Spinal implant with expandable fixation

1. A spinal implant for placement in a space between opposed vertebral bodies, the implant being a single body comprising:

a. a first surface for engaging a first vertebral body;

b. a second surface for engaging a second vertebral body; and

c. at least two extendable fixation elements, each having a distal tip, a contracted configuration within the implant to facilitate deployment of the implant between the first and second vertebral bodies and an extended configuration to extend the distal tip beyond the second surface to engage the second vertebral body and to fix the implant within the space between the first and second vertebral bodies, said at least two extendable fixation elements being independently extendable and laterally spaced apart to define a central cavity between the laterally spaced fixation elements and the opposed vertebral body engaging surfaces, said cavity configured to receive bone graft material for infusion from said cavity into said space between the vertebral bodies,

wherein the second surface includes an opening for the at least two extendable fixation elements to extend therethrough at a plurality of angles relative to the second surface.

2. The implant of claim 1 wherein the first surface for engaging the first vertebral body includes a base member and the second surface for engaging the second vertebral body includes a pressure applying member.

3. The implant of claim 2 wherein at least two support members cooperate with the base and are coupled to the pressure applying member.

4. The implant of claim 3 wherein the pressure applying member has at least one passageway through which the distal tip of each said fixation element extends to engage the second vertebral body.

5. The implant of claim 3 wherein each support member is adapted to be extended.

6. The implant of claim 5 wherein each support member is adapted to be extended by fluid.

7. The implant of claim 6 wherein the fluid is hydraulic fluid.

8. The implant of claim 5 wherein each extendable fixation element is extendable with respect to a support member.

9. The implant of claim 5 wherein each extendable fixation element is extendable independent of a support member.

10. The implant of claim 5 wherein the extendable fixation element is slidably disposed within a bore of an extendable member.

11. The implant of claim 10 wherein the extendable fixation elements are extended by hydraulic fluid within the bore of the extendable member.

12. The implant of claim 5 wherein:

the base member defines at least two cylinders configured to sealingly receive the support members;

said central cavity is defined between said at least two cylinders, open to said space between the vertebral bodies; and

the support members each define an internal cylinder configured to sealingly receive the extendable fixation elements.

13. The implant of claim 12 wherein at least two of the extendable support members are adapted to be independently extended.

14. The implant of claim 12 wherein the support members are coupled to the pressure applying member with ball shaped connections.

15. The implant of claim 14 wherein at least two of the support members define bores extending from the internal cylinders and the extendable fixation elements extend through said bores.

16. The implant of claim 1 wherein the extendable fixation elements are adapted to be extended by fluid.

17. The implant of claim 10 wherein the fluid is hydraulic fluid.

18. The implant of claim 17 wherein the hydraulic fluid comprises a curable polymer having a fluid state for providing hydraulic communication of mechanical force to extend the fixation elements to engage a vertebral body.

19. The implant of claim 18 wherein the polymer is cured to a solid state to lock the extended fixation element to hold the spinal implant in the space between vertebral bodies.

20. The implant of claim 19 wherein the polymer comprises methyl methacrylate.

21. A spinal implant for placement in an intervertebral space between opposed vertebral bodies, comprising:

a base member defining first and second spaced apart cylinders;

first and second extendable members disposed, respectively, in said first and second cylinders;

first and second extendable fixation elements disposed, respectively, in said first and second extendable members and are independently extendable; and

a pressure applying plate cooperating with said first and second extendable members, and disposed opposite said base member to define a central cavity configured to receive bone graft material between said first and second cylinders and between said base member and pressure applying plate, said central cavity being open to the intervertebral space for communication therewith,

wherein the pressure applying plate includes an opening for the first and second fixation elements to extend therethrough at a plurality of angles relative to the pressure applying plate.

22. The spinal implant of claim 21 , wherein:

said base member has an outer surface opposite the central cavity configured for engaging a surface of a vertebral body; and

said pressure applying plate has an outer surface opposite the central cavity configured for engaging a surface of a vertebral body.

23. The spinal implant of claim 22 , wherein said extendable members and extendable fixation elements are extendable by fluid pressure exerted within said cylinders.

24. The spinal implant of claim 21 , wherein the central cavity is configured for infusion of bone graft material into an intervertebral space.