Piezoelectric spinal implant and methods of making and using same
A spinal implant capable of generating an electric output includes a first endplate, a second endplate, and a piezoelectric component disposed between the first and second endplates. The spinal implant may further include an intermediate body and a second piezoelectric component disposed between the intermediate body and the second endplate. The inner surfaces of the endplates and/or the intermediate body may be non-planar, such as having an undulating shape. The electric output is produced when the endplates of the spinal implant undergo a force, including a compressive force and/or a shear force.
1 . A spinal implant assembly comprising:
a first endplate having a first non-planar inner surface;
a second endplate attached to the first endplate and having a second non-planar inner surface facing toward the first non-planar inner surface; and
a component made entirely of a piezoelectric material, the component disposed between the first non-planar inner surface and the second non-planar inner surface and having a non-planar upper surface facing toward the first non-planar inner surface and a non-planar lower surface facing toward the second non-planar inner surface, wherein the first non-planar inner surface has first undulations and the second non-planar inner surface has second undulations, the first undulations including a first concave surface and a first convex surface, the first concave surface and the first convex surface together defining a first wavelike surface, the second undulations including a second concave surface and a second convex surface, the second concave surface and the second convex surface together defining a second wavelike surface.
2 . The spinal implant assembly of claim 1 , wherein the piezoelectric material includes a piezoelectric polymer.
3 . The spinal implant assembly of claim 2 , wherein the piezoelectric polymer includes polyvinylidene difluoride.
4 . The spinal implant assembly of claim 1 , wherein the first undulations and the second undulations are defined in a longitudinal direction of the spinal implant assembly and conform to one another, the first undulations and the second undulations to distribute compressive forces or shear forces applied to the first endplate and to the second endplate unevenly to the component.
5 . The spinal implant assembly of claim 1 , wherein the non-planar upper surface of the component conforms to and is adjacent to the first non-planar inner surface, and the non-planar lower surface of the component conforms to and is adjacent to the second non-planar inner surface.
6 . The spinal implant assembly of claim 4 , wherein the first undulations and the second undulations are further defined in a lateral direction of the spinal implant assembly.
7 . The spinal implant assembly of claim 1 , wherein the first endplate, the second endplate and the component are configured such that the first endplate and the second endplate are to cause a compressive force and a shear force on the component, at least one of the compressive force or the shear force to be distributed unevenly throughout the component.
8 . The spinal implant assembly of claim 7 , wherein the first endplate has a first outer surface and second endplates has a second outer surface, and wherein the component is configured to produce an electrical output corresponding to a load applied to the first outer surface and to the second outer surface.
9 . The spinal implant assembly of claim 1 , wherein the component is a first component, the piezoelectric material is a first piezoelectric material, the non-planar upper surface is a first non-planar upper surface, and the non-planar lower surface is a first non-planar lower surface, the spinal implant assembly further comprising:
a second component including a second piezoelectric material the second component disposed between the first non-planar inner surface and the second non-planar inner surface and having a second non-planar upper surface facing toward the first non-planar inner surface and a second non-planar lower surface facing toward the second non-planar inner surface; and
an intermediate body having a non-planar intermediate body top surface and a non-planar intermediate body bottom surface, the intermediate body disposed between the first component and the second component.
10 . The spinal implant assembly of claim 9 , wherein:
the first non-planar upper surface conforms to and is adjacent to the first non-planar inner surface, and the first non-planar lower surface conforms to and is adjacent to the non-planar intermediate body top surface of the intermediate body; and
the second non-planar upper surface conforms to and is adjacent to the non-planar intermediate body bottom surface of the intermediate body, and the second non-planar lower surface conforms to and is adjacent to the second non-planar inner surface.
11 . The spinal implant assembly of claim 9 , wherein the intermediate body includes an electrically insulating material.
12 . The spinal implant assembly of claim 1 , further comprising at least one fastener connecting the first endplate and the second endplate to one another.
13 . The spinal implant assembly of claim 12 , wherein:
the first endplate defines a first lumen therein and a plurality of first holes through sides thereof;
the second endplate defines a second lumen therein and a plurality of second holes through sides thereof; and
said at least one fastener includes:
a plurality of connecting brackets extending within the first lumen and the second lumen, each of the plurality of connecting brackets defining a top hole therein and a bottom hole therein, the top hole in registration with corresponding ones of the plurality of first holes, and the bottom hole in registration with corresponding ones of the plurality of second holes;
a plurality of top pins, respective ones of the plurality of top pins extending through the top hole of a corresponding one of said each of the plurality of connecting brackets and through corresponding ones of the plurality of first holes; and
a plurality of bottom pins, respective ones of the plurality of bottom pins extending through the bottom hole of a corresponding one of said each of the plurality of connecting brackets and through corresponding ones of the plurality of second holes.
14 . The spinal implant assembly of claim 13 , wherein the plurality of connecting brackets include an electrically insulating material.
15 . The spinal implant assembly of claim 13 , wherein individual ones of the plurality of connecting brackets have flat side surfaces and rounded top and bottom ends.
16 . The spinal implant assembly of claim 13 , wherein the plurality of first holes, the plurality of second holes, the top hole of said each of the plurality of connecting brackets, the bottom hole of said each of the plurality of connecting brackets, the plurality of top pins, and the plurality of bottom pins have a cylindrical configuration.
17 . The spinal implant assembly of claim 13 , wherein the plurality of connecting brackets includes two connecting brackets spaced from one another in a longitudinal direction of the spinal implant assembly.
18 . The spinal implant assembly of claim 12 , wherein:
the first endplate defines a plurality of threaded first holes therein extending vertically;
the second endplate defines a plurality of threaded second holes therein extending vertically, respective ones of the plurality of threaded second holes in registration with respective corresponding ones of the plurality of threaded first holes to form respective threaded vertical fastener holes; and
said at least one fastener includes a plurality of screws, respective ones of the plurality of screws extending through and engaging threads of respective ones of the threaded vertical fastener holes.
19 . The spinal implant assembly of claim 18 , wherein the plurality of screws include lag screws.
20 . The spinal implant assembly of claim 18 , wherein:
the first endplate has a first outer surface including first protrusions thereon, and the second endplate has a second outer surface including second protrusions thereon, the first protrusions and the second protrusions including at least one of teeth or spikes; and
the plurality of screws include respective heads at a vertical distance below a topmost portion of the first protrusions.
21 . The spinal implant assembly of claim 18 , the plurality of screws including two screws spaced from one another in a longitudinal direction of the spinal implant assembly.
22 . The spinal implant assembly of claim 1 , wherein the first endplate has a first outer surface including first protrusions thereon, and the second endplate has a second outer surface including second protrusions thereon, the first protrusions and the second protrusions including at least one of teeth or spikes.
23 . The spinal implant assembly of claim 1 , wherein the component includes a plurality of distinct layers, wherein at least one of the distinct layers includes the piezoelectric material.
24 . The spinal implant assembly of claim 1 , wherein the first undulations extend across an entirety of the first inner surface, and the second undulations extend across an entirety of the second inner surface.
25 . The spinal implant assembly of claim 1 , wherein the second wavelike surface conforms to the first wavelike surface.
26 . A kit to make a spinal implant assembly, the kit comprising:
a first endplate having a first non-planar inner surface;
a second endplate having a second non-planar inner surface, the first endplate and the second endplate configured to be attached to one another to form the spinal implant assembly; and
a component made entirely of a piezoelectric material, the component to be disposed between the first non-planar inner surface and the second non-planar inner surface in the spinal implant assembly, the component further configured to a have, when part of the spinal implant assembly, a non-planar upper surface facing toward the first non-planar inner surface and a non-planar lower surface facing toward the second non-planar inner surface, wherein the first non-planar inner surface has first undulations and the second non-planar inner surface has second undulations, the first undulations including a first concave surface and a first convex surface, the first concave surface and the first convex surface together defining a first wavelike surface, the second undulations including a second concave surface and a second convex surface, the second concave surface and the second convex surface together defining a second wavelike surface.
27 . The kit of claim 26 , wherein the first undulations and the second undulations are defined in a longitudinal direction of corresponding ones of the first endplate and of the second endplate, and configured to conform to one another, and wherein, in the spinal implant assembly, the non-planar upper surface of the component conforms to and is adjacent to the first non-planar inner surface, and the non-planar lower surface of the component conforms to and is adjacent to the second non-planar inner surface.
28 . The kit of claim 26 , further comprising at least one fastener to connect the first endplate and the second endplate to one another to form the spinal implant assembly.
29 . The kit of claim 28 , wherein:
the first endplate defines a first lumen therein and a plurality of first holes through sides thereof;
the second endplate defines a second lumen therein and a plurality of second holes through sides thereof; and
said at least one fastener includes:
a plurality of connecting brackets configured to extend within the first lumen and the second lumen, each of the plurality of connecting brackets defining a top hole therein and a bottom hole therein, the top hole configured to be in registration with corresponding ones of the plurality of first holes in the spinal implant assembly, and the bottom hole configured to be in registration with corresponding ones of the plurality of second holes in the spinal implant assembly;
a plurality of top pins, respective ones of the plurality of top pins configured to extend through the top hole of a corresponding one of said each of the plurality of connecting brackets and through corresponding ones of the plurality of first holes; and
a plurality of bottom pins, respective ones of the plurality of bottom pins configured to extend through the bottom hole of a corresponding one of said each of the plurality of connecting brackets and through corresponding ones of the plurality of second holes.
30 . The kit of claim 28 , wherein:
the first endplate defines a plurality of threaded first holes therein extending vertically;
the second endplate defines a plurality of threaded second holes therein extending vertically, respective ones of the plurality of threaded second holes to be, in the spinal implant assembly, in registration with respective corresponding ones of the plurality of threaded first holes to form respective threaded vertical fastener holes; and
said at least one fastener includes a plurality of screws, respective ones of the plurality of screws to extend through and to engage threads of respective ones of the threaded vertical fastener holes in the spinal implant assembly.
31 . A method of making a kit for a spinal implant assembly, the method comprising:
forming a first endplate having a first non-planar inner surface;
forming a second endplate having a second non-planar inner surface, the first endplate and the second endplate configured to be attached to one another to form the spinal implant assembly;
forming a component made entirely of a piezoelectric material, the component to be disposed between the first non-planar inner surface and the second non-planar inner surface in the spinal implant assembly, the component further configured to a have, when part of the spinal implant assembly, a non-planar upper surface facing toward the first non-planar inner surface and a non-planar lower surface facing toward the second non-planar inner surface, wherein the first non-planar inner surface has first undulations and the second non-planar inner surface has second undulations, the first undulations including a first concave surface and a first convex surface, the first concave surface and the first convex surface together defining a first wavelike surface, the second undulations including a second concave surface and a second convex surface, the second concave surface and the second convex surface together defining a second wavelike surface; and
organizing the first endplate, the second endplate, and the component together for joint provision as a kit for subsequent assembly into the spinal implant assembly.
32 . The method of claim 31 , wherein at least one of providing the first endplate or providing the second endplate includes using 3D printing.