Non-metallic spinal screw

Abstract

A medical implant (10) includes a non-metallic core (26) comprising polyetheretherketone, and a non-metallic reinforcement layer (34) coupled to the core. The core is at least partially encapsulated by the reinforcement layer, and the reinforcement layer includes carbon fiber strands.

Description

NON-METALLIC SPINAL SCREWBACKGROUND

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 593,383, filed 26 October 2023, the entire content of which is incorporated herein by reference.

[0002] Treatment of spinal disorders, such as degenerative disc disease, disc herniations, scoliosis or other curvature abnormalities, and fractures, often requires surgical treatments. For example, implants may be used to preserve motion between vertebral members.

[0003] Surgical treatment typically involves the use of longitudinal members, such as spinal rods. Spinal rods may be attached to the exterior of two or more vertebral members to assist with the treatment of a spinal disorder. Spinal rods may provide a stable, rigid column that helps bones to fuse, and may redirect stresses over a wider area away from a damaged or defective region. Also, rigid spinal rods may help in spinal alignment. Spinal rods are secured to the vertebral members using a connector body and a spinal screw that is fastened to the vertebral members.SUMMARY

[0004] The techniques of this disclosure generally relate to treatment of spinal disorders, and the use of medical implants having non-metallic cores and non-metallic (e.g., woven) reinforcement layers.

[0005] In one aspect, the disclosure provides a medical implant having a non-metallic core comprising polyetheretherketone, and a non-metallic reinforcement layer coupled to the core. The core is at least partially encapsulated by the reinforcement layer, and the reinforcement layer includes carbon fiber strands.

[0006] In another aspect, the disclosure provides a method of forming a non-metallic medical implant. The method includes forming a non-metallic core comprising polyetheretherketone,weaving carbon fiber strands together to form a non-metallic reinforcement layer, and placing the reinforcement layer on the core.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the aspects of the invention and together with the written description serve to explain the principles, characteristics, and features of the invention. In the drawings:

[0008] FIG. 1 illustrates a perspective view of a spinal screw, according to some aspects of the present disclosure.

[0009] FIG. 2 illustrates a partial cross-sectional view of the screw of FIG. 1.

[0010] FIG. 3A is a sketch of an exemplary weave, according to some aspects of the present disclosure.

[0011] FIG. 3B is a sketch of a top view of an exemplary weave, according to some aspects of the present disclosure.

[0012] FIG. 3C is a sketch of a vertical cross section of a weave wrapped around a core, according to some aspects of the present disclosure.

[0013] FIG. 4 is a sketch of another exemplary weave, according to some aspects of the present disclosure.

[0014] FIG. 5 is a sketch of illustrating the manufacturing of a screw, according to some aspects of the present disclosure.DETAILED DESCRIPTION

[0015] The following description of the depicted aspect(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Before any aspects of the disclosure are explained in detail, it is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other aspects and of being practiced or of being carried out in various ways.

[0016] Aspects of the presently disclosed system are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

[0017] Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Use of “including” and “comprising” and variations thereof as used herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

[0018] In spinal procedures, a spinal screw is used to attach a rod to vertebrates to align sections of the spine. Frequently, the spinal screws are made from metal. In some patients that need spinal screws, for example patients with cancer, metal screws can interfere with additional therapeutic treatments. Some patients need a spinal screw with no, or less, metal than might be ordinarily used for a surgical procedure to allow the patient to be eligible for therapeutic treatments that are only available to patients that have non-metallic implants or implants fabricated with a limited amount of metal. The disclosed aspect of the spinal screw 10 is formed with carbon fiber reinforced PEEK instead of metal.

[0019] Referring now to FIG. 1, a perspective view of an exemplary spinal screw 10 is illustrated. Spinal screw 10 is formed with a carbon-fiber-reinforced poly etheretherketone (“CFR-PEEK”) material, which is a reinforced strong medical grade plastic. The screw 10 may be formed using compression molding. The spinal screw 10 includes an elongated body 14 andan end 18. The elongated body 14 has a thread 22 that extends along the length of the body 14. The end 18 is an at least partially rounded head. Screw 10 is depicted having more than one pitch along the length of the body. In some aspects, the body of screw 10 may have a constant pitch.

[0020] Turning now to FIG. 2, an exemplary sketch of a partial cross section of the elongated body 14 between two threads 22 of spinal screw 10 is illustrated. The elongated body 14 includes a core 26 encapsulated or surrounded by a reinforcement layer 34. A portion of the reinforcement layer 34 forms the threads 22. The core 26 may be a solid core, or the core may be hollow core, such as a hollow core along at least a portion of the longitudinal axis (e.g., along center line in FIG. 2) of the core 26. In some aspects, the elongated body 14 may include a reinforcement layer 34 and does not include a core 26.

[0021] The core 26 is formed from polyetheretherketone (PEEK). In some aspects, the core 26 may be about a quarter of a millimeter thick. The reinforcement layer 34 is formed from CFR PEEK. CFR PEEK includes carbon fibers that have been dipped in or covered with PEEK, for example, in a prepreg form before the PEEK material sets. CFR PEEK has an increased compressive strength and load carrying capacity compared to non-reinforced PEEK. In the illustrated aspect of FIG. 2, the reinforcement layer 34 may be a weave 36 (see also weaves 136, 236, 336 in FIGS. 3A-4) of CFR PEEK that has been wrapped or laid around core 26 or carbon fiber strands 42 that have been wound around the core (see FIG. 5). In the illustrated aspect of FIG. 2, the reinforcement layer 34 is thicker than the core 26. In some aspects, the reinforcement layer 34 includes one weave layer. If the reinforcement layer 34 includes one weave layer, the weave 36, 136, 236, 336 of the weave layer may be a thick weave such that that majority of the thickness of the body 14 is provided by the weave 36, 136, 236, 336. In some aspects, the reinforcement layer 34 includes more than one weave layer wrapped or laid around the core 26. The overall thickness of the reinforcement layer can depend on the fiber or strand thickness and also the number of weave layers or wound carbon fiber layers used to construct the reinforcement layer 34. In some aspects, after the final layer is wrapped, laid, or wound around the core or formed around a mandrel, compression molding techniques are applied to reinforcement layer 34, including the PEEK that is on the fibers or strands, thereby causing thePEEK, fibers, and / or strand to compress in a mold to form what becomes the spinal screw 10 with threads 22 upon the hardening of the PEEK.

[0022] FIGS. 3A-3C illustrate exemplary aspects of the weave that can be used in the reinforcement layer 34 (FIG. 2) of the body 14. The different weaves 36, 136, 236 in FIGS. 3A- 3C are three-dimensional (3-D) weaves. Each weave 36, 136, 236 includes multiple carbon fibers strands 42A, 42B, 42C that are woven together. In some aspects, the weave 36, 136, 236 may include about 5 carbon fiber strands to about 20 carbon fiber strands that are weaved together. In some aspects, the weave 36, 136, 236, 336 may include 14 to 16 carbon fiber strands that are weaved together.

[0023] The 3-D weave is a complex weave. The carbon fiber strands 42A,42B, and 42C may cross each other in multiple directions and locations. In the 3-D weave, all of the carbon fiber strands 42A, 42B, 42C may cross each other at some point. In some aspects, the 3-D weave may be similar to a braid. In some aspects, the 3-D weave may be similar to a caning-style weave. The 3-D weave of any one of the weaves 36, 136, 236 in FIGS. 3A-3C increases the strength of the weave in multiple directions in comparison to a non-woven CFR layer. For example, the strength of the weave 36, 136, 236 and of the body 14 may be increased in the longitudinal direction, the transverse direction, and the radial direction. The 3-D weave of the exemplary weaves 36, 136, 236 in FIGS. 3A-3C also allows the PEEK to move through the carbon fiber strands 42A, 42B, 42C more easily, and through the thickness of the weave 36, 136, 236.

[0024] As shown in FIG. 3C, in the 3-D weave of the weave 236 the carbon fiber strands 42A, 42B, 42C are weaved together such that when the weave 236 is wrapped around the core 26, the carbon fiber strands 42A, 42B, 42C have changing radial positions throughout the weave. For example, when the weave 236 is wrapped around the core 26, at some radial positions the carbon fiber strand 42A is adjacent the core 26 and at radial some positions the carbon fiber strand 42A is adjacent the outer periphery of the weave 236. This increases the strength of the weave 236 in multiple directions.

[0025] FIG. 4 illustrates another aspect of a weave 336. The weave 336 is what may be referred to as a two-dimensional weave (2-D). The weave 336 includes multiple carbon fiberstrands 42A, 42B, 42C, 42D that are woven together. The weave 336 is a simple weave. In the 2-D weave, only certain carbon fiber strands overlap with each other. For example, the carbon fiber strand 42A cross over the strands 42B and 42C, but never crosses over the strand 42D. The surface of a weave 36 may have a plaid-like appearance.

[0026] In the weave 36, 136, 236, 336, the thickness of the carbon fiber strands may be increased or decreased to control the strength, flexibility, and thickness of the weave 36, 136, 236, 336. Increasing the thickness of the carbon fiber strands may increase the amount of neat PEEK in the threads 22 and decrease the amount of carbon fiber strands that extends into the threads 22. Decreasing the thickness of the carbon fiber strands may decrease the amount of neat PEEK in the threads 22 and increase the amount of carbon fiber strands that extends into the threads 22.

[0027] Referring back to FIG. 2, in some aspects, a marker 46 may be positioned between the core 26 and the reinforcement layer 34. The marker 46 allows the spinal screw 10 (FIG. 1) to be easily identified in an X-ray (e.g., a visualizing component of the spinal screw 10). The marker 46 may be a thin wire (e.g., about 0.005 inches in diameter) or piece of material that extends the length of the body 14 such that in an X-ray it is easily identifiable if the spinal screw 10 is bent or broken. The marker 46 may be made of a high-density biocompatible material, such as stainless steel or tantalum. In some aspects, the marker 46 may only extend along a portion of the length of the body 14. In some aspects, it is contemplated that the marker material can also or in the alternative be included as a strand in the weave of reinforcement layer 34. In some aspects, the marker 46 can be arranged as a ring or multiple rings around the core of the spinal screw 10.

[0028] A method of forming the body 14 of the spinal screw 10 may first include creating the core 26. The core 26 may be created by painting or adding a thin layer of neat PEEK to a cylindrical mandrel thereby creating a hollow core cylinder of a neat PEEK material. Alternatively, the core 26 can be formed by machining the core 26 directly from PEEK without using a mandrel. In some implementations, a hollow core can be formed by coring or drilling along the longitudinal axis (e.g., the center line) of the core 26. A neat PEEK core 26 increasesthe efficiency of manufacturing because a neat PEEK is an easier material to drill than a CFR PEEK. A marker 46 may be added to the outer surface of the core 26.

[0029] As depicted in FIGS. 3A-4, the weave 36, 136, 236, 336 can be created by weaving the carbon fiber strands 42A, 42B, and 42C together. Prepreg carbon fiber strands may be further used to create the weave 36, 136, 236, 336 . After the weave 36, 136, 236, 336 is woven, the weave 36, 136, 236, 336 can be dipped in PEEK and laid on the core 26. In some aspects, the prepreg weave 36, 136, 236, 336 is laid on the core 26 and a layer of PEEK may be painted or spread onto the weave 36, 136, 236, 336 . In some aspects, one layer of the weave 36, 136, 236, 336 is positioned on the core 26. In some aspects, additional layers of the weave 36, 136, 236, 336 are positioned on the core 26 to increase the strength or the thickness of the screw 10. In some aspects, layer(s) of weave(s) 36, 136, 236, 336 are positioned on a mandrel and no PEEK core 26 is used.

[0030] After the weave 36, 136, 236, 336 is placed on the core 26, the core 26 is placed in a mold and are compression molded to cure the CFR PEEK. Pressure and heat are applied to the mold to cure the CFR PEEK and create the body 14. The mold also creates the threads 22. The mold includes a threaded section such that when pressure is applied to the mold, some of the PEEK in the reinforcement layer 34 is pushed out of the carbon reinforcement and into the threaded section of the mold to create the threads 22. In some aspects, a majority of the threads 22 is formed from PEEK with little to no CFR or having a CFR distribution that is less than the CFR distribution in the reinforcement layer 34. As discussed above, the ratio of PEEK and CFR in the threads 22 can be adjusted by adjusting the thickness of the individual carbon fiber strands.

[0031] The end 18 of the screw 10 may be formed in a manner similar to the formation of the body 14. In some aspects, the same mandrel used to create the core 26 is also used to create the end 18 of the screw 10. In other aspects, a different mandrel may be used to create the end 18 of the screw 10. The end 18 may be created using the weaves 36, 136, 236, 336 . In another aspect, the end 18 may be formed by using a winding method (described below in detail with respect to FIG. 5). When the end 18 of the spinal screw 10 is formed, the carbon fibers can be arranged in a way to increase the circumferential strength of the end 18 in order to decrease thechances of the end 18 being stripped. For example, in some aspects, the end 18 can be formed by arranging the carbon fiber strands parallel to the elongated body 14 and extending in the same direction up through the end 18 along the contour of the end 18. In the alternative, or in addition, carbon fiber strands can be arranged around the circumference of the end 18.

[0032] FIG. 5 illustrates another method of creating a screw body 14 and the screw end 18 (FIG. 1). In FIG. 5, the reinforcement layer 34 (FIG. 2) is not created by a weave 36, 136, 236, 336 (FIGS. 3A-4), but by winding parallel carbon fiber strands 42 around a PEEK core 26. The carbon fiber strands 42 are wound around the core 26 and then are impregnated with PEEK. The carbon fiber strands 42 may be wound around the core 26 in a first direction to create a first layer and then wound around the core 26 in a second direction to create a second layer. The two layers having two different directions of carbon fiber strands increases the strength of the body 14. In some aspects, the reinforcement layer 34 may be created by using a first layer of a weave 36, 136, 236, 336 and then a winding layer of carbon fiber strands 42. In some aspects, the reinforcement layer may be created using a winding layer of carbon fiber strands 42 and then a second layer of a weave 36, 136, 236, 336.

[0033] Although this disclosure focuses on manufacturing a screw, a similar process can be used to manufacture other medical implants such as nails.

[0034] As various modifications could be made to the exemplary aspects, as described above with reference to the corresponding illustrations, without departing from the scope of the invention, it is intended that all matter contained in the foregoing description and shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the invention should not be limited by any of the above-described exemplary aspects but should be defined only in accordance with the claims and their equivalents.

[0035] Example 1. A non-metallic medical implant comprising: a non-metallic core comprising polyetheretherketone; and a non-metallic reinforcement layer coupled to the core, wherein the core is at least partially encapsulated by the reinforcement layer, and wherein the reinforcement layer includes carbon fiber strands.

[0036] Example 2. The medical implant of example 1 , wherein the medical implant is a spinal screw, and wherein the reinforcement layer defines outer threads of the spinal screw.

[0037] Example 3. The medical implant of any of the preceding examples, wherein the core consists of only polyetheretherketone.

[0038] Example 4. The medical implant of any of the preceding examples, wherein the reinforcement layer is thicker than the core.

[0039] Example 5. The medical implant of any of the preceding examples, wherein the carbon fiber strands extend parallel to one another, and are wrapped around the core.

[0040] Example 6. The medical implant of any of examples 1-4, wherein the reinforcement layer includes a weave layer of the carbon fiber strands.

[0041] Example 7. The medical implant of example 6, wherein the carbon fiber strands in the weave layer have been dipped in or covered with poly etheretherketone, in a prepreg form.

[0042] Example 8. The medical implant of any examples 6 or 7, wherein the weave layer includes between 5-20 carbon fiber strands that are woven together.

[0043] Example 9. The medical implant of any of examples 6-8, wherein the carbon fiber strands cross each other in multiple directions and locations in the weave layer.

[0044] Example 10. The medical implant of any of examples 6-9, wherein the carbon fiber strands in the weave layer have changing radial positions throughout the weave layer.

[0045] Example 11. The medical implant of any of examples 6-10, wherein the carbon fiber strands are woven together in a three-dimensional weave in the weave layer.

[0046] Example 12. The medical implant of any of examples 6-10, wherein the carbon fiber strands are woven together in a two-dimensional weave in the weave layer.

[0047] Example 13. The medical implant of any of examples 6-12, wherein the weave layer is a first weave layer, wherein the reinforcement layer includes a second weave layer.

[0048] Example 14. The medical implant of any of the preceding examples, wherein a thickness of one of the carbon fiber strands is larger in one portion of the reinforcement layer than another portion of the reinforcement layer.

[0049] Example 15. The medical implant of any of the preceding examples, further comprising a marker positioned between the core and the reinforcement layer.

[0050] Example 16. A method of forming a non-metallic medical implant, the method comprising: forming a non-metallic core comprising poly etheretherke tone; weaving carbon fiber strands together to form a non-metallic reinforcement layer; and placing the reinforcement layer on the core.

[0051] Example 17. The method of example 16, wherein the step of forming the non- metallic core includes painting a layer of polyetheretherketone onto a cylindrical mandrel, creating a hollow core.

[0052] Example 18. The method of examples 16, wherein the step of forming the non- metallic core includes machining the core directly from polyetheretherketone.

[0053] Example 19. The method of any of examples 16-18, wherein the step of weaving includes weaving the carbon fiber strands into a first weave layer and a second weave layer.

[0054] Example 20. The method of any of examples 16-19, wherein the step of weaving includes weaving the carbon fiber strands such that the carbon fiber strands cross each other in multiple directions and locations.

Claims

CLAIMSWhat is claimed is:

1. A non-metallic medical implant comprising: a non-metallic core comprising polyetheretherketone; and a non-metallic reinforcement layer coupled to the core, wherein the core is at least partially encapsulated by the reinforcement layer, and wherein the reinforcement layer includes carbon fiber strands.

2. The medical implant of claim 1 , wherein the medical implant is a spinal screw, and wherein the reinforcement layer defines outer threads of the spinal screw.

3. The medical implant of any of the preceding claims, wherein the core consists of only polyetheretherketone.

4. The medical implant of any of the preceding claims, wherein the reinforcement layer is thicker than the core.

5. The medical implant of any of the preceding claims, wherein the carbon fiber strands extend parallel to one another, and are wrapped around the core.

6. The medical implant of any of claims 1 -4, wherein the reinforcement layer includes a weave layer of the carbon fiber strands.

7. The medical implant of claim 6, wherein the carbon fiber strands in the weave layer have been dipped in or covered with polyetheretherketone, in a prepreg form.

8. The medical implant of any claims 6 or 7, wherein the weave layer includes between 5-20 carbon fiber strands that are woven together.

9. The medical implant of any of claims 6-8, wherein the carbon fiber strands cross each other in multiple directions and locations in the weave layer.

10. The medical implant of any of claims 6-9, wherein the carbon fiber strands in the weave layer have changing radial positions throughout the weave layer.

11. The medical implant of any of claims 6-10, wherein the carbon fiber strands are woven together in a three-dimensional weave in the weave layer.

12. The medical implant of any of claims 6-10, wherein the carbon fiber strands are woven together in a two-dimensional weave in the weave layer.

13. The medical implant of claims 6-12, wherein the weave layer is a first weave layer, wherein the reinforcement layer includes a second weave layer.

14. The medical implant of any of the preceding claims, wherein a thickness of one of the carbon fiber strands is larger in one portion of the reinforcement layer than another portion of the reinforcement layer.

15. The medical implant of any of the preceding claims, further comprising a marker positioned between the core and the reinforcement layer.

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