and

b) a plurality of radially positioned apertures for permitting bone fragments in said chamber to join and fuse with bone in the adjacent vertebrae.

7. An apparatus for positionally stabilizing adjacent vertebrae of a spine by promotion of bone fusion between the adjacent vertebrae, said apparatus comprising:

a) a pair of anteriorly expandable implants for implanting in side-by-side relationship between a pair of adjacent vertebrae, each of said implants adapted to promote bone growth between the adjacent vertebrae;

b) an expansion unit intercoupling said implants and expanding an anterior portion of each implant for placing upper and lower surfaces of said implants into a predetermined angle relative to each other so as to be adapted to produce a desired alignment of the adjacent vertebrae; and

c) fasteners securing said expansion module to each of said implants.

8. The apparatus according to claim 7 wherein said implants each include:

a) an interior chamber for receiving bone fragments; and

b) a plurality of radially positioned apertures for permitting bone fragments in said chamber to join and fuse with bone in the adjacent vertebrae.

9. The apparatus according to claim 7 wherein:

a) said expansion unit includes a pair of expansion caps coupled by a connector with each cap being associated with a respective implant.

10. The apparatus according to claim 9 wherein:

a) each of said expansion caps includes a face; and

b) said connector is recessed posteriorly relative to said expansion cap faces.

11. An apparatus for positionally stabilizing adjacent vertebrae of a spine by promotion of bone fusion between the adjacent vertebrae, said apparatus comprising:

a) an anteriorly expandable implant adapted to promote bone growth between the adjacent vertebrae;

said implant having upper and lower legs joined posteriorly by a wall;

said wall operably preventing posterior expansion of said implant;

b) an expansion member coupled with said implant for operably expanding an anterior portion of said implant so as to modify the angular configuration of the upper and lower legs by spacing the anterior ends of the upper and lower legs;

c) an anterior cover assembly having upper and lower support surfaces for supporting an anterior region of the adjacent vertebrae; and

d) a fastener mechanism operably securing said cover assembly and said expansion member to said implant during use.

12. The apparatus according to claim 11 wherein:

a) said implant includes an interior chamber for receiving bone fragments; and

b) a plurality of radially positioned apertures for permitting bone fragments in said chamber to join and fuse with bone in the adjacent vertebrae.

14. The method according to claim 13 wherein said step of providing an expansion cap includes the step of:

a) providing a plurality of expansion caps of graduated sizes that are each independently and selectively usable to expand the anterior end of said implant.

15. The method according to claim 14 including the steps of:

a) selecting a first expansion cap;

b) coupling said first expansion cap with said implant and expanding said implant; and

c) removing said first expansion cap and repeating steps (a) through (c)with subsequent longer expansion caps, until said implant anterior end is expanded to a predetermined angle to produce a desired alignment of the adjacent vertebrae.

17. The apparatus according to claim 16 wherein:

a) said cap includes upper and lower surfaces shaped, sized and positioned to engage an anterior region of the vertebrae.

18. The apparatus according to claim 16 wherein:

a) said fusion cage is a threaded fusion cage that is cylindrical upon insertion between vertebrae.

19. The apparatus according to claim 16 including:

a) a pair of cages and a pair of caps; and

b) said caps being joined together by a link.

20. The apparatus according to claim 16 wherein:

a) said link is sized and positioned such that when said caps are joined with said cages, said cages are biased into non-parallel alignment with one another.

13. A method of stabilizing and promoting bone fusion between two adjacent vertebrae comprising the steps of:

a) providing an implant adapted to promote bone growth;

b) anteriorly implanting said implant between a pair of adjacent vertebrae;

c) providing an anteriorly positioned expansion cap adapted for expanding an anterior portion of upper and lower legs of said implant to a predetermined angle;

d) providing a fastener that extends between said cap and a posterior wall of said implant with said fastener being threadedly connected to said posterior wall; and

e) coupling said expansion cap with said implant and rotating said fastener so as to advance said fastener to expand an anterior end of said implant by operation of said expansion cap to position said legs in a predetermined angle relative to each other to produce a change in the alignment of the adjacent vertebrae.

16. In an anterior inserted fusion cage apparatus having a fusion cage for operably positioning between vertebrae and having a posterior wall, the improvement comprising:

a) an anterior expansion cap for expanding an anterior end of said cage to a selected degree of expansion; and

b) a fastener extending between said cap and said wall;

said fastener cooperating with said cap and said wall to expand said anterior end of said cage.

21. In an expandable fusion cage apparatus having a fusion cage for insertion between vertebrae, the improvement comprising:

a) a set of interchangeable expansion caps of different sizes and cooperating with said fusion cage to allow a surgeon to selectively adjust the expansion of said fusion cage.

22. An implant apparatus for positioning between adjacent vertebrae and comprising:

a) an anteriorly inserted fusion cage having a pair of legs interconnected at one end of each leg by a posterior wall, said legs having free ends opposite said wall, said cage being adapted for implanting between said adjacent vertebrae with outer surfaces of said legs engaging said vertebrae respectively; and

b) an expansion cap positioned between said free ends of said legs and including a fastener extending between said cap and said wall;

said fastener being threadably received in said wall and advancable so as to urge said cap toward said wall, whereby said leg free ends are urged apart and the spacing between the top and bottom of said cage at an anterior end thereof is increased, said cap not expanding the size of said cage from side to side or at a posterior end thereof.

24. The apparatus according to claim 23 wherein:

a) said expansion cap includes a recess for receiving a fastener to secure said cap to said implant.

25. The apparatus according to claim 23 wherein:

a) said implant includes an interior chamber for receiving bone fragments; and

b) a plurality of radially positioned apertures for permitting bone fragments in said chamber to join and fuse with bone in the adjacent vertebrae.

26. The apparatus according to claim 23 wherein:

a) said expansion cap and said implant include structure for cooperatively locking together said cap and said implant when fully joined.

28. The apparatus according to claim 27 wherein:

a) said expansion caps and said implants each include structure for cooperatively locking together said caps and said implants such that said implants are aligned in nonparallel configuration with respect to each other.

29. The apparatus according to claim 27 wherein:

a) each of said implants includes an interior chamber for receiving bone fragments; and

b) a plurality of radially positioned apertures for permitting bone fragments in said chamber to join and fuse with bone in the adjacent vertebrae.

23. An apparatus for positionally stabilizing adjacent vertebrae of a spine by promotion of bone fusion between the adjacent vertebrae, said apparatus comprising:

a) an implant for implanting between a pair of adjacent vertebrae, said implant adapted to promote bone growth between the adjacent vertebrae;

b) an expansion cap coupled with said implant for expanding an anterior portion of said implant to a predetermined angle to cause alignment of the adjacent vertebrae; and

c) said expansion cap including upper and lower support surfaces for supporting an anterior region of said adjacent vertebrae.

27. An apparatus for stabilizing between adjacent vertebrae of a spine by promotion of bone fusion between the adjacent vertebrae, said apparatus comprising:

a) a pair of anteriorly expandable implants for implanting in side-by-side relationship between a pair of adjacent vertebrae, each of said implants adapted to promote bone growth between the adjacent vertebrae;

b) a pair of expansion caps, each of said caps expanding an anterior portion of a respective implant for forming upper and lower surfaces of said implants into a predetermined angle relative to each other so as to be adapted to produce a desired alignment of the adjacent vertebrae;

c) said expansion caps each including cap upper and lower support surfaces for supporting an anterior region of said adjacent vertebrae;

d) a connector for connecting said implants in spaced relationship; and

e) a fastening mechanism operably securing said connector to each of said implants during use.