Polyethylene joint implant, manufacturing method thereof, and joint prosthesis

Abstract

The present invention relates to a polyethylene joint implant, a manufacturing method thereof, and a joint prosthesis, comprising the following steps: compression molding ultra-high molecular weight polyethylene powder in a mold cavity, wherein the hot pressing temperature of the hot pressing section of the compression molding is 210°C to 260°C, and the hot pressing is maintained for 20 minutes to 45 minutes; after compression molding, demolding; and the friction surface of the polyethylene joint implant is molded by the molding surface of the molding mold, wherein the roughness of the molding surface Ra is ≤ 0.1 micron. The above-mentioned manufacturing method optimizes the roughness of the molding surface to reduce the roughness of the friction surface; and in combination with a specific hot pressing process for specific compression molding, it prevents the problem of flashing during the molding process that affects the roughness of the friction surface of the molded product, thereby significantly reducing the roughness of the friction surface of the polyethylene joint implant.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, in particular to a polyethylene joint implant and a manufacturing method thereof, and a joint prosthesis. Background Art

[0002] Artificial joint replacement refers to the use of metal, high-molecular polyethylene, ceramics and other materials to make joint prostheses according to the shape, structure and function of human joints. They are implanted into the human body through surgical techniques to replace the function of diseased joints, thereby relieving joint pain and restoring joint function.

[0003] Ultra-high molecular weight polyethylene (UHMWPE) is a kind of polyethylene with a viscosity-average molecular weight of more than 3×10 6 Polyethylene products with a molecular weight of 0.1 g / mol exhibit a linear molecular structure. Due to its high molecular weight, ultra-high molecular weight polyethylene (UHMWPE) possesses superior properties not found in conventional molecular weight polyethylene, such as impact resistance, high strength, biocompatibility, self-lubrication, and wear resistance. Currently, UHMWPE is widely used in the field of artificial joint replacement, manufacturing polyethylene joint implants for joint prostheses. For example, over 70% of artificial hip replacements utilize a metal or ceramic femoral head component in combination with an UHMWPE acetabular cup liner. UHMWPE liners are also widely used in knee replacements. Although artificial joint replacement technology has matured, the friction between the hip liner and femoral head component, and between the knee liner and femoral condyle, during long-term use generates a large amount of UHMWPE wear debris. These micron-sized wear debris can trigger macrophage phagocytosis, causing osteolysis, leading to aseptic loosening and late failure of the joint prosthesis, ultimately requiring revision or replacement of the implanted joint prosthesis. Summary of the Invention

[0004] Based on this, it is necessary to provide a polyethylene joint implant and a manufacturing method thereof and a joint prosthesis that can reduce the generation of wear particles.

[0005] A method for manufacturing a polyethylene joint implant comprises the following steps:

[0006] The ultra-high molecular weight polyethylene powder is compression molded in the cavity of a molding die by a compression molding method. The compression molding method includes a hot pressing section, the hot pressing temperature of the hot pressing section is 210° C. to 260° C., and the hot pressing and heat preservation time is 20 minutes to 45 minutes.

[0007] After the compression molding, demoulding;

[0008] The molding die has a molding surface, the friction surface of the polyethylene joint implant is molded by the molding surface of the upper die, and the roughness of the molding surface is Ra≤0.1 micron.

[0009] In some embodiments, the molding mold includes an upper mold, a lower mold and a sleeve, the upper mold and the lower mold cooperate with each other to form the cavity, the upper mold and the lower mold are arranged in the sleeve and the assembly gap between them is no more than 0.04 mm, and the molding surface is located on the upper mold.

[0010] In some embodiments, the upper die and the lower die are arranged in the sleeve and an assembly gap between the upper die and the lower die and the sleeve is 0.02 mm to 0.04 mm.

[0011] In some embodiments, during the compression molding process, the lower mold is arranged in the sleeve and the bottom surface of the lower mold is on the same plane as the lower surface of the sleeve, the upper mold is arranged in the sleeve and cooperates with the lower mold to form the cavity, and the top surface of the upper mold is on the same plane as the upper surface of the sleeve.

[0012] In some embodiments, the compression molding comprises a cold pressing stage, the hot pressing stage, and a crystallization stage performed sequentially;

[0013] The conditions of the cold pressing section are: under a molding pressure of 30MPa to 50MPa, the temperature is raised to 50°C to 80°C;

[0014] The conditions of the hot pressing section are as follows: under a molding pressure of 0.2 MPa to 1 MPa, the temperature is continuously raised to 210°C to 260°C at a heating rate of 5°C / min to 10°C / min, the temperature is kept at 210°C to 260°C for 20 min to 45 min, and then the temperature is lowered to 120°C to 140°C at a cooling rate of 5°C / min to 10°C / min;

[0015] The conditions of the crystallization stage are: under a molding pressure of 30MPa to 50MPa, keeping at 120°C to 140°C for 20min to 45min, and then cooling;

[0016] After the compression molding, the mold is released.

[0017] In some embodiments, the cooling rate is no higher than 10°C / min.

[0018] In some embodiments, the cooling step is: naturally cooling to room temperature in air.

[0019] In some embodiments, the molding pressures of the cold pressing section, the hot pressing section, and the crystallization section are 35 MPa to 45 MPa, 0.4 MPa to 0.6 MPa, and 35 MPa to 45 MPa, respectively.

[0020] In some embodiments, the heating rate of the cold pressing section is 5° C. / min to 10° C. / min.

[0021] In some embodiments, the weight average molecular weight of the ultra-high molecular weight polyethylene powder is (3-5)×10 6 g / mol; the average particle size of the ultra-high molecular weight polyethylene powder is 100 microns to 200 microns.

[0022] A polyethylene joint implant is manufactured by any of the above-mentioned manufacturing methods.

[0023] In some embodiments, the polyethylene joint implant is a hip liner or a knee liner.

[0024] A joint prosthesis comprises a first supporting body, a second supporting body and the above-mentioned polyethylene joint implant; the polyethylene joint implant is arranged between the first supporting body and the second supporting body.

[0025] The manufacturing method of the above-mentioned polyethylene joint implant adopts a compression molding method, and utilizes the molding surface of the upper mold with a specific roughness to mold the friction surface of the polyethylene joint implant. The molding surface largely determines the roughness of the friction surface, so the roughness of the friction surface is reduced by optimizing the roughness of the molding surface; and combined with the specific hot pressing process of specific compression molding, the problem of overflow during the molding process affecting the roughness of the friction surface of the molded product is prevented, thereby significantly reducing the roughness of the friction surface.

[0026] The above-mentioned manufacturing method of polyethylene joint implants greatly reduces the roughness of the friction surface of the polyethylene joint implant products. The roughness Ra can be as low as below 0.2 microns, or even below 0.1 microns, reducing the wear particles generated by friction, thereby reducing the risk of bone dissolution, reducing the revision rate of polyethylene joint implant replacements, and extending the service life of its implant-grade polyethylene joint implant products in the human body, making it more suitable for artificial joint replacement technology.

[0027] In addition, the above-mentioned manufacturing method of polyethylene joint implants also optimizes the molding process, which is conducive to promoting the fusion of ultra-high molecular weight polyethylene powder particles and controlling the polyethylene joint implant product after ultra-high molecular weight polyethylene molding to have a smaller deformation amount, which meets the design standards of polyethylene joint implants such as artificial hip / knee. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 FIG1 is a structural schematic diagram of a forming die for forming an acetabular cup liner blank in a specific example;

[0029] Figure 2FIG1 is a schematic structural diagram of a forming die for forming a knee joint liner blank in a specific example;

[0030] Figure 3 Graph showing the molding and temperature process parameters for the molding process of Example 1;

[0031] Figure 4 Schematic diagram of the structure of the hip joint lining product and the knee joint lining product of Example 1;

[0032] Figure 5 This is a scanning electron microscope comparison of the friction surfaces of the hip joint lining product prepared in Example 1 and the hip joint lining product prepared in Control Group 1;

[0033] Figure 6 This is a scanning electron microscope comparison of the friction surfaces of the knee joint liner product prepared in Example 1 and the knee joint liner product prepared in Control Group 2;

[0034] Figure 7 The following are scanning electron microscope images of the friction surfaces of the hip joint lining product and the knee joint lining product prepared in Example 4;

[0035] Figure 8 These are scanning electron microscope images of the friction surfaces of the hip joint lining product and the knee joint lining product prepared in Example 13. DETAILED DESCRIPTION

[0036] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] In order to reduce the generation of ultra-high molecular weight polyethylene wear particles in polyethylene joint implants, some technologies use highly cross-linked ultra-high molecular weight polyethylene to improve the friction resistance of acetabular cup liners or knee joint pads.

[0039] Researchers have discovered that another major cause of ultra-high molecular weight polyethylene (UHMWPE) wear particles in polyethylene joint implants is the high roughness of the friction surface of polyethylene joint implants, such as acetabular cup liners and knee liners. This is because conventional polyethylene joint implants, such as hip liners and knee liners, are manufactured by directly machining UHMWPE rods. This process creates numerous tool marks on the friction surface, resulting in a high friction surface roughness (Ra) of up to 0.7 microns. The higher the roughness of the polyethylene joint implant's friction surface, the greater the friction force when used together, for example, when using a hip liner with a femoral head component, or a knee liner with a femoral condyle component. This increases the likelihood of adhesive and abrasive wear, and increases wear on the polyethylene joint implant material. Research has shown that in friction and wear tests of hip liners with femoral head components, and knee liners with femoral condyle components, the first 500,000 to 1,000,000 cycles are dominated by wear from the machining tool marks, which in turn generates a large number of UHMWPE wear particles.

[0040] One embodiment of the present invention provides a method for manufacturing a polyethylene joint implant, comprising the following steps S10 to S20:

[0041] Step S10: Using a compression molding method, the ultra-high molecular weight polyethylene powder is compression molded in a mold cavity. The compression molding includes a hot pressing section, the hot pressing temperature of the hot pressing section is 210° C. to 260° C., and the hot pressing and heat preservation time is 20 minutes to 45 minutes.

[0042] The forming mold has a forming surface, and the roughness of the forming surface is Ra≤0.1 micrometer. In some embodiments, the compression molding comprises a cold pressing stage, a hot pressing stage, and a crystallization stage performed sequentially.

[0043] The conditions of the cold pressing section are: heating to 50-80°C under a molding pressure of 30MPa-50MPa.

[0044] The conditions of the hot pressing section are: under a molding pressure of 0.2MPa~1MPa, continue to heat up to 210℃~260℃ at a heating rate of 5℃ / min~10℃ / min, keep at 210℃~260℃ for 20min~45min, and then cool to 120℃~140℃ at a cooling rate of 5℃ / min~10℃ / min.

[0045] The conditions of the crystallization stage are: keeping the temperature at 120°C to 140°C for 20 minutes to 45 minutes under a molding pressure of 30 MPa to 50 MPa, and then cooling.

[0046] In this way, by optimizing the compression molding process, it is beneficial to promote the fusion of ultra-high molecular weight polyethylene powder particles, control the ultra-high molecular weight polyethylene molding polyethylene joint implant product to have a smaller deformation, and meet the design standards of polyethylene joint implants such as artificial hip / knee.

[0047] Step S20: After compression molding, demoulding.

[0048] The manufacturing method of the above-mentioned polyethylene joint implant adopts a compression molding method, and utilizes the molding surface of the upper mold with a specific roughness to mold the friction surface of the polyethylene joint implant. The molding surface largely determines the roughness of the friction surface, so the roughness of the friction surface is reduced by optimizing the roughness of the molding surface; and combined with the specific hot pressing process of specific compression molding, the problem of overflow during the molding process affecting the roughness of the friction surface of the molded product is prevented, thereby significantly reducing the roughness of the friction surface.

[0049] The above-mentioned manufacturing method of polyethylene joint implants greatly reduces the roughness of the friction surface of the polyethylene joint implant products. The roughness Ra can be as low as below 0.2 microns, or even below 0.1 microns, reducing the wear particles generated by friction, thereby reducing the risk of bone dissolution, reducing the revision rate of polyethylene joint implant replacements, and extending the service life of its implant-grade polyethylene joint implant products in the human body, making it more suitable for artificial joint replacement technology.

[0050] In some embodiments, the forming mold includes an upper mold, a lower mold, and a sleeve. The upper mold and the lower mold cooperate with each other to form a mold cavity. The upper mold and the lower mold are disposed in the sleeve with an assembly clearance of no more than 0.04 mm. Furthermore, the forming surface is located on the upper mold.

[0051] In some embodiments, the friction surface of the polyethylene joint implant is formed by the molding surface of the upper mold having the specific roughness.

[0052] In addition, by optimizing the roughness of the molding surface of the upper mold, the assembly clearance of the mold, and the compression molding process, the present invention can ensure that the roughness of the friction surface of the acetabular cup liner and the knee joint pad products is basically completely consistent with the roughness of the molding surface of the upper mold, that is, the roughness Ra is guaranteed to be as low as below 0.1 microns.

[0053] In some embodiments, the upper die and the lower die are arranged in the sleeve and the assembly gap between the upper die and the sleeve is 0.02 mm to 0.04 mm, preferably 0.03 mm.

[0054] In some embodiments, the cooling rate is no higher than 10°C / min, further 5°C / min to 10°C / min. Furthermore, the cooling step is: naturally cooling to room temperature in air.

[0055] In some embodiments, the molding pressures of the cold pressing section, the hot pressing section, and the crystallization section are 35 MPa to 45 MPa, 0.4 MPa to 0.6 MPa, and 35 MPa to 45 MPa, respectively.

[0056] In some embodiments, the heating rate of the cold pressing section is 5° C. / min to 10° C. / min.

[0057] The hot pressing holding temperature in the hot pressing section is preferably 220-240°C, more preferably 230°C, the holding time is preferably 25-35 minutes, more preferably 30 minutes, the cooling rate in the hot pressing section is preferably 6-8°C / min, and the holding temperature in the crystallization section is preferably 130-140°C. Within the above range, the melting effect and fluidity of the ultra-high molecular weight polyethylene powder particles, as well as the shrinkage and deformation of the blank can be taken into account, resulting in a lower surface roughness and better friction performance of the resulting product.

[0058] It can be understood that both ends of the sleeve are open. Furthermore, the lower mold is used to be installed in the sleeve and the bottom surface of the lower mold is on the same plane as the lower surface of the sleeve. The upper mold is used to be installed in the sleeve and cooperate with the lower mold to form a cavity. The top surface of the upper mold is on the same plane as the upper surface of the sleeve. When in use, the lower mold is first installed in the sleeve so that the bottom surface of the lower mold is on the same plane as the lower surface of the sleeve; then fill it with ultra-high molecular weight polyethylene powder, and then install the upper mold in the sleeve so that the top surface of the upper mold is on the same plane as the upper surface of the sleeve. The shape of the cavity between the upper mold and the lower mold is the shape of the corresponding molded product.

[0059] During the compression molding process, the lower mold serves as a support, and the hot press applies the molding pressure to the upper mold through the pressure head. Polyethylene joint implants have a friction surface for matching. For example, acetabular cup liner blanks and knee joint liner blanks are generally made of ultra-high molecular weight polyethylene and have a friction surface for matching. Therefore, the molding surface of the upper mold is designed to have a shape corresponding to the friction surface to achieve a profiling effect. In this way, the molding pressure acts on the upper mold, and through the cooperation between the upper mold and the lower mold, the ultra-high molecular weight polyethylene powder is prompted to form a profiling friction surface on the molding surface. Therefore, the upper mold is also called a profiling pressure head. In one example, compression molding is performed using a hot press.

[0060] Furthermore, the sleeve is a cylindrical sleeve.

[0061] It is understood that the forming die used to form the acetabular cup liner blank or the knee liner blank can be set according to its shape.

[0062] In the acetabular cup liner blank mold, the interior of the lower mold is a contoured body, and the upper mold is designed as a hemispherical pressure head according to the structural characteristics of the acetabular cup liner product; in the knee joint liner blank mold, the lower mold is a pad, and the upper mold is designed as a contoured pressure head according to the structural characteristics of the knee joint liner product.

[0063] like Figure 1 As shown in a specific example, a molding die for molding an acetabular cup liner blank includes an upper mold 11, a lower mold 12, and a sleeve 13. The upper mold 11 is designed to be hemispherical according to the structural characteristics of the acetabular cup liner product, that is, the molding surface of the upper mold 11 is a hemispherical convex surface, and the corresponding molding surface of the lower mold 12 is a hemispherical concave surface. Specifically, the upper mold 11 includes a cylindrical body and a hemispherical pressure head connected to the cylindrical body, and the molding groove of the lower mold 12 is composed of a hemispherical groove and a cylindrical groove connected thereto. The top surface of the upper mold 11 and the bottom surface of the lower mold 12 are both flat. The hollow shape of the sleeve 13 is cylindrical.

[0064] like Figure 2 In a specific example, the mold used to form a knee lining blank comprises an upper mold 21, a lower mold 22, and a sleeve 23. Lower mold 22 serves as a cushion block, while upper mold 21 is designed as a contoured indenter based on the structural characteristics of the knee lining product. The outer shapes of upper and lower molds 21, 22, resemble the shape of a knee joint, and the hollow shape of sleeve 23 is similar.

[0065] In some embodiments, the weight average molecular weight of the ultra-high molecular weight polyethylene powder is (3-5)×10 6 g / mol; the average particle size of the ultra-high molecular weight polyethylene powder is 100 microns to 200 microns.

[0066] In some embodiments, the demoulding step in step S20 includes the following steps: using a hot press to press the upper mold, the molded polyethylene joint implant and the lower mold out of the sleeve, and taking out the polyethylene joint implant molded part.

[0067] In some embodiments, after the demolding step in step S20, the process further includes machining the residual edges and other areas of the polyethylene joint implant molded part using the reference surface on the ultra-high molecular weight polyethylene hip liner or knee liner blank. It is understood that this step only machines the residual edges and other areas, while the friction surface is not machined. After machining, the polyethylene joint implant product is obtained.

[0068] Compared with traditional polyethylene joint implants such as acetabular cup liners or knee joint pads that are directly machined, the above-mentioned manufacturing method of the polyethylene joint implant greatly reduces the wear of the ultra-high molecular weight polyethylene during use of the polyethylene joint implant product.

[0069] In some embodiments, the ultra-high molecular weight polyethylene is highly cross-linked ultra-high molecular weight polyethylene. After demolding, the polyethylene joint implant molded product with a low-roughness friction surface can be irradiated and cross-linked to prepare a polyethylene joint implant made of highly cross-linked ultra-high molecular weight polyethylene.

[0070] Another embodiment of the present invention further provides a polyethylene joint implant produced by the above-mentioned method for producing a polyethylene joint implant.

[0071] The polyethylene joint implant produced by the aforementioned method has a low friction surface roughness, reaching a roughness of Ra ≤ 0.2 microns, or even less than 0.1 microns. Furthermore, the aforementioned polyethylene joint implant can be used as a hip liner or knee pad. When used in conjunction with a femoral head or femoral condyle made of a metal or ceramic material, the resulting hip liner or knee pad can significantly reduce wear of the ultra-high molecular weight polyethylene during the first 500,000 to 1,000,000 wear cycles, thereby significantly reducing the risk of osteolysis, lowering the revision rate for polyethylene joint implant replacements, and extending the service life of the implantable polyethylene joint implant product in the human body.

[0072] Another embodiment of the present invention provides a joint prosthesis, comprising a first support, a second support, and the above-mentioned polyethylene joint implant, wherein the polyethylene joint implant is disposed between the first support and the second support.

[0073] In some embodiments, the joint prosthesis is a hip joint, a knee joint, a condylar joint, an elbow joint, a wrist joint, a finger joint or a shoulder joint. It is understood that the joint prosthesis includes but is not limited to the above.

[0074] Specifically, taking the hip joint prosthesis as an example, the polyethylene joint implant can be an acetabular cup liner. Furthermore, the first support body and the second support body are the acetabular prosthesis and the femoral head prosthesis respectively; the friction surface of the polyethylene joint implant is the side thereof close to the femoral head prosthesis.

[0075] Taking the knee joint prosthesis as an example, the polyethylene joint implant can be a knee joint pad. Further, the first support body and the second support body are the tibial tray and the femoral condyle prosthesis respectively, and the friction surface of the polyethylene joint implant is the side close to the femoral condyle prosthesis.

[0076] In order to make the purpose, technical solutions and advantages of the present invention more concise and clear, the present invention is illustrated by the following specific embodiments, but the present invention is by no means limited to these embodiments. The embodiments described below are only preferred embodiments of the present invention and can be used to describe the present invention. They should not be understood as limiting the scope of the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0077] In order to better illustrate the present invention, the present invention will be further described below with reference to the following embodiments.

[0078] Example 1

[0079] Use Figure 1 and Figure 2 The molding molds are used to manufacture ultra-high molecular weight polyethylene hip joint liner products and knee joint liner products. The specific steps are as follows:

[0080] The raw materials used are: weight average molecular weight of 4.5×10 6 g / mol, ultra-high molecular weight polyethylene powder with a particle size of 150 microns.

[0081] Filling: First install the lower mold into the sleeve so that the bottom surface of the lower mold and the lower surface of the sleeve are on the same plane; then fill it with ultra-high molecular weight polyethylene powder, and then install the upper mold into the sleeve so that the top surface of the upper mold and the upper surface of the sleeve are on the same plane.

[0082] Compression molding: Transfer the filled mold to a hot press for compression molding.

[0083] The assembly clearance between the lower die and the sleeve, and the assembly clearance between the upper die and the sleeve are both set to 0.03 mm. In a specific example, the molding surface of the upper die is ground and polished, and the surface roughness Ra is ≤ 0.1 micron.

[0084] Compression molding includes cold pressing section, hot pressing section and crystallization section which are carried out in sequence. Among them, cold pressing section: the molding pressure is 40MPa, the heating rate is 10℃ / min to 50℃, and the heating time is 5min. Hot pressing section: the molding pressure is 0.5MPa, and the hot pressing temperature is continuously raised to 230℃ at a heating rate of 10℃ / min and kept warm for 30min, and then cooled to 140℃ at a cooling rate of 8℃ / min. Crystallization section: the molding pressure is 40MPa, kept at 140℃ for 30min, and then naturally cooled to room temperature in the air. The molding and temperature process parameters of compression molding are as follows: Figure 3 As shown, a is the pressure curve of molding and b is the temperature curve of molding.

[0085] Demoulding: Use a hot press to demould and take out the UHMWPE hip liner and knee liner blank products.

[0086] After machining and milling, ultra-high molecular weight polyethylene hip joint liner products and knee joint liner products are obtained, such as Figure 4 As shown, a is a hip joint liner product (i.e., acetabular cup liner) and b is a knee joint liner product (i.e., tibial liner).

[0087] Control group 1-2

[0088] The ultra-high molecular weight polyethylene hip liner products and knee liner products are machined and directly formed respectively.

[0089] Scanning electron microscopy test: The friction surfaces of the ultra-high molecular weight polyethylene hip joint liner product and knee joint liner product prepared in Example 1 and the directly molded ultra-high molecular weight polyethylene hip joint liner product and knee joint liner product of control groups 1-2 were tested by scanning electron microscopy. The results are as follows: Figure 5 and Figure 6 shown.

[0090] Figure 5 These are scanning electron microscope comparison images of the friction surfaces of the hip joint lining product prepared in Example 1 and the hip joint lining product prepared in Control Group 1, where a is the hip joint lining product prepared in Example 1 and b is the hip joint lining product prepared in Control Group 1.

[0091] Figure 6 3 are scanning electron microscope comparison images of the friction surfaces of the knee joint liner product prepared in Example 1 and the knee joint liner product prepared in Control Group 2, wherein a is the knee joint liner product prepared in Example 1 and b is the knee joint liner product prepared in Control Group 2.

[0092] from Figure 5 and Figure 6 It can be seen that the friction surfaces of the compression-molded hip and knee lining products of the present invention have no machining marks, are uniform in surface roughness, and have low roughness. In contrast, the friction surfaces of the directly machined hip and knee lining products have obvious marks and are relatively rough.

[0093] Roughness test: The roughness of the friction surfaces of the acetabular cup liner product and the knee joint liner product molded in Example 1 was tested using a roughness tester.

[0094] The results show that the friction surface roughness Ra of directly machined hip and knee liner products is approximately 0.7 microns. The friction surface roughness Ra of the acetabular cup liner product of Example 1 of the present invention is 0.05-0.08 microns, and the friction surface roughness Ra of the knee liner product is 0.04-0.07 microns. This is consistent with the roughness Ra ≤ 0.1 microns of the upper mold's molding surface, indicating that the upper mold's molding surface largely determines the friction surface roughness. This embodiment significantly reduces the friction surface roughness by optimizing the upper mold's molding surface roughness and the aforementioned assembly clearance.

[0095] Through the above comparison of the morphology and roughness of the friction surface, it can be concluded that the compression molding process of the present invention can obtain polyethylene joint implant products such as ultra-high molecular weight polyethylene hip / knee joints with low friction surface roughness. When used in conjunction with metal or ceramic femoral heads / condyles, the wear of ultra-high molecular weight polyethylene acetabular cup liners or knee joint liner products can be reduced, ensuring the long-term use effect of the matching components.

[0096] Furthermore, this embodiment optimizes the roughness of the molding surface of the upper mold, the assembly clearance of the mold, and the compression molding process, so that the roughness of the friction surface of the acetabular cup liner and the knee joint liner product is basically consistent with the roughness of the molding surface of the upper mold.

[0097] Example 2

[0098] Use Figure 1 and Figure 2 The molding molds were used to manufacture ultra-high molecular weight polyethylene hip and knee lining products, respectively. The specific steps were essentially the same as those in Example 1, with the exception of a different holding temperature during the crystallization phase, specifically 120°C, and a different termination temperature during the cold pressing phase, specifically a molding pressure of 40 MPa, a heating rate of 10°C / min to 80°C, and a heating period of 8 minutes.

[0099] Roughness test: The friction surface roughness Ra of the hip joint lining product and the knee joint lining product were measured using a roughness tester and were found to be 0.06-0.1 microns and 0.06-0.09 microns respectively.

[0100] Example 3

[0101] Use Figure 1 and Figure 2 The molding dies were used to manufacture ultra-high molecular weight polyethylene hip lining products and knee lining products, respectively. The specific steps were essentially the same as those in Example 1, except that the assembly clearances between the lower die and sleeve, and between the upper die and sleeve, were different. Specifically, the assembly clearances between the lower die and sleeve, and between the upper die and sleeve, were both set to 0.04 mm.

[0102] Roughness test: When the assembly gap is 0.04mm, the roughness Ra of the hip joint liner product and the knee joint liner product measured by the roughness tester is 0.07~0.11 microns, which is consistent with the roughness Ra≤0.1 of the molding surface of the upper mold.

[0103] Example 4

[0104] Use Figure 1 and Figure 2 The molding molds are used to manufacture ultra-high molecular weight polyethylene hip joint lining products and knee joint lining products. The specific steps are basically the same as those in Example 1, except that the process parameters of the hot pressing section are different.

[0105] Specifically, in the hot pressing section, the molding pressure was 0.5 MPa, and the hot pressing temperature was continuously raised to 260° C. at a heating rate of 8° C. / min and kept at that temperature for 30 min, and then lowered to 140° C. at a cooling rate of 8° C. / min.

[0106] Scanning electron microscope test: Figure 7Scanning electron microscope images of the friction surfaces of the hip joint lining product and the knee joint lining product molded at a hot pressing temperature of 260° C. in Example 4 are shown as a and b, respectively.

[0107] Depend on Figure 7 It can be seen that when the hot pressing temperature is 260°C, the ultra-high molecular weight polyethylene powder particles have a good melting effect, and the friction surface roughness of the hip joint lining product and the knee joint lining product is low.

[0108] Roughness tester: The roughness Ra of hip joint lining products and knee joint lining products is 0.06~0.09 microns, which is consistent with the roughness Ra≤0.1 microns of the molding surface of the upper mold.

[0109] Example 5

[0110] Use Figure 1 and Figure 2 The molding molds were used to manufacture ultra-high molecular weight polyethylene hip joint liners and knee joint liner products, respectively. The specific steps were essentially the same as those in Example 1, except that the heating rate parameters in the hot pressing section were different. Specifically, the molding pressure was 0.5 MPa, the hot pressing temperature was continuously increased at a rate of 10°C / min to 230°C, held at that temperature for 30 minutes, and then cooled at a rate of 10°C / min to 140°C.

[0111] The experimental results show that when the cooling rate in the hot pressing section is low, not higher than 10°C / min, the shrinkage rate of the ultra-high molecular weight polyethylene acetabular cup liner and knee joint liner blank of Example 5 is very small, meeting the design standards of artificial hip / knee polyethylene joint implants.

[0112] Example 6

[0113] Use Figure 1 and Figure 2 The molding molds are used to manufacture ultra-high molecular weight polyethylene hip joint lining products and knee joint lining products. The specific steps are basically the same as those in Example 1, except that the assembly clearance between the lower mold and the sleeve and the assembly clearance between the upper mold and the sleeve are both 0.02 mm.

[0114] Example 7

[0115] Use Figure 1 and Figure 2 The molding molds are used to manufacture ultra-high molecular weight polyethylene hip joint lining products and knee joint lining products. The specific steps are basically the same as those in Example 1, except that the temperature of the hot pressing section is set to 210°C.

[0116] Example 8

[0117] Use Figure 1 and Figure 2The molding molds were used to manufacture ultra-high molecular weight polyethylene hip joint liners and knee joint liner products, respectively. The specific steps were essentially the same as those in Example 1, except that the heat preservation time in the hot pressing section was set to 20 minutes, i.e., the temperature was maintained at 230°C for 30 minutes, and then cooled to 120°C at a cooling rate of 8°C / min.

[0118] Example 9

[0119] Use Figure 1 and Figure 2 The molding molds are used to manufacture ultra-high molecular weight polyethylene hip joint liner products and knee joint liner products. The specific steps are basically the same as those in Example 1, except that the holding time of the hot pressing section is set to 45 minutes.

[0120] Example 10

[0121] Use Figure 1 and Figure 2 The molding molds are used to manufacture ultra-high molecular weight polyethylene hip joint liner products and knee joint liner products. The specific steps are basically the same as those in Example 1, except that the cooling rate in the hot pressing section is set to 5°C / min.

[0122] In Examples 6 to 10, the assembly gaps between the lower die, upper die and sleeve are set to 0.02 mm, the hot pressing temperature is set to 210°C, the holding time of the hot pressing section is set to 20 min and 45 min, and the cooling rate in the hot pressing section is set to 5°C / min.

[0123] Under these conditions, the friction surface roughness of both the hip and knee inserts is guaranteed to match the roughness of the upper mold's forming surface, achieving Ra ≤ 0.1 microns. Furthermore, product deformation is minimal, meeting design and use requirements.

[0124] Example 11

[0125] Use Figure 1 and Figure 2 The molding molds are used to manufacture ultra-high molecular weight polyethylene hip joint lining products and knee joint lining products. The specific steps are basically the same as those in Example 1, except that the molding pressures in the cold pressing section, hot pressing section, and crystallization section are 30 MPa, 1 MPa, and 50 MPa, respectively.

[0126] Under these conditions, the friction surface roughness of the hip and knee lining products reaches Ra ≤ 0.1 microns. At the same time, the product deformation is very small, meeting the product design and use requirements.

[0127] Example 12

[0128] Use Figure 1 and Figure 2The molding molds are used to manufacture ultra-high molecular weight polyethylene hip joint lining products and knee joint lining products. The specific steps are basically the same as those in Example 1, except that the molding pressures in the cold pressing section, hot pressing section, and crystallization section are 50 MPa, 0.2 MPa, and 30 MPa, respectively.

[0129] Under these conditions, the friction surface roughness of the hip and knee lining products reaches Ra ≤ 0.1 microns. At the same time, the product deformation is very small, meeting the product design and use requirements.

[0130] Example 13

[0131] Use Figure 1 and Figure 2 The molding molds were used to manufacture ultra-high molecular weight polyethylene hip and knee lining products, respectively. The specific steps were essentially the same as those in Example 1, with the following differences: The hot pressing stage was set to a temperature of 220°C for 30 minutes, then cooled to 140°C at a rate of 20°C / min; in the crystallization stage, the temperature was cooled to room temperature via water cooling at a rate of 20°C / min from 140°C.

[0132] Experimental results show that when the cooling rate during the hot pressing and crystallization stages is high (i.e., 20°C / min), the UHMWPE acetabular liner and knee liner blanks experience significant deformation and shrinkage, failing to meet the design standards for polyethylene artificial hip / knee implants. In this example, the friction surface roughness of the resulting UHMWPE acetabular liner and knee liner products ranged from Ra = 0.07 to 0.1 microns, meeting the roughness requirement of Ra ≤ 0.1 microns.

[0133] Example 14

[0134] Use Figure 1 and Figure 2 The molding molds are used to manufacture ultra-high molecular weight polyethylene hip joint lining products and knee joint lining products. The specific steps are basically the same as those in Example 1, except that the assembly gap between the lower mold and the sleeve and the assembly gap between the upper mold and the sleeve are set to 0.06 mm.

[0135] Scanning electron microscopy tests showed that when the assembly gap was 0.06 mm, flashing occurred during the molding process in Example 14, and defects such as depressions and pores appeared on the friction surfaces of the hip joint liner product and the knee joint pad product, as well as unmelted powder particles.

[0136] Roughness test: The roughness Ra of the hip and knee lining products tested using a roughness tester was 0.2 microns. This verifies that if flash occurs during the molding process, it will affect the roughness of the friction surface of the hip and knee lining products.

[0137] Comparative Example 1

[0138] Use Figure 1 and Figure 2 The molding dies are used to manufacture ultra-high molecular weight polyethylene hip joint inserts and knee joint inserts, respectively. The specific steps are essentially the same as those in Example 1, except that the surface roughness of the molding surface of the upper mold is different. Specifically, the molding surface of the upper mold is not ground or polished, and has a surface roughness Ra of approximately 0.5 microns.

[0139] Roughness test: The roughness Ra of hip joint lining products and knee joint lining products tested using a roughness tester were between 0.45 and 0.55 microns and 0.5 and 0.57 microns respectively; the roughness is equivalent to that of directly machined products.

[0140] Comparative Example 2

[0141] Comparative Example 2 uses Figure 1 and Figure 2 The molding molds are used to manufacture ultra-high molecular weight polyethylene hip joint liner products and knee joint liner products. The specific steps are basically the same as those in Example 1, except that the hot pressing temperature in the hot pressing section is set to 190° C. and the temperature is maintained for 15 minutes.

[0142] Scanning electron microscope test: Figure 8 The scanning electron microscope images of the friction surfaces of the hip joint liner and knee joint liner prepared in Example 13 are shown as a and b respectively. Figure 8 As shown in the figure, under lower hot pressing temperature (190℃) and shorter hot pressing time (15min), there are obvious unmelted particle boundaries on the friction surfaces of hip joint liner and knee joint liner. The size of the particle boundary (100μm to 200μm) is close to the particle size of polyethylene powder, indicating that the fusion effect of polyethylene powder is poor.

[0143] Roughness Testing: A roughness tester was used to measure the friction surface roughness of compression-molded products at two different hot-pressing temperatures. The results showed that the friction surface roughness Ra of the hip and knee lining products, pressed at 190°C for 15 minutes, was approximately 0.4 and 0.5 microns, respectively. This indicates that the lower hot-pressing temperature results in poor melting of the ultra-high molecular weight polyethylene powder particles, resulting in higher friction surface roughness for the hip and knee linings.

[0144] Comparative Example 3

[0145] Use Figure 1 and Figure 2The molding dies are used to manufacture ultra-high molecular weight polyethylene hip joint lining products and knee joint pad products, respectively. The specific steps are basically the same as those in Example 1, except that the hot pressing temperature of the hot pressing section is set to 270°C. The experimental results show that when the hot pressing temperature of the hot pressing section is high, reaching 270°C, the friction surface roughness of the hip joint lining products and the knee joint pad products is poor, reaching Ra = 0.25 to 0.42 microns. This is because the temperature of the hot pressing section is too high and the polyethylene powder has good fluidity, resulting in obvious overflow of the polyethylene powder during the molding process. Pits, pores and other phenomena appear on the surface of the hip joint lining products and the knee joint pad products, and the surface polyethylene particles have poor melting effect.

[0146] Some key parameters of the embodiments and comparative examples are shown in Table 1 below, where the crystallization temperature refers to the holding temperature in the crystallization section.

[0147] Table 1

[0148]

[0149]

[0150] By comparing Examples 1 to 14 with Comparative Examples 1 to 3, it can be seen that the present invention, by optimizing the roughness of the molding surface of the upper mold and the compression molding process, can ensure that the roughness of the friction surface of the acetabular cup liner and the knee joint liner products is substantially consistent with the roughness of the molding surface of the upper mold, that is, the roughness Ra is ensured to be as low as below 0.2 microns.

[0151] By comparing Example 14 with Example 1, it can be seen that the present invention can ensure that the roughness of the friction surface of the acetabular cup liner and the knee joint liner products is substantially consistent with the roughness of the molding surface of the upper mold by optimizing the roughness of the molding surface of the upper mold, the assembly clearance of the mold, and the compression molding process, that is, the roughness Ra is ensured to be as low as below 0.1 microns.

[0152] The products prepared in the above examples and comparative examples were further subjected to wear tests. The wear test objects were a cobalt-chromium-molybdenum ball head (32 mm) versus a molded acetabular liner (Examples 1-2, Example 14, and Comparative Example 1), and a cobalt-chromium-molybdenum condyle (CR8) versus a molded tibial liner (Examples 1-2, Example 14, and Comparative Example 1). The friction and wear tester was displacement-controlled, and the wear was repeated 5 million times, with weights being measured every 500,000 times. The test results are shown in the following table:

[0153] Table 2

[0154]

[0155] The surface roughness of the hip and knee liners of Examples 1 and 2 used in the wear tests was both less than 0.1 μm, while the surface roughness of the hip and knee liners of Example 14 and Comparative Example 1 was both greater than 0.1 μm. The wear test results demonstrate that the compression molding method of the present invention reduces the friction surface roughness of the hip and knee liners, lowering the wear rate during the first 500,000 cycles of the friction and wear test and further reducing the average breakage rate during the 5,000,000 cycles.

[0156] The optimal combination is (Example 1): the upper mold roughness Ra is ≤ 0.1 micron, and the clearance between the upper and lower molds and the sleeve is 0.03 mm. During the cold pressing stage, the mold pressure is 40 MPa, and the temperature is increased at a rate of 10°C / min to 50°C for 5 minutes. During the hot pressing stage, the mold pressure is 0.5 MPa, and the temperature is continuously increased at a rate of 10°C / min to 230°C and held for 30 minutes, followed by a cooling rate of 8°C / min to 140°C. During the crystallization stage, the mold pressure is 40 MPa, and the temperature is maintained at 140°C for 30 minutes, followed by natural cooling in air to room temperature.

[0157] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0158] The above-described embodiments merely represent several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art may make several modifications and improvements without departing from the concept of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be based on the appended claims, and the description and drawings may be used to interpret the content of the claims.

Claims

1. A method for manufacturing a polyethylene joint implant, characterized in that: The steps include: The ultra-high molecular weight polyethylene powder is compression molded in the cavity of a molding die by a compression molding method. The compression molding method includes a hot pressing section, the hot pressing temperature of the hot pressing section is 210° C. to 260° C., and the hot pressing and heat preservation time is 20 min to 45 min. After the compression molding, demoulding; Wherein, the molding die has a molding surface, the friction surface of the polyethylene joint implant is molded by the molding surface, and the roughness of the molding surface Ra is less than or equal to 0.1 micrometer; The molding die includes an upper die, a lower die, and a sleeve. The upper die and the lower die cooperate with each other to form the cavity. The upper die and the lower die are arranged in the sleeve and the assembly clearance between them and the sleeve is no more than 0.04 mm. The molding surface is located on the upper die. During the compression molding process, the lower mold is arranged in the sleeve and the bottom surface of the lower mold is in the same plane as the lower surface of the sleeve. The upper mold is arranged in the sleeve and cooperates with the lower mold to form the cavity. The top surface of the upper mold is in the same plane as the upper surface of the sleeve. The compression molding comprises a cold pressing section, a hot pressing section and a crystallization section which are performed in sequence; The conditions of the cold pressing section are: under a molding pressure of 30 MPa ~ 50 MPa, the temperature is raised to 50 ° C ~ 80 ° C; The conditions of the hot pressing section are as follows: under a molding pressure of 0.2 MPa to 1 MPa, continue to heat up to 210°C to 260°C at a heating rate of 5°C / min to 10°C / min, keep at 210°C to 260°C for 20 minutes to 45 minutes, and then cool down to 120°C to 140°C at a cooling rate of 5°C / min to 10°C / min; The conditions of the crystallization stage are: under a molding pressure of 30 MPa ~ 50 MPa, keeping at 120 ° C ~ 140 ° C for 20 min ~ 45 min, and then cooling; The cooling rate is no higher than 10°C / min; The heating rate of the cold pressing section is 5°C / min to 10°C / min; The weight average molecular weight of the ultra-high molecular weight polyethylene powder is (3-5)×10 6 g / mol; the average particle size of the ultra-high molecular weight polyethylene powder is 100 microns to 200 microns.

2. The manufacturing method according to claim 1, wherein The upper die and the lower die are arranged in the sleeve, and the assembly clearance between the upper die and the lower die and the sleeve is 0.02mm-0.04mm.

3. The manufacturing method according to claim 1, wherein: The sleeve is a cylindrical sleeve.

4. The manufacturing method according to claim 1, wherein: The hot pressing and heat preservation temperature of the hot pressing section is 220-240°C.

5. The manufacturing method according to claim 1, wherein: The cooling rate is 5°C / min to 10°C / min.

6. The manufacturing method according to claim 1, wherein: The molding pressures of the cold pressing section, the hot pressing section and the crystallization section are 35MPa~45MPa, 0.4MPa~0.6MPa and 35MPa~45MPa respectively.

7. A polyethylene joint implant, characterized in that: The method is as claimed in any one of claims 1 to 6.

8. A joint prosthesis, characterized in that: It comprises a first supporting body, a second supporting body and the polyethylene joint implant as claimed in claim 7; the polyethylene joint implant is arranged between the first supporting body and the second supporting body.

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