A separate nub component between the plate and an intervertebral fusion cage, wherein the nub is attached to the plate. The nub lessens the undesired pivotal movement of the plate. It is believed that when the nub fits snugly between the endplates of the adjacent vertebral bodies, it acts as a stop against the undesired pivotal movement of the plate.
1. An intervertebral fusion device comprising:
a) an intervertebral fusion cage having an anterior wall, a posterior wall, leading and trailing walls connecting the anterior and posterior walls to form a central vertical throughhole, an upper surface adapted for gripping an upper endplate and a lower surface adapted for gripping a lower endplate;
b) a bone plate comprising a bone contacting surface, an inner surface, an outer surface, a plurality of sidewalls, upper and lower holes, and a central hole that opens laterally to at least one of the plurality of sidewalls,
c) a separate nub component interposed between the inner surface of the bone plate and the trailing wall of the cage, the separate nub component comprising a first wall facing the trailing wall of the cage and a second wall facing the inner surface of the bone plate, and a post extending from the second wall and wherein the post is disposed in the central hole that opens laterally;
wherein the inner surface of the bone plate is concave and the second wall of the separate nub is convex to provide tilting of the plate with respect to the nub component.
2. The device of claim 1 further comprising:
a) upper and lower bone anchors received in the respective upper and lower screw holes, each bone anchor having a proximal head and a shaft.
3. The device of claim 2 wherein each bone anchor is a bone screw, and the upper and lower holes in the bone plate are screw holes.
4. The device of claim 2 wherein the bone plate has first and second threaded recesses adjoining the respective upper and lower holes.
5. The device of claim 4 further comprising
a) first and second cams threadably received in the respective threaded recesses of the bone plate and bearing against the respective heads of the bone anchors.
6. The device of claim 2 wherein the shaft of the upper bone anchor and the upper surface of the cage define a first angle α, wherein the shaft of the lower bone anchor and the lower surface of the cage define a second angle β, and wherein the first angle α is not equal to the second angle β.
7. The device of claim 1 wherein the nub comprises:
a) a first wall contacting the trailing wall of the cage,
b) a second wall contacting the bone plate,
c) a threaded recess extending from the first wall to the second wall, and
wherein the post comprises a threaded post received in the threaded recess of the nub and passing through the hole of the bone plate.
8. The device of claim 7 wherein the threaded post has a proximal head, and wherein the proximal head of the threaded post and the hole of the bone plate form a polyaxial joint.
9. The device of claim 1 wherein the nub comprises:
a) a first wall contacting the trailing wall of the cage,
b) a second wall contacting the bone plate,
c) an upper surface adapted for gripping an upper endplate, and
d) a lower surface adapted for gripping a lower endplate
wherein each of the upper and lower surfaces of the nub is disposed between the first and second walls of the nub.
10. The device of claim 9 wherein the upper surface and lower surface of the cage define a cage height, wherein the lower surface and upper surface of the nub define a nub height, and wherein the nub height is substantially the same as the cage height.
11. The device of claim 1 wherein the leading wall of the cage has a rounded nose.
12. The device of claim 1 wherein the post snap fits in the hole that opens laterally.
13. The device of claim 1 wherein the post is generally cylindrically shaped.
14. The device of claim 13 wherein the post has a cylindrically shaped lateral outer portion.
15. The device of claim 1 wherein the post has a generally cylindrically shaped lateral outer portion, the central hole of the plate has a wall that is generally cylindrically shaped, and the outer portion of the post contact the wall of the central hole of the plate.
16. A method of performing surgery on a functional spinal unit comprising an intervertebral space and opposing vertebral bodies, comprising the steps of:
a) inserting the cage of the device of claim 1 into the disc space, and
b) fixing the plate of the device of claim 1 on the opposing vertebral bodies.
17. The method of claim 16 wherein the nub supports an ipsilateral rim of each vertebral body and the cage supports a contralateral rim of each vertebral body.