Dynamic plate with inserts
View Patent ↗A spinal plate that is self-adjusting along its longitudinal axis to accommodate subsidence that may occur and aid in loading the bone graft to promote boney fusion while providing rigid fixation. The spinal plate is configured to inhibit loosening or backing out of bone screws.
1. A bone plate system operatively attachable to a bone, the bone plate system comprising:
a screw formed of titanium alloy having a first hardness;
a first segment including an alignment pin;
a second segment, the first and second segments positioned along a longitudinal axis and movable relative to one another, the first and second segments including respective screw holes configured to receive the screw, at least one of the first or second segments formed of an alloy different from the titanium alloy and having a second hardness;
an insert removably receivable in one of the screw holes to retain the screw therein, the insert formed of commercially pure titanium having a third hardness less than the first hardness and different from the second hardness;
a locking mechanism that inhibits relative axial movement of the first and second segments along the longitudinal axis away from one another and any non-axial movement of the first and second segments relative to one another, the locking mechanism defining a slot configured to slidably receive the alignment pin of the first segment; and
a rail extending axially from the first segment, wherein a portion of the rail is slidably engageable with the second segment independent of the locking mechanism.
2. The bone plate system of claim 1 , wherein the locking mechanism is releasable to permit axial movement of the first and second segments apart from one another.
3. The bone plate system of claim 2 , wherein moving the first and second segments apart from one another necessitates performing a secondary procedure.
4. The bone plate system of claim 1 , wherein the locking mechanism includes a tongue and a series of grooves, the tongue extending from one of the first and second segments, the series of grooves defined in the other of the first and second segments, the tongue operatively engaging the grooves to sequentially and releasably lock the first and second segments, thereby inhibiting axial movement of the first and second segments apart from one another while enabling axial movement of the first and second segments towards each other.
5. The bone plate system of claim 1 , wherein the first and second segments are attachable to vertebral bodies and the first and second segments automatically move toward one another in response to subsidence of the vertebral bodies.
6. The bone plate system of claim 1 , wherein the rail has a circular cross-section.
7. The bone plate system of claim 1 , wherein the second segment includes an engaging portion configured to slidably receive the rail therein.
8. The bone plate system of claim 7 , wherein the engaging portion includes a cross-section complementary to a cross-section of the rail.
9. The bone plate system of claim 1 , wherein the insert includes an inward facing lip configured to engage threads of the screw.
10. The bone plate system of claim 1 , wherein the rail extends axially from the first segment toward the second segment.
11. The bone plate system of claim 1 , wherein the screw is formed of implant grade titanium alloy.
12. The bone plate system of claim 1 , wherein the insert is configured to be deformed by the screw inserted therethrough.
13. The bone plate system of claim 12 , wherein the insert is press-fitted into one of the screw holes.
14. The bone plate system of claim 1 , wherein the slot of the locking mechanism is defined along a length of the locking mechanism.
15. The bone plate system of claim 1 , wherein the alignment pin of the first segment is configured to be received in the slot of the locking mechanism for axial displacement in the slot.
16. A bone plate operatively attachable to a bone comprising:
a first segment including an alignment pin;
a second segment, the first and second segments positioned along a common longitudinal axis, the first and second segments including respective screw holes for the reception of a screw formed of a first titanium alloy having a first hardness, at least one of the first or second segments formed of a second titanium alloy different from the first titanium alloy and having a second hardness;
an insert removably receivable within one of the screw holes, the insert formed from a material having a third hardness less than the first hardness and different from the second hardness;
a locking mechanism including a first locking structure defining a slot configured to receive the alignment pin of the first segment, and a second locking structure; and
a rail extending axially from the first segment, wherein a portion of the rail is slidably engageable with the second segment independent of the locking mechanism, wherein the first locking structure is secured to the first segment and the second locking structure is secured to the second segment, the first and second locking structures engaging each other to permit relative axial movement of the first and second segments toward each other and inhibit relative axial movement of the first and second segments away from one another.
17. The bone plate of claim 16 , wherein the first locking structure and the first segment are formed as a single construct.
18. The bone plate of claim 16 , wherein the second locking structure and the second segment are formed as a single construct.
19. The bone plate of claim 16 , wherein the insert is formed of commercially pure implant grade titanium, and the first or second segment is formed of implant grade titanium alloy.