Spinal implants

1. An interbody spinal implant for insertion into an implantation space formed at least in part between and into two adjacent vertebral bodies of the human spine, said implant comprising:

a body having a leading end, a trailing end, an upper surface adapted to contact one of the adjacent vertebral bodies, and a lower surface adapted to contact the other of the adjacent vertebral bodies, a central longitudinal axis through said leading and trailing ends, and a width perpendicular to the central longitudinal axis, each of said upper and lower surfaces having an arcuate surface extending across at least a portion of the width of said body;

a first plurality of surface projections, each of said first plurality of surface projections having a head and a neck, said head and said neck each having a width in a plane parallel to the width of said body, the width of said head being greater than the width of said neck, said head having a linear portion along at least a portion of the width of said head, said head having a curved portion along at least a portion of the width of said head, said head being configured to extend above said arcuate surface of one of said upper and lower surfaces, said first plurality of surface projections being configured for rotation into at least one of the adjacent vertebral bodies; and

a second plurality of surface projections, each of said second plurality of surface projections having a sharp edge extending generally along at least a portion of the width of said body, said second plurality of surface projections being configured for rotation into at least one of the adjacent vertebral bodies.

2. The implant of claim 1 , wherein said leading end is curved across the width of said implant, said trailing end having a linear portion across the width of said implant.

3. The implant of claim 1 , wherein said arcuate surfaces extend across the entire width of said implant.

4. The implant of claim 1 , wherein said first plurality of surface projections includes a plurality of posts.

5. The implant of claim 4 , wherein said posts are integrally formed with at least one of said upper and lower surfaces.

6. The implant of claim 5 , wherein said posts are integrally formed on both of said upper and lower surfaces.

7. The implant of claim 1 , wherein said second plurality of surface projections includes threads.

8. The implant of claim 7 , wherein said threads extend from at least one of said upper and lower surfaces.

9. The implant of claim 7 , wherein said threads extend from both of said upper and lower surfaces.

10. The implant of claim 9 , wherein said threads have a frusto-conical outer locus.

11. The implant of claim 1 , wherein said body has a substantially circular cross-section perpendicular to the central longitudinal axis.

12. The implant of claim 1 , wherein said trailing end includes an engagement area configured to engage an instrument to rotate at least a portion of said implant into the implantation space.

13. The implant of claim 1 , wherein each of said upper and lower surfaces include a plurality of recesses.

14. The implant of claim 13 , wherein said recesses are in communication with one another.

15. The implant of claim 1 , wherein said implant is a spinal fusion implant.

16. The implant of claim 1 , in combination with a fusion promoting substance.

17. The implant of claim 1 , wherein said implant is at least in part bioabsorbable.