Porous interbody fusion device having integrated polyaxial locking interference screws
View Patent ↗A porous metal intervertebral spacer having at least one angled through hole extending from the side of the implant to a surface which interfaces with a vertebral body end plate such that an interference screw may be driven through the implant and into the bone, thereby securing the implant from undesired motion. In particular, the through holes are tapered to receive a screw and coupling element therethrough such that once fully seated, the screw is locked to the implant by virtue of a coupling element-through hole mutually tapered nesting. The head of the screw is round, as is the interior of the coupling element, thereby allowing the screw to be inserted at various angles relative to the hole without interfering with the proper seating of the coupling element in the through hole.
1. An intervertebral spacer device comprising:
a member constructed of a porous material with pore sizes ranging from 100 to 500 microns, the member having a top surface, a bottom surface, a side surface, and at least one hole extending from the side surface through the member to and through one of the top or bottom surfaces, the at least one hole including a continuous taper that extends fully through the spacer forming a larger diameter at the side surface and a smaller diameter at the one of the top or bottom surfaces;
at least one screw including a semi-spherical head; and
at least one coupling element including a semi-spherical interior volume with a width that is larger at an interior than at either opposing ends and a continuous exterior taper that reduces in width from a top side to a bottom side, the at least one coupling element mountable to the semi-spherical head of the at least one screw such that the at least one screw and the at least one coupling element are rotatable relative to each other, the at least one screw insertable into the at least one hole such that the at least one coupling element is lockable within the at least one hole, the at least one coupling element responsive to compressive loads between the screw and the member to cause the at least one coupling element to frictionally engage the semi-spherical head of the at least one screw and lock the at least one screw in the at least one hole, wherein the at least one coupling element includes a slot, the slot extending an axial length of the at least one coupling element such that the at least one coupling element has an incomplete periphery.
2. The intervertebral spacer device of claim 1 , wherein the porous material is a porous metal material which forms a bone-like lattice microstructure.
3. The intervertebral spacer device of claim 1 , wherein the top surface and the bottom surface of the member are convex.
4. The intervertebral spacer device of claim 1 , wherein the slot includes opposed inner surfaces that move together in response to the applied compressive load to reduce a size of the semi-spherical interior volume and lock onto the semi spherical head of the at least one screw.
5. An intervertebral spacer device comprising:
a member having a top surface, a bottom surface, a side surface, and at least one hole, the at least one hole defining a passage through the member between the side surface and at least one of the top or bottom surfaces, the at least one hole including a continuous taper forming a larger diameter at the side surface and a smaller diameter at the one of the top or bottom surfaces, the member constructed of a porous material with pore sizes ranging from 100 to 500 microns;
at least one screw including a semi-spherical head; and
at least one coupling element including a tapered exterior that decreases in width from a top side to a bottom side, the coupling element mountable to the semi-spherical head of the at least one screw such that the at least one screw and the at least one coupling element are rotatable relative to each other, the at least one coupling element responsive to compressive loads between the screw and the member to cause the at least one coupling element to frictionally engage the semi-spherical head of the at least one screw and secure the at least one screw in the at least one hole, wherein the at least one hole at the side surface has a first diameter that is greater than a diameter of the semi-spherical head and has a second diameter at the one of the top or bottom surfaces that is less than a diameter of the coupling portion.
6. The intervertebral spacer device of claim 5 , wherein the exterior taper of the at least one coupling element corresponds to the taper of the at least one hole.
7. The intervertebral spacer device of claim 5 , wherein insertion of the at least one screw and the at least one coupling element into the at least one hole compresses the at least one coupling element causing the at least one coupling element to secure the at least one screw at an angle relative to the at least one hole.
8. The intervertebral spacer device of claim 5 , wherein the at least one coupling element includes a slot, the slot having opposed inner surfaces that move together in response to the applied compressive load.
9. The intervertebral spacer device of claim 5 , wherein the at least one coupling element includes a slot, the slot extending an axial length of the at least one coupling element such that the at least one coupling element has an incomplete periphery.