A method for manufacturing a low-wear knee joint replacement prosthesis

Abstract

The application relates to the technical field of knee joint replacement prostheses, in particular to a low-wear knee joint replacement prosthesis preparation method.The technical scheme of the joint replacement prosthesis comprises a tibial pad, a femoral prosthesis, a tibial support and a neodymium magnet; the tibial pad, the femoral prosthesis and the tibial support are injection molded by adopting the same type of mold structure; the preparation steps of the replacement prosthesis are as follows: step one, preparing raw materials required for composing the prosthesis; step two, preparing the tibial pad, the femoral prosthesis and the tibial support by combining an injection mold, realizing the preparation of the neodymium magnet block by combining a smelting furnace, alloy smelting, mold forming, vacuum sintering and tempering treatment; and step three, assembling the replacement prosthesis.The application avoids the appearance of wear metals from the material, thereby avoiding the release of inflammatory mediators, ensuring the long-term stability of the replacement prosthesis, applying the same-pole repulsion principle between magnets, realizing the magnetic suspension state between the prosthesis structures, thereby avoiding contact wear and prolonging the service life of the prosthesis.

Description

Technical Field

[0001] This invention relates to the field of knee joint replacement prosthesis technology, and in particular to a method for preparing a low-wear knee joint replacement prosthesis. Background Technology

[0002] Prosthetic material systems mostly employ a "metal-polyethylene" composite structure: femoral components are primarily made of cobalt-chromium-molybdenum alloys, with some high-end products utilizing ceramicized zirconia or titanium nitride surface treatments; tibial supports are mostly made of titanium alloys; and polyethylene liners are generally made of ultra-high molecular weight polyethylene, with recent upgrades towards antioxidant-treated highly cross-linked polyethylene and vitamin E-doped polyethylene. The clinical lifespan of current prostheses shows significant differentiation: prostheses using ordinary polyethylene liners have a 10-year survival rate of 85%-90%, decreasing to 75%-80% after 15 years; while prostheses using highly cross-linked polyethylene can achieve a 15-year survival rate of 92%-95%. However, the annual prosthesis failure rate in obese patients (BMI>30) is 2.3 times that of patients with normal body weight. Wear and tear remains the core challenge limiting prosthesis lifespan, with 67% of joint replacement revision surgeries related to prosthesis wear. While many studies attempt to mitigate prosthesis wear through material improvements or prosthesis structural design—for example, using carbon fiber-reinforced polyetheretherketone (CFR-PEEK) can reduce wear rates by 40%-60%—and new-generation prostheses have reduced contact stress from 35 MPa to 22 MPa through optimized tibiofemoral joint surface matching (increasing contact area by 30%-50%) and restrictive design, these measures still cannot completely prevent the generation of wear particles. Polymer materials, especially ultra-high molecular weight polyethylene (UHMWPE), are widely used as padding materials for articular surfaces due to their good biocompatibility and moderate flexibility. They can buffer the impact forces during joint movement and reduce hard friction between joints. However, during long-term reciprocating joint movements, the friction between UHMWPE and metal or ceramic gradually generates tiny wear particles. Once these particles detach and enter the surrounding tissues, they trigger a macrophage phagocytic response, releasing inflammatory mediators, which in turn leads to osteolysis and loosens the fixation between the prosthesis and bone tissue. This is one of the core issues affecting the long-term stability of knee replacement prostheses. In view of the above reasons, this application proposes a method for preparing a low-wear knee replacement prosthesis that utilizes the principle of magnetic repulsion between like poles of a magnetic field to form a magnetically levitated microgap between the femoral prosthesis and the tibial pad, thereby extending the service life of the prosthesis. Summary of the Invention

[0003] The purpose of this invention is to address the problems existing in the background art by proposing a method for preparing a low-wear knee replacement prosthesis that utilizes the principle of magnetic repulsion between like poles of a magnetic field to form a magnetically levitated micro-gap between the femoral prosthesis and the tibial pad, thereby extending the service life of the prosthesis.

[0004] The technical solution of the present invention: a method for preparing a low-wear knee joint replacement prosthesis, wherein the joint replacement prosthesis includes a tibial pad, a femoral prosthesis, a tibial support, and a neodymium magnet;

[0005] The preparation method of the replacement prosthesis includes the following steps:

[0006] Step 1: Prepare the materials needed to assemble the implant:

[0007] The tibial liner comprises the following parts by weight: 99.5-99.8 parts of highly cross-linked ultra-high molecular weight polyethylene and 0.2-0.5 parts of antioxidant; the femoral prosthesis comprises the following parts by weight: 80-88 parts of polyetheretherketone and 0.5-1.2 parts of reinforcing composite material; the tibial support comprises the following parts by weight: 98-99.8 parts of polyurethane and 0.2-0.5 parts of catalyst; the neodymium magnet comprises the following parts by weight: 29-32 parts of neodymium, 63-67 parts of iron, 1-1.2 parts of boron, and 1-5 parts of dysprosium;

[0008] Step 2: Combine injection molding to prepare tibial pads, femoral prostheses, and tibial supports; combine alloy melting in a smelting furnace, mold forming, vacuum sintering, and tempering to prepare neodymium magnet blocks.

[0009] Step 3: Assembly of the replacement prosthesis: Multiple sets of neodymium magnet blocks are respectively encapsulated in the tibial liner and the femoral prosthesis. The neodymium magnet blocks on the contact surfaces of the tibial liner and the femoral prosthesis have the same magnetism.

[0010] Optionally, the tibial pad, femoral prosthesis, and tibial support are injection molded using the same type of mold structure.

[0011] Optionally, the antioxidant used in the tibial liner is one or more combinations of vitamin E and hindered phenolic antioxidants;

[0012] The reinforcing composite material used in the femoral prosthesis is carbon fiber, which accounts for 0.5%-3% of the raw materials required for the femoral prosthesis, and the length of the carbon fiber is between 0.1mm and 5mm.

[0013] The catalyst used in the tibial support is dibutyltin dilaurate, which accounts for 0.05%-0.2% of the total mass of the tibial support raw materials.

[0014] Optionally, the highly cross-linked ultra-high molecular weight polyethylene has a molecular weight range of 1 million to 6 million and a degree of cross-linking range of 60% to 90%.

[0015] The polyurethane is prepared by reacting polyol with isocyanate, wherein the molar ratio of polyol to isocyanate is in the range of 1:1.1-1:1.5.

[0016] Optionally, the polyol is any one of polyether polyol and polyester polyol, with a number average molecular weight range of 500-3000.

[0017] The isocyanate is either toluene diisocyanate or diphenylmethane diisocyanate.

[0018] Optionally, the molding die includes a material storage head, a material storage cavity, a heating plate one, an upper molding cavity, a lower molding cavity, and a heating plate two;

[0019] The upper and lower molding cavities are combined with the shape changes of the tibial liner, femoral prosthesis, and tibial support.

[0020] Optionally, after the upper and lower molding cavities are molded together, the shape of the molding cavity is matched 1:1 with the designed tibial pad, femoral prosthesis, and tibial support model;

[0021] The molding cavity is made of S136 mold steel, and the inner wall of the molding cavity is coated with polytetrafluoroethylene.

[0022] Optionally, the tibial pad is divided into an upper tibial pad and a lower tibial pad. Both the upper and lower tibial pads are provided with elliptical mounting grooves. The two sets of elliptical mounting grooves form a magnet mounting cavity, and the neodymium magnet is encapsulated in the mounting cavity.

[0023] The upper and lower tibial liner pads are sealed together by a snap-fit ​​structure.

[0024] Optionally, the femoral prosthesis consists of upper and lower parts, which are closed and installed using a snap-fit ​​structure to achieve a sealed installation of the neodymium magnet block and prevent the infiltration of body fluids.

[0025] Optionally, the tibial liner comprises the following raw materials in parts by weight: 99.6 parts of highly cross-linked ultra-high molecular weight polyethylene and 0.35 parts of antioxidant;

[0026] The femoral prosthesis comprises the following raw materials in parts by weight: 84 parts polyetheretherketone and 0.9 parts reinforcing composite material;

[0027] The tibial support comprises the following raw materials in parts by weight: 99 parts polyurethane and 0.35 parts catalyst;

[0028] The neodymium magnet comprises the following raw materials in parts by weight: 30 parts neodymium, 65 parts iron, 1.1 parts boron, and 3 parts dysprosium.

[0029] Compared with the prior art, the present invention has the following beneficial technical effects:

[0030] 1. This invention achieves magnetic levitation of the joint prosthesis by setting neodymium magnet blocks and combining the principle of like poles repulsion between magnets. This results in a gap between the tibial pad and the femoral prosthesis, thereby minimizing prosthesis wear, extending the prosthesis's service life, and ensuring high safety in the use of the replacement joint. It also reduces the probability of inflammation and makes the replacement joint safer.

[0031] 2. In order to maximize magnetic field conduction and reduce the generation of metal wear particles, the femoral prosthesis, tibial liner and tibial support are injection molded from polymer materials, which avoids the metal particles generated by the wear of traditional metal materials, thereby reducing the risk of postoperative osteolysis. In addition, the hardness of polymer materials is closer to that of natural articular cartilage, which is more in line with the bionic concept.

[0032] 3. The femoral prosthesis in this invention is similar in design to current posterior stabilized knee prostheses. The tibial pad is located between the femoral prosthesis and the tibial support, and it assumes the function of a natural meniscus. It can serve as a mechanical buffer structure. Furthermore, the parts of the pad that connect with the medial and lateral condyles of the femoral prosthesis are concave arc-shaped surfaces. Because the medial and lateral condyles of the femoral prosthesis are convex structures, the concave arc-shaped surface of the pad can match the convex surface of the femoral prosthesis condyle structure. This structure is designed to mimic the matching of the femoral condyle and meniscus structure in a normal knee joint, and therefore is more ergonomic and the joint is used more smoothly.

[0033] In summary, this invention avoids metal wear from the material perspective, thereby preventing the release of inflammatory mediators and ensuring the long-term stability of the replacement prosthesis. It also utilizes the principle of like poles repulsion between magnets to achieve a magnetic levitation state between the various prosthesis structures, thus avoiding contact wear and extending the service life of the prosthesis. Attached Figure Description

[0034] Figure 1 A schematic diagram of the snap-fit ​​structure in this invention is provided;

[0035] Figure 2 A schematic diagram illustrating the magnetic levitation principle of the tibial liner and femoral prosthesis under different bending angles;

[0036] Figure 3 This is a structural diagram of the molding die in this invention.

[0037] Figure label:

[0038] 1. Material storage head;

[0039] 2. Material storage chamber;

[0040] 3. Heating plate one;

[0041] 4. Forming the upper cavity;

[0042] 5. Form the lower cavity;

[0043] 6. Heating plate two. Detailed Implementation

[0044] The technical solutions of this disclosure will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments.

[0045] The components of the embodiments of this disclosure, which are typically described and shown in the accompanying drawings, can be arranged and designed in a variety of different configurations. Therefore, the following detailed description of embodiments of this disclosure provided in the drawings is not intended to limit the scope of the claimed disclosure, but merely to illustrate selected embodiments of the disclosure.

[0046] All other embodiments obtained by those skilled in the art based on the embodiments in this disclosure without inventive effort are within the scope of protection of this disclosure.

[0047] In the description of this disclosure, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0048] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure based on the specific circumstances.

[0049] Example

[0050] like Figures 1-2 As shown, the present invention proposes a method for preparing a low-wear knee joint replacement prosthesis, wherein the joint replacement prosthesis includes a tibial pad, a femoral prosthesis, a tibial support, and a neodymium magnet;

[0051] The tibial pad, femoral prosthesis, and tibial support are injection molded using the same type of mold structure.

[0052] The preparation method of the replacement prosthesis includes the following steps:

[0053] Step 1: Prepare the materials needed to assemble the implant:

[0054] The tibial liner comprises the following raw materials in parts by weight: 99.6 parts of highly cross-linked ultra-high molecular weight polyethylene and 0.35 parts of vitamin E; the highly cross-linked ultra-high molecular weight polyethylene has a molecular weight range of 1 million to 6 million and a degree of cross-linking range of 88%.

[0055] The femoral prosthesis comprises the following raw materials in parts by weight: 84 parts polyetheretherketone and 0.9 parts carbon fiber;

[0056] The tibial support comprises the following raw materials in parts by weight: 99 parts polyurethane and 0.35 parts dibutyltin dilaurate; the polyurethane is prepared by reacting a polyol with an isocyanate, wherein the polyol is a polyether polyol and the isocyanate is toluene diisocyanate. The specific preparation process is as follows: in a reaction vessel, the polyether polyol and toluene diisocyanate are mixed in a molar ratio of 1:1.5, and 0.12% dibutyltin dilaurate is added as a catalyst. The reaction temperature is controlled at 90°C and the reaction time is 4 hours to prepare the polyurethane material.

[0057] The neodymium magnet comprises the following raw materials in parts by weight: 30 parts neodymium, 65 parts iron, 1.1 parts boron, and 3 parts dysprosium;

[0058] Step Two, as follows Figure 3 As shown, tibial pads, femoral prostheses, and tibial supports are prepared by combining injection molding molds; the molding mold includes a material storage head 1, a material storage cavity 2, a heating plate 1 3, an upper molding cavity 4, a lower molding cavity 5, and a second heating plate 6;

[0059] The upper and lower shaping cavities are combined with the shape changes of the tibial liner, femoral prosthesis, and tibial support;

[0060] After the upper and lower molding cavities are molded together, the shape of the molding cavity matches the designed tibial pad, femoral prosthesis, and tibial support model 1:1.

[0061] The molding cavity is made of S136 mold steel, and the inner wall of the molding cavity is coated with polytetrafluoroethylene.

[0062] Neodymium magnet blocks are prepared by combining alloy melting in a melting furnace, mold forming, vacuum sintering, and tempering treatment; the specific preparation process is as follows:

[0063] 1. Raw material preparation: Prepare neodymium, iron, boron, and dysprosium auxiliary additives according to the mass percentage. All raw materials must be of high purity to reduce the impact of impurities on magnetic properties.

[0064] 2. Alloy melting: The prepared raw materials are placed in a vacuum induction melting furnace. Under high vacuum, the raw materials are melted and fully mixed by induction heating. The melting temperature is usually controlled at 1550℃ and maintained at this temperature for 0.5 hours to ensure uniform alloy composition. Then, the melted alloy liquid is poured into a specific mold and cooled and solidified to obtain an ingot.

[0065] 3. Powdering: The ingot is crushed first by coarse crushing equipment into smaller particles, and then fine powdering equipment such as air jet mill is used to further pulverize the particles into micron-sized alloy powder. The powdering process is carried out under argon protection.

[0066] 4. Molding: The alloy powder and epoxy resin are thoroughly mixed and placed into a mold. The powder is then molded into neodymium magnet blanks of the required shape under a pressure of 100MPa by compression molding or injection molding.

[0067] 5. Sintering: The billet is placed in a vacuum sintering furnace and sintered at a high temperature of 1100℃. The sintering process can eliminate the porosity inside the billet, increase the density, and enhance the magnetic properties of the magnet. The sintering time is 2.5 hours, after which it is cooled to room temperature with the furnace.

[0068] 6. Tempering treatment: In order to further optimize the magnetic properties, the sintered magnet is tempered. The magnet is heated to 700℃, held at that temperature for 2 hours, and then slowly cooled. Tempering can adjust the internal structure of the magnet and improve its stability and remanence.

[0069] 7. Surface treatment: Electroplating or coating the magnet with protective paint or other surface treatments enhance its corrosion resistance and extend its service life;

[0070] Step 3: Assembly of the replacement prosthesis: Multiple sets of neodymium magnets are respectively encapsulated in the tibial liner and the femoral prosthesis. The neodymium magnets on the contact surfaces of the tibial liner and the femoral prosthesis have the same magnetism. Specifically, the tibial liner is divided into an upper tibial liner and a lower tibial liner. Both the upper and lower tibial liners have elliptical mounting grooves. The two sets of elliptical mounting grooves form a magnet mounting cavity, and the neodymium magnets are encapsulated in the mounting cavity.

[0071] The upper and lower tibial liner pads are sealed together by a snap-fit ​​structure. The femoral prosthesis consists of upper and lower parts, which are closed together by a snap-fit ​​structure to achieve a sealed installation of the neodymium magnet block and prevent the infiltration of body fluids. The snap-fit ​​structure is divided into two parts: the upper part of multiple sets of snaps is fixedly connected to the upper liner pad of the tibial liner and the upper part of the femoral prosthesis, and the lower part of the snaps is fixedly connected to the lower liner pad of the tibial liner and the lower part of the femoral prosthesis, thereby achieving a sealed encapsulation.

[0072] Prosthesis performance testing:

[0073] Magnetic positioning effect: In the simulated joint movement experiment, the repulsive force generated by the neodymium magnet block at the contact surface between the tibial liner and the femoral prosthesis was stable through monitoring by magnetic field detection equipment. This ensured that the positioning accuracy error of the joint during movement was controlled within ±0.2mm, effectively improving the stability of joint movement.

[0074] Overall mechanical performance: The mechanical performance of the assembled joint replacement prosthesis was tested. In the loading test simulating human walking, running and jumping, the prosthesis was able to withstand a pressure of up to 2000N without deformation or damage, meeting the needs of daily human movement.

[0075] The details are shown in the table below:

[0076]

[0077] Combination Figure 2 As shown, the prosthesis performance was tested under different bending conditions:

[0078] The details are shown in the table below:

[0079]

[0080]

[0081] Based on the data table above, it can be seen that the prosthesis in this embodiment has superior mechanical properties and higher durability in meeting the complex movement needs of the human body, and can provide patients with more reliable joint replacement results.

[0082] The above specific embodiments are merely optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A method for preparing a low-wear knee joint replacement prosthesis, characterized in that, The joint replacement prosthesis includes a tibial pad, a femoral prosthesis, a tibial support, and a neodymium magnet; The preparation method of joint replacement prostheses includes the following steps: Step 1: Prepare the materials needed to assemble the implant: The tibial liner comprises the following raw materials in parts by weight: 99.5-99.8 parts of highly cross-linked ultra-high molecular weight polyethylene and 0.2-0.5 parts of antioxidant; the highly cross-linked ultra-high molecular weight polyethylene has a molecular weight range of 1 million to 6 million and a degree of cross-linking range of 60% to 90%. The femoral prosthesis comprises the following raw materials in parts by weight: 80-88 parts of polyetheretherketone and 0.5-1.2 parts of reinforcing composite material; The tibial support comprises the following raw materials in parts by weight: 98-99.8 parts polyurethane and 0.2-0.5 parts catalyst; the polyurethane is prepared by reacting polyol with isocyanate, and the molar ratio of polyol to isocyanate is in the range of 1:1.1-1:1.

5. The neodymium magnet comprises the following raw materials in parts by weight: 29-32 parts neodymium, 63-67 parts iron, 1-1.2 parts boron, and 1-5 parts dysprosium; Step 2: Combine injection molding to prepare tibial pads, femoral prostheses, and tibial supports; combine alloy melting in a smelting furnace, mold forming, vacuum sintering, and tempering to prepare neodymium magnet blocks. Step 3: Assembly of the replacement prosthesis: Multiple sets of neodymium magnet blocks are respectively encapsulated in the tibial liner and the femoral prosthesis. The neodymium magnet blocks on the contact surfaces of the tibial liner and the femoral prosthesis have the same magnetism. The antioxidants used in the tibial liner are one or more combinations of vitamin E and hindered phenolic antioxidants. The reinforcing composite material used in the femoral prosthesis is carbon fiber, which accounts for 0.5%-3% of the raw materials required for the femoral prosthesis, and the length of the carbon fiber is between 0.1mm and 5mm. The catalyst used in the tibial support is dibutyltin dilaurate, which accounts for 0.05%-0.2% of the total mass of the tibial support raw materials. The molding die includes a material storage head (1), a material storage cavity (2), a heating plate one (3), an upper molding cavity (4), a lower molding cavity (5), and a second heating plate (6); The upper and lower molding cavities are combined with the shape changes of the tibial liner, femoral prosthesis, and tibial support; after the upper and lower molding cavities are molded together, the shape of the molding cavity matches the designed tibial liner, femoral prosthesis, and tibial support model 1:

1. The tibial liner is divided into an upper tibial liner and a lower tibial liner. Both the upper and lower tibial liners are provided with elliptical mounting grooves. The two sets of elliptical mounting grooves form a magnet mounting cavity, and the neodymium magnet is encapsulated in the mounting cavity. The upper and lower tibial liner pads are sealed together by a snap-fit ​​structure. The femoral prosthesis consists of two parts, upper and lower, which are connected by a snap-fit ​​structure to achieve a sealed installation of the neodymium magnet and prevent the infiltration of body fluids.

2. The method for preparing a low-wear knee joint replacement prosthesis according to claim 1, characterized in that, The tibial pad, femoral prosthesis, and tibial support are injection molded using the same type of mold structure.

3. The method for preparing a low-wear knee joint replacement prosthesis according to claim 1, characterized in that, The polyol is any one of polyether polyol and polyester polyol, with a number average molecular weight range of 500-3000. The isocyanate is either toluene diisocyanate or diphenylmethane diisocyanate.

4. The method for preparing a low-wear knee joint replacement prosthesis according to claim 1, characterized in that, The molding cavity is made of S136 mold steel, and the inner wall of the molding cavity is coated with polytetrafluoroethylene.

5. The method for preparing a low-wear knee joint replacement prosthesis according to claim 1, characterized in that, The tibial liner comprises the following raw materials in parts by weight: 99.6 parts of highly cross-linked ultra-high molecular weight polyethylene and 0.35 parts of antioxidant; The femoral prosthesis comprises the following raw materials in parts by weight: 84 parts polyetheretherketone and 0.9 parts reinforcing composite material; The tibial support comprises the following raw materials in parts by weight: 99 parts polyurethane and 0.35 parts catalyst; The neodymium magnet comprises the following raw materials in parts by weight: 30 parts neodymium, 65 parts iron, 1.1 parts boron, and 3 parts dysprosium.

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