Orthopedic implant composite sandwich structure

Abstract

This invention discloses a composite sandwich structure for orthopedic implants, comprising: a core body, a reinforcing layer covering the outer surface of the core body, and an affinity layer covering the outer surface of the reinforcing layer. The core body material comprises polyaryletherketone (PAK), the reinforcing layer comprises at least one woven layer composed of carbon fiber bundles, and the affinity layer material comprises PAK and / or a composite material of bioceramics.

Description

Technical Field

[0001] This invention relates to composite sandwich structures for orthopedic implants, and particularly to composite sandwich structures for orthopedic implants made of polyaryletherketone material coated with carbon fiber bundles. Background Technology

[0002] Ideal bone materials need to possess mechanical properties similar to hard bone, such as an elastic coefficient of approximately 14.1–27.6 GPa and a tensile strength of approximately 150 MPa. Currently, commonly used implants can be broadly categorized into two types: metallic and non-metallic. However, commonly used metallic bone materials (such as Ti-6Al-4V, with an elastic coefficient of approximately 95–117.4 GPa and a tensile strength of approximately 900 MPa), while possessing high mechanical strength, also suffer from excessive stiffness that is incompatible with human skeletal mechanics. Over time, this can lead to stress shielding effects, resulting in bone atrophy, resorption, and structural collapse. On the other hand, polymers used as non-metallic materials (such as PEEK, with an elastic coefficient of approximately 3–4 GPa and a tensile strength of approximately 50 MPa) offer moderate mechanical strength compared to metallic bone materials and are more similar to the mechanical properties of human bone, but are still insufficient to withstand high loads.

[0003] Furthermore, patients with spinal tumors now require radiation therapy after tumor resection surgery. During tumor resection surgery, after removing the vertebral segment invaded by cancer cells, pedicle screws are used to fix the upper and lower vertebral segments to maintain spinal stability. However, when obtaining radiographic images, the metal implant may cause image scattering, making it difficult to pinpoint the tumor location and causing damage to normal tissues during radiation therapy. Moreover, metal shielding may attenuate radiation energy, preventing the radiation therapy from achieving the desired therapeutic effect. Although non-metallic implants do not have the problems of image scattering and energy attenuation, most commercially available non-metallic spinal implants are currently made of polyetheretherketone (PEEK). However, spinal fixation requires high mechanical strength; therefore, this type of implant often carries the risk of breakage or damage when used for spinal fixation, leading to the need for repeat surgery or other complications.

[0004] Although in recent years some major foreign manufacturers have used micron-sized carbon fibers to blend with PEEK to develop orthopedic materials and enhance the mechanical strength of PEEK, the carbon fibers alter the material properties of the PEEK polymer, causing the material's ductility to drop from about 15% of PEEK to less than 1%. Therefore, this material is hard and brittle, making it difficult to use. Furthermore, there is a risk of inflammatory reactions caused by the release of carbon fiber particles.

[0005] Therefore, there is still a lack of non-metallic biomedical materials in clinical practice that possess both high mechanical strength and ductility. Summary of the Invention

[0006] In view of the above problems, the present invention provides a composite sandwich structure for orthopedic implants, which reinforces non-metallic materials with a reinforcing layer having a carbon fiber bundle braided layer. In addition, the present invention, through a variable braided structure, allows for the use of different braided structures at different parts of the same implant to adjust the mechanical properties to match mechanical requirements.

[0007] An embodiment of the present invention discloses a composite sandwich structure for orthopedic implants, comprising: a core body comprising polyaryletherketone (PAEK); a reinforcing layer covering the surface of the core body; and an affinity layer covering the surface of the reinforcing layer. The reinforcing layer includes at least one woven layer composed of carbon fiber bundles, and the affinity layer material comprises a composite material of PAEK and / or bioceramics. Attached Figure Description

[0008] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, in accordance with industry standard practice, the various features are not drawn to scale and are for illustrative purposes only. In fact, the dimensions of the components can be arbitrarily enlarged or reduced to clearly demonstrate the features of the embodiments of the present invention.

[0009] Figures 1A to 1D A cross-sectional schematic diagram of a composite sandwich structure for orthopedic implants is shown for some embodiments of the present invention;

[0010] Figures 2A to 2D A cross-sectional schematic diagram of a composite sandwich structure for orthopedic implants is shown for some other embodiments of the present invention.

[0011] Symbol Explanation

[0012] 10: Core

[0013] 10s: Surface

[0014] 20: Reinforcement Layer

[0015] 22: Braided layer

[0016] 22p1: First part

[0017] 22p2: Second part

[0018] 23: Structural layer

[0019] 24: Affinity Layer

[0020] 100: Composite sandwich structure for orthopedic implants Detailed Implementation

[0021] The following disclosure provides numerous embodiments or examples for implementing different elements of the provided subject matter. Specific examples of each element and its configuration are described below to simplify the description of embodiments of the invention. Of course, these are merely examples and are not intended to limit the embodiments of the invention. For example, if the description refers to a first element formed on a second element, it may include embodiments where the first and second elements are in direct contact, or embodiments where an additional element is formed between the first and second elements such that they are not in direct contact. Furthermore, the embodiments of the invention may repeat reference values ​​and / or letters in various examples. Such repetition is for the purpose of brevity and clarity, and is not intended to indicate a relationship between the different embodiments and / or configurations discussed.

[0022] Furthermore, when using terms such as "approximately" or "around" to describe a number or range of numbers, this terminology is intended to cover a reasonable range of numbers that takes into account the inherent variations in the manufacturing process as understood by one of ordinary skill in the art. For example, based on known manufacturing tolerances for manufacturing parts with characteristics related to that number, the number or range of numbers covers a reasonable range that includes the number, such as within + / - 10% of the number.

[0023] This invention reinforces the high-performance polymer, which is the core of the orthopedic implant, with a reinforcing layer having a carbon fiber bundle braided layer, and coats it with an affinity layer containing polyarylether ketone (PAEK) material as the outermost layer of the orthopedic implant. In addition to avoiding the inflammatory reaction caused by carbon fiber exposure and improving biocompatibility, it can also retain the original mechanical properties of PAEK material and avoid excessive reduction in ductility, which would make the material hard and brittle.

[0024] Furthermore, literature shows that different parts of the human body have different biomechanical requirements for implants; for example, the proximal end of the femoral plate experiences much greater forces than the distal end. Therefore, this invention develops a variable braided structure, which allows for the use of different braided structures in different parts of the same implant to adjust the mechanical properties, thus giving the implant the desired mechanical properties.

[0025] Reference Figure 1A According to some embodiments of the present invention, a cross-sectional view of an orthopedic implant composite sandwich structure 100 is shown. The orthopedic implant composite sandwich structure 100 includes: a core body 10, a reinforcing layer 20 covering the surface of the core body 10, and an affinity layer 24 covering the reinforcing layer 20, or the outermost woven layer 22; wherein... Figure 1A Only the reinforcement layer 20 is shown, which contains only a single layer of braided layer 22.

[0026] This application uses polyaryletherketone (PAEK) series materials as the core body 10. PAEK is a high-performance thermoplastic engineering plastic family with excellent mechanical properties, thermal stability, chemical resistance, and biocompatibility. Examples of PAEK materials that can be used as the core body 10 in this application include: polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), and polyetherketoneetherketoneketone (PEKEKK). The size and shape of the core body 10 can be customized according to the implant requirements.

[0027] In some embodiments, the core body 10 material may be mixed with short fibers or short fibers of carbon fiber. The core body 10 may contain about 0% to 35% carbon fiber short fibers by weight, such as about 3% to 33%, or 5% to 28%, about 10% to 25%, about 13% to 20%, about 15% to 18% by weight, etc. By containing carbon fiber short fibers within the above range in the core body 10, the core tensile strength, bending strength, etc., of the orthopedic implant composite sandwich structure 100 can be improved. In some embodiments, the core body 10 may be manufactured by injection molding or CNC machining, etc.

[0028] Next, continue to refer to Figure 1A A reinforcing layer 20 is formed to cover the surface of the core body 10, and the reinforcing layer 20 includes at least one braided layer 22. In this embodiment, the braided layer 22 is formed with carbon fiber bundles, and the outermost braided layer 22 is then covered with an affinity layer 24 of PAEK material to prevent the carbon fibers from being exposed. The number and order of the reinforcing layers 20 are not particularly limited. In some embodiments, the braided layer 22 is located as the innermost layer on the core body 10. The affinity layer 24 constitutes the outermost layer of the orthopedic implant composite sandwich structure 100. In some embodiments, the innermost braided layer 22 is in direct contact with the core body 10.

[0029] The number of fibers in the carbon fiber bundles used in the braided layer 22 is not particularly limited. Each carbon fiber bundle can have 1,000 to 12,000 carbon fibers, that is, the K number of the carbon fiber bundle can be 1 to 12, such as 2 to 11, 3 to 10, 4 to 9, 5 to 8, 6 to 7, etc. Having a fiber bundle number within the above range can enhance the mechanical strength of the core body 10. The average fiber diameter of the carbon fibers contained in the carbon fiber bundle is not particularly limited, for example, it can be 1 to 10 μm, 2 to 9 μm, 3 to 8 μm, 4 to 7 μm, 5 to 6 μm, etc. Having an average fiber diameter within the above range can also enhance the mechanical strength of the core body 10. In some embodiments, the thickness of each braided layer 22 formed can also enhance the mechanical strength of the core body 10; however, this invention does not impose any limitations on these aspects.

[0030] The braided layer 22 can be formed on the core body 10 using radial composite braiding equipment. Radial composite braiding equipment is a ring-shaped braiding technology and machine that can effectively weave braided materials onto a 3D curved surface. Therefore, the core body 10 in this case can have different three-dimensional shapes, such as cubes, cones, pyramids, cylinders, spheres, ellipsoids, hemispheres, tetrahedrons, triangular prisms, square prisms, hexagonal prisms, irregular shapes, etc. Even if the core body 10 is an irregular shape, the braided layer 22 can still be formed conformally on the core body 10. In some embodiments, the feed rate during weaving can be approximately 1–50 mm / s, such as approximately 5–45 mm / s, approximately 10–40 mm / s, approximately 12–40 mm / s, approximately 15–35 mm / s, approximately 18–30 mm / s, approximately 20–25 mm / s, etc.; the rotation speed can be approximately 10 rpm–100 rpm, such as approximately 15–95 rpm, approximately 20–90 rpm, approximately 25–85 rpm, approximately 30–80 rpm, approximately 35–75 rpm, approximately 40–70 rpm, approximately 45–65 rpm, approximately 50–60 rpm, approximately 52–55 rpm, etc.; the weaving angle can be approximately 20 degrees–80 degrees, such as approximately 20 degrees–75 degrees, approximately 25 degrees–70 degrees, approximately 30 degrees–65 degrees, approximately 35 degrees–60 degrees, approximately 40 degrees–55 degrees, approximately 45 degrees–50 degrees, etc. The weaving parameters mentioned above can be the same or different when forming each layer of the weaving 22.

[0031] Approximately 0-99% of the upper surface area of ​​the underlying structure of the braided layer 22 can be covered by the braided layer 22, for example, Figure 1AIn the illustrated embodiment, approximately 0-99% of the surface area of ​​the core body 10 is covered by the braided layer 22. In other words, the braided coverage of the braided layer 22 can be approximately 0-99%, for example, approximately 5-98%, approximately 10-95%, approximately 15-93%, approximately 20-91%, approximately 25-90%, approximately 30-85%, approximately 35-80%, approximately 40-75%, approximately 45-70%, approximately 50-65%, approximately 55-60%, etc. The braided coverage of each braided layer 22 to its underlying structure can be the same or different.

[0032] The braided layer 22 has a variable braided structure, meaning that the braiding parameters, such as the braiding angle, can not be kept consistent when braiding each layer 22, and different parts of each layer 22 can have different braid coverage rates. In other words, each braided layer 22 can independently have more than one braiding angle and more than one braid coverage rate. For example, refer to... Figure 1A In some embodiments, the weaving angle of the first portion 22p1 of the braided layer 22 may be the same as or different from that of the second portion 22p2 of the braided layer 22, and the weaving coverage of the first portion 22p1 of the braided layer 22 may be the same as or different from that of the second portion 22p2 of the braided layer 22. This invention allows for the adjustment of the weaving parameters and weaving coverage of different portions of each braided layer 22 according to usage requirements, thereby locally strengthening the orthopedic implant composite sandwich structure 100 and expanding the application range of the orthopedic implant composite sandwich structure 100.

[0033] After the braided layer 22 is formed, the material of the core body 10 can be partially melted and penetrated into the gaps of the braided layer 22 by hot pressing, so that the braided layer 22 is better fixed to the core body 10. The hot pressing temperature can be about 350℃ to 500℃, for example, about 360 to 490℃, about 370 to 480℃, about 380 to 470℃, about 390 to 460℃, about 400 to 450℃, about 410 to 440℃, about 420 to 430℃, etc. The hot pressing time can be about 1 to 10 minutes, for example, about 2 to 9 minutes, about 3 to 8 minutes, about 4 to 7 minutes, about 5 to 6 minutes, etc. The cylinder pressure can be approximately 50–100 psi, such as approximately 55–95 psi, 60–95 psi, 65–90 psi, 70–88 psi, 73–85 psi, 75–82 psi, or 78–80 psi. After hot pressing, the temperature can be lowered to approximately 200–300°C and the pressure maintained for approximately 1–10 minutes to prevent warping. For example, the temperature can be lowered to approximately 210–290°C, 220–280°C, 230–270°C, 240–260°C, or 250–255°C and the pressure maintained for approximately 2–9 minutes, 3–8 minutes, 4–7 minutes, or 5–6 minutes, respectively. Afterward, once the temperature has slowly decreased to normal atmospheric pressure and room temperature, the sample can be removed from the hot press and further processed as needed. By controlling appropriate hot pressing parameters, the braided layer 22 can be completely fused with the material of the underlying layer, such as the material of the core body 10, and the overflow and deformation of the material can be avoided.

[0034] Next, an affinity layer 24 is formed on the braided layer 22. The affinity layer 24 can be made of PAEK alone, using PAEK series materials such as PEK, PEEK, PEKK, PEEKK, and PEEKKK, or a composite material made by mixing it with bioceramic materials such as bioglass, calcium phosphate, and calcium sulfate. In some embodiments, the affinity layer 24 can be encapsulated onto the braided layer 22 by injection molding, for example, by micro-injection molding of biomedical polymers, using a highly biocompatible material, and its surface can be coated with materials such as collagen to improve biocompatibility after implantation. The orthopedic implant composite sandwich structure 100 can have more than one affinity layer 24, and the thickness of each affinity layer 24 can be adjusted as needed.

[0035] This invention allows for the repeated application of the aforementioned winding, hot pressing, and injection molding steps as needed to form a reinforcing layer 20 with multiple braided layers 22 and multiple structural layers 23, such as... Figures 1B to 1DAs shown. The material of this structural layer 23 is similar to that of the affinity layer 24, both containing polyaryletherketone (PAEK), but not bioceramics or collagen. There is no particular limitation on the number and order of the reinforcing layers 20. For example, the braided layer 22, structural layer 23, and braided layer 22 can be formed alternately. An affinity layer 24 can be formed on the outermost layer after forming a single layer or multiple alternating layers of braided layer 22 and structural layer 23. Alternatively, a braided layer 22 can be inserted between the layers of the multiple structural layers 23 to facilitate hot-pressing fusion. The number of braided layers 22 and structural layers 23 can be the same or different. In the case of continuously forming multiple braided layers 22, hot pressing can be performed before or after finally covering the affinity layer 24, or hot pressing can be performed immediately after forming a single braided layer 22.

[0036] In some embodiments, the reinforcing layer 20 may have alternating woven layers 22 and structural layers 23. For example, as Figure 1B As shown, the reinforcing layer 20 may have two woven layers 22 and one structural layer 23. The core body 10 is sequentially covered with a first woven layer 22 (the innermost layer of the reinforcing layer 20), a first structural layer 23, a second woven layer 22 (the outermost layer of the reinforcing layer 20), and an affinity layer 24 covering the outermost surface of the reinforcing layer 20, thereby forming a five-layer orthopedic implant composite sandwich structure 100. The reinforcing layer 20 may also have three woven layers 22 and two structural layers 23, for example... Figure 1C As shown, the core body 10 is sequentially covered with a first braided layer 22, a first structural layer 23, a second braided layer 22, a second structural layer 23, a third braided layer 22 as the outermost layer of the reinforcing layer 20, and an affinity layer 24 covering the outermost surface of the reinforcing layer 20, thereby forming a 7-layer orthopedic implant composite sandwich structure 100. During the alternating formation of the braided layer 22 and structural layer 23, a hot-pressing process can be performed after each layer of braided layer 22 is formed.

[0037] In some embodiments, the braided layer 22 in the reinforcing layer 20 may be repeatedly braided multiple times before being covered by a single or multiple structural layer 23. For example Figure 1D As shown, the core body 10 is sequentially covered with a first braided layer 22, a second braided layer 22, a first structural layer 23, a third braided layer 22 (as the innermost layer of the reinforcing layer 20), a second structural layer 23 (as the outermost layer of the reinforcing layer 20), and an affinity layer 24 covering the outermost surface of the reinforcing layer 20, thereby constituting a 7-layer orthopedic implant composite sandwich structure 100. In some embodiments, hot pressing is not performed after the formation of the first braided layer 22, a first hot pressing is performed after the formation of the second braided layer 22, and a second hot pressing is performed after the formation of the third braided layer 22. In some embodiments, a first hot pressing is performed after the formation of the first braided layer 22, a second hot pressing is performed after the formation of the second braided layer 22, and a third hot pressing is performed after the formation of the third braided layer 22.

[0038] Due to its bioinertness, PAEK material does not easily fuse with bone tissue, and in some medical devices requiring bone fusion, it may loosen due to poor fusion. Therefore, the outer layer of this invention can use a composite material containing bioceramics or undergo surface treatment to improve cell affinity and bone fusion effect.

[0039] In some embodiments, the affinity layer 24 may further include bioceramics, such as alumina, zirconium oxide, carbon biomaterials, calcium phosphate, bioglass, calcium sulfate, or combinations thereof. One affinity layer 24 may contain about 0.5 to 5% by weight of bioceramics, for example, about 1 to 4.5%, about 1.5% to 4%, about 2 to 3.5%, about 2.5% to 3%, etc. The orthopedic implant composite sandwich structure 100 of this invention may include bioceramics or be coated with collagen only in the outermost affinity layer 24.

[0040] In some embodiments, the surface of the affinity layer 24 may be further surface-treated, such as by radiation surface treatment, plasma surface treatment, collagen surface coating, chemical solution treatment, or a combination thereof. Plasma surface treatment, for example, can generate highly reactive free radicals or peroxides on the surface, enabling better bonding with bioactive materials such as collagen.

[0041] It should be noted that, although Figures 1A to 1D The cross-sectional shape of the core body 10 is shown as a circle, but the cross-section of the core body 10 in this case is not limited to a circle; it can also be an ellipse, trapezoid, triangle, quadrilateral, polygon, irregular shape, etc. For example, refer to... Figures 2A-2D The core body 10 may also have a rectangular cross-section, and the reinforcing layer 20 covering the core body 10 may have one or more alternating or non-alternating woven layers 22 and structural layers 23. Figure 2A Only a single woven layer 22 is displayed, and it is compliantly formed on the core body with a rectangular cross-section. Figures 2A-2D The materials and formation method of the orthopedic implant composite sandwich structure 100 shown can be referred to Figures 1A-1D The relevant description of the orthopedic implant composite sandwich structure 100 shown will not be repeated here.

[0042] In summary, this invention strengthens PAEK material with a reinforcing layer containing a carbon fiber bundle braid, and then coats the carbon fiber bundle braid with a PAEK material affinity layer as the outermost layer of the orthopedic implant, thereby forming an orthopedic implant that combines mechanical strength and ductility. Furthermore, because the carbon fiber bundle braid has a variable braid structure, the mechanical properties of different parts of the implant can be adjusted according to requirements. Simultaneously, the number and arrangement of the carbon fiber bundle braid, structural, and affinity layers can be adjusted as needed; therefore, this invention has a wide range of applications.

[0043] The foregoing outlines components of several embodiments to facilitate a better understanding of the embodiments of the present invention by those skilled in the art. Those skilled in the art should understand that they can design or modify other manufacturing processes and structures based on the embodiments of the present invention to achieve the same purpose and / or advantages as the embodiments described herein. Those skilled in the art should also understand that such equivalent manufacturing processes and structures do not depart from the spirit and scope of the present invention, and that various changes, substitutions, and replacements can be made without departing from the spirit and scope of the present invention.

Claims

1. A composite sandwich structure for orthopedic implants, comprising: The core body, wherein the material of the core body comprises polyaryl ether ketone (PAEK); A reinforcing layer, covering the surface of the core body, and comprising at least one woven layer composed of carbon fiber bundles; and An affinity layer, covering the surface of the reinforcing layer, wherein the material of the affinity layer comprises polyaryletherketone.

2. The orthopedic implant composite sandwich structure of claim 1, wherein the reinforcing layer further includes at least one structural layer and covers the surface of the at least one braided layer, wherein the material of the at least one structural layer comprises polyaryletherketone.

3. The orthopedic implant composite sandwich structure as described in claim 2, wherein the reinforcing layer further includes the at least one woven layer and covers the surface of the at least one structural layer.

4. The orthopedic implant composite sandwich structure as described in claim 1, wherein the core body further comprises 0% to 35% carbon fiber short fibers by weight.

5. The orthopedic implant composite sandwich structure as described in claim 1, wherein the material of the affinity layer further comprises 0.5% to 5% by weight of bioceramic.

6. The orthopedic implant composite sandwich structure as described in claim 5, wherein the bioceramic comprises alumina, zirconium oxide, carbon biomaterials, calcium phosphate, bioglass, calcium sulfate, and combinations thereof.

7. The orthopedic implant composite sandwich structure of claim 1, wherein the surface of the affinity layer is subjected to radiation surface treatment, plasma surface treatment, collagen surface coating treatment, chemical solution treatment, and combinations thereof.

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