Rod for internal spinal fixation device

Abstract

The invention provides a rod for an internal fixation tool, which reduces damage during fixation of a screw, has high rigidity and high durability of deformation load, and greatly reduces the risk of injury to the human body during breakage. A rod for a fastener according to one embodiment of the present invention is provided with a core member containing a fiber-reinforced resin and a coating resin layer covering the core member, the coating resin layer having an elongation of 30% or more and a thickness in the range of 0.05 mm to 0.4 mm.

Description

Technical Field

[0001] Cross-reference

[0002] This application claims priority based on Japanese patent application No. 2023-054349 (filed on March 29, 2023), the contents of which are incorporated herein by reference in their entirety.

[0003] The present invention relates to a spinal internal fixation device rod (referred to as a fixation device rod in this specification for convenience) used in a fixation device for fixing the spine. Background Art

[0004] Conventionally, as a fixation tool for fixing the spine, a fixation tool rod made of metal is known.

[0005] As such a fixing rod, Patent Document 1 discloses, for example, a spinal pedicle rod including an internally reinforced polymer core at least partially embedded in a polymer coating.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application No. 2011-508623 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] Metal fixture rods generally offer excellent fixing force and strength. However, when imaging with MRI or other methods, the metal magnetizes in the magnetic field, affecting the magnetic field and causing image distortion, making diagnosis based on the captured images difficult. On the other hand, the rod disclosed in Patent Document 1, while not subject to this problem, has a low fiber density, making it difficult to achieve the desired rigidity. This not only poses challenges in strength and durability, but also presents safety concerns due to the exposure of spinous fibers when broken.

[0011] One object of the present invention is to provide a fastener rod that reduces breakage during screw fastening, exhibits high rigidity and durability against deformation loads, and significantly reduces the risk of injury to the human body in the event of breakage. These and other objects of the present invention will become apparent upon reference to this entire specification.

[0012] Means for solving problems

[0013] A fixing rod according to one embodiment of the present invention includes a core member made of fiber-reinforced resin and a covering resin layer covering the core member. The covering resin layer has an elongation of 30% or more and a thickness ranging from 0.05 mm to 0.4 mm.

[0014] In the fastener rod according to one embodiment of the present invention, the fiber volume fraction (VF) near the surface layer of the core member is in the range of 50% to 70%.

[0015] In the fastener rod according to one embodiment of the present invention, the fiber volume fraction (VF) near the surface layer of the core member is in the range of 55% to 65%.

[0016] In the fastener rod according to one embodiment of the present invention, the core member is formed by laminating a plurality of layers.

[0017] In the fastener rod according to one embodiment of the present invention, the resin of the core member and the resin of the covering resin layer are the same thermoplastic resin.

[0018] In the fixing rod according to one embodiment of the present invention, the resin coating layer is formed by welding a resin tube.

[0019] In the fixing rod according to one embodiment of the present invention, when the above-mentioned multiple layers of the above-mentioned core member are observed in cross section, the reinforcing fiber layer and any one of the resin layer, the reinforcing fiber layer with fibers different from those of the reinforcing fiber layer, or the reinforcing fiber layer with fibers inclined with respect to the fiber direction of the reinforcing fiber layer are alternately formed into multiple layers.

[0020] In the fixing rod of one embodiment of the present invention, the above-mentioned reinforced fiber layer is a fiber-reinforced resin, and carbon, glass, boron, SiC or aramid is used as the fiber, and epoxy resin, phenolic resin, unsaturated polyester, PA, PC, PPSU, POM, PP, PE, ABS, PS, PAEK or PEEK is used as the resin.

[0021] In the fixing rod according to one embodiment of the present invention, the resin of the resin layer is epoxy resin, phenolic resin, unsaturated polyester, PA, PC, PPSU, POM, PP, PE, ABS, PS, PAEK or PEEK.

[0022] In a rod for a fixing device according to one embodiment of the present invention, a reinforcing fiber layer having fibers different from those of the above-mentioned reinforcing fiber layer is a fiber-reinforced resin, and carbon, glass, boron, SiC or aramid is used as the fiber, and epoxy resin, phenolic resin, unsaturated polyester, PA, PC, PPSU, POM, PP, PE, ABS, PS, PAEK or PEEK is used as the resin.

[0023] In one embodiment of the fastener rod of the present invention, the fibers in the reinforcing fiber layer or in a reinforcing fiber layer having fibers different from those in the reinforcing fiber layer are aligned in one direction, formed into a woven pattern, or randomly oriented. Furthermore, in one embodiment of the fastener rod of the present invention, the fiber direction of the reinforcing fiber layer having fibers tilted relative to the fiber direction of the reinforcing fiber layer is tilted within a range of 10° to 90°.

[0024] In a fixing rod according to one embodiment of the present invention, when multiple layers are provided in any one of a resin layer, a reinforcing fiber layer having fibers different from those of the reinforcing fiber layer, or a reinforcing fiber layer having fibers inclined relative to the fiber direction of the reinforcing fiber layer, each layer may be the same layer or different layers.

[0025] In the fixing rod according to one embodiment of the present invention, the fibers of the reinforcing fiber layer are long fibers.

[0026] In the fixing rod according to one embodiment of the present invention, the fiber content of the reinforcing fiber layer is 60% by weight or more.

[0027] In the fixing rod according to one embodiment of the present invention, the fiber directions of the reinforcing fiber layer are aligned, and the thickness of the layer is in the range of 0.02 mm to 0.3 mm.

[0028] In the fastener rod according to one embodiment of the present invention, a marker is embedded in the core member.

[0029] Effects of the Invention

[0030] According to the above-described embodiments of the present invention, a fixing rod can be provided that reduces breakage during screw fixing, has high rigidity and high durability against deformation loads, and significantly reduces the risk of injury to the human body in the event of breakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 1 is a diagram showing a spine fastening tool 10 including a fastening tool rod according to an embodiment of the present invention.

[0032] Figure 2 This is a diagram schematically showing a cross section of a fixing rod according to one embodiment of the present invention, taken along a plane perpendicular to the central axis thereof.

[0033] Figure 3 This is a diagram schematically showing a cross section of a core member of a fixing rod according to an embodiment of the present invention, taken along a plane perpendicular to the central axis thereof.

[0034] Figure 4This is a diagram schematically showing a cross section of a core member of a fixing rod according to an embodiment of the present invention, taken along a plane perpendicular to the central axis thereof.

[0035] Figure 5 This is a diagram schematically showing a cross section of a core member of a fixing rod according to an embodiment of the present invention, taken along a plane perpendicular to the central axis thereof. DETAILED DESCRIPTION

[0036] The following describes embodiments of the fastener rod according to the present invention in detail with reference to the accompanying drawings. Components that are common to multiple drawings are designated by the same reference numerals across the drawings. It should be noted that for ease of description, the drawings are not necessarily drawn to scale.

[0037] Figure 1 This figure shows a spinal fastener 10 including a fastener rod 1 according to one embodiment of the present invention. As shown, the spinal fastener 10 includes: a plurality of screw members 18 (two screw members 18 in the example shown), which are fixed to the bones of the spine; a plurality of rod fasteners 20 (two rod fasteners 20 in the example shown), which are attached to the screw members 18 and have recesses 21 for receiving the fastener rods and pressing members 22; and the fastener rod 1, which is inserted into the recesses 21 of the plurality of rod fasteners 20 and secured by the pressing members 22.

[0038] Next, refer to Figure 2 Next, a fastening rod 1 according to an embodiment of the present invention, which is used in a spine fastening device 10, will be described. Figure 2 Therefore Figure 1 Observation of the XX section shown Figure 1Figure 1 shows a fastener rod 1. One embodiment of the fastener rod 1 of the present invention comprises a core member 6 made of fiber-reinforced resin, as described in detail below, and a coating resin layer 7 covering the core member 6. The coating resin layer 7 has an elongation of 30% or greater and a thickness ranging from 0.05 mm to 0.4 mm. This coating resin layer 7 prevents damage even if the core member 6 breaks, ensuring that the core member 6 remains covered. This prevents the fibers of the core member 6 from being exposed, significantly reducing the risk of injury to the human body even in the event of a break. Specifically, the coating resin's elongation is sufficiently high relative to the standard elongation of carbon fibers, approximately 2%, so the carbon fibers break. Furthermore, if the coating resin has a certain thickness and strength, it can suppress the impact force that would otherwise damage the carbon fibers. However, if the thickness of the coating resin exceeds 0.4 mm, the coating is less likely to break, but the outer diameter of the rod itself increases, which has a greater impact on in-vivo placement. Furthermore, the core component, described later, can reduce breakage during screw fixation, providing high rigidity and improved durability against deformation loads. The coating resin layer further enhances the aforementioned technical effects. Here, in one embodiment of the fixing rod 1 of the present invention, a marker is embedded in the core component 6. It should be noted that the marker is composed of a radiopaque material and serves to indicate the position of the implant product within the body.

[0039] In the fixing rod 1 according to one embodiment of the present invention, the fiber volume fraction (VF) near the surface of the core member 6 is preferably in the range of 50% to 70%, and more preferably in the range of 55% to 65%. Here, the fiber volume fraction (VF) near the surface of the core member 6 refers to the area 0.2 mm inward from the core member surface toward the center. When the fiber volume fraction (VF) near the surface of the core member 6 is 50% or more, the bending rigidity can be effectively increased, and a rod that is difficult to break can be formed. In addition, when the volume fraction near the surface of the core member is 50% or more, the bond with the coating resin is not completely integrated. In other words, the resin on the surface of the core member and the coating resin are easily firmly integrated, while the carbon fibers on the surface of the core member and the coating resin form a relatively weak bond. In contrast, if the fiber volume fraction (VF) near the surface of the core member 6 exceeds 70%, there is too little resin on the surface, and therefore, a sufficient bond cannot be obtained between the coating resin and the resin of the core member. Since the core member and the coating resin are not completely integrated and are weakly bonded, when the inner core member is damaged, cracks develop between the core member surface and the coating resin layer, releasing stress, making it difficult for the coating resin to break.

[0040] In one embodiment of the fixing rod 1 of the present invention, the resin of the core member 6 and the resin of the coating resin layer 7 are the same thermoplastic resin. Examples of such thermoplastic resins include PEEK, nylon, PPSU, and PET. This allows for stable integration of the core member and the coating resin.

[0041] In the fixing rod 1 according to one embodiment of the present invention, the resin coating layer is formed by welding a resin tube. Thus, by pre-molding the coating layer into a tube shape, a coating layer with stable thickness and quality can be formed.

[0042] In the fixing rod 1 according to one embodiment of the present invention, the core member 6 is formed by laminating a plurality of layers, as will be described in detail later.

[0043] Next, refer to Figure 3 、 4 5. The multiple layers of the core member 6 of the fixing rod 1 according to one embodiment of the present invention used in the spine fixing device 10 will be described. Figure 3 、 4 、5 is Figure 1 Observation of the XX section shown Figure 1 FIG. 1 is a diagram showing a core member 6 of a fixing rod 1. Note that the coating resin layer 7 is omitted for ease of description.

[0044] As shown in the figure, when the multiple layers of the core member 6 of the fixing rod 1 according to one embodiment of the present invention are viewed in cross section, the reinforcing fiber layer 2 ( Figures 3-5 In the example of 8 layers of reinforcing fiber layers), and the resin layer 3 ( Figure 3 In the example shown, each of the seven resin layers 3) includes a reinforcing fiber layer 4 having fibers different from those of the reinforcing fiber layer 2 ( Figure 4 In the example shown, each of the seven reinforcing fiber layers 4) or the reinforcing fiber layer 5 ( Figure 5 In the example shown, each of the seven reinforcing fiber layers 5 is alternately formed with multiple layers. Figure 3 Example shown), a reinforcing fiber layer 4 ( Figure 4 The example shown) or the reinforcing fiber layer 5 having fibers inclined relative to the fiber direction of the reinforcing fiber layer ( Figure 5Each layer in the example shown in the figure is formed to have a thickness of 0.01 mm to 0.25 mm, but the thickness of the layer can be different depending on the position of the layer (that is, the thickness of the layer can be formed to have both thin and thick parts). In addition, the layer can be formed intermittently (that is, the thickness of the layer can have both thin and thick parts, and can also have parts with zero thickness). Here, the reinforcing fiber layer 5 is a fiber-reinforced resin. As the fiber, carbon, glass, boron, SiC or aramid is used, and as the resin, epoxy resin, phenolic resin, unsaturated polyester, PA, PC, PPSU, POM, PP, PE, ABS, PS, PAEK or PEEK is used.

[0045] The core member 6 of the fastener rod 1 according to one embodiment of the present invention can provide a fastener rod that reduces breakage during screw fastening, exhibits high rigidity and durability against deformation loads, and significantly improves safety in the event of breakage. In particular, it has been found that when the fastener rod 1 according to one embodiment of the present invention breaks, stress is concentrated on either the resin layer sandwiched between the reinforcing fiber layers, the reinforcing fiber layer having fibers different from those in the reinforcing fiber layer, or the reinforcing fiber layer having fibers oriented obliquely relative to those in the reinforcing fiber layer. This reduces the likelihood of the reinforcing fiber layer becoming spiny when the rod breaks, significantly improving safety for the human body.

[0046] In the core member 6 of the fastener rod 1 according to one embodiment of the present invention, the reinforcing fiber layer 2 is a fiber-reinforced resin, using carbon, glass, boron, SiC, or aramid as the fiber, and epoxy resin, phenolic resin, unsaturated polyester, PA, PC, PPSU, POM, PP, PE, ABS, PS, PAEK, or PEEK as the resin. This increases the flexural rigidity and strength of the fastener rod 1.

[0047] In the core member 6 of the fixing rod 1 according to one embodiment of the present invention, the resin of the resin layer 3 is epoxy resin, phenolic resin, unsaturated polyester, PA, PC, PPSU, POM, PP, PE, ABS, PS, PAEK or PEEK.

[0048] In the core member 6 of the fixing rod 1 according to one embodiment of the present invention, the reinforcing fiber layer 4, comprising fibers different from those in the reinforcing fiber layer 2, is a fiber-reinforced resin. Carbon, glass, boron, SiC, or aramid are used as the fibers, and epoxy resin, phenolic resin, unsaturated polyester, PA, PC, PPSU, POM, PP, PE, ABS, PS, PAEK, or PEEK are used as the resin. This increases the bending rigidity and strength of the fixing rod. Furthermore, the reason for using a reinforcing fiber layer comprising fibers different from those in the reinforcing fiber layer 2 is that using different materials can impart different properties, such as flexibility and vibration absorption, in addition to rigidity and strength.

[0049] In the core member 6 of the fastener rod 1 according to one embodiment of the present invention, the reinforcing fiber layer 2 or the reinforcing fiber layer 4, which has fibers different from those of the reinforcing fiber layer 2, may have fibers aligned in a single direction, formed into a woven pattern, or randomly oriented. Furthermore, in the core member 6 of the fastener rod 1 according to one embodiment of the present invention, the reinforcing fiber layer 5, which has fibers tilted relative to the fiber direction of the reinforcing fiber layer 2, may have a fiber direction tilted within a range of 10° to 90°. By configuring an appropriate layered structure in this manner, the desired strength and rigidity can be achieved.

[0050] In the core member 6 of the fixing rod 1 according to one embodiment of the present invention, when multiple layers are provided for any of the following: the resin layer 3, the reinforcing fiber layer 4 having fibers different from those of the reinforcing fiber layer 2, or the reinforcing fiber layer 5 having fibers with an oblique fiber direction relative to the reinforcing fiber layer 2, each layer may be the same layer or different layers (the same shall apply hereinafter). For example, when two layers are provided, the two layers may be two resin layers 3 (in which case, the layers are the same), or two different layers may be provided, such as a resin layer 3 and a reinforcing fiber layer 4 having fibers different from those of the reinforcing fiber layer. When three or more layers are provided, a desired combination of the layers may be selected from the above. In this way, by configuring an appropriate stacked structure, the desired strength and rigidity can be achieved.

[0051] In the core member 6 of the fixing rod 1 according to one embodiment of the present invention, the fibers constituting the reinforcing fiber layer 2 are long fibers. By making the fibers of the reinforcing fiber layer 2 long fibers, it is possible to further increase the bending rigidity and increase the strength.

[0052] Furthermore, in the core member 6 of the fastener rod 1 according to one embodiment of the present invention, the fiber content of the reinforcing fiber layer 2 is 50% by volume or greater. This high density of long fibers in the fiber layer allows for a fastener rod 1 with high rigidity and excellent durability.

[0053] In the core member 6 of the fastener rod 1 according to one embodiment of the present invention, the fibers of the reinforcing fiber layer 2 are aligned, and the thickness of the reinforcing fiber layer 2 is, for example, in the range of 0.02 mm to 0.3 mm. This uniformizes the resin density and reduces variations in strength due to location.

[0054] Next, a method for manufacturing a fixing rod 1 according to an embodiment of the present invention is described. First, as step 1, any one of the reinforcing fiber layer 2, the resin layer 3, the reinforcing fiber layer 4 having fibers different from those of the reinforcing fiber layer, or the reinforcing fiber layer 5 having fibers inclined relative to the fiber direction of the reinforcing fiber layer is cut into a specified size (layer cutting process). Then, as step 2, the layers are stacked in a specified configuration (layer stacking process). As step 3, a specified mold is set and molded under specified conditions (for example, a temperature of 380°C and a pressure of 5MPa to 15MPa) (molding process). Then, as step 4, the core component 6 is formed by processing it into the final shape and size (processing process). Finally, as step 5, the resin tube is melted to form a coating resin layer 7 on the outer surface of the formed core component 6. In this way, a fixing rod 1 according to an embodiment of the present invention is formed. Furthermore, it should be noted that, instead of the aforementioned method for manufacturing the fastener rod 1, a method (pultrusion) of preparing a plurality of reinforcing fiber bundles impregnated with a liquid resin, pulling them through a mold, and then heating or cooling them to solidify them can also be used to form the fastener rod 1 according to one embodiment of the present invention. Furthermore, either thermosetting resins or thermoplastic resins can also be used.

[0055] The thus formed fastener rod 1 according to one embodiment of the present invention provides a fastener rod that reduces breakage during screw fastening, exhibits high rigidity and durability against deformation loads, and significantly reduces the risk of injury to the human body in the event of breakage. More specifically, when the core member breaks, the crack develops between the core member surface and the coating resin layer, releasing stress and making the coating resin less susceptible to breakage. This prevents the scattering of fragments and fibers caused by damage to the main body.

[0056] The dimensions, materials, and configurations of the various components described in this specification are not limited to those explicitly described in the embodiments, and the various components can be modified to have any dimensions, materials, and configurations that are within the scope of the present invention. In addition, components not explicitly described in this specification can be added to the described embodiments, and some of the components described in the various embodiments can be omitted.

[0057] Explanation of symbols

[0058] 1 Fixation rod (rod for spinal internal fixation device)

[0059] 2 Reinforced fiber layer

[0060] 3 Resin layer

[0061] 4. A reinforcing fiber layer having fibers different from those of the reinforcing fiber layer 2.

[0062] 5 A reinforcing fiber layer having fibers inclined relative to the fiber direction of the reinforcing fiber layer 2

[0063] 6-core components

[0064] 7 Coating resin layer

[0065] 10. Spinal Fixation Devices

[0066] 18 screw components

[0067] 20 Rod fixing parts

[0068] 21 recess

[0069] 22 Pressing parts

Claims

1. A fixing rod, characterized in that: The fixing rod has: a core member comprising a fiber-reinforced resin; and a coating resin layer covering the core member, The coating resin layer has an elongation of 30% or more and a thickness in the range of 0.05 mm to 0.4 mm.

2. The fixing rod according to claim 1, wherein: The fiber volume fraction VF near the surface layer of the core member is in the range of 50% to 70%.

3. The fixing rod according to claim 1, wherein: The fiber volume fraction VF near the surface layer of the core member is in the range of 55% to 65%.

4. The fixing rod according to claim 1, wherein The core member is formed by laminating a plurality of layers.

5. The fixing rod according to claim 1, wherein The resin of the core member and the resin of the covering resin layer are the same thermoplastic resin.

6. The fixing rod according to claim 1, wherein: The resin of the coating resin layer is formed by welding a resin tube.

7. The fixing rod according to claim 4, wherein: When the core member is viewed in cross section, the plurality of layers are alternately formed of multiple layers of reinforcing fiber layers, and any of the following: a resin layer, a reinforcing fiber layer having fibers different from those of the reinforcing fiber layer, or a reinforcing fiber layer having fibers inclined relative to the fiber direction of the reinforcing fiber layer.

8. The fixing rod according to claim 7, wherein: The reinforced fiber layer is a fiber-reinforced resin, and carbon, glass, boron, SiC or aramid is used as the fiber, and epoxy resin, phenolic resin, unsaturated polyester, PA, PC, PPSU, POM, PP, PE, ABS, PS, PAEK or PEEK is used as the resin.

9. The fixing rod according to claim 7, wherein: The resin of the resin layer is epoxy resin, phenolic resin, unsaturated polyester, PA, PC, PPSU, POM, PP, PE, ABS, PS, PAEK or PEEK.

10. The fixing rod according to claim 7, wherein: The reinforcing fiber layer having fibers different from those of the reinforcing fiber layer is a fiber-reinforced resin, and carbon, glass, boron, SiC or aramid is used as the fiber, and epoxy resin, phenolic resin, unsaturated polyester, PA, PC, PPSU, POM, PP, PE, ABS, PS, PAEK or PEEK is used as the resin.

11. The fixing rod according to claim 7, wherein: In the reinforcing fiber layer or the reinforcing fiber layer having fibers different from those in the reinforcing fiber layer, the fibers are aligned in one direction, formed into a woven shape, or randomly oriented.

12. The fixing rod according to claim 7, wherein: The fiber direction of the reinforcing fiber layer having fibers inclined relative to the fiber direction of the reinforcing fiber layer is inclined within a range of 10° to 90°.

13. The fixing rod according to claim 7, wherein: When a plurality of layers are provided, including a resin layer, a reinforcing fiber layer having fibers different from those of the reinforcing fiber layer, or a reinforcing fiber layer having fibers inclined relative to the fiber direction of the reinforcing fiber layer, each layer may be the same layer or different layers.

14. The fixing rod according to claim 7, wherein: The fibers of the reinforcing fiber layer are long fibers.

15. The fixing rod according to claim 7, wherein: The fiber content of the reinforcing fiber layer is 50% by volume or more.

16. The fixing rod according to claim 7, wherein: The fiber directions of the reinforcing fiber layer are aligned, and the thickness of the reinforcing fiber layer is in the range of 0.02 mm to 0.3 mm.

17. The fixing rod according to claim 1, wherein: A marker is embedded in the core member.

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