Artificial meniscus and method of making

Abstract

The application discloses an artificial meniscus and a preparation method thereof. The preparation method of the artificial meniscus comprises the following steps: dispersing hydrophilic polytetrafluoroethylene in a hydrophilic polyurethane solution to obtain a composite slurry; pouring the composite slurry into a particle mold and then performing freezing treatment, and then drying and solidifying to obtain a composite material; mixing the composite material with a plasticizer to obtain a to-be-injection-molded material; injecting the to-be-injection-molded material into an injection molding machine for melt extrusion, and then injecting the to-be-injection-molded material into a meniscus mold, and cooling to obtain the artificial meniscus; the temperature of a first section of the injection molding machine is 180-190 DEG C; and the temperature of a second section is 150-160 DEG C. The preparation method of the application can retain the uniformity of the original material, heat injection mold under a relatively mild processing window, avoid thermal degradation of the composite material caused by high temperature, coordinate melt extrusion and precise mold filling, improve the production efficiency and the yield of the artificial meniscus, and accelerate the process from research and development to market application of the artificial meniscus.

Description

Technical Field

[0001] This invention relates to the field of meniscus technology, and in particular to an artificial meniscus and its preparation method. Background Technology

[0002] The meniscus is the core cushioning and stabilizing structure of the knee joint, playing an irreplaceable role in maintaining normal knee joint movement, distributing joint load, and protecting articular cartilage. Clinically, meniscus tears, degenerative changes, and traumatic injuries are common causes of knee pain and impaired mobility. With the continued aging of the global population and the widespread participation in sports, the incidence of meniscus injuries is rising annually. This has led to a surge in market demand for artificial meniscus implants with high durability, excellent biocompatibility, and high mechanical performance matching, placing higher demands on the manufacturing process, product performance, and production safety of artificial meniscus materials.

[0003] Currently, common methods for molding artificial menisci include freeze-drying, often used in the preparation of collagen or hydrogel-based scaffolds to create porous structures that promote tissue regeneration. However, this process relies on solvent freeze-drying or phase separation, requiring a long drying cycle (often exceeding 48 hours) and subsequent washing to remove residual solvent. This leads to high energy consumption, low production efficiency, and introduces potential solvent residue risks, affecting the cytotoxicity assessment and clinical safety of artificial meniscus materials. Furthermore, when molding complex curved structures (such as the C-curve and gradient thickness of the meniscus), this process struggles to maintain shape and ensure internal density and uniformity, easily creating micropores or stress concentration points, thereby weakening the fatigue resistance and joint load-bearing capacity of the artificial meniscus.

[0004] Therefore, there is an urgent need to develop a new preparation and molding process to solve the core problems of solution freeze-curing molding process for new meniscus materials, such as low molding accuracy, long production cycle, high cost, and solvent residue, so as to achieve efficient, safe and large-scale production of artificial meniscus, while further improving the structural accuracy and clinical performance of finished artificial meniscus. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the first objective of the present invention is to provide a method for preparing an artificial meniscus. The second objective of the present invention is to provide an artificial meniscus prepared by this method.

[0006] The inventive concept of this invention is as follows: This invention prepares a composite material from hydrophilic polyurethane (PU) and hydrophilic polytetrafluoroethylene (PTFE) using a premixed freezing method, achieving uniform dispersion and ensuring stable embedding of PTFE particles into the PU matrix, resulting in a dense composite microstructure. Then, the composite material is used as raw material for injection molding. By controlling the injection molding process conditions, thermal oxidative degradation of the composite material is avoided, while wrinkling of the artificial meniscus is prevented, and the production efficiency of artificial menisci is improved, thereby producing customizable, highly repeatable, and consistently high-quality artificial meniscus products.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing an artificial meniscus, comprising the following steps: S1: Disperse hydrophilic polytetrafluoroethylene in a hydrophilic polyurethane solution to obtain a composite slurry; S2: After pouring the composite slurry described in step S1 into a particle mold, freeze it and then dry and cure it to obtain the composite material; S3: Mix the composite material described in step S2 with the plasticizer solution to obtain the material to be injection molded, wherein the material to be injection molded is a composite material with a plasticizer coating on its surface; S4: The material to be injected into the injection molding machine is melted and extruded, then injected into the meniscus mold, and cooled to obtain the artificial meniscus; the first stage temperature (barrel heating temperature) of the injection molding machine is 180~190℃; the second stage temperature (extrusion temperature) is 150~160℃.

[0008] This invention disperses hydrophilic polytetrafluoroethylene (PTFE) in a hydrophilic polyurethane solution to obtain a composite slurry. Then, a cryogenic treatment (low temperature) method is used to prepare a composite material from the composite slurry. Uniform dispersion is achieved at low temperatures, ensuring stable embedding of PTFE particles into the PU matrix, forming a dense composite microstructure. This effectively optimizes the biocompatibility and mechanical compatibility of traditional artificial meniscus materials. Furthermore, this invention uses these composite material particles as raw materials for thermo-injection molding, preserving the uniformity of the original materials while avoiding the thermal stress problems associated with high-temperature mixing (such as direct thermo-injection of PTFE and PU). In addition, this invention improves the storage stability of the raw materials (the particle morphology of the composite material facilitates moisture-proof sealing) and transportation convenience, reduces dust emission and equipment corrosion during injection molding, and is suitable for large-scale industrial production.

[0009] Compared to the process of directly injecting the composite slurry into a meniscus mold and then freeze-drying it, the hot injection molding method of this invention exhibits significant advantages. The synergy between melt extrusion and precision filling of the meniscus mold enables efficient continuous production. Because the composite slurry contains a large amount of solvent, directly freeze-drying it into an artificial meniscus results in significant volume changes during solvent evaporation and product curing. Furthermore, the varying solvent evaporation rates in different parts of the artificial meniscus due to factors such as ventilation control inevitably lead to deformations such as shrinkage and depressions during curing. In addition, the drastic volume changes during meniscus curing make direct freeze-drying impossible to perfectly meet the need for customized artificial meniscus shapes. This invention, by first preparing the composite material through low-temperature freezing and then using hot injection molding, avoids shrinkage of the artificial meniscus and improves production efficiency, thereby producing customizable, highly repeatable, and consistently high-quality artificial meniscus products.

[0010] Furthermore, if PTFE and PU are directly hot-melted and injection molded, high centrifugation (>3000-5000 rpm) is required before injection molding to improve dispersibility and ensure uniform dispersion of PTFE in the molten PU. However, this operation is difficult, requires stringent conditions, and nano-sized PTFE is prone to re-agglomeration, leading to inhomogeneous microstructure and ultimately affecting the surface lubricity and biomechanical compatibility of the meniscus. Moreover, direct injection molding requires processing at high temperatures (>220°C), which may damage the surface modification layer and weaken interfacial bonding strength, increasing the risk of early delamination or failure after artificial meniscus implantation. This invention employs a method of first preparing the composite material through low-temperature freezing before injection molding. This not only ensures uniform dispersion of PTFE in the composite material but also allows the composite material to operate within a relatively mild processing window of 150-190°C, avoiding thermal degradation caused by high temperatures (>220°C) and ensuring the stability of the composite material's core properties.

[0011] In summary, this invention, while preserving the excellent biocompatibility and mechanical properties of hydrophilic PU-PTFE composite materials, solves the technical problems of existing processes, such as long production cycles, high energy consumption, solvent residue, and uneven finished product structure. Furthermore, the preparation method of this invention supports automated integration, significantly reducing manufacturing costs and facilitating quality control, thus helping to accelerate the process of artificial menisci from research and development to market application.

[0012] Preferably, the preparation method of the composite slurry in step S1 is as follows: hydrophilic polyurethane is dissolved in an aqueous ethanol solution to obtain solution A; hydrophilic polytetrafluoroethylene is dispersed in an activation solution for activation, and activated polytetrafluoroethylene is obtained by solid-liquid separation; the activated polytetrafluoroethylene is dispersed in an aqueous ethanol solution to obtain dispersion B; dispersion B is mixed with solution A and allowed to stand at room temperature to obtain composite slurry.

[0013] Preferably, the hydrophilic polytetrafluoroethylene includes at least one of blended modified hydrophilic PTFE, grafted modified hydrophilic PTFE, surface-coated hydrophilic PTFE, and plasma-modified hydrophilic PTFE; more preferably, the hydrophilic polytetrafluoroethylene is plasma-modified hydrophilic PTFE.

[0014] Preferably, the hydrophilic polytetrafluoroethylene has a particle size of 250-350 nm; more preferably, the hydrophilic polytetrafluoroethylene has a particle size of 260-330 nm; and even more preferably, the hydrophilic polytetrafluoroethylene has a particle size of 280-320 nm.

[0015] Preferably, the ethanol-water solution comprises an ethanol-water solution with a volume ratio of (8.5). 9.5): (0.8 1.2) Ethanol and water; more preferably, the aqueous ethanol solution comprises ethanol and water in a volume ratio of 9:1.

[0016] Preferably, the specific operation of dissolving the hydrophilic polyurethane in the ethanol aqueous solution is as follows: stirring at 750-850 rpm at 70-80°C until the hydrophilic polyurethane is completely dissolved in the ethanol aqueous solution.

[0017] Preferably, the mass-to-volume ratio of hydrophilic polyurethane to ethanol aqueous solution is (0.8~1.2) g:10 mL; more preferably, the mass-to-volume ratio of hydrophilic polyurethane to ethanol aqueous solution is (0.85~1.1) g:10 mL.

[0018] Preferably, the activation solution comprises 3 aminopropyltriethoxysilane, in the activation solution 3 The volume content of aminopropyltriethoxysilane is 1.5%. 2.5%; more preferably, the activation solution contains 3 The volume content of aminopropyltriethoxysilane is 2%.

[0019] Preferably, the pH of the activation solution is 4-5.

[0020] Preferably, the activation conditions are: activation temperature 30~40℃, stirring speed 200~300rpm, and stirring time 1.5~2.5h.

[0021] Preferably, the mass of hydrophilic polytetrafluoroethylene in dispersion B is 3% of the mass of hydrophilic polyurethane in solution A. 20% can be any value from 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, or a range of values ​​formed by any two of these.

[0022] Preferably, the mass-to-volume ratio of activated polytetrafluoroethylene to aqueous ethanol solution in dispersion B is (0.1~1) g: (4~6) mL; more preferably, the mass-to-volume ratio of activated polytetrafluoroethylene to aqueous ethanol solution in dispersion B is (0.2~0.6) g: (4~6) mL; even more preferably, the mass-to-volume ratio of activated polytetrafluoroethylene to aqueous ethanol solution in dispersion B is (0.25~0.4) g: (4~6) mL.

[0023] Preferably, the dispersion B is mixed with solution A by heating and stirring.

[0024] More preferably, the heating temperature is 50~60℃, the stirring speed is 600~1000rpm, and the stirring time is 35~45min.

[0025] Preferably, the diameter of the particle mold in step S2 is 8-12 mm; more preferably, the diameter of the particle mold in step S2 is 9-11 mm. Within the defined particle mold diameter range, the composite material obtained after freeze-drying the composite slurry has a suitable particle size, which can be effectively propelled in the injection molding machine.

[0026] Preferably, the particle size of the composite material in step S2 is 3~5mm; more preferably, the particle size of the composite material in step S2 is 3.2~4.5mm; even more preferably, the particle size of the composite material in step S2 is 3.5~4.2mm.

[0027] Preferably, the freezing temperature in step S2 is -50℃ to -30℃; more preferably, the freezing temperature in step S2 is -45℃ to -35℃; and even more preferably, the freezing temperature in step S2 is -42℃ to -38℃.

[0028] Preferably, the freezing time in step S2 is 30-60 min; more preferably, the freezing time in step S2 is 32-50 min; and even more preferably, the freezing time in step S2 is 35-45 min.

[0029] Preferably, the drying and curing time in step S2 is 2 to 5 days; more preferably, the drying and curing time in step S2 is 3 to 4 days.

[0030] Preferably, the plasticizer mentioned in step S3 is tributyl acetyl citrate (ATBC).

[0031] Based on the hot injection molding method employed in this invention, the inventors discovered through research on the state of the composite material after melting that its high viscosity and large flow resistance during melting easily lead to insufficient injection filling or the formation of internal bubbles / defects, affecting the surface smoothness and overall mechanical uniformity of the meniscus. Therefore, this invention optimizes the flowability and injection success rate of the composite material in its molten state at 150~190℃ by mixing the composite material with a plasticizer before injection molding.

[0032] The ATBC used in this invention exhibits significant compatibility and synergy with the hydrophilic PU in the composite material. The hydrophilic PU contains a large number of urethane groups (…). NH COO ATBC, possessing a strong dipole moment, has a molecular structure rich in four ester groups and one acetyl group. Its Hansen solubility parameters are highly compatible with the polar segments of PU. Compared to plasticizers containing symmetrical large benzene rings and long alkyl chains, such as dioctyl terephthalate (DOTP) or other commonly used industrial benzene ring-containing plasticizers, ATBC can more effectively penetrate the hard segment microdomains of hydrophilic PU. Through transient dipole-dipole interactions, it weakens the strong hydrogen bond network between hydrophilic PU molecular chains, thereby significantly enhancing the slippage ability of the molecular chains, effectively reducing melt viscosity (by 30%–50%), promoting shear thinning, and achieving lower processing temperatures and higher extrusion rates. Furthermore, from a biochemical metabolic mechanism perspective, as a citric acid derivative, ATBC's potential hydrolysis products in the biological environment (such as citric acid and acetic acid) are endogenous metabolic intermediates or precursors of the human tricarboxylic acid cycle (TCA cycle). This means that the degradation products of ATBC can be recognized and utilized by the normal metabolic pathways of organisms, avoiding the risk of tissue accumulation and immune rejection caused by non-natural heterologous metabolites (such as benzene ring compounds). Mechanistically, this gives ATBC a higher potential for biocompatibility compared to benzene ring plasticizers.

[0033] Preferably, the plasticizer accounts for 3% to 5% of the mass percentage of the composite material; more preferably, the plasticizer accounts for 3.2% to 4.8% of the mass percentage of the composite material; and even more preferably, the plasticizer accounts for 3.5% to 4.5% of the mass percentage of the composite material.

[0034] Preferably, in step S4, the interior of the meniscus mold is coated with a dimethyl silicone oil coating.

[0035] This invention, by coating the inside of the meniscus mold with dimethyl silicone oil, effectively reduces mold surface friction, improves the spreadability of the injection slurry, and allows the injection slurry to quickly and completely fill the meniscus mold. This results in uniform and smooth material output from the injection molding machine, free of air bubbles, and easier mold opening after cooling, increasing the injection molding success rate by at least 10%. In actual production, the inventors previously studied adding dimethyl silicone oil to the material to be injection molded to improve the success rate; however, this method caused the injection molding machine to be unable to advance effectively, and the dimethyl silicone oil and injection slurry to separate, making injection molding impossible. Therefore, only by coating the inside of the meniscus mold with dimethyl silicone oil to form a coating can a complete, dense, deformation-free, air bubble-free artificial meniscus with a tough, elastic feel and a smooth surface be produced.

[0036] Furthermore, the dimethyl silicone oil used in this invention exhibits excellent compatibility with the composite material. When other conventional surface coating materials, such as polytetrafluoroethylene (PTFE), are used, although the injection molding machine can ensure uniform and smooth material output without air bubbles, the injection slurry cannot completely fill the mold. After cooling, the artificial meniscus product adheres severely to the PTFE coating, making it impossible to open the mold or causing the artificial meniscus product to deform and break after opening. This is because during injection molding, the plasticizer ATBC migrates to the interface and causes local swelling. When the coating material is water-based PTFE, the polyurethane segments penetrate the PTFE coating and become entangled with it; at the same time, the hydrophilic PTFE in the composite material breaks its chemical inertness and forms strong hydrogen bonds with residual additives in the PTFE coating (such as polyamide-imide (PAI), polyethersulfone (PES), or polyphenylene sulfide (PPS) resin adhesives), constructing a reverse chemical bridge and strengthening the adhesion between the composite material and the coating. In addition, the slurry after melt extrusion will enter the micropores of the PTFE coating to form mechanical anchoring, resulting in the interfacial adhesion strength being far greater than the cohesive strength of the composite material. When the mold is opened, the stress cannot be delaminated at the interface, which will cause cohesive failure, ultimately resulting in the inability to open the mold or the appearance of tears and pits on the surface of the artificial meniscus.

[0037] Preferably, the mass of the dimethyl silicone oil is 0.3% to 0.6% of the mass of the artificial meniscus; more preferably, the mass of the dimethyl silicone oil is 0.35% to 0.58% of the mass of the artificial meniscus; even more preferably, the mass of the dimethyl silicone oil is 0.4% to 0.57% of the mass of the artificial meniscus; and even more preferably, the mass of the dimethyl silicone oil is 0.45% to 0.55% of the mass of the artificial meniscus.

[0038] Preferably, the first-stage temperature of the injection molding machine is 180~190℃; the second-stage temperature is 150~160℃. If the first and second-stage temperatures are too high, the injection slurry will be too thin, failing to effectively generate pressure for injection molding; if the first and second-stage temperatures are too low, extrusion resistance will be high, and small air bubbles will be trapped at the outer edge of the injection slurry. Within the first and second-stage temperature ranges defined in this invention, the injection slurry is uniform in size, free of small air bubbles, has good fluidity, and can generate effective pressure for rapid injection molding.

[0039] Preferably, a meniscus steel frame is pre-fixed within the meniscus mold. This invention achieves complete embedding of the steel frame by first fixing the meniscus steel frame within the mold and then injecting the slurry to be injected into the mold using hot injection molding. This invention forms a reinforcing structure within the artificial meniscus through the introduction of the steel frame, improving the overall fatigue resistance and joint load-bearing capacity of the meniscus, extending its fatigue life by 20-50%. In contrast, methods that directly freeze-treat the composite slurry to obtain the meniscus without hot injection molding result in significant volume changes during the evaporation and curing process after the steel frame is inserted, leading to deformation of both the meniscus and the steel frame, and ultimately, steel frame breakage.

[0040] Preferably, the steel frame is fixed to the center of the meniscus mold using strong thread or surgical sutures. This invention uses strong thread or surgical sutures to fix the steel frame; after thermoforming, the strong thread or surgical sutures will be exposed outside the meniscus, facilitating clinical fixation.

[0041] Preferably, the cooling method in step S4 includes at least one of cold air cooling, pipeline circulating water cooling, cooling fixture cooling, and spray cooling.

[0042] Preferably, the cooling rate in step S4 is 5~20℃ / min; more preferably, the cooling rate in step S4 is 6~18℃ / min; and even more preferably, the cooling rate in step S4 is 8~15℃ / min.

[0043] Secondly, the present invention provides an artificial meniscus, which is prepared by the artificial meniscus preparation method described in the first aspect.

[0044] The beneficial effects of this invention are: (1) In this invention, hydrophilic polytetrafluoroethylene (PTFE) is dispersed in a hydrophilic polyurethane solution to obtain a composite slurry. Then, a cryogenic treatment (low temperature) method is used to prepare the composite material. Uniform dispersion is achieved under low temperature conditions, ensuring that the PTFE particles are stably embedded in the PU matrix, forming a dense composite microstructure. This effectively optimizes the biocompatibility and mechanical compatibility of traditional artificial meniscus materials. Then, this invention uses these composite material particles as raw materials for thermo-injection molding, retaining the uniformity of the original materials while avoiding the thermal stress problems associated with high-temperature mixing. Furthermore, this invention improves the storage stability and transportation convenience of the raw materials, reduces dust emission and equipment corrosion during the injection molding process, and is suitable for large-scale industrial production.

[0045] (2) The present invention optimizes the flowability of the composite material in the molten state and the injection success rate by mixing the composite material with the plasticizer before injection molding.

[0046] (3) By coating the inside of the meniscus mold with dimethyl silicone oil, the present invention can effectively reduce the friction of the mold surface, improve the spreadability of the injection slurry, and make the injection slurry quickly and completely fill the meniscus mold. The injection molding machine output is uniform and smooth, without any air bubbles, and it is easier to open the mold after cooling, thus increasing the injection success rate by at least 10%.

[0047] (4) This invention first fixes the meniscus steel frame inside the meniscus mold, and then injects the slurry to be injected into the meniscus mold by hot injection molding, thus achieving complete embedding of the steel frame. This invention forms a reinforcing structure inside the artificial meniscus by introducing the steel frame, thereby improving the overall fatigue resistance and joint load bearing capacity of the meniscus, and extending the fatigue life of the meniscus by 20-50%. Attached Figure Description

[0048] Figure 1 A photograph of the artificial meniscus prepared in Example 1; Figure 2 A schematic diagram of the steel frame fixing method during the preparation of the artificial meniscus with an internal steel frame in Example 2 ( Figure 2 (a) and a picture of the assembled artificial meniscus mold with a built-in steel frame. Figure 2 (b) Figure 3 A picture of an artificial meniscus with an internal steel frame; Figure 4 Schematic diagram of the steel frame fixing method when preparing an artificial sheep meniscus with an internal steel frame ( Figure 4 (a) and a picture of an artificial sheep meniscus with a built-in steel frame ( Figure 4 (b) Figure 5Thermogravimetric analysis (TGA) of the composite material obtained in step 4 of Example 1; Figure 6 A photograph of the actual specimen after cryotreatment during the preparation of the artificial meniscus for Comparative Example 1. Figure 6 Image a) and actual image of the artificial meniscus after curing and drying. Figure 6 (b) Figure 7 The image shows the actual artificial meniscus prepared in Example 1. Figure 8 A photograph of the cryogenically treated artificial meniscus used in Comparative Example 2. Figure 8 Image a) and actual image of the artificial meniscus after curing and drying. Figure 8 (b) Figure 9 The image shows the actual artificial meniscus prepared in Example 2. Figure 10 The image shows the effect after adjusting the type of surface coating and plasticizer in the preparation method of Example 1. Figure 11 SEM images and EDS images of F atoms of the artificial menisci of Example 1 and Comparative Example 1. Figure 12 These are images of artificial meniscus compression experiments from Examples 1 and 2. Figure 13 The stress-strain curves of the artificial meniscus and natural meniscus under compression tests in Examples 1 and 2 are shown. Figure 14 The stress-strain curves of the artificial meniscus and natural meniscus under tensile tests in Examples 1 and 2 are shown. Figure 15 The diagram shows the friction properties of the artificial meniscus in Example 1 and the artificial meniscus prepared using DOTP as a plasticizer. Figure 16 The image shows the time-dynamic water contact angle measurement of the artificial meniscus in Example 1 and the artificial meniscus prepared using DOTP as a plasticizer. Detailed Implementation

[0049] To enable those skilled in the art to better understand this application, the present invention will be further described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims.

[0050] In the description of this invention, it should be noted that unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available products. Furthermore, to better illustrate this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be practiced even without certain specific details. In some embodiments, raw materials, methods, and means well known to those skilled in the art are not described in detail in order to highlight the main points of this invention.

[0051] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprising" shall be understood to include the stated elements or components without excluding other elements or other components.

[0052] The materials used in the embodiments of this invention are as follows: Hydrophilic PU: Hydrothane AL25 80A, purchased from the Rayjing platform; Hydrophilic PTFE: XM 102, particle size in the 300nm range, purchased from Shanghai Yisucheng Electronics Co., Ltd. 3 Aminopropyltriethoxysilane (APTES): ST1087 100ml, purchased from Rayjing platform; Natural meniscus: Commercially available natural meniscus from healthy adult goats, purchased from Longgui Xingke Experimental Animal Center. The instruments used in this invention are as follows: Universal testing machine: Name: Testometric AX, Model: M350-10kN, Manufacturer: Testometric Co. Ltd., Rochdale, UK.

[0053] Example 1 This embodiment provides a method for preparing an artificial meniscus, including the following steps: Step 1: Mix 18 mL of anhydrous ethanol and 2 mL of deionized water to prepare an ethanol-water solution. Pour the solution into a 50 mL flask and preheat it in an oil bath at 40°C. Place a magnetic stirrer in the flask and set the magnetic stirrer speed to 800 rpm. Set the oil bath temperature to 75°C. Take 2 g of hydrophilic PU and pour it all into the flask. Stir overnight until the solid particles are completely dissolved to obtain solution A. Step 2: Mix 18 mL of anhydrous ethanol and 2 mL of deionized water to prepare an ethanol-water solution. Add the APTES solution to the ethanol-water solution and mix well to prepare an ethanol-water solution containing 2% APTES by volume. Add 1 drop of APTES solution to the solution. Adjust the pH of the solution to 4 with 2 drops of glacial acetic acid. 5. Obtain the activated solution; mix 0.3g of hydrophilic PTFE with the activated solution, mix gently, and place the beaker in an ultrasonic shaker. Sonicate for 5 minutes to disperse the hydrophilic PTFE evenly in the solution. Then transfer to a 50mL flask, place a magnetic stirrer, adjust the temperature of the oil bath of the temperature-controlled magnetic stirrer to 35℃, the stirring speed to 250rpm, and stir for 2 hours to obtain an activated PTFE suspension. Centrifuge at 5000rpm for 5 minutes, discard the supernatant, and obtain the activated PTFE precipitate. Add 4mL of ethanol-water solution (anhydrous ethanol and deionized water volume ratio of 9:1) to the activated PTFE precipitate, and sonicate until the precipitate is completely dispersed to obtain dispersion B. Step 3: Mix dispersion B with solution A, wherein the mass of hydrophilic PTFE is 15% of the mass of hydrophilic PU. Set the magnetic stirring speed to 800 rpm and the oil bath temperature to 55℃. Stir for 40 min and then let stand at room temperature for 1 hour to obtain the composite slurry. Step 4: Pour the composite slurry into a particle mold containing dozens of spherical chambers with a diameter of 10 mm, freeze at -30℃ for 40 min, and then air-dry and cure at room temperature and pressure for 3 days to obtain the composite material. The volume after curing is approximately 1 / 10 to 1 / 8 of the volume before curing, and the final particle size (diameter) of the composite material is 3~5 mm. Step 5: Set the first stage temperature (barrel heating temperature) of the injection molding machine to 185±5℃ and the second stage temperature (extrusion temperature) to 155±5℃ for preheating; Step 6: Drip 0.5% dimethyl silicone oil (approximately 2.5-3.0g of the meniscus mass) into the meniscus mold and evenly coat it to form a dimethyl silicone oil coating. Close the mold and tighten the screws for reinforcement. Finally, preheat the entire meniscus mold to 160-180℃. Step 7: Mix the composite material with the ATBC solution (the mass of the ATBC solution is 4% of the mass of the composite material), stir evenly to cover the surface of the composite material with the ATBC solution, and obtain the material to be injection molded; Step 8: Set the screw speed of the injection molding machine to 30±10 rpm, and gradually pour the material to be injected into the injection molding machine from the hopper. After the material is heated and melted and evenly extruded, quickly adjust the screw speed to 80±10 rpm so that the molten injection slurry is instantly injected into the meniscus mold until the mold is full and overflows. Then, use cold air to cool it rapidly at a rate of 12℃ / min. After the mold has completely cooled, take it out to obtain the artificial meniscus.

[0054] The actual image of the artificial meniscus prepared in this embodiment is shown below. Figure 1 As shown, it is white overall, with a tough, elastic texture and a smooth surface.

[0055] Example 2 This embodiment provides a method for preparing an artificial meniscus, including the following steps: Steps 1-5: Same as in Example 1; Step 6: Press as Figure 2 As shown in Figure a, the meniscus steel frame is fixed inside the meniscus mold using strong wires. Then, 0.5% dimethyl silicone oil (approximately 2.5-3.0g of the estimated weight of the meniscus) is dripped into the mold and evenly coated to form a dimethyl silicone oil coating. The mold is then closed and screwed in for reinforcement. Simultaneously, the strong wires connecting the steel frame are tightened to ensure the frame remains centered within the meniscus mold. Finally, the entire meniscus mold is preheated to 160-180℃. A picture of the closed artificial meniscus mold with the internal steel frame is shown below. Figure 2 As shown in b; Step 7: Mix the composite material with the ATBC solution (the mass of the ATBC solution is 4% of the mass of the composite material), stir evenly to cover the surface of the composite material with the ATBC solution, and obtain the material to be injection molded; Step 8: Set the injection molding machine screw speed to 30±10 rpm. Gradually pour the material to be injected into the injection molding machine from the hopper. After the material is heated, melted, and evenly extruded, quickly adjust the screw speed to 80±10 rpm so that the molten injection slurry is instantly injected into the meniscus mold until the mold is full and overflows. Then, use cold air cooling at a controlled cooling rate of 12℃ / min for rapid cooling. After the mold has completely cooled, remove it to obtain an artificial meniscus with an internal steel frame. An artificial meniscus with an internal steel frame is shown below. Figure 3 As shown. Figure 3 The meniscus mold used is a human meniscus mold, and the resulting meniscus is a human artificial meniscus. Different artificial menisci can be obtained depending on the mold used. Figure 4 To produce an artificial meniscus using the same method with a sheep meniscus mold, Figure 4 Figure a is a schematic diagram showing how the steel frame is fixed to the sheep meniscus mold. Figure 4In the image, b represents the artificial sheep meniscus with an internal steel frame that was prepared.

[0056] Comparative Example 1 This comparative example refers to a method for preparing an artificial meniscus provided by patent CN121550502A, which includes the following steps: Step 1: Mix 18 mL of anhydrous ethanol and 2 mL of deionized water to prepare an ethanol-water solution. Pour the solution into a 50 mL flask and preheat it in an oil bath at 40°C. Place a magnetic stirrer in the flask and set the magnetic stirrer speed to 800 rpm. Set the oil bath temperature to 75°C. Take 2 g of hydrophilic PU and pour it all into the flask. Stir overnight until the solid particles are completely dissolved to obtain solution A. Step 2: Mix 18 mL of anhydrous ethanol and 2 mL of deionized water to prepare an ethanol-water solution. Add the APTES solution to the ethanol-water solution and mix well to prepare an ethanol-water solution containing 2% APTES by volume. Add 1 drop of APTES solution to the solution. Adjust the pH of the solution to 4 with 2 drops of glacial acetic acid. 5. Obtain the activated solution; mix 0.3g of hydrophilic PTFE with the activated solution, mix gently, and place the beaker in an ultrasonic shaker. Sonicate for 5 minutes to disperse the hydrophilic PTFE evenly in the solution. Then transfer to a 50mL flask, place a magnetic stirrer, adjust the temperature of the oil bath of the temperature-controlled magnetic stirrer to 35℃, the stirring speed to 250rpm, and stir for 2 hours to obtain an activated PTFE suspension. Centrifuge at 5000rpm for 5 minutes, discard the supernatant, and obtain the activated PTFE precipitate. Add 4mL of ethanol-water solution (anhydrous ethanol and deionized water volume ratio of 9:1) to the activated PTFE precipitate, and sonicate until the precipitate is completely dispersed to obtain dispersion B. Step 3: Mix dispersion B with solution A, wherein the mass of hydrophilic PTFE is 15% of the mass of hydrophilic PU. Set the magnetic stirring speed to 800 rpm and the oil bath temperature to 55℃. Stir for 40 min and then let stand at room temperature for 1 hour to obtain the composite slurry. Step 4: Inject the composite slurry, which has been left to stand for 1 hour, into the meniscus mold and place it in a freezer. Set the freezing temperature to [temperature value missing]. Freeze at 40℃ for 50 minutes; the frozen PU will then become a gel-like solid. The PTFE composite was removed from the mold and left at room temperature and atmospheric pressure for 30 minutes to allow the solid surface to slightly solidify and the volume to slightly shrink; then the surface-cured PU was... The PTFE composite is placed back into the mold, with openings around the mold. It is then ventilated and dried at room temperature and pressure for 3 days to allow the material to dry and solidify completely. The ethanol and water solvent in the composite are then removed to obtain the artificial meniscus.

[0057] Comparative Example 2 This comparative example provides a method for preparing an artificial meniscus with an internal steel frame. Steps 1-3 are the same as in Comparative Example 1. Step 4 involves first placing the steel frame in a meniscus mold, then injecting the composite slurry, which has been left to stand for 1 hour, into the mold containing the steel frame, and placing it in a freezer. The freezing temperature is set to... Freeze at 40℃ for 50 minutes; the frozen PU will then become a gel-like solid. The PTFE composite was removed from the mold and left at room temperature and atmospheric pressure for 30 minutes to allow the solid surface to slightly solidify and the volume to slightly shrink; then the surface-cured PU was... The PTFE composite is placed back into the mold, with openings around the mold. It is then ventilated and dried at room temperature and pressure for 3 days to allow the material to dry and solidify completely. The ethanol and water solvent in the composite are then removed to obtain an artificial meniscus with an internal steel frame.

[0058] Feasibility study of the hot injection molding method of the present invention The composite material obtained in step 4 of Example 1 was subjected to thermogravimetric analysis. The test results are as follows: Figure 5 As shown. By Figure 5 It is known that the composite material exhibits a slow mass decrease (from 100% to approximately 96%) during the low-temperature stage (60-200℃), with DTG showing small fluctuations or a positive peak (around ~100℃). This corresponds to the loss of volatiles, such as adsorbed water, residual ethanol solvent, or low molecular weight components, with a low loss rate (<10%). The initial degradation temperature of the composite material is approximately 200-250℃, indicating that the composite material is stable within the injection molding temperature range (150-190℃) without significant decomposition risk. Therefore, this invention allows for injection molding of the composite material at a controlled injection molding temperature of 150-190℃, while also avoiding bubble defects induced by excessively rapid expulsion of mixed air during the injection molding process.

[0059] Appearance characterization and parameter study 1. An artificial meniscus was prepared using the method described in Comparative Example 1. The state of the artificial meniscus after freeze-drying and before curing and drying is as follows: Figure 6 As shown in Figure a, the artificial meniscus obtained after curing and drying is as follows: Figure 6 As shown in b. From Figure 6 It can be seen that the method of Comparative Example 1 causes deformation of the artificial meniscus due to uneven evaporation rates during the evaporation and curing process. However, the artificial meniscus prepared using the method of Example 1 of this invention... Figure 7 As shown. By Figure 7 It can be seen that the artificial meniscus prepared in Example 1 of the present invention is complete and dense, without deformation or impurities, and has a tough, elastic feel and a smooth surface.

[0060] 2. An artificial meniscus was prepared using the method described in Comparative Example 2 (an experimental model was used instead of a steel frame for testing). The state of the artificial meniscus after freeze-drying and before curing and drying is as follows: Figure 8 As shown in Figure a, the artificial sheep meniscus obtained after curing and drying is as follows: Figure 8 As shown in b. From Figure 8 It can be seen that the preparation method of Comparative Example 2 resulted in deformation of both the meniscus and the steel frame (experimental model) and fracture of the steel frame (experimental model) due to the large volume change of the meniscus during the evaporation and curing process. In contrast, the artificial meniscus prepared using the method of Example 2 is shown in the image below. Figure 9 As shown. By Figure 9 It can be seen that the preparation method of Example 2 can effectively embed the steel frame, form a reinforcing structure inside the artificial meniscus, and improve the overall fatigue resistance and joint load bearing capacity of the meniscus.

[0061] 3. The effects of the surface coating and plasticizer on the injection molding effect of the meniscus mold were tested. The preparation method of Example 1 was used, but the types of surface coating and plasticizers were adjusted, and different experiments were conducted. The experimental results are shown in Table 1 and... Figure 10 As shown. Figure 10 In Figure 'a', the extrusion effect diagram of Experiment 1 in Table 1 is shown. Figure 10 In the middle, b is the finished product effect diagram of Experiment 2 in Table 1. Figure 10 In the middle, c represents the finished product effect diagram of Experiment 3 in Table 1. Figure 10 In the figure, d represents the extrusion effect of experiment 6 in Table 1. Figure 10 In Table 1, 'e' represents the finished product of Experiment 6. Experiment 4 in Table 1 is the preparation method of Example 1 of this invention, and the corresponding finished product image is shown below. Figure 7 Experiment 5, however, could not be pushed or extruded, so there are no related effect diagrams.

[0062] Table 1. Effects of coatings and plasticizers on the inner surface of the meniscus mold on injection molding results

[0063] From Table 1 and Figure 10 It can be seen that, under the condition of constant injection temperature, considering the fluidity and formability of injection slurry, the internal resistance of the mold, and the safety of the finished product, the preparation method of Example 1 of this invention, which uses 4% ATBC as a plasticizer and dimethyl silicone oil as a coating on the inner surface of the mold, has the best technical effect.

[0064] 4. Test the effect of different injection temperatures on the injection molding effect. Referring to step 5 of Example 1, the injection molding machine's first and second stage temperatures were adjusted to different temperatures, and the injection molding effect was tested. The test results are shown in Table 2.

[0065] Table 2. Effect of different injection temperatures on injection molding results

[0066] As shown in Table 2, the first-stage temperature of 180~190℃ and the second-stage temperature of 150~160℃ used in Embodiment 1 of the present invention have the best injection molding effect.

[0067] Performance testing 1. SEM scanning electron microscopy images and EDS analysis of F atoms were performed on the artificial menisci prepared in Example 1 and Comparative Example 1. The test results are as follows: Figure 11 As shown. Figure 11 Image a in Figure 1 is a SEM image of the artificial meniscus from Comparative Example 1. Figure 11 In Figure b, the F-atom EDS test result of the artificial meniscus in Comparative Example 1 is shown. Figure 11 In the image, c is a SEM image of the artificial meniscus from Example 1. Figure 11 Image d shows the EDS test result of F atoms in the artificial meniscus of Example 1. Figure 11 It can be seen that the F atoms in the artificial meniscus prepared in Comparative Example 1 are uniformly distributed in the matrix. This indicates that the preparation method of Comparative Example 1, specifically the mixing and dispersion technology of PTFE in PU, can achieve uniform distribution of PTFE particles in PU. In contrast, the F atoms in the artificial meniscus prepared in Example 1 are still uniformly distributed in the matrix. This demonstrates that the method of first preparing the composite material through freeze-drying and then hot-injection molding, used in Example 1 of this invention, avoids deformation of the artificial meniscus and improves production efficiency while still ensuring that PTFE remains stably bonded and uniformly distributed in PU.

[0068] 2. Compression tests (compression rate of 20 mm / min) were conducted on the artificial menisci and natural menisci from Examples 1 and 2 using a universal testing machine equipped with a transcell (range of 500 N). The experimental results are as follows: Figure 12 and Figure 13 As shown. Figure 12 These are images of artificial meniscus compression experiments in Examples 1 and 2. Figure 12 Image a shows the artificial meniscus of Example 1 after it has been fully compressed to its maximum load (500N) by a compressor. Figure 12 Image b is a photograph of the artificial meniscus of Example 1 after compression and release of pressure, showing its full rebound to its original shape before compression. Figure 12 Image c shows the artificial meniscus of Example 2 after it has been fully compressed to its maximum load (500N) by a compressor. Figure 12 Image d shows the artificial meniscus of Example 1 after compression and subsequent release of pressure, fully rebounding to its pre-compression state. The natural meniscus, after being compressed to 500N by a compressor, tore. Figure 13The figures show the stress-strain curves of the artificial and natural menisci under compression tests in Examples 1 and 2. Figure 13 The red dashed line represents the natural meniscus, the green dashed line represents the artificial meniscus of Example 1, and the orange dashed line represents the artificial meniscus of Example 2. Figure 12 and Figure 13 It can be seen that, compared with the natural meniscus, the artificial meniscus prepared in Examples 1 and 2 of this invention is softer and more elastic. After reaching the maximum load, it deforms fully without tearing, and after the pressure is removed, it fully rebounds to the shape before the test, indicating that it has better load-bearing capacity and the potential to adapt to compression deformation during joint movement.

[0069] 3. Tensile tests (tensile rate 50 mm / min) were conducted on the artificial and natural menisci from Examples 1 and 2 using a universal testing machine equipped with a transcell (range 500 N). The menisci were stretched to their maximum load until fracture. The tensile results are as follows: Figure 14 As shown. Figure 14 The stress-strain curves of the artificial meniscus and natural meniscus under tensile tests in Examples 1 and 2 are shown. Figure 14 In the diagram, the red dashed line represents the natural meniscus, the orange dashed line represents the artificial meniscus of Example 1, and the green dashed line represents the artificial meniscus of Example 2. Figure 14 It can be seen that the tensile curve of a natural meniscus gradually rises, and the meniscus fractures after reaching its maximum load. Compared with the natural meniscus, the artificial meniscus of Example 1 has a similar curve curvature, indicating that the stiffness of the two is similar, but the artificial meniscus of Example 1 has a greater tensile load resistance. Compared with the natural meniscus, the artificial meniscus of Example 2 has greater stiffness in the initial stage of tension. Its curve shows an inflection point after reaching the failure load at which the natural meniscus fractures, indicating that the steel frame fractures. However, as the tensile load continues to increase, the tensile curve of the artificial meniscus of Example 2 rises again and the curvature is similar to that of the natural meniscus, but the maximum load is much greater than that of the natural meniscus. This indicates that the artificial meniscus of Example 2 has stronger tensile properties and can still exhibit good tensile properties even after the steel frame fractures.

[0070] 4. Anti-friction and wear performance test Friction tests were conducted on the artificial meniscus of Example 1 in a simulated normal human synovial fluid environment (PBS buffer + 3 mg / mL hyaluronic acid, 37℃). The testing instrument was an RtecMFT-5000 disc-type multi-functional tribometer, with SiN ceramic balls as the grinding balls. The test parameters were a constant load of 5 N (equivalent to a pressure of 2.4 MPa), a reciprocating stroke of 10 mm, a reciprocating speed of 10 mm / s, and a single test time of 30 min. Friction curves were obtained, the surface friction coefficient (COF) was calculated, and the surface wear marks were observed using an electron microscope.

[0071] Figure 15 The diagram shows the friction performance of the artificial meniscus of Example 1 and the artificial meniscus prepared using DOTP as a plasticizer (ATBC in Example 1 is replaced with DOTP, and all other parameters remain unchanged). Figure 15 The red curve represents the artificial meniscus of Example 1 (ATBC group in the figure), and the blue curve represents the artificial meniscus prepared using DOTP as a plasticizer (DOTP group in the figure). Figure 15 It can be seen that the average coefficient of friction of the artificial meniscus in Example 1 is 0.0674. In contrast, the average coefficient of friction of the artificial meniscus prepared using DOTP as a plasticizer is 0.0756, indicating significantly lower anti-friction performance compared to Example 1. Furthermore, the COF of the artificial meniscus in Example 1 is between 0.05 and 0.1, suggesting that it has the potential to approach the friction performance of a natural meniscus under long-term wet conditions. Simultaneously, the artificial meniscus in Example 1 showed no wear marks under electron microscopy after a 30-minute friction test, indicating excellent wear resistance under low-intensity meniscus loads.

[0072] 5. Hydrophilicity test The artificial meniscus of Example 1 and the artificial meniscus prepared using DOTP as a plasticizer (ATBC in Example 1 was replaced with DOTP, all other parameters remained unchanged) were measured using the ultrapure water droplet method and a KRUSS dsa100 measuring instrument to determine the time-dynamic water contact angle. The test results are as follows: Figure 16 As shown, Figure 16 In the image, 'a' represents the artificial meniscus from Example 1. Figure 16 Image b shows an artificial meniscus prepared using DOTP as a plasticizer. Figure 16It can be seen that the artificial meniscus of Example 1 had an initial average contact angle of 93.38 degrees, reaching a minimum average contact angle of 66.34 degrees after 55 seconds. This is superior to the artificial meniscus material of CN121550502 A (95.489 degrees). This indicates that the artificial meniscus of Example 1 exhibits stronger hydrophilicity when exposed to synovial fluid for an extended period. In contrast, the artificial meniscus prepared using DOTP as a plasticizer had a stable average water droplet angle of 80 degrees, indicating inferior performance compared to Example 1.

[0073] In summary, this invention utilizes a cryogenic process to prepare a composite material from a compound slurry. This low-temperature treatment ensures uniform dispersion of PTFE particles, guaranteeing stable embedding within the PU matrix and forming a dense composite microstructure. Subsequently, these particles are used as raw materials for thermoforming within a relatively mild processing window of 150-190°C. This process not only preserves the uniformity of the original materials but also avoids the thermal stress problems associated with high-temperature mixing, while improving production efficiency and injection molding success rate. The resulting injection-molded artificial meniscus is complete, dense, deformation-free, and free of air bubbles. It has a tough, elastic feel and a smooth surface, exhibiting excellent mechanical and hydrophilic properties.

[0074] In the embodiment of this invention, when performing hot injection molding of composite materials, by coating the inside of the meniscus mold with dimethyl silicone oil and using ATBC as a plasticizer, the friction on the mold surface can be effectively reduced, the spreadability of the injection slurry can be improved, the injection molding machine output is uniform and smooth, the injection slurry can be quickly and completely filled into the meniscus mold without air bubbles, and the mold opening is easier after cooling. Compared with other conventional coatings (such as PTFE) and plasticizers (such as DOTP), the injection success rate is significantly improved.

[0075] This invention also achieves complete embedding of the steel frame by first fixing the meniscus steel frame inside a meniscus mold, and then injecting the slurry to be injected into the meniscus mold using a thermoforming method. This invention, through the introduction of the steel frame, forms a reinforcing structure within the artificial meniscus, improving the overall fatigue resistance and joint load-bearing capacity of the meniscus.

[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an artificial meniscus, characterized in that, Includes the following steps: S1: Disperse hydrophilic polytetrafluoroethylene in a hydrophilic polyurethane solution to obtain a composite slurry; S2: After pouring the composite slurry described in step S1 into a particle mold, freeze it and then dry and cure it to obtain the composite material; S3: Mix the composite material described in step S2 with the plasticizer to obtain the material to be injection molded; S4: The material to be injected into the injection molding machine is melted and extruded, then injected into the meniscus mold, and after cooling, the artificial meniscus is obtained; the temperature of the first stage of the injection molding machine is 180~190℃; the temperature of the second stage is 150~160℃.

2. The method for preparing an artificial meniscus according to claim 1, characterized in that, The method for preparing the composite slurry in step S1 is as follows: dissolve the hydrophilic polyurethane in an aqueous ethanol solution to obtain solution A; Hydrophilic polytetrafluoroethylene is dispersed in an activation solution for activation, and the activated polytetrafluoroethylene is obtained by solid-liquid separation. The activated polytetrafluoroethylene is then dispersed in an aqueous ethanol solution to obtain dispersion B. Dispersion B is mixed with solution A and allowed to stand at room temperature to obtain the composite slurry.

3. The method for preparing an artificial meniscus according to claim 1, characterized in that, In step S2, the diameter of the particle mold is 8~12mm; And / or, the particle size of the composite material in step S2 is 3~5mm.

4. The method for preparing an artificial meniscus according to claim 1, characterized in that, The freezing temperature in step S2 is -50℃ to -30℃; And / or, the freezing time in step S2 is 30~60 min.

5. The method for preparing an artificial meniscus according to claim 1, characterized in that, The drying and curing time in step S2 is 2 to 5 days.

6. The method for preparing an artificial meniscus according to claim 1, characterized in that, The plasticizer mentioned in step S3 is tributyl acetyl citrate; And / or, the plasticizer accounts for 3% to 5% of the mass percentage of the composite material.

7. The method for preparing an artificial meniscus according to claim 1, characterized in that, In step S4, the interior of the meniscus mold is coated with a dimethyl silicone oil coating.

8. The method for preparing an artificial meniscus according to claim 1, characterized in that, The cooling method in step S4 includes at least one of cold air cooling, pipeline circulating water cooling, cooling fixture cooling, and spray cooling.

9. The method for preparing an artificial meniscus according to claim 1, characterized in that, The meniscus mold has a pre-fixed meniscus steel frame.

10. An artificial meniscus, characterized in that, The artificial meniscus was prepared using the method described in any one of claims 1 to 9.

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