In-vitro test method and device for artificial meniscus

Abstract

The invention belongs to the technical field of biomedical engineering, and particularly relates to an in-vitro testing method and device for an artificial meniscus, and the device comprises a femur model, a tibia model, a pressure sensor a, a low-modulus high-strain sensor, a high-modulus low-strain sensor, two fixing sheets, an upper chuck, a servo motor, a transmission device and a pressure sensor b, according to the method, the artificial meniscus is fixed between the femur model and the tibia model according to the human body structure, axial pressure is applied to the artificial meniscus through the femur model, and the axial pressure, acting on the tibia model, of the artificial meniscus, the actual circumferential bulging strain value of the artificial meniscus and the actual circumferential bulging stress value of the artificial meniscus are monitored. The testing method is simple and convenient, the characteristic that the wedge-shaped structure of the meniscus bulges outwards during extrusion is utilized, the stress condition of the material can be reflected in multiple directions through multiple cooperation of the sensors, and the complex mechanical property of the meniscus is accurately measured.

Description

Technical Field

[0001] This invention belongs to the field of biomedical engineering technology, specifically relating to an in vitro testing method and apparatus for artificial menisci. Background Technology

[0002] The meniscus is a wedge-shaped piece of cartilage located between the femoral condyle and the tibial plateau. It contains circumferentially arranged collagen fibers that extend to the junction of the anterior and posterior horns of the meniscus and the tibial plateau, forming a closed-loop structure. Its main functions are to stabilize the knee joint, transmit and distribute joint loads, and promote the even distribution of synovial fluid, acting as a shock absorber to effectively protect the femoral condyle and tibial articular surfaces from impact. However, with the rise of the national fitness craze and the exacerbation of population aging, cases of meniscus injuries and degeneration have increased significantly. Such injuries not only cause pain and limit motor function but may also accelerate the progression of arthritis. Although existing treatments such as meniscectomy or suture can alleviate symptoms to some extent, they often fail to restore the original biomechanical function of the knee joint.

[0003] Due to its wedge-shaped cross-section, the meniscus tends to be squeezed out of the joint space and deviate from the center of the contact area when subjected to compressive stress. This radial displacement causes the meniscus to undergo proportional expansion deformation in the circumferential direction, thus generating "hoop stress," which converts the compressive force into a circumferential tensile force, such as... Figure 1 As shown. Furthermore, the viscoelastic properties of the meniscus enable it to exhibit nonlinear deformation capabilities under various load conditions. Given the complex mechanical behavior of the natural meniscus, the design of an artificial meniscus requires a high degree of simulation of its unique load-bearing state and structural characteristics. To achieve this goal, accurately quantifying the strain behavior of the artificial meniscus under different loads is crucial. This not only ensures that the artificial meniscus can effectively distribute load and buffer impact in practical applications, but also maintains knee joint stability. In conclusion, accurate measurement of the stress state of the artificial meniscus is not only a core aspect of research and development testing, but also key to verifying its therapeutic efficacy and effectiveness.

[0004] Current methods for in vitro biomechanical measurement of artificial menisci involve fixing a meniscus sample onto the knee joint plateau and placing pressure sensors underneath to measure the force exerted on the tibial plateau through axial compression. This testing method can only preliminarily assess the similarity of the artificial material of the bionic meniscus to the natural meniscus in terms of basic mechanical properties through single compression data, and cannot comprehensively capture and measure the complex mechanical behavior exhibited by the material itself during stress. Therefore, this deficiency may lead to the implanted artificial meniscus failing to effectively buffer joint stress, thereby accelerating the progression of arthritis. For example, patent US10758358B2 discloses a method for systematically selecting artificial menisci, including medical imaging, size setting, and in vitro testing, which fully realizes the customization of artificial menisci. However, the in vitro testing only uses the method of placing pressure sensors on the tibial plateau for experiments, which cannot accurately determine the required material properties, sample size, and other parameters of the artificial meniscus.

[0005] Related research also appeared in the paper. Reference 1 (Effects of a novel medial meniscus implant on the knee compartments: imaging and biomechanical aspects[J].Biomechanics and Modeling in Mechanobiology,2020,19(9).) is based on a well-developed free-floating artificial meniscus. An in vitro biomechanical study was conducted, employing an in vitro in-situ / simulation combined experimental method to verify the effect of this type of artificial meniscus in reducing knee joint contact pressure, such as... Figure 2 As shown, an in vitro knee joint testing platform was constructed to simulate the stress environment after an artificial meniscus is implanted in the human body. Although this method uses real knee joint materials to conduct uniaxial compression experiments and compares the experimental results, the measurement method is singular, and it is difficult to reflect the stress buffering ability of the artificial meniscus by only testing the pressure on the tibial platform.

[0006] Reference 2 (Autologous semitendinosus meniscus graft significantly improves sknee joint kinematics and the tibiofemoral contact after complete lateral meniscectomy[J]. Knee Surgery, Sports Traumatology, Arthroscopy: 1-10.) investigated the feasibility of autologous tendon grafts as meniscus replacements using adult cadaver knee joints. Figure 3As shown, this experiment simulates the stress on the real human knee joint and has sufficient biomimicry. However, this experiment can only apply a small axial pressure (200N) to the meniscus, which makes it difficult to explain the stability of the material function under physiological load.

[0007] Therefore, given the complex compressive deformation effects of the meniscus due to its material structure, and the fact that current in vitro measuring devices have a single measurement target and cannot comprehensively assess the adaptability of the tested meniscus in the complex stress environment of the knee joint, it is necessary to improve the existing in vitro measuring devices to achieve accurate measurement of the stress state of the artificial meniscus, thereby ensuring that the artificial meniscus can effectively distribute load, buffer impact, and maintain knee joint stability in practical applications. Summary of the Invention

[0008] The purpose of this invention is to solve the problems existing in the prior art and to provide an in vitro testing method and apparatus for artificial menisci.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] An in vitro testing method for an artificial meniscus involves fixing the artificial meniscus between a femoral model and a tibial model, referencing human anatomy, applying axial pressure to the artificial meniscus through the femoral model, and monitoring the axial pressure exerted by the artificial meniscus on the tibial model, the actual value of the circumferential bulging strain of the artificial meniscus, and the actual value of the circumferential bulging stress of the artificial meniscus.

[0011] When the axial pressure applied to the artificial meniscus is 0N-1000N, if the axial pressure exerted by the artificial meniscus on the tibial model is ≤8MPa (indicating that the artificial meniscus has not failed under pressure), and the actual value of the circumferential bulging strain of the artificial meniscus is 0.82-1.18 times the theoretical value of the circumferential bulging strain of the artificial meniscus, and the actual value of the circumferential bulging stress of the artificial meniscus is 0.86-1.14 times the theoretical value of the circumferential bulging stress of the artificial meniscus, then the artificial meniscus meets the mechanical requirements for transplantation; otherwise, the artificial meniscus does not meet the mechanical requirements for transplantation.

[0012] The theoretical formula for calculating the circumferential bulging strain of an artificial meniscus is: y1 = -2.89 + 2.1e -9 *e -(x / 48) +2.65e -(x / 547) In the formula, x represents the value of the axial pressure applied to the artificial meniscus in N, and y1 represents the value of the theoretical value of the circumferential bulging strain of the artificial meniscus in % of the total circumferential bulging strain.

[0013] The theoretical formula for calculating the circumferential bulging stress of an artificial meniscus is: y2 = -0.095 + 0.16e x / 317In the formula, x represents the axial pressure applied to the artificial meniscus in N, and y2 represents the theoretical value of the circumferential bulging stress of the artificial meniscus in MPa.

[0014] The process of obtaining the above two calculation formulas is as follows:

[0015] A theoretical model of the knee joint was imported into Abaqus for finite element simulation to analyze the circumferential bulging strain of the meniscus under knee compression. To ensure the representativeness of the results, 10 healthy knee joints from different populations were selected for medial and lateral meniscus model analysis: adult male right knee (25 years old), adult male left knee (30 years old), adult male right knee (40 years old), adult male left knee (40 years old), adult male right knee (60 years old), adult male left knee (60 years old), adult female right knee (25 years old), adult female left knee (25 years old), adult female right knee (40 years old), and adult female left knee (60 years old). In detail, the meniscus material was defined as an anisotropic linear elastic material. This definition can effectively reflect the actual mechanical behavior of the meniscus under stress. The anisotropic elastic modulus and Poisson's ratio in different orientations were obtained through in vitro mechanical testing of natural menisci to complete the attribution of material properties. The parameters of the remaining materials were assigned based on existing literature. The femur and tibia were set as linear elastic with a Young's modulus of 17 GPa and a Poisson's ratio of 0.33; the cartilage was set as linear elastic with a Young's modulus of 5 MPa and a Poisson's ratio of 0.35. Mesh convergence analysis was performed on each knee joint simulation. Subsequently, uniaxial compression simulation of the knee joint was conducted, with the compressive force increasing from 0 N to 1000 N. The circumferential bulging strain of the meniscus under the corresponding pressure was simulated. The circumferential bulging stress was simulated by covering the outer periphery of the meniscus with a 5 mm thick circumferential plate, fixed at the anterior and posterior angles of the meniscus and defined as a rigid body. The compressive force of the meniscus on this circumferential plate under axial pressure of 0-1000 N was observed. Subsequent research summarized previous studies and modified the material property settings of the meniscus. The axial pressure versus bulging strain / stress curves were plotted by analyzing the data and fitted with formulas. Combined with in vitro validation, the above two calculation formulas were obtained.

[0016] As a preferred technical solution:

[0017] As described above, in vitro testing method for an artificial meniscus uses pressure sensor a to monitor the axial pressure exerted by the artificial meniscus on the tibial model. Pressure sensor a is positioned between the artificial meniscus and the tibial model.

[0018] The above-described in vitro testing method for artificial meniscus involves monitoring the actual values ​​of circumferential bulging strain and circumferential bulging stress of the artificial meniscus in steps, using different flexible strain sensors.

[0019] The in vitro testing method for an artificial meniscus, as described above, uses a low-modulus high-strain flexible strain sensor to monitor the actual value of the circumferential bulging strain of the artificial meniscus. The low-modulus high-strain sensor covers the outer periphery of the artificial meniscus and extends to its anterior and posterior angles. The tensile modulus of the low-modulus high-strain sensor is 100 Pa - 0.5 MPa, and the effective strain is 0% - 100%. The low-modulus high-strain sensor consists of a matrix material and a dispersion filler, with the dispersion filler content ranging from 0.5 wt% to 2 wt%. The materials used include polydimethylsiloxane, polyacrylamide, and sodium alginate, with carbon nanotubes, graphene, and conductive polymers as the dispersing fillers. The low-modulus high-strain sensor has excellent bending deformation capabilities, can cover artificial menisci of different shapes, and fits tightly to the artificial menisci. The sensitivity is 10-100, and the response time is 1ms-20ms. Due to its low-modulus high-strain characteristics, the low-modulus high-strain sensor does not affect the compressive mechanical performance of the artificial menisci under test, and can accurately reflect the compressive bulging of the artificial menisci in the tensile properties of the sensor.

[0020] The flexible strain sensor used to monitor the actual value of the circumferential bulging stress of the artificial meniscus is a high-modulus low-strain sensor. The high-modulus low-strain sensor covers the outer periphery of the artificial meniscus and extends to its anterior and posterior angles. The tensile modulus of the high-modulus low-strain sensor is 3GPa-200GPa, and the effective strain is 0%-10%. The high-modulus low-strain sensor consists of a matrix material and a dispersion filler, with the dispersion filler content ranging from 0.1wt% to 3wt%. The matrix material includes nickel-titanium oxide, stainless steel, alumina, polyetheretherketone, and carbon fiber composite matrix, while the dispersion filler includes copper, silver, carbon nanotubes, and polyaniline. The high-modulus low-strain sensor possesses excellent bending deformation capability, can cover artificial menisci of different shapes, and fits tightly to the artificial meniscus. Its sensitivity is 20-500, and its response time is 1ms-10ms. The high-modulus low-strain sensor does not generate significant strain during testing; its main function is to reflect the bulging force generated by the artificial meniscus under pressure.

[0021] As described above, an in vitro testing method for an artificial meniscus involves fixing the artificial meniscus between a femoral model and a tibial model using two fixation plates. One end of each fixation plate is simultaneously connected to the tibial model via bolts. The other end of one fixation plate presses against the anterior horn of the artificial meniscus and a flexible strain sensor, while the other end of the other fixation plate presses against the posterior horn of the artificial meniscus and a flexible strain sensor. The fixation plates of this invention serve to fix the anterior and posterior horns of the artificial meniscus to the tibial model, simulating the fixation of collagen fiber bundles at the anterior and posterior horns of a natural meniscus.

[0022] The above-described in vitro testing method for an artificial meniscus involves applying axial pressure to the artificial meniscus using a femoral model. This method employs an upper clamp, a servo motor, a transmission device, and a pressure sensor b. The upper clamp is fixedly connected to the upper end of the femoral model. The servo motor controls the lifting and lowering of the upper clamp through the transmission device. The pressure sensor b is used to monitor the axial pressure applied to the artificial meniscus.

[0023] The above-described in vitro testing method for artificial meniscus has an adjustable clamp that can accommodate femurs of different sizes.

[0024] In the in vitro testing method for an artificial meniscus as described above, the lower end of the tibial model is fixedly connected to the lower support.

[0025] An in vitro testing device for an artificial meniscus, which implements an in vitro testing method for an artificial meniscus as described in any of the preceding claims, includes the femoral model, the tibia model, the pressure sensor a, the low-modulus high-strain sensor, the high-modulus low-strain sensor, the two fixation plates, the upper clamp, the servo motor, the transmission device, and the pressure sensor b.

[0026] Beneficial effects:

[0027] The present invention provides an in vitro testing method and apparatus for artificial menisci. The testing method is simple and utilizes the outward bulging characteristic of the wedge-shaped structure of the meniscus under compression. Through the combination of multiple sensors, it can reflect the stress on the material from multiple perspectives, achieving the effect of accurately measuring the complex mechanical properties of the meniscus. It has important reference significance for the preparation before artificial meniscus transplantation. Attached Figure Description

[0028] Figure 1 The diagram shows the stress distribution on a natural meniscus; (a) is a side view of the stress distribution on a natural meniscus, and (b) is a top view of the stress distribution on a natural meniscus.

[0029] Figure 2 Schematic diagram of an in vitro testing device for artificial meniscus;

[0030] Figure 3 This is a schematic diagram of a meniscus internal pressure test. A is a normal meniscus, B is a total meniscectomy, and C is a tendon-replaced meniscus.

[0031] Figure 4 This is a schematic diagram of an in vitro testing device for an artificial meniscus according to the present invention.

[0032] Figure 5 This is a schematic diagram showing the positional distribution of the various sensors and the artificial meniscus in this invention;

[0033] Figure 6The figure shows a comparison of circumferential bulging strain curves. The two curves in the figure represent the upper and lower limits of the theoretical circumferential bulging strain of the artificial meniscus.

[0034] Figure 7 This is a comparison chart of circumferential bulging stress curves. The two curves in the chart represent the upper and lower limits of the theoretical circumferential bulging stress of artificial menisci.

[0035] Figure 8 The image shows a comparison of interleukin concentrations in the synovial fluid of sheep knees with implanted artificial menisci (Example 1). The control group in the image represents the interleukin concentration in normal sheep joints.

[0036] Figure 9 The image shows a comparison of interleukin concentrations in the synovial fluid of sheep knees with implanted artificial menisci (Example 2). The control group in the image represents the interleukin concentration in normal sheep joints.

[0037] Among them, 1-pressure sensor b, 2-transmission device, 3-upper clamp, 4-femoral model, 5-artificial meniscus, 6-flexible strain sensor, 7-pressure sensor a, 8-tibia model, 9-lower support, 10-fixation plate. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0039] An in vitro testing device for an artificial meniscus, such as Figures 4-5 As shown, it includes a femoral model 4, a tibia model 8, a pressure sensor a 7, a flexible strain sensor 6 (low modulus high strain sensor or high modulus low strain sensor), two fixing plates 10, an upper clamp 3, a lower support 9, a servo motor, a transmission device 2, and a pressure sensor b 1.

[0040] The tensile modulus of the low-modulus high-strain sensor is 100Pa-0.5MPa, and the effective strain is 0%-100%.

[0041] The tensile modulus of the high-modulus, low-strain sensor is 3GPa-200GPa, and the effective strain is 0%-10%.

[0042] The upper clamp 3 has an adjustable tension to accommodate different sizes of femurs;

[0043] like Figure 4 As shown, the upper end of the femoral model 4 is fixedly connected to the upper clamp 3; the lower end of the tibia model 8 is fixedly connected to the lower support 9.

[0044] An in vitro testing method for artificial menisci, employing the aforementioned in vitro testing device for artificial menisci, such as... Figure 5 As shown, the flexible strain sensor 6 covers the outer periphery of the artificial meniscus 5 and extends to the anterior and posterior horns of the artificial meniscus 5. Referring to the human anatomy, two fixation plates 10 are used to fix the artificial meniscus 5 between the femoral model 4 and the tibial model 8. One end of each fixation plate 10 is simultaneously fixed to the tibial model 8 by bolts. The other end of one fixation plate 10 presses against the anterior horn of the artificial meniscus 5 and the flexible strain sensor 6, and the other end of the other fixation plate 10 presses against the posterior horn of the artificial meniscus 5 and the flexible strain sensor 6. The pressure sensor a 7 is set between the artificial meniscus 5 and the tibial model 8.

[0045] Monitoring the actual value of circumferential bulging strain of artificial meniscus: Flexible strain sensor 6 is a low modulus high strain sensor; Servo motor controls the upper clamp 3 to lift and lower through transmission device 2 to apply axial pressure to artificial meniscus 5, pressure sensor b1 monitors the axial pressure applied to artificial meniscus 5, pressure sensor a 7 monitors the axial pressure of artificial meniscus 5 on tibial model 8, and low modulus high strain sensor monitors the actual value of circumferential bulging strain of artificial meniscus 5;

[0046] Monitoring the actual value of circumferential bulging stress of artificial meniscus: Flexible strain sensor 6 is a high modulus low strain sensor; Servo motor controls the upper clamp 3 to lift and lower through transmission device 2 to apply axial pressure to artificial meniscus 5; Pressure sensor b1 monitors the axial pressure applied to artificial meniscus 5, pressure sensor a 7 monitors the axial pressure of artificial meniscus 5 on tibial model 8, and high modulus low strain sensor monitors the actual value of circumferential bulging stress of artificial meniscus 5;

[0047] When the axial pressure applied to the artificial meniscus is 0N-1000N, if the axial pressure exerted by the artificial meniscus 5 on the tibial model 8 is ≤8MPa, it indicates that the artificial meniscus 5 has not failed under pressure. The actual value of the circumferential bulging strain of the artificial meniscus 5 is 0.82-1.18 times the theoretical value of the circumferential bulging strain of the artificial meniscus 5, and the actual value of the circumferential bulging stress of the artificial meniscus 5 is 0.86-1.14 times the theoretical value of the circumferential bulging stress of the artificial meniscus 5. In this case, the artificial meniscus 5 meets the mechanical requirements for transplantation; otherwise, the artificial meniscus 5 does not meet the mechanical requirements for transplantation.

[0048] The theoretical formula for calculating the circumferential bulging stress of the artificial meniscus 5 is: y2 = -0.095 + 0.16e x / 317 In the formula, x represents the axial pressure applied to the artificial meniscus in N, and y2 represents the theoretical value of the circumferential bulging stress of the artificial meniscus in MPa.

[0049] The theoretical formula for calculating the circumferential bulging strain of the artificial meniscus 5 is: y1 = -2.89 + 2.1e -9 *e -(x / 48) +2.65e -(x / 547) In the formula, x represents the axial pressure applied to the artificial meniscus in N, and y1 represents the theoretical value of the circumferential bulging strain of the artificial meniscus in % of the total circumferential bulging strain.

[0050] The invention will be described below with reference to specific examples:

[0051] First, the circumferential bulging stress of the natural meniscus under physiological load and peripheral constraint is defined as 0MPa-4MPa, and the circumferential bulging strain is defined as 0%-15%.

[0052] Example 1

[0053] Preparation of the artificial meniscus to be tested: Knee joint imaging data were acquired by NMR, and a three-dimensional model of the knee joint was reconstructed using medical reverse engineering software. The model was sliced ​​into a series of two-dimensional layers using Slic3r slicing software and imported into the 3D printer to complete the pre-printing preparation. 1g of cellulose nanocrystals and 50mg of 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone were dissolved in 8.1g of dimethyl sulfoxide as hydrogel precursors. The ink mixture used a 4:2 mass ratio of phenyl acrylate (PA) and acrylamide (AAm). The 3D-printed artificial meniscus was used for in vitro testing. After printing, the artificial meniscus (compression modulus of 40MPa) was obtained by crosslinking under ultraviolet light in a nitrogen atmosphere for 10 minutes.

[0054] like Figures 4-5 As shown, in order to evaluate the performance of the artificial meniscus 5 prepared by the above method, according to the above in vitro testing method for the artificial meniscus 5, a low-modulus high-strain sensor is wrapped around the periphery of the artificial meniscus 5 and extends to the anterior and posterior horns of the artificial meniscus 5; referring to the human body structure, two fixation plates 10 are used to fix the artificial meniscus 5 between the femoral model 4 and the tibial model 8. One end of the two fixation plates 10 is simultaneously fixed to the tibial model 8 by bolts. The other end of one fixation plate 10 presses against the anterior horn of the artificial meniscus 5 and the low-modulus high-strain sensor, and the other end of the other fixation plate 10 presses against the posterior horn of the artificial meniscus 5 and the low-modulus high-strain sensor; pressure sensor a 7 is set between the artificial meniscus 5 and the tibial model 8.

[0055] The upper clamp 3 is lowered to apply axial pressure to the artificial meniscus 5. Pressure sensor b1 monitors the axial pressure applied to the artificial meniscus 5. The test found that when the applied axial pressure increased to 1000N, the maximum tensile rate of the low-modulus high-strain sensor circumferentially covered by the artificial meniscus 5 was 7% ± 1%. Pressure sensor a7 reflected that the peak pressure on the tibial model was 4.4MPa.

[0056] The low-modulus high-strain sensor was then replaced with a high-modulus low-strain sensor. The upper clamp 3 was then lowered to apply axial pressure to the artificial meniscus 5. When the pressure sensor b1 detected that the axial pressure applied to the artificial meniscus 5 increased to 1000N, the pressure sensor a7 reflected that the peak pressure on the tibial model was 3.9MPa, and the high-modulus low-strain sensor reflected that the peak compressive force caused by the bulging of the artificial meniscus 5 was 1.8MPa.

[0057] Example 2

[0058] Preparation of the artificial meniscus to be tested: Knee joint imaging data were acquired by nuclear magnetic resonance, and a three-dimensional model of the knee joint was reconstructed by medical reverse engineering software. Based on the obtained meniscus model, a mold was prepared. A 20wt% PVA solution was poured into the mold and subjected to three freeze-thaw cycles (12h at -20℃ and 2h at 25℃). The resulting gel was then immersed in a 1.25% formaldehyde solution with a pH of 2 and crosslinked at 25℃ for 24h. After repeated washing with deionized water to remove excess crosslinking agent, a PVA artificial meniscus with a compression modulus of 4MPa was obtained.

[0059] like Figures 4-5 As shown, in order to evaluate the performance of the artificial meniscus 5 prepared by the above method, according to the above in vitro testing method for the artificial meniscus 5, a low-modulus high-strain sensor is wrapped around the periphery of the artificial meniscus 5 and extends to the anterior and posterior horns of the artificial meniscus 5; referring to the human body structure, two fixation plates 10 are used to fix the artificial meniscus 5 between the femoral model 4 and the tibial model 8. One end of the two fixation plates 10 is simultaneously fixed to the tibial model 8 by bolts. The other end of one fixation plate 10 presses against the anterior horn of the artificial meniscus 5 and the low-modulus high-strain sensor, and the other end of the other fixation plate 10 presses against the posterior horn of the artificial meniscus 5 and the low-modulus high-strain sensor; pressure sensor a 7 is set between the artificial meniscus 5 and the tibial model 8.

[0060] The upper clamp 3 is lowered to apply axial pressure to the artificial meniscus 5. Pressure sensor b 1 monitors the axial pressure applied to the artificial meniscus 5. The test found that when the applied axial pressure increased to 600N, the maximum tensile rate of the low modulus high strain sensor circumferentially covered by the artificial meniscus 5 was 20% ± 2%. Pressure sensor a 7 reflects that the peak pressure on the tibial model is 4.9MPa.

[0061] The low-modulus high-strain sensor was then replaced with a high-modulus low-strain sensor. The upper clamp 3 was then lowered to apply axial pressure to the artificial meniscus 5. When the pressure sensor b1 detected that the axial pressure applied to the artificial meniscus 5 increased to 600N, the pressure sensor a7 reflected that the peak pressure on the tibial model was 4.2MPa, and the high-modulus low-strain sensor reflected that the peak compressive force caused by the bulging of the artificial meniscus 5 was 2.2MPa.

[0062] Plot the circumferential bulging stress and circumferential bulging strain curves (actual values) of the artificial meniscus 5 during the tests in Examples 1 and 2, and compare them with the upper and lower limits of the theoretical values ​​of circumferential bulging stress and circumferential bulging strain. Figures 6-7 As shown, the circumferential bulging stress and circumferential bulging strain curves (actual values) of this type of artificial meniscus 5 differed significantly from the theoretical values, indicating that the artificial meniscus did not meet the mechanical requirements for transplantation.

[0063] To further verify the accuracy of the test results of Examples 1 and 2, animal transplantation experiments were also conducted on the artificial menisci of Examples 1 and 2:

[0064] The artificial meniscus 5 from Example 1 was used in an animal transplantation experiment. A 50 kg sheep (a large animal closely approximating the load of a human knee joint, thus physiologically representative) was selected. The medial meniscus was removed, and an appropriately sized artificial meniscus implant was selected and implanted in situ using suture bone tunnel fixation, based on preoperative joint X-rays and intraoperative measurements of the natural meniscus. The unoperated contralateral joint served as a control. Animals were allowed free movement post-surgery, and joint fixation was removed after 2 weeks. Knee synovial fluid was collected at 3 and 6 months post-transplantation, and the concentration of interleukin-1α (IL-1α, an upregulated cytokine in the progression of osteoarthritis) in the synovial fluid was measured using an ELISA kit. Figure 8 As shown, the IL-1α concentration was significantly higher in the experimental group compared to the control group, indicating the occurrence of osteoarthritis; and severe wear of the femoral cartilage was observed in the experimental group after 6 months. In summary, this type of artificial meniscus cannot generate sufficient strain to buffer energy under stress, easily leading to stress concentration at the contact point between the femoral condyle and the meniscus, thus triggering osteoarthritis and making it unsuitable for long-term implantation.

[0065] The artificial meniscus 5 from Example 2 was used in an animal transplantation experiment. A 50 kg sheep (a large animal closely approximating the load of a human knee joint, thus physiologically representative) was selected. The medial meniscus was removed, and an appropriately sized artificial meniscus implant was selected and implanted in situ using suture bone tunnel fixation based on preoperative joint X-rays and intraoperative measurements of the natural meniscus. The unoperated contralateral joint served as a control. Animals were allowed free movement post-surgery, and joint fixation was removed after 2 weeks. Knee synovial fluid was collected at 3 and 6 months post-transplantation, and the concentration of interleukin-1α (IL-1α, an upregulated cytokine in the progression of osteoarthritis) in the synovial fluid was measured using an ELISA kit. Figure 9 As shown, the IL-1α concentration was significantly higher in the experimental group compared to the control group, indicating the occurrence of osteoarthritis. Furthermore, severe wear of the femoral cartilage and tibial plateau were observed in the experimental group after 6 months. In summary, this type of artificial meniscus is prone to significant bulging under stress, which can easily lead to contact between the femur and tibial plateau under physiological load, damaging the articular cartilage and hindering long-term implantation.

Claims

1. An in vitro testing method for an artificial meniscus, characterized in that: The artificial meniscus is fixed between the femoral model (4) and the tibial model (8) with reference to the human body structure, an axial pressure is applied to the artificial meniscus through the femoral model (4), and the axial pressure of the artificial meniscus on the tibial model (8), the actual value of the circumferential bulging strain of the artificial meniscus, and the actual value of the circumferential bulging stress of the artificial meniscus are monitored; When the axial pressure applied to the artificial meniscus is 0N-1000N, if the axial pressure of the artificial meniscus acting on the tibia model (8) is ≤8MPa, the actual value of the circumferential bulging strain of the artificial meniscus is 0.82-1.18 times the theoretical value of the circumferential bulging strain of the artificial meniscus, and the actual value of the circumferential bulging stress of the artificial meniscus is 0.86-1.14 times the theoretical value of the circumferential bulging stress of the artificial meniscus, then the artificial meniscus meets the mechanical requirements for transplantation; otherwise, the artificial meniscus does not meet the mechanical requirements for transplantation; The calculation formula of the theoretical value of the circumferential bulging strain of the artificial meniscus is: y1 = -2.89 + 2.1e -9 *e -(x / 48) +2.65e -(x / 547) , where x represents the value of the axial pressure applied to the artificial meniscus in N, and y1 represents the value of the theoretical value of the circumferential bulging strain of the artificial meniscus in %. The calculation formula of the theoretical value of the circumferential bulging stress of the artificial meniscus is: y2 = -0.095 + 0.16e x / 317 , where x represents the value of the axial pressure applied to the artificial meniscus in N, and y2 represents the value of the theoretical value of the circumferential bulging stress of the artificial meniscus in MPa.

2. The in vitro testing method of an artificial meniscus according to claim 1, characterized in that: A pressure sensor a (7) is used to monitor the axial pressure of the artificial meniscus on the tibia model (8); the pressure sensor a (7) is arranged between the artificial meniscus and the tibia model (8).

3. The in vitro testing method of an artificial meniscus according to claim 2, characterized in that: Monitoring the actual value of the circumferential bulging strain of the artificial meniscus and the actual value of the circumferential bulging stress of the artificial meniscus is performed step by step and different flexible strain sensors (6) are used.

4. The in vitro testing method of an artificial meniscus according to claim 3, characterized in that: The flexible strain sensor (6) used to monitor the actual value of the circumferential bulging strain of the artificial meniscus is a low modulus high strain sensor, which covers the periphery of the artificial meniscus and extends to the anterior and posterior corners of the artificial meniscus; the tensile modulus of the low modulus high strain sensor is 100Pa-0.5MPa, and the effective strain is 0%-100%; The flexible strain sensor (6) used to monitor the actual value of the circumferential bulging stress of the artificial meniscus is a high modulus low strain sensor, which covers the periphery of the artificial meniscus and extends to the anterior and posterior corners of the artificial meniscus; The high modulus low strain sensor has a tensile modulus of 3GPa-200GPa and an effective strain of 0%-10%.

5. The in vitro testing method of an artificial meniscus according to claim 4, characterized in that: The artificial meniscus is fixed between the femoral model (4) and the tibial model (8) using two fixing plates (10), one end of the two fixing plates (10) is fixedly connected to the tibial model (8) at the same time, the other end of one fixing plate (10) squeezes the front corner of the artificial meniscus and the flexible strain sensor (6), and the other end of the other fixing plate (10) squeezes the posterior corner of the artificial meniscus and the flexible strain sensor (6).

6. The in vitro testing method of an artificial meniscus according to claim 5, characterized in that: An upper chuck (3), a servo motor, a transmission device (2), and a pressure sensor b (1) are used to apply axial pressure to an artificial meniscus through a femoral model (4); the upper chuck (3) is fixedly connected to the upper end of the femoral model (4); the servo motor controls the lifting and lowering of the upper chuck (3) through the transmission device (2); and the pressure sensor b (1) is used to monitor the axial pressure applied to the artificial meniscus.

7. The in vitro testing method of an artificial meniscus according to claim 6, characterized in that: The lower end of the tibia model (8) is fixedly connected to the lower support (9).

8. An in vitro testing device for artificial meniscus for implementing the in vitro testing method for artificial meniscus as claimed in any one of claims 6 to 7, characterized in that: It comprises the femur model (4), the tibia model (8), the pressure sensor a (7), the low modulus high strain sensor, the high modulus low strain sensor, the two fixing plates (10), the upper chuck (3), the servo motor, the transmission device (2), and the pressure sensor b (1).

Images