Spinal fixation system
A spinal fixation system includes an expandable disc replacement body and an adjustment mechanism. The expandable disc replacement body includes a first wall, a second wall, a hinge connecting the first wall and the second wall, and a first bone-screw receiving section at a proximal end of the first wall. The adjustment mechanism is positioned between the first wall and the second wall, and an angle between the first wall and the second wall can be varied by movement of the adjustment mechanism.
1. A spinal fixation system comprising:
an expandable disc replacement body including a first wall, a second wall, a hinge at a posterior position of the expandable disc replacement body hingedly coupling the first wall to the second wall, and a first bone-screw receiving section at an anterior position of the expandable disc replacement body and at a proximal end of the first wall, the first wall including a first bone contacting surface for engaging a superior vertebra of a spine, the second wall including a second bone contacting surface for engaging an inferior vertebra of the spine; and
an adjustment mechanism positioned between the first wall and the second wall, the adjustment mechanism includes a first wedge, a second wedge, a first wedge translating screw, a second wedge translating screw, a first internally threaded cylinder and a second internally threaded cylinder, wherein the first wedge and the second wedge are independent from each other and slidably engage the first and second walls,
wherein the first wedge includes a first wedge screw aperture for receiving the first wedge translating screw which is threadably connected to the first internally threaded cylinder that is directly coupled to a first lateral side of the hinge of the expandable disc replacement body at the posterior position,
wherein the second wedge includes a second wedge screw aperture for receiving the second wedge translating screw which is threadably connected to the second internally threaded cylinder that is directly coupled to a second lateral side of the hinge of the expandable disc replacement body at the posterior position, wherein the second lateral side is opposite to the first lateral side,
wherein an angle between the first wall and the second wall is configured to be continuously varied between a lower value of the angle and an upper value of the angle by rotating either of the first wedge translating screw and the second wedge translating screw to slide the corresponding one of the first wedge and second wedge from the anterior position towards the posterior position along the first and second walls to pivot the first wall relative to the second wall about the hinge at the posterior position.
2. The system of claim 1 wherein:
the expandable disc replacement body includes a second bone-screw receiving section at a proximal end of the second wall.
3. The system of claim 2 wherein:
the second bone-screw receiving section has a third opening for receiving a third bone screw, the third opening having a third longitudinal axis and
the second bone-screw receiving section has a fourth opening for receiving a fourth bone screw, the fourth opening having a fourth longitudinal axis and
the third longitudinal axis and the fourth longitudinal axis diverge in a direction toward a distal end of the expandable disc replacement body.
4. The system of claim 3 wherein:
the third opening includes a third snap ring recess containing a third snap ring, and
the fourth opening includes a fourth snap ring recess containing a fourth snap ring.
5. The system of claim 4 wherein:
when the third bone screw is received within the third opening, the third snap ring expands into the third snap ring recess to allow entry of the third bone screw and once the third bone screw passes the third snap ring, the third snap ring contracts, effectively blocking the third bone screw from backing out, and
when the fourth bone screw is received within the fourth opening, the fourth snap ring expands into the fourth snap ring recess to allow entry of the fourth bone screw and once the fourth bone screw passes the fourth snap ring, the fourth snap ring contracts, effectively blocking the fourth bone screw from backing out.
6. The system of claim 1 wherein:
the first bone-screw receiving section has a first opening for receiving a first bone screw, the first opening having a first longitudinal axis, and
the first bone-screw receiving section has a second opening for receiving a second bone screw, the second opening having a second longitudinal axis and
the first longitudinal axis and the second longitudinal axis diverge in a direction toward a distal end of the expandable disc replacement body.
7. The system of claim 6 wherein:
the first bone-screw receiving section has a first recessed edge between the first opening and the second opening.
8. The system of claim 6 wherein:
the first bone-screw receiving section has a first grasping recess between the first opening and the second opening.
9. The system of claim 8 further comprising:
a disc replacement holder including four angled drill guide holes and a grasping mechanism which detachably couples to the grasping recess of the first wall.
10. The system of claim 6 wherein:
the first opening includes a first snap ring recess containing a first snap ring, and
the second opening includes a second snap ring recess containing a second snap ring.
11. The system of claim 10 wherein:
when the first bone screw is received within the first opening, the first snap ring expands into the first snap ring recess to allow entry of the first bone screw and once the first bone screw passes the first snap ring, the first snap ring contracts, effectively blocking the first bone screw from backing out, and
when the second bone screw is received within the second opening, the second snap ring expands into the second snap ring recess to allow entry of the second bone screw and once the second bone screw passes the second snap ring, the second snap ring contracts, effectively blocking the second bone screw from backing out.
12. The system of claim 1 wherein,
the first wedge screw aperture includes a first wedge snap ring recess containing a first wedge snap ring.
13. The system of claim 12 wherein,
when the first wedge translating screw is received within the first wedge screw aperture, the first wedge snap ring expands into the first wedge snap ring recess to allow entry of the first wedge translating screw and once the first wedge translating screw passes the first wedge snap ring, the first wedge snap ring contracts, effectively blocking the first wedge translating screw from backing out.
14. The system of claim 1 wherein:
the rotation of either of the first wedge translating screw and the second wedge translating screw correlates to a predetermined change in the angle between the first and second walls.
15. The system of claim 1 wherein:
the first wedge and the second wedge are configured for sliding along the first and second wall in at least one of equal and unequal amount to make a first adjustment angle between the first wall and the second wall on one of the first and second lateral sides of the expandable disc replacement body same as or different than a second adjustment angle between the first wall and the second wall on another of the first and second lateral sides of the expandable disc replacement body.
16. The system of claim 1 wherein:
the first wall has a first space to allow for insertion of bone graft, and
the second wall has a second space to allow for insertion of bone graft.
17. The system of claim 1 wherein:
the hinge is formed by a pliable material.
18. The system of claim 1 wherein:
either of the first and second wedge translating screws is configured to provide a feedback indicating an increment of sliding of the corresponding first and second wedges relative to the first wall and the second wall.
19. The system of claim 18 wherein:
a head of either the first and second wedge translating screws includes markings which provides the feedback.
20. The system of claim 1 wherein:
at least one of the first bone contacting surface and the second bone contacting surface is a contoured bone engaging surface.
21. The system of claim 1 wherein:
the hinge comprises a pair of arcuate structures, a pair of cylindrical structures, one of the pair of arcuate structures surrounding one of the pair of cylindrical structures, the other of pair of arcuate structures surrounding the other of the pair of cylindrical structures,
the pair of arcuate structures is connected to at least one of the first wall and the second wall, and
the pair of cylindrical structures is connected to the other of the first wall and the second wall.
22. The system of claim 21 wherein:
an arcuate length of at least one of the pair of arcuate structures is used to limit the upper value of the angle by contacting one of the first wall and the second wall.
23. The system of claim 21 wherein:
the first wall has a first space to allow for insertion of bone graft, and
the hinge comprises a bar connecting the pair of arcuate structures or the pair of cylindrical structures.
24. The system of claim 23 wherein:
the bar is convex on a side facing the first space.
25. The system of claim 21 wherein:
one of the first wall and the second wall includes a pair of channels,
the first wedge includes a protrusion which extends into and is slidable in one of the pair of channels, and
the second wedge includes a protrusion which extends into and is slidable in the other of the pair of channels.
26. The system of claim 25 wherein:
the first wedge and the second wedge are located at the opposite first and second lateral sides of the first and second walls.
27. The system of claim 21 wherein:
the first wedge translating screw and the second wedge translating screw are configured to be inserted in unequal amounts to make a first adjustment angle between the first wall and the second wall on the first lateral side of the expandable disc replacement body different than a second adjustment angle between the first wall and the second wall on the second lateral side of the expandable disc replacement body.
28. The system of claim 1 wherein:
at least one of the first wall and the second wall includes a channel, and
the first wedge includes a protrusion which extends into and is slidable in the channel.
29. The system of claim 28 wherein:
the sliding of the first wedge is along an axis parallel to the second wall.
30. The system of claim 1 wherein:
the adjustment mechanism includes a locking component which prevents the adjustment mechanism from changing the angle between the first wall and the second wall when engaged with either of the first wedge translating screw and the second wedge translating screw, and at least one of the first wall and the second wall.
31. The system of claim 30 wherein:
the locking component comprises a locking tine if contacting the expandable disc replacement body configured to be inserted into a head of either of the first wedge translating screw and the second wedge translating screw in order to prevent further rotational motion.
32. The system of claim 30 wherein:
the locking component comprises a locking ring contacting the expandable disc replacement body configured to surround a head of either of the first wedge translating screw and the second wedge translating screw in order to prevent further rotational motion.
33. The system of claim 32 wherein:
the locking ring comprises at least one of teeth, one or more insertable posts, one or more insertable spades, a square cover, a hex cover, or a torx cover for contacting the head of either of the first wedge translating screw and the second wedge translating screw.
34. A multi-level spinal fixation system comprising:
a first spinal fixation system according to claim 1 ;
a second spinal fixation system according to claim 1 ; and
a clamp dimensioned to couple together the first spinal fixation system according to claim 1 and the second spinal fixation system according to claim 1 when the first spinal fixation system according to claim 1 and the second spinal fixation system according to claim 1 are implanted in different intervertebral disc spaces.