Testing device for evaluating degradation behavior of degradable bone fixing instrument under complex mechanical loading

Abstract

The invention provides a testing device for evaluating the degradation behavior of a degradable bone fixing instrument under complex mechanical loading, and the device can simulate complex mechanical conditions and liquid environment after the degradable bone fixing instrument is implanted into a human body in vitro, and can load pressure and fluid impact force in 1-3 directions at the same time; the temperature can be regulated and controlled to realize degradation at a specific temperature, and a plurality of test samples and degradation liquid can be collected at the same time for characterization analysis due to the multi-flux design, so that the degradation condition of the degradable bone fixation instrument under the complex mechanical loading condition is evaluated. The mechanical loading device is easy and convenient to operate, low in cost, good in universality and expansibility and adjustable in parameter, and the simulation condition is closer to the in-vivo real condition. Compared with a traditional non-mechanical condition, the device can provide a new thought for in-vitro prediction in vivo and short-term prediction of degradation evaluation of the degradable bone implant, and finally facilitates promotion of marketing of the novel degradable bone implant.

Description

Technical Field

[0001] The present invention belongs to the field of medical devices, and in particular relates to a testing device for evaluating the degradation behavior of a degradable bone fixation device under complex mechanical loading. Background Art

[0002] New degradable bone fixation devices, such as magnesium and polylactic acid, are expected to solve the problems of corrosion, stress concentration, and the need for secondary surgery for removal that exist in traditional stainless steel and titanium alloy bone fixation devices due to their good biocompatibility, degradability, and mechanical properties. Therefore, they have been widely used in fracture treatment and bone defect repair. However, the degree of matching between the degradation behavior of such degradable materials in the body and bone tissue repair directly affects the application and therapeutic effect of related implants. On the one hand, the in vivo degradation behavior of such materials will affect the maintenance of the mechanical strength of the material itself, causing the implant to loosen or even fail. On the other hand, the microenvironment generated by its degradation and the release of its degradation products will directly affect the surrounding tissues and cells, producing corresponding biological effects. Therefore, the evaluation of the degradation behavior of such medical devices is crucial to ensuring the safety and effectiveness of related products.

[0003] As specified in the GB / T 16886 series of national standards, current in vitro experiments evaluating the degradation performance of bone fixation devices mostly use static immersion, which fails to consider the complex mechanical environment within the human body. High-strength implantable devices, regardless of their location in the body, are subject to complex mechanical forces. While some studies of degradation under simple mechanical conditions have been reported, most of these studies only applied uniaxial stress and failed to consider the complex in vivo mechanical environment, particularly the fluid dynamics. Flushing with blood or tissue fluid accelerates the release of degradation products, leading to changes in cell and tissue behavior. Therefore, to more realistically simulate the complex mechanical and physiological environment within the body, developing testing devices capable of simultaneously applying multiaxial stress and fluid forces, providing a controllable fluid and temperature environment, and collecting and analyzing degradation products is essential not only to improve the accuracy of preclinical evaluation of degradable bone fixation devices and accelerate the launch of related products, but also to understand the interaction between materials and the body, leading to better design and use of such devices. Summary of the Invention

[0004] Based on the above problems, the present invention provides a testing device for evaluating the degradation behavior of degradable bone fixation devices under complex mechanical loading, aiming to achieve accurate evaluation of the degradation behavior of degradable bone fixation devices by simulating the static force, fluid force, liquid and temperature environment in the body.

[0005] The technical solutions of the present invention are as follows:

[0006] Static Loading Unit: This static loading unit applies compressive stress to the sample in one to three directions to meet the loading requirements of bone fixation devices in different application areas. Four to eight loading units are available, enabling simultaneous loading of multiple samples for parallel experiments and reducing random errors. The loading unit comprises a loading bolt assembly and a support frame, both made of corrosion-resistant 316 stainless steel to prevent interference with sample degradation product analysis. The loading bolt assembly consists of a loading bolt, a loading spring, a gasket, and a cap. The threads of the loading bolt are marked with length scales to precisely control the deformation of the loading spring. The loading spring wire diameter is adjustable to adjust the range of loadable pressure. The gasket is positioned between the loading bolt and the loading spring to ensure proper coordination between the three. The end of the cap that contacts the loading spring is a cylindrical, recessed structure with an inner diameter larger than the outer diameter of the bolt and spring to facilitate relative sliding movement. The other end of the cap features a slot to secure the loaded sample. Customized design of the cap and the fixing base in the support frame allows for securement of samples of varying shapes and different locations on the same sample. The bone fixation instruments commonly used in current research are generally strip-shaped bone plates or cylindrical screws. In experiments, the slots of the cap can be designed to be correspondingly rectangular or cylindrical to achieve a tighter fit with the sample and reduce errors in calculating the sample deformation. The support frame includes a fixed base and a loading surface. The fixed base fixes the sample with an embedded structure to ensure the stability of the sample during loading. The loading surface is connected to the fixed base by M6 bolts. By adjusting the number and direction of the loading surfaces that are compatible with the fixed base, 1-3 axis static pressure loading can be achieved.

[0007] Static loading parameters: The setting of the static loading parameters is achieved by selecting different support frames and loading springs. By changing the number of loading surfaces in the support frame, pressure in different directions can be loaded on the sample (1-3). By changing the wire diameter (elastic coefficient) and deformation of the loading spring, precise control of the pressure loaded on the sample can be achieved. The setting of the static loading parameters needs to be combined with the stress conditions of the bone fixation device during actual service and the mechanical properties of the device. The fracture sites of the human body can be divided into load-bearing bones and non-load-bearing bones according to the mechanical strength required by the internal fixation material. For typical load-bearing lower limb bones, for a 70kg adult male, when standing, the human tibial plateau bears a force of about 95% of the body weight, and the unilateral tibia bears a force of about 320N. When lying flat with the legs raised, the human lower limbs account for about 30% of the body weight, and the lower unilateral femur is subjected to a shear force of about 105N. During static loading, load-bearing bone internal fixation device samples are subjected to axial compression of 50-300N and tangential shear forces of 20-100N to approximately simulate the mechanical environment experienced during daily activities after implantation in the human body. For non-load-bearing bones, such as the craniofacial bones, internal fixation devices are primarily subjected to tangential shear forces during service. The head of an adult male accounts for approximately 7%-8% of body weight, or approximately 5-6kg. In a standing position, the load on a craniofacial internal fixation device is approximately equal to the head's own weight (50-60N). In a recumbent position, the load is approximately one-third of the head's own weight (15-20N). Furthermore, studies have shown that excessive mechanical loads can lead to premature material failure. Therefore, the recommended static loading force should be within 20%-60% of the sample's compressive and flexural strengths to ensure stable loading.

[0008] Fluid dynamic loading unit: The fluid dynamic loading unit is used to apply fluid impact force to the sample, and specifically includes a degradation liquid container, a nozzle and a liquid pump. The degradation liquid container is sealed by a sealing cover on the top to eliminate the influence of the external environment during the degradation process and reduce the evaporation of the liquid during the degradation process. The nozzle is provided with 36-81 water outlets, each of which can be opened and closed individually to achieve selective loading of different positions of the sample. The inner diameter of the circulation pipe of the liquid pump is 1 cm and the wall thickness is 0.2-0.4 cm. In a quiet state, the average blood flow rate in the aorta is about 18-22 cm / s, and the blood flow rate in the capillaries is relatively slow, about 0.3-0.7 cm / s. Taking into account the inner diameter of the circulation pipe, the circulation flow rate of the liquid pump can be set in the range of 30 mL / min-2000 mL / min, which can approximately simulate the fluid mechanics conditions in the body. To accelerate the in vitro degradation rate of a sample, the degradation temperature is often increased. For example, in polymer degradation experiments, temperatures above 37°C but below the melting or softening temperature of the polymer, such as (70±2)°C, are used for accelerated degradation testing. Therefore, the liquid pump is designed to withstand temperatures above 80°C, meeting the temperature requirements of most degradation tests.

[0009] Degradation fluid: The types of degradation fluid include but are not limited to simulated body fluid (SBF), phosphate buffered saline (PBS), Earle's balanced salt solution (EBSS), Hank's balanced salt solution and normal saline. In actual use, the appropriate type of degradation fluid can be selected according to the test purpose and the characteristics of the tested sample. Degradable bone fixation device: The degradable bone fixation device is a degradable bone screw, bone plate or plate, and the material is a degradable polymer, degradable ceramic, degradable metal or a composite of the three. The bending strength of the bone plate and plate is ≥200MPa, the bending modulus is ≥5000MPa, the maximum torque of the bone screw is ≥400N·mm, and the axial pull-out force is ≥250N. The material has no long-term inflammatory reaction in the body, and the strength remains above 80% after 3 months of implantation, which is consistent with the performance of medical bone fixation devices used clinically.

[0010] Liquid environment control unit: The liquid environment control unit includes pH and conductivity controllers. The pH and conductivity controllers are used to monitor the liquid environment, while the automatic reagent addition device is used to automatically adjust the liquid environment.

[0011] Temperature control unit: The temperature control unit includes a liquid temperature sensor and a heating device. The temperature control unit liquid temperature control range is 25℃-80℃, and the control accuracy is 0.1℃, which can meet the temperature conditions required by most tests.

[0012] Degradation product collection unit: After the test is completed, the sample and its degradation products are collected through the degradation product collection unit for further relevant physical, chemical and biological analysis, such as sample surface morphology, hydrophilicity, mass loss, mechanical properties, and composition analysis of degradation products.

[0013] Compared with the prior art, the present invention has the following advantages: (1) Higher evaluation accuracy: The device of the present invention solves the limitations of the non-loaded static immersion in the prior art by simulating the complex mechanical and physiological environment in the body, and provides an efficient and accurate solution for evaluating the degradation behavior of degradable bone fixation devices. (2) Realistic simulation of the in vivo mechanical environment: Compared with the prior art, the present invention can simultaneously apply multi-axial stress and fluid force, more realistically simulating the complex mechanical and physiological environment in the body. This comprehensive simulation method can more accurately reflect the actual degradation behavior of degradable bone fixation devices in the body. (3) Comprehensive consideration of multiple factors: The prior art usually only considers a single mechanical factor or chemical environment, while the present invention comprehensively considers multiple factors such as multi-axial stress, fluid mechanics, liquid composition and temperature, providing a more comprehensive evaluation system, thereby improving the accuracy and reliability of the evaluation results. (4) Better control of experimental conditions: The present invention can provide a controllable liquid and temperature environment to ensure the stability and repeatability of the experimental conditions. This helps to reduce experimental errors and improve the consistency and credibility of experimental results. The device has a flexible parameter adjustment function. It can adjust the magnitude and loading direction of multiaxial stress, liquid flow rate and pressure, temperature and other parameters according to different types of degradable bone fixation devices and research needs, thereby realizing personalized experimental design. (5) Good versatility and scalability: The test device of the present invention has good versatility and can be applied to various types of degradable bone fixation devices, such as magnesium alloy devices, polylactic acid devices, etc., to meet different research and clinical needs. In addition, the design of the device takes into account the needs of future research and has a certain degree of scalability. New functional modules can be easily added or used in conjunction with other analytical instruments to achieve more complex and in-depth research. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The figure shows the main part of the degradation test device in the present application; 1 is a sealing cover, 2 and 3 are circulation pipes of the liquid pump, 4 is an internal drain port, 5 is a nozzle, 6 is a degradation liquid container containing degradation liquid, 7 is a biaxial static loading unit, and 8 is a uniaxial static loading unit;

[0015] Figure 2 A schematic diagram of a uniaxial static loading unit in the present application is shown; 1 is a connecting bolt, 2 is a loading surface, 3 is a loading bolt group, 4 is a fixed base, and 5 is a wafer sample;

[0016] Figure 3 A schematic diagram of a loading bolt group in a uniaxial static loading unit of the present application is shown; 1 is a loading bolt, 2 is a gasket, 3 is a loading spring, and 4 is a cap;

[0017] Figure 4A schematic diagram of a biaxial static loading unit in the present application is shown; 1 is a connecting bolt, 2 and 5 are loading surfaces, 3 and 4 are loading bolts, 6 and 8 are caps, 7 is a bone plate sample, and 9 is a fixed base;

[0018] Figure 5 A physical diagram of the uniaxial static loading unit in Example 1 of the present application is shown;

[0019] Figure 6 A physical diagram of the biaxial static loading unit in Example 3 of the present application is shown; DETAILED DESCRIPTION

[0020] Below, in conjunction with the accompanying drawings, the preferred embodiments of the present invention are described in detail. The described embodiments are only some examples of the present invention and are not exhaustive. The following embodiments are provided to deepen the understanding of the present invention, but should not be regarded as limiting the content or scope of protection of the present invention. Any product that is identical or substantially similar to the present invention and is produced under the guidance of the present invention or by combining the technical features of the present invention with other prior art features should be included in the protection scope of the present invention. In addition, the drawings are only schematic depictions, and their size ratios, shapes and details may differ from the actual products. The actual design and manufacturing should be used as the basis for specific implementation.

[0021] It should be noted that the terms used in the present invention should be understood as open terms (for example, the term "including" should be interpreted as "including but not limited to", the term "having" should be interpreted as "having at least", etc.). Unless otherwise explicitly defined in the present invention, the technical and scientific terms used in the present invention should have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs.

[0022] Example 1

[0023] The present invention provides a testing device for evaluating the degradation behavior of degradable bone fixation devices, which is used to simulate the complex mechanical and physiological environment in the body to improve the accuracy of degradation behavior evaluation. The specific use of the device includes the following steps:

[0024] (1) The applicable scenario of this embodiment is maxillofacial fracture, standing still state.

[0025] (2) Fix the biodegradable bone fixation device sample on the static loading unit.

[0026] The biodegradable bone fixation device sample used was made of pure PLLA and processed by injection molding. The sample shape was a disc with a diameter of 26 mm and a thickness of 2 mm.

[0027] The static loading unit selected is the uniaxial static loading unit (see Figure 4), with a loading surface and a fixed base; the loading threaded hole on the loading surface is M18, and the threaded hole connected to the fixed base is M6; the fixed base fixing the sample is a cylindrical depression with an inner diameter of 27mm and a depth of 2mm; the loading bolt is an M18 bolt and a length of 20mm; the cap is a hollow cylindrical sleeve with a bottom circle diameter of 22.5mm, an inner diameter of 18.5mm, a wall thickness of 2mm, and a height of 22mm; the loading spring has an outer diameter of 18mm, a wire diameter of 1.8mm, a length of 20mm, and an elastic modulus of 7.55N / mm; the gasket is a disc with a diameter of 18mm and a thickness of 1mm;

[0028] The uniaxial static pressure applied to the sample was set to 60N to simulate the weight of the head of an adult male in a standing state, and the deformation of the loading spring was 7.92mm.

[0029] (3) Assemble the static loading unit with the sample fixed in the fluid dynamics loading unit.

[0030] Fix the static loading unit in the groove at the bottom of the degradation liquid container, and open the nozzle aligned with the sample position so that the nozzle outlet completely covers the sample;

[0031] Load PBS solution into the degradation solution container with a volume of 200 mL, completely immerse the static loading unit, and assemble the sealing cover to make the degradation solution container completely airtight to reduce liquid evaporation during the degradation process;

[0032] The pH of the solution was adjusted to 7.4 and the phosphate ion concentration was adjusted to 0.01 M using the liquid environment monitoring unit to simulate the initial human body fluid environment; the temperature adjustment unit was set to 37°C to simulate normal human body temperature;

[0033] Set the experimental parameters of the fluid dynamic loading unit to a single-channel flow rate of 50 mL / min to simulate the flow of small blood vessels in the maxillofacial region, and start the liquid pump.

[0034] (4) In vitro degradation experiments were started, and five degradation time points were set, namely 0 h, 2 weeks, 4 weeks, 8 weeks, and 12 weeks, where 0 h represented the blank control. The changes in pH and conductivity of the liquid in the degradation liquid container were recorded in real time using a liquid environment monitoring unit.

[0035] (5) Collect samples and degradation products and conduct relevant physical, chemical and biological analyses.

[0036] Sample mass loss: Each sample was weighed before the experiment, and the mass was recorded as m0. After the experiment, the degraded samples at each time point were collected, rinsed with deionized water three times, and placed in a 50°C oven. After 48 hours, they were weighed again and recorded as mdry. The sample mass loss was calculated according to the following formula;

[0037]

[0038] Sample hydrophilicity: The hydrophilicity of the material will affect the spreading and adhesion of cells on the surface of the material. The change in the surface contact angle of the sample before and after degradation is tested to detect the change in the sample's hydrophilicity. The hydrophilicity is measured using a contact angle tester at 37°C, with 4 points measured for each sample. Sample surface morphology: By observing the surface morphology of the sample, the occurrence and development process of surface microcracks can be known, which can better understand the degradation process of the material. After the sample is dried and treated with gold spraying for 75 seconds, a field emission scanning electron microscope is used to observe the changes in the surface morphology of each group of samples after the degradation experiment.

[0039] Sample molecular weight distribution: The degradation rate of the material can be predicted by measuring the molecular weight and distribution of the sample. Cut a sample (3-5 mg) into a 2 mL sample vial, add 1 mL of chloroform solution, and dissolve at room temperature for 4 hours. After complete dissolution, filter with a sterile syringe filter (0.45 μm polytetrafluoroethylene filter membrane) and use gel permeation chromatography (GPC) to measure the molecular weight distribution of PLLA before and after degradation. Set the column temperature to 30°C, the injection flow rate to 1 mL / min, and the injection volume to 20 μL:

[0040] Sample Bending Performance: Bend tests are performed on degraded samples to determine changes in their bending performance. Using wire cutting technology, the sample disc at each time point is cut into three strips, 16 mm long, 4 mm wide, and 2 mm thick. The strips are placed flat on the center of the roller and the compression speed is set to 0.01 mm / min. Testing is stopped when the sample fails. Force and displacement data are collected and a load-displacement curve is plotted. The slope of the linear interval is calculated, which is the bending stiffness.

[0041] Degradation solution pH: PLLA degradation produces lactic acid monomers, which triggers a self-accelerating effect. The pH of the degradation solution can be measured to predict the impact of degradation conditions on the self-accelerating effect of PLLA degradation. The pH data of the degradation solution recorded in real time by the liquid environment monitoring unit can be exported to compare the pH changes during the sample degradation process.

[0042] PLA content in degradation solution: PLLA degradation produces lactic acid monomers. The PLA content in the degradation solution can be measured to predict the degradation rate of the sample. 40 mg of the degradation solution at each time point was collected, enriched, and analyzed using gas chromatography-mass spectrometry (GC-MS) to determine the PLA concentration in the degradation solution.

[0043] Example 2

[0044] The difference between Example 1 and step (1) is that the applicable scenario of this embodiment is a skull fracture and a lying state;

[0045] Different from Example 1, the material of the degradable bone fixation device sample used in step (2) of this embodiment is PLLA doped with HA, and the processing method is melt blending and compression molding, and the mass fraction of HA is 30%;

[0046] Different from Example 1, the wire diameter and elastic coefficient of the loading spring used in step (2) of this embodiment are different, specifically, the wire diameter is 1.5 mm and the elastic coefficient is 3.24 N / mm;

[0047] Different from Example 1, in this example, the uniaxial static pressure applied to the sample in step (2) is 20 N to simulate the weight of the head of an adult man lying down, and the deformation of the loading spring is 6.11 mm;

[0048] Different from Example 1, in step (3), lactate dehydrogenase was added to the PBS solution in this example to simulate the enzymatic environment of lactic acid degradation in vivo;

[0049] Unlike Example 1, this example adds the determination of the calcium ion content in the degradation solution in step (5) to detect the effect of complex degradation conditions on the release of HA during the degradation of the PLLA / HA composite material. The specific method is as follows:

[0050] The calcium ion concentration in the degradation solution was determined by inductively coupled plasma mass spectrometry (ICP-MS). Scandium (Sc, 45) was used as the internal standard at a concentration of 1 μg / mL. A dual peristaltic pump was used for injection at a speed of 0.1 rps and an injection volume of 50 to 100 μL. Each sample was measured three times with an integration time of 0.3 seconds, and the average value was calculated.

[0051] Example 3

[0052] Different from Example 1, the applicable scenario in step (1) of this embodiment is a distal radius fracture, and the patient is lying down with the arm flat:

[0053] Different from Example 1, the material of the degradable bone fixation device sample used in step (2) of this embodiment is PLLA doped with 10% strontium, and the sample is in the shape of a plate, 30 mm long, 5 mm wide, and 2 mm thick, with 4 circular openings of 1 mm radius evenly distributed in the center, and the hole spacing is 4 mm; Different from Example 1, the static loading unit used in step (2) of this embodiment is a biaxial static loading unit (see Figure 5), with two loading surfaces and a fixed base; the loading threaded holes on the loading surface and the threaded holes in the fixed base are both M6; the fixed base has a rectangular recessed area 5mm long, 2mm wide, and 3mm deep to secure the sample; both loading bolts are M6 bolts, 12mm long; the cap is a sleeve, and the contact side of the cap and the loading bolt is a hollow cylinder with an inner diameter of 6mm, a wall thickness of 1mm, and a depth of 3mm. The sample-fixing side of the cap has a rectangular recessed area 5mm long, 2mm wide, and 2mm deep.

[0054] Different from Example 1, in step (2), the biaxial static pressure applied to the sample in this embodiment is 15N in the axial direction and 5N in the tangential direction, respectively, to simulate the force on the distal radius fracture fixation plate in the lying position with the arm flat;

[0055] Different from Example 1, in step (3), the single-channel flow rate of the hydrodynamic loading in this example is 120 mL / min to simulate the flow rate of the middle vein;

[0056] Different from Example 1, this example adds a test of the surface roughness of the sample in step (5), and the specific method is as follows:

[0057] The surface morphology and roughness of the bone plate material were measured using an atomic force microscope. The non-contact scanning mode was selected to scan different locations of the bone plate, including the opening, center, and edge, in a high-purity argon environment to detect the effect of composite mechanical loading on the degradation of different parts of the sample.

[0058] Example 4

[0059] Different from Example 1, the material of the degradable bone fixation instrument sample used in step (2) of this embodiment is magnesium alloy doped with 0.7% zirconium, and the molding method is melt blending;

[0060] Different from Example 1, the degradation solution used in step (3) of this example is Earle's balanced salt solution (EBSS) with a volume of 160 mL;

[0061] Different from Example 1, in step (3), this embodiment uses a liquid environment monitoring unit to adjust the solution pH to 6.8 to simulate the acidic microenvironment of the inflammatory site in the body;

[0062] Different from Example 1, the degradation temperature in step (3) of this example is set to 50°C to achieve the purpose of accelerating in vitro degradation;

[0063] Unlike Example 1, the degradation time points in step (4) of this embodiment are set as follows: 0 h, 1 week, 2 weeks and 5 weeks respectively; through the above embodiment, the present invention can simultaneously apply multiaxial stress and fluid force, provide a controllable liquid and temperature environment, and realize the collection and analysis of samples and degradation products. The present invention has been illustrated by the above embodiment, but it should be understood that the above embodiment is only used to illustrate the principles and applications of the present invention and is not intended to limit the scope of protection of the present invention. Based on the enlightenment of the present invention, those skilled in the art, without departing from the scope of the thought and essence of the present invention, any changes and improvements made to the specific implementation and application scope are still within the scope of protection of the present invention.

Claims

1. A testing device for evaluating the degradation behavior of a degradable bone fixation device under complex mechanical loading, characterized in that: The device comprises: a static loading unit for applying compressive stress in 1-3 directions; Fluid power loading unit, used to load fluid impact force and perform liquid circulation; Liquid environment control unit, used to simulate the liquid environment after the degradable bone fixation device is implanted; Temperature control unit, used to regulate the real-time degradation temperature; The degradation product collection unit is used to collect degradation products and perform product analysis.

2. The degradation testing device according to claim 1, characterized in that: The static loading unit comprises: A loading bolt assembly, comprising a loading bolt, a loading spring, a gasket, and a cap. The loading bolt, the loading spring, and the gasket form an assembly for applying compressive stress. One side of the cap wraps the assembly, and the other side is used to fix the sample. The support frame includes a fixed base and a loading surface. The fixed base is used to fix the sample. The loading surface has a through hole that matches the loading bolt. The number of loading surfaces can be adjusted from 1 to 3. The loading surface and the fixed base are connected by 2 to 4 bolts.

3. The degradation testing device according to claim 1 or 2, characterized in that: The static loading unit controls the size and direction of the loading pressure by controlling the deformation of the loading spring and the loading surface. There are 4 to 8 loading units to realize a multi-flux loading system.

4. The degradation testing device according to claim 1, characterized in that: The fluid power loading unit comprises: A degradation liquid container, the degradation liquid container is used to load the degradation liquid and the static loading unit, the degradation liquid container fixes one of the static loading units through a groove at the bottom of the degradation liquid container, and the degradation liquid container is sealed through a sealing cover on the top; A nozzle, the nozzle being located inside the degradation liquid container, and having 36-81 water outlets arranged in a dot matrix, each of which can be opened and closed individually; A liquid pump is provided for each degradation liquid container. One end of the liquid pump is connected to the nozzle, and the other end is connected to the degradation liquid container through a circulation pipe. The circulation flow rate can be adjusted in the range of 30 mL / min-2000 mL / min, and the temperature tolerance is higher than 80°C.

5. The degradation testing device according to claim 1 or 4, characterized in that: The types of degradation fluids include simulated body fluid (SBF), phosphate buffered saline (PBS), Earle's balanced salt solution (EBSS), Hank's balanced salt solution and physiological saline.

6. The degradation testing device according to claim 1, characterized in that: The sample is a degradable bone nail, bone plate or plate, and the degradable bone nail, bone plate or plate is composed of degradable polymers, degradable ceramics, degradable metals and their composites.

7. The degradation testing device according to claim 1, characterized in that: The liquid environment control unit includes a pH and conductivity controller.

8. The degradation testing device according to claim 1, characterized in that: The temperature control unit includes a liquid temperature sensor and a heating device. The temperature control unit liquid temperature control range is 25 ° C -80 ° C.

9. The degradation testing device according to claim 1, characterized in that: The sample and degradation liquid are collected by the degradation product collection unit to evaluate the degradation condition of the sample.

10. The testing device for evaluating the degradation behavior of a degradable bone fixation device under complex mechanical loading according to claim 1, wherein the method for using the testing device comprises the following steps performed in sequence: According to the service scenario of the degradable bone fixation device, a loading spring with an appropriate wire diameter and the number of loading surfaces are selected, and the sample is fixed on the static loading unit and loaded statically; Fix the static loading unit in the groove at the bottom of each degradation liquid container, and adjust the opening and closing of the nozzle outlet as needed; Load the degradation liquid to immerse the entire static loading unit, and seal the degradation liquid container; Adjust the temperature control unit to the temperature designed for the experiment; Set the experimental parameters of the fluid dynamic loading unit and start the liquid pump; Conduct in vitro degradation experiments under complex mechanical loading and constant temperature conditions; Collect samples and degradation liquid, and perform relevant physical, chemical and biological analyses.

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